This chapter will cover items estimated in the framing phase of construction, including wall framing, floor framing, door framing, window header framing, specialty framing, stair framing, and roof framing. The discussion will begin with wall framing.

Wall Framing

Typical residential wall framing construction usually includes several distinct wall framing types. We will discuss three general subphases: basement and pony walls, exterior walls, and interior walls. Each discrete wall type may share some common framing elements with other wall types such as the same size and type of wall studs; however, distinctive wall types will also have framing elements that are different, which make it desirable to estimate the wall type separately.

In the typical construction sequence, load bearing basement and pony walls, which support the floor system, are constructed first. Next, the floor system is framed. Then, the exterior and interior walls are built. Normally the construction sequence is followed in preparing an estimate, however, for the sake of brevity and because estimating all wall framing types will use a similar process, estimating the walls will be covered before floor framing is discussed. The three-wall estimating subphases, basement and pony walls, exterior walls, and interior walls, will be covered separately.

Basement and Pony Walls

Basement and pony walls are commonly used in construction where there is a foundation that is below grade and a wood framed floor built on top of the foundation. The basement and pony walls provide intermediate support for the floor system when distance is more than the floor system can bridge in a single span.

Pony Walls

Pony walls are short walls that extend from footing or foundation stem walls to the floor joists. In addition, a short wall that doesn’t extend to the ceiling, such as could be built around a stairwell opening, could also be classified as a pony wall. Pony walls could be identified by other names such as a cripple wall, stem wall, or half wall. Figures 9-1 to 9-4 show some examples of pony walls in wood framed construction.

Pony walls typically have top and bottom plates and a stud spacing, such as 16 or 24 inches on-center, similar to what is common in wall framing. If the base of the pony wall rests upon a concrete surface, the plate will need to be of pressure treated lumber or other rot resistant material. There may be either single or double top plates, depending upon the needs of the pony wall. When estimating the material to be used for the studs in pony walls, the typical stud material purchased for the project would be cut into shorter lengths for the studs. For example, if a wall required 20 studs and each stud was to be cut to a 30-inch length, a typical 92 5/8-inch wall stud could be cut into three pony wall studs of 30 inches each and seven studs would need to be purchased. However, if the pony wall studs were 32 inches long, ten 92 5/8-inch studs would need to be purchased because each stud could be cut into only two pony wall studs.

Basement Walls

The construction of basement walls can vary depending upon the use of the wall. Walls that are used to support the floor system and that rest upon a concrete surface will typically have pressure treated bottom plate material and a double top plate. The wall could be either 2 × 4 or 2 × 6 construction, depending upon the load supported by the wall. Basement walls that are load bearing will also require load bearing headers. Headers will be discussed in a later section. Other types of basement walls are also common. Secondary wood framed walls are often installed inside of the concrete foundation walls to provide space for insulation, electrical wiring, and provide convenient attachment for drywall material. If this secondary wall type rests upon a concrete surface, a pressure treated bottom plate will need to be provided. The top plate of these secondary walls, however, may be either a single top plate or double top plate, and the stud spacing may be either 16 or 24 inches on-center. Other basement walls used to separate the space into individual rooms may also have unique construction. Figure 9-5 shows some examples of three types of basement wall construction. The wall in the forefront is a load bearing wall with 16 inch on-center spacing, double top plates, and a load bearing door header. The wall behind also has 16 inch on-center spacing and a double top plate but utilizes a non-load bearing header. The wall along the foundation has a single top plate and 24 inch on-center spacing.

Figure 9-6 also shows examples of basement wall construction further along in the construction process. The construction is similar with several load bearing walls using double top plates, 16 inch on-center spacing and load bearing headers. In the background, walls framed around the foundation with single top plates and 24 inch on-center spacing can be seen. The insulation and vapor barrier have been installed.

Exterior Walls Subphase

Several exterior type walls are included in the exterior walls subphase. Two common exterior type walls are exterior walls and garage walls. Exterior walls will be covered first.

Exterior Walls

Exterior walls are commonly created using 2 × 6 construction to allow for additional space for insulation. The stud spacing can be either 16 or 24 inches on-center. Typically, a single bottom plate is used and double top plates. The bottom plate is placed upon the floor system, so treated lumber is usually not needed. The walls are commonly sheathed using 1/2 or 7/16-inch OSB sheathing. Doors and windows are installed in exterior walls, which requires additional framing including load bearing headers, jack, king, and cripple studs and sills.

In many instances, exterior walls are also load bearing, so headers need to be structural and supported on jack studs.

Figure 9-7 shows an example of typical exterior wall framing. The wall is framed with 2 × 6 studs spaced 16 inches on-center. There is a single bottom plate and double top plates. The window framing is supported by a single trimmer and king stud assembly on each side. A single 2 × 10 header is installed to carry to roof load over the window; however, 2 × 6 head sills are installed on each side of the header to provide attachment for the cripple studs and drywall. Cripple studs fill in the wall below the rough window sill, and because the wall is framed over eight feet tall, cripple studs are also installed between the top of the header assembly and the double top plate to carry the load down to the 2 × 10 header. The view also shows a 2 × 4 intersection partition assembly where a single 2 × 6 wall stud is turned flat to provide support for the partition wall and backing for the drywall to be installed. In addition, 2 × 6 horizontal blocking is used to provide backing for the horizontal seam in the 1/2-inch OSB sheathing.

Garage Walls

Garage walls are also exterior type walls but often utilize a different construction method and materials. Garage walls are often constructed directly on the garage foundation and have a bottom plate of a pressure treated material. In addition, because the walls are built on the foundation and not the floor framing, they are taller than other exterior walls. They are also often constructed out of 2 × 4 material instead of 2 × 6 material. Figure 9-8 shows a garage wall and where it meets with a common wall.

Common Walls

The common wall is the wall that is shared between the garage and the house. Technically, it could be considered an interior wall as both sides are commonly covered in drywall the same as interior walls, but it also has insulation, and the garage side could be considered exterior as it is usually not heated, which is one of the reasons for placing it in the exterior wall subphase. It usually does not have sheathing such as an exterior wall. Common walls are usually 2 × 6 construction to allow for the installation of sufficient depth of insulation (Figure 9-9).

Interior Wall Subphase

A number of wall types are estimated in the interior wall subphase including 2 × 4 interior partition walls, common walls, plumbing walls, and rake walls.

2 × 4 Interior Walls

Interior partition walls are usually 2 × 4 construction. The stud spacing can be either 16 or 24 inches on-center with a single bottom plate. Either a single or double top plate can be used. Headers over interior non-load bearing walls are commonly a single flat 2 × 4 with cripple studs filling into the top plate (Figure 9-10).

2 × 6 Plumbing Walls

2 × 6 plumbing walls are usually installed as part of the bathroom. Most residential construction is required to have at least one 3-inch diameter plumbing vent pipe. Often, a 2 × 6 stud wall is installed to allow access for the plumbing vent pipe and appropriate fittings (Figure 9-11).

Tall Walls

Tall walls are framed walls that are taller than the normal wall height. They could be either an exterior or interior wall and be either 2 × 4 or 2 × 6 construction, depending upon the needs. Examples of tall walls in exterior construction could be walls that are framed around fireplace chimneys or for two-story entrances or rooms. Interior tall walls could be walls that separate two rooms that share a tall ceiling, such as those structures that have cathedral ceilings in them.

Rake Walls

Rake walls are angled walls that are commonly built upon standard walls, either interior or exterior. Figure 9-12 shows an example of a rake wall built on top of an interior partition wall. The wall is built as a straight pony wall with a single top and bottom plate. Sloped ceiling joists are attached to the rake wall, and the wall is tied into the trusses with blocking between the trusses and ceiling joists.

Figure 9-13 shows another example of a rake wall. In this case, the rake wall is created by filling in between the chords of the W truss in the roof. There is also a plant shelf built on top of the interior partition walls that steps back to the rake wall. The sloped ceiling is framed on the rake wall by attaching a ceiling joist to the W truss chord members.

Exterior Walls Framing Material

Despite the variations in wall framing styles, most framed walls will be estimated using similar formulas. The difference in each wall type will be accounted for by making changes in the header section of the estimating template. Excel Figure 9-1 shows the header section for the exterior wall subphase of the framing. It will be used as an example for completing each of the three different wall framing subphases.

Figure 9-14 shows a representation of the main floor wall framing for the Arts and Crafts sample house. The various exterior and interior walls are displayed using the following color code:

• Exterior Walls = Red
• Interior Walls = Green
• Common Wall = Violet
• Garage Walls = Blue

Exterior Wall Framing Material

The exterior wall length and wall height parameters of 114 lineal feet and eight feet, respectively, will be the measurements that we use as an example in this chapter. The walls are constructed with two top plates and a single bottom plate and a stud spacing of 16 inches on-center. The number of corners, partitions, and hold downs are determined from the floor plan. The corners, partitions, and hold downs are numbered in red circles on the representation in Figure 9-14. The determining factor in including a particular intersection with a particular wall style is where the extra studs are located. In actual construction, the right-front exterior wall and the common wall would be built as a single wall, and intersections 1 and 12 could be considered as part of the common wall or part of the garage walls but, in this case, will be counted as part of the exterior walls. Two studs will be added to the estimate for each corner or intersection. Figure 9-15 shows a close-up view of intersections 6, 7, and 8. Intersection 6 falls on the location of a regular on-center stud spacing where ladder blocking is used to create the intersection. Intersections 7 and 8 are created by turning a single 2 × 6 stud sideways to provide anchoring for the intersecting wall and backing for the drywall.

Windows and Doors Less Than Six Feet

Framed openings for windows and doors require trimmer studs on each end to support the header. The estimating template calculates two additional wall studs for each framed window and door opening that is less than six feet in width. King studs are also used in conjunction with each trimmer stud, however, extra studs are usually not added to the estimate because the two king studs can be accounted for by the normal on-center studs that are left out of the opening. The location of window openings in the on-center stud layout may make additional studs needed in specific circumstances, but adding two additional studs for smaller window and door openings is sufficient.

Windows Six Feet or Greater

Building code generally requires double trimmer studs supporting headers for openings that are six feet wide or greater. In accordance with the requirement, six additional studs will be added to the estimate for window openings that are six feet or wider. The extra studs are only added to windows, not door openings, because even though the double stud requirement also exists for doors, several studs in the standard on-center layout will be left out of the wider door opening that can be used for trimmer studs. On the other hand, windows have the window sill and cripple stud requirements that will need the additional studs.

Wall Sheathing

When you are determining the different wall assemblies, be sure that you know if there is sheathing on both sides or only one side of the wall. You only will be accounting for OSB, plywood or foam sheathing when doing exterior walls. Drywall will be accounted for when we estimate the interior walls.

Wall Sheathing Height

You will need to know the height of the wall sheathing. The exterior walls are installed on the floor system, but the wall sheathing is installed from the top of the wall to the top of the foundation, and the total wall sheathing height would be totaled as follows:

• Wall Height = 8′ 1-1/8″
• Mudsill = 1-1/2″
• Floor Joists 11-7/8″
• Floor Sheathing = 3/4″
• Total Height = 9′ 3-1/4″ or 9.3

Wall Plates

The amount of plates that you will need in order to frame your walls can be determined by the following formula:

Wall Length × Number of Plates (either top or bottom) × (1 + Waste Factor) / Size

Wall Plates = Wall Length × NumberPlates × (1+ WasteFactor) / Size

Floor Framing

Elements of a typical floor framing assembly in residential construction could include floor beams or girders, girder support posts, mudsill, floor joists, rim joists, opening headers, bridging and blocking, joist hanger, and floor sheathing. The discussion will begin with floor beams and girders.

Floor Beams and Girders

All floor joist systems have a limited design span which restricts the distance that the floor joist can span without intermittent support. Most often, residential construction is designed with this in mind, and bearing walls are strategically placed to support the floor system within the limits of the design span; however, there are occasions where the desire for a more open style of design prevents the placing of wall supports within the limits of the floor system design span. In this case, the installation of intermittent floor beams or girders are needed. The terms girder or beams could be used to signify the same thing. Generally speaking, a girder is considered a larger, heavier beam that supports other beams; but in practical usage, the terms are often used interchangeably. There are many different materials that can be used in residential construction as beams or girders. The list of possible girder or beam material includes traditional materials such as solid beams or built-up beams; engineered material, such as laminated veneer lumber (LVL), laminated strand lumber (LSL), glulam lumber, or parallel strand lumber; and steel beams, such as I beams, W beams, or flitch beams.

Traditional Beams and Girders

Traditionally wooden beams have been made of solid lumber, but solid wood beams are seldom used any longer because of the difficulty in finding sufficient stock of large trees to mill the beams, the time it takes to adequately dry the lumber, and the overall high cost. There are some cases in residential construction where traditional post and beam construction is used, but those are more of a specialty type of construction than is common. In many instances where traditional wooden beams are used, the beams are salvaged from older buildings and are used as more of an architectural feature, rather than a true structural element as shown in Figure 9-18 where hand-hewn salvaged beams were used.

Another traditional method of creating beams and girders is to create a built-up beam by assembling multiple layers of dimensional framing lumber together. The layers could be nailed or bolted together. Figure 9-22 shows a floor support beam consisting of lengths of framing lumber, which are cut so that the seams end over a support post and the layers overlap so that the seams do not line up.

Engineered Beams and Girders

Most contemporary beams are constructed using engineered material. Some possible types of engineered beams include: glulam, parallel lam, laminated veneer lumber (LVL), and laminated strand lumber (LSL). Some types of engineered beams such as LVLs and LSLs are frequently joined together to form built-up beams, such as can be done with framing lumber. One major advantage of engineered lumber is that it is eco-friendlier than traditional types of beams because they are usually manufactured from smaller second and third growth forests and plantations while engineered lumber tends to be stronger and able to span greater distances than traditional solid or built-up beams.

Glulam Beams

Glulam beams are made from smaller pieces of dimensional lumber that are laminated and glued together. The individual pieces are usually stacked and glued together horizontally in layers as shown in Figure 9-20.

Glulam beams have the advantage of being able to be manufactured in a wide number of sizes and shapes. Curved architectural shapes can be created, as well as beams designed for outdoor and weather resistant applications (Figure 9-21).

Parallel strand lumber (PSL) is a type of engineered lumber where long pencil diameter strands of lumber are chopped from the timber and bundled and compressed into shapes for beams and columns (Figure 9-22).

Laminated strand lumber, which is often abbreviated as LVL lumber, is manufactured by bonding thin veneers of wood with waterproof glue to form thick billets of lumber. The billets are then sawed into the desired size. The grain in the veneers of wood mostly runs parallel to each other, as opposed to plywood where the grain of each layer alternates direction. LVL lumber is most often manufactured in thicknesses similar to dimensional lumber and can be combined together to make thicker dimensions as done with traditional built-up beams. LVL lumber has the advantage of being stronger and able to carry bigger loads than traditional built-up beams (Figure 9-23).

Laminated Strand Lumber

Laminated strand lumber (LSL) is an engineered lumber that is manufactured by bonding together large chopped flakes of wood material. It looks similar to oriented strand lumber (OSL), but the wood fibers are larger. Typically, LSL lumber has a length-to-thickness ratio of the fibers of 150 to one, while OSL lumber has a length-to-thickness ratio of 75 to one. The fibers are combined with glue and pressed into a mat of the appropriate thickness and sawed to size. LSL lumber is not as strong as LVL lumber and LSL rim joist. While in appropriate circumstances they can be used as beams, and they are most often used in applications, such as floor headers and rim joists (Figure 9-24).

Steel Beams and Girders

Steel beams can be used as structural components in residential construction, especially when spanning longer distances and carrying larger loads. In addition, steel can be laminated with structural wood elements to form a flitch beam.

I Beams

Standard steel I beam shapes include both W beams and S beams. The horizontal elements of the beam are known as the flanges and the vertical portion the web. Beams are manufactured in standard shapes and sizes. W beams, which are also known as wide-flange beams, typically have wider flange shapes. In addition, the flanges are essentially parallel to each other, while S beams (standard beams) have narrower flanges and angled web shapes as shown in Figure 9-25. The American standard for specifying steel beams is to designate the height in inches followed by the weight in pounds per lineal foot. A W 12 × 40 beam is a wide flange beam that is nominally 12 inches tall and has a weight of 40 pounds per lineal foot. The W12 beams range in size from a W12 × 14 beam, which is 11.91 inches tall, 3.97 inches wide, and it has a weight of 14 pounds per lineal foot, to W12 × 136, which has a height of 13.91 inches, a width of 12.4 inches, and a weight of 136 pounds per lineal foot.

Steel is commonly used in residential construction in combination with wood for carrying greater loads. Figure 9-26 shows an example of an apartment building framing that uses a combination of wood and steel construction.

Flitch Beams

Another way of utilizing steel for beams in residential construction is to use flitch beams. A flitch beam is constructed of one or more layers of steel plate sandwiched between structural wood framing lumber. The assembly is commonly bolted together. The combination of steel and wood sandwiched together forms a stronger beam than wood alone and is much lighter than steel. Flitch beams are seldom used any longer as modern engineered lumber such as glulam and LVL beams are comparable in strength to flitch beams and require much less fabrication cost (Figure 9-52).

Posts are used to support beams and girders. Posts can be made of a number of different types of materials including solid wood, engineered wood, and structural steel. Posts also require some method of attachment to both the beam and the supporting base structure.

Solid Wood Posts

Solid wood posts are often used in residential construction. They come in standard sizes and lengths, such as 4 × 4, 6 × 6, and 4 × 6. Standard lengths would be from eight feet to 20 feet long (Figure 9-53).

Figure 9-29 shows a hand-hewn solid wood post supporting traditional hand-hewn solid wood beams.

Engineered Wood Posts

Wooden posts can be made of engineered wood products, such as LVL, LSL, and PSL lumber (Figure 9-30).

Steel Posts

Both wood and steel beams can be supported by steel posts, but steel beams cannot be supported by wood posts. Steel beams are required by code to be supported by steel posts. Steel posts can be fabricated from a number of standard steel shapes including wide flange shapes, square tubing, and round tubing. Figure 9-31 shows wide flange beams supported by a wide flange column.

Figure 9-32 shows multiple steel W beams supported by a single square tubular steel post.

Steel posts for wooden beams are commonly fabricated with steel base plates and steel top plates. The top plate can be flat or fabricated in a U saddle shape. Square steel posts are specified by the size of the post and the thickness of the steel. For example, a 4 × 4 × 3/16 steel post is a 4-inch square with walls that are 3/16 inches thick. Round steel posts are specified by the diameter of the post and the wall thickness such as 4 OD × 3/16. Figure 9-33 shows an example of floor beams supported by steel posts.

Post and Beam Anchors

Posts need to be anchored to both the base and the beams. Many different styles of prefabricated post and beam connectors are available. Some posts are anchored by bolts inset in the concrete. Code also requires a minimum 1-inch standoff from a concrete base. Figure 9-34 shows an example of a post base that is anchored by a bolt cast in the concrete. The base is bolted down. A 1 inch steel spacer is placed in the bottom, and the sides are folded up and nailed to the post; anchors are cast directly in the concrete, and the top of the post is also attached to the beam using a bracket as shown in Figure 9-35.

Examples of different types of anchors are pictured in Figure 9-36.

Mudsill

The mudsill is the framing element that attaches the floor or the wall to the foundation. Typically, the mudsill is firmly anchored to the foundation using bolts bedded into the concrete or other commercial dedicated mudsill anchors. Because the mudsill is in direct contact with the concrete of the foundation, a rot resistant material is used. Traditionally, that material was redwood, cedar, cypress or other naturally rot resistant wood. The material most often used today is pressure treated lumber. This is lumber that has been placed in pressurized vats along with liquid chemical preservatives. The pressure forces the chemicals into the pores of the wood, increasing its resistance to rot-causing insects and microorganisms.

The mudsill is attached by drilling holes that line up with the preinstalled concrete anchor bolts, slipping the sill over the embedded bolts, and placing washers and nuts on the bolts. In addition, mudsills, which are installed in prominent earthquake zones, are required to have large plate washers placed between the bolt and nut. The building code requires the placement of anchor bolts a maximum of six feet on-center, with the distance decreasing to four feet in structures that are over two stories in height. In addition, each mudsill piece must have a minimum of two bolts installed in it, anchoring it to the foundation. The bolts must be placed a minimum of seven bolts’ diameters (3-1/2″ for 1/2″ diameter bolts) and no farther than 12 inches from the end of each plate section. Figure 9-37 shows an example of a 2 × 6 pressure-treated mudsill bolted to a foundation using plate washers.

Estimating mudsill is calculating the length of the perimeter of the wood floor system. In addition, walls like garage walls that are attached directly to the foundation are drilled and bolted to the foundation.

Mudsill Sealer

The mudsill sealer is a gasket that is placed between the rough concrete foundation and the mudsill. The purpose of the sill sealer is to fill in the small gaps and crevices. This helps with both air and insect penetration. Most commonly, a commercial foam sill sealer material is used. The material comes in rolls of standard length, such as 50′, and it is cut at the site and installed over the foundation anchor bolts between the foundation and the mudsill. Sill sealer is also used between the foundation and bottom plate of walls that are directly bolted to the foundations, such as garage walls. Estimating sill seal is a simple matter of determining the length of the mudsill and how many full rolls of sill sealer material will need to be purchased.

Floor Joists

The main structural element of a wood framed floor system is the floor joists. Traditionally floor joists have been constructed out of dimensional lumber such as 2 × 8, 2 × 10, and 2 × 12. Solid dimensional lumber wood floor joist can be used still, however, the practice has declined dramatically in recent years due to the ready availability, higher strength, and lower cost of engineered floor systems such as wooden I joist and floor truss systems.

Solid Wood Dimensional Floor Joists

While the use of solid wood dimensional lumber floor joists has declined in recent years, it is still a viable option for framing floor systems. Solid wood floor joists have typically been limited to the wider dimensions of the material such as 2 × 8’s, 2 × 10’s, and 2 × 12’s. Standard lengths of dimensional lumber are in two-foot increments from eight feet long to 20 feet long. Often, this is not sufficient to cover a floor in a single span. Commonly, what is done in this situation is to join the two joists of a span in the center by lapping and nailing them together. The building code has specific requirements that the joint must lap at least three inches and cannot lap more than 12 inches. Figure 9-38 shows an example of a solid wood floor system that has been lapped and joined over the center load bearing span.

Engineered Wooden I Joists

Engineered wooden I Joists have several advantages over solid wood joists. They are lighter and stronger and can span greater distances than traditional joists. They are also straighter and stiffer and contribute to floors that have fewer squeaks. They can be manufactured out of smaller second growth and plantation grown forests. The one downside of engineered I joists is that they rapidly fail in the case of a fire, which can lead to premature building failure.

I joists consist of two main elements: flanges and a web. The web is sandwiched between the flanges that form an I shape. The flanges are typically made of either solid, finger jointed lumber, or LVL lumber. The web can be manufactured from plywood, LVL lumber, or oriented strand board. They are manufactured in standard sizes from 9½ inches tall to 24 inches tall, and in lengths up to 80′, although lengths of 40′ to 42′ are more common. The web thickness is commonly around 3/8 inches thick, but it can be thicker. The flanges range in size from 1⅜ inches thick to 1½ inches thick and 1¾ inches to 3½ inches wide (Figure 9-39). I joist with wide webs and thicker, wider flanges can span great distances.

The size, layout, and spacing for engineered floor joists are usually designed by the supplier using specific computer software. They are typically purchased in full span lengths and are not lapped over bearing walls. Figure 9-40 shows an example of a typical engineered floor joist layout.

Floor Trusses

A third option for floor layout is an engineered floor truss system. Floor trusses have several advantages over both solid wood joists and engineered I joists. They can span longer distances than conventional floor joists. In addition, they can be engineered with chases and open space for the installation of electrical and HVAC ductwork inside the floor system. Floor truss systems are designed and engineered by the truss manufacture. Figure 9-41 shows an example of a floor truss system installed.

Rim Joists

Rim joists are used to cap the end of floor joists. They hold the joist the required distance apart. They also serve as the starting and ending joist of a floor system and the box in the entire floor system. Traditional solid wood dimensional floor joists typically use lengths of the same material as the floor joists. Engineered wood I joists typically use engineered LSL rim board material. Figure 9-42 shows an example of LSL rim joist installed and ready for floor joists. The quantity of rim joist material is calculated by determining the length of the rim of the floor system.

Framing Floor Openings

Many floor systems have openings in them which require framing. Some openings are supported by load bearing walls, post, or beams and others are framed and supported by the floor structure. Often, the openings require strengthening the floor structure by adding additional floor framing members. Floor members that run parallel to the main floor joists are known as trimmers and floor members that run perpendicular to the main floor joist are known as headers. If the floor opening is supported only by the floor structure, the code allows for framing the opening using single trimmers and single headers if the opening is less than 48 inches. This is shown in Figure 9-43.

Floor openings supported only by the floor structure that are greater than 48 inches are required by code to be framed with double trimmers and double headers (Figure 9-44).

Floor systems supported by bearing walls can use single headers and trimmers around the opening as long as there is at least 1 ½ inches of bearing for the wall supported floor joists. Figure 9-45 shows a stairway opening that has been framed with a single LSL header around all four sides. The headers are supported underneath with load bearing walls.

Bridging and Blocking

Code requires that the ends of floor joists be supported from rotation by solid blocking or by being attached to a solid band joist. The standard LSL rim joist qualifies as the end support in typical situations. Intermediate blocking or bridging is also required in situations where the nominal depth to thickness ratio of the floor joist exceeds a six-to-one ratio. This means that any standard 2 × 12 floor joist or smaller does not require intermediate blocking. Floor joists that exceed the 2 × 12 depth-to-thickness ratio require blocking placed at eight-foot intervals. There is an exception to the normal blocking and bridging rule in areas of high earthquake probability that require solid blocking at the intermediate supports. Figure 9-46 shows an example of intermediate blocking on an engineered I joist floor using short I joist blocks. Estimating blocking is a matter of calculating the lineal footage of the blocking.

Joist Hangers

The ends of floor joists that are not supported by a bearing surface of at least 1½ inches are required to be supported by joist hangers that are appropriate for the flooring material. Figure 9-47 shows an example of engineered I joists attached to a LVL beam. Figure 9-48 shows special top mounted joist hangers that are used for engineered I joists. The web on the I joist is not thick enough to support standard nails on joist hangers and requires the top mounted variety. In addition, a double joist hanger is also shown, which is required when double joists need to be supported. The web of the engineered I joists has been strengthened by filling in the web with OSB sheet material.

Floor Sheathing

Plywood or OSB subflooring is used over the floor joists to form the subflooring. Traditionally a two-layer flooring has been used: a base layer of 5/8 inches to 3/4-inch plywood followed by a layer of particle board sheeting. Most commonly today the subfloor is constructed of a single layer of tongue and groove plywood or OSB sheeting. Figure 9-49 shows an example of a stack of OSB tongue and groove subfloor.

The subflooring is laid perpendicular to the major direction of the floor joists. The floor is usually covered from the exterior of the rim joist to the exterior of the rim joists. Standard sheets of subfloor come in 4′ × 8′. Figure 9-50 shows an example of the first couple of rows of OSB subflooring laid down. Estimating subflooring is done by calculating the area to be covered by the size of each sheet, which is commonly 32 square feet.

Frequently the subflooring is glued down with construction adhesive. The adhesive is supplied in tubes of either 10 or 28 ounces and is applied with a caulking gun. It is estimated that one tube of 28-ounce adhesive can cover 88 lineal feet of joist using a standard 1/4-inch diameter bead of construction adhesive (Figure 9-51). This means that each ounce can cover 3.14 lineal feet of joist. The spacing of the floor joists determines the amount of adhesive needed. Spacing floor joists at 16 inches O/C means that each sheet will need seven beads of adhesive multiplied by the four-foot sheet width or 28 lineal feet of adhesive. One tube of adhesive is needed for every three sheets. Spacing the sheathing at 19.2 inches reduces the amount by four feet, meaning one tube will be needed for every three and a half sheets. Increasing the spacing to 24 inches on-center means that each tube will cover over four sheets.

Estimating Floor Framing

The first step in completing a floor framing estimate will be to determine the framing members of your floor. . This will be discussed first. Second, the quantity of material for the floor framing will be calculated. Third, the labor cost for the floor framing will be determined.

Determining the Floor Framing Material

The following are the variables that you will need to know regarding your framing members and methods.

Square Foot of Floor Area

We will use the example of a floor with an area of 1,152 square feet. This will be used to calculate the area of floor sheathing.

Floor Girder

The floor girder is determined by calculating the length of any girders that are supporting the floor. Built-up girders such as one constructed of two pieces of 1¾ inches × 11⅞ inches. Microlam lumber will need to account for both pieces. For example, if the built-up girder spanned 10′, then 20′ of material would need to be purchased. In addition, it is customary to only sell material in two-foot increments, so if the total were less or more than full two-foot increments, the total would need to be rounded up to the next two-foot length.

Girder Support Post

This is the quantity of girder support posts that are needed. This is a simple count of the posts. The height of the posts would be accounted for in the length of the purchased material.

Sill Sealer

The sill sealer length is determined by calculating the length of the sill sealer underneath the mudsill plates on the foundation. In addition, sill sealer will be used underneath the garage walls built upon the foundation. Figure 9-52 shows the sill sealer installed on the foundation wall underneath the mudsill and the garage walls. The total distance is added together.

36′ + 32′ + 36′ + 32′ + 0′-5-1/2″ + 10′-9 + 3′ + 3′ + 20′-4″ = 173′-6 ½″

Mudsill

The mudsill length is determined by calculating the length of the mudsill underneath the rim joists. Figure 9-53 shows a representation of the mudsill. It extends around the four sides of the floor. The floor dimensions are 36 feet wide by 32 feet deep. The dimensions for the mudsill are

2 sides × 36 feet long = 72 feet

2 sides × 32 feet long = 64 feet

Total = 136 feet

Rim Joist

The rim joist in our example is constructed out of 1¼ inches × 11⅞ inches of LSL rim joist material. In the example shown above, the length of the rim joist is the same as is for the mudsill. This amount of 136 feet as was previously calculated for the mudsill will be used for the rim joist.

Floor Joist

The quantity of floor joist is determined by calculating the individual length of each joist and adding them together. In practice, joists of specific lengths and specific joist sizes are determined and multiplied by the number of joists that are that length. The table that follows shows an example of calculating the quantity of floor joists. The totals would be calculated as follows:

9 Floor Joist × 31′ 8-1/2″ = 285′ 4-1/2″

5 Floor Joists × 15′ 10-3/4″ = 79′ 5-3/4″

4 Floor Joist × 12′ 6-3/4″ = 50′ 3″

8 Floor Joists × 31′ 8-1/2″ = 253′ 8″

1 Floor Joist 7′ 7-1/4″ = 7′ 7-1/4″

Total = 676′ 4-1/2″

The total of 676′ 4½ inches would be rounded up to 677 feet.

Joist Headers

Joist headers represent the floor joist headers that are needed to frame any openings in the floor. Figure 9-54 shows the area around the framed stair opening highlighted in red. Most of the opening will be framed with 1¼ inches LSL rim joist material. All the floor headers in this instance sit upon load bearing basement walls or are less than the four feet required for double header and trimmers, so it will not be necessary to double up any of the trimmers or headers around the floor opening.

The total of floor opening headers would be as follows:

The total would be rounded up to 22 feet.

Bridging and Blocking

Figure 9-54 shows a single row of blocking along the center of the load bearing basement wall. In the example shown, there is a stairwell header along a part of the bearing wall that will serve as the blocking along that portion of the wall. One method of determining the lineal footage of blocking is to count the spaces in the floor joist and multiply the number by the length of each joist blocking.

The floor joists in this instance are spaced at 19.2 inches on-center. Each engineered I joist is 1¾ inches wide. Each block will need to be equal to

19.2″ -1.75″ = 17.45″

There are 16 individual sections of blocking, so the total lineal footage of blocking is equal to

17.45 in × 16 pcs. = 23.27 ft.

Completing the Floor Framing Material Quantities

The formulas for quantity are all very similar. If you are calculating lineal feet, you simply multiply the needed lineal feet that you have determined by the waste factor and then divide by the length of the framing member. For example, if you determined that there were 500 feet of rim joist on your project and you wanted a 5% waste factor, then you would multiply 500 by 1.05, which is 525 lineal feet. If your rim joists were each 20 feet long, you would then divide 525 by 20, which is 26.25. Since you are buying complete joists, you would round up and buy 27 rim joists.

Hangers

Hangers are needed when there are floor system elements that are not supported on load bearing surfaces. The joist hangers are usually just a counted item with no formula associated with them. Most of the floor joists and headers in the example are placed upon bearing surfaces and no hangers are required. The exception is the small header at the end of the stairwell. Hangers are needed to support the header on each end of the floor joist, and the single floor joist attached to the header. This will require two types of hangers: a 1¼ inches wide hanger to support the LSL rim board header and a 1¾ inches hanger to support the 1¾ inches wide I joist. Three-quarter-inch thick OSB filler strips will be needed on the web of the floor joist supporting the LSL header. This is shown in Figure 9-56.

Floor Sheathing

The floor sheathing quantity will be determined by calculating the area of the floor to be covered and dividing by the square footage of coverage per sheet, which is 32 square feet per sheet for common four-foot × eight-foot sheets.

Adhesive

The quantity of construction adhesive is determined by the square footage of the floor area and the spacing of the floor joists. As previously discussed, one ounce of construction adhesive can cover approximately 3.14 lineal feet of floor joist. The floor joist spacing will tell you how many joists you need per square foot of area.

The LF joist per SF floor area will be used in a formula to calculate the quantity of floor adhesive. The number determined will need to be increased by a small amount because double beads of floor adhesive will be needed on each floor joist at eight-foot intervals where the sheets are butted together. The value determined will be increased by 0.125.

The formula is as follows:

(LF Joist per SF Floor Area +.125) × Square Foot Floor Area ×(1 + Waste Factor) / 3.14 / Size

Nails

Nails used for framing are usually bought in bulk and the surplus carried forward to new jobs. In this case, the nail quantities will be estimated as two boxes of 16 penny and eight penny framing nails for our example project.

Door and Window Header Framing

Most residential construction requires some form of framing support over door and window openings. The support often comes in the form of headers. Many different types of headers and header material are possible based upon the specific needs of the project.

Traditional Header Styles

Traditionally, headers were most often constructed of two pieces of dimensional framing lumber nailed together. At times, a piece of 1/2-inch-thick sheet stock was placed in between the dimensional lumber pieces to serve as a spacer to make the thickness of the header match the 3½ inch thickness of 2 × 4 framed walls. This style of header is still used with 3½-inch-thick walls. There can be a variation in the width of the header. For example, headers spanning short distances can use two pieces of 2 × 4 lumber, while headers spanning greater distances can be built with up to four 2 × 12 pieces of dimensional lumber. Non-load bearing walls can use a single piece of flat 2 × 4 for the header. Figure 9-57 shows an example of three traditional header styles.

Figure 9-58 shows a view of the construction of traditional three-layer header construction using two pieces of 2 × 12-inch dimensional lumber and a single layer of 1/2-inch OSB spacer.

Single Piece Headers

Efforts to improve both energy efficiency and material usage in framing construction has resulted in changes in the style of header construction that have become common. Many headers installed now only have a single structural framing element as a header. These headers usually require an additional top sill to bring the width to match that of the existing wall. The advantage of this type of header is not only a savings of cost for framing material, but it allows for space for installing insulation to assist in the energy efficiency of the structure. Figure 9-59 shows an example of a single two-by-ten-inch header installed in a two-by-six-inch framed wall. This header style allows for the installation of four inches in insulation to improve the energy efficiency of the house.

Figure 9-60 shows a single solid lumber two-by-ten-inch header.

Box Beam Headers

Code also allows for the installation of box beam headers. A box beam header is a framed box with plywood on one or both sides. Code requires a minimum of 15/32-inch structural sheathing on one or both sides. The interior of the header must also have cripples with a spacing that equals the stud spacing of the wall. The interior of the header may also contain insulation to aid in energy efficiency (Figure 9-61).

Engineered Lumber Headers

Headers could be made from glulam, LVL, LSL, and PSL lumber. The engineered lumber such as LVL and LSL can be built up in multiple layers as is common with dimensional lumber to build stronger headers. Figure 9-62 shows an example of two windows with single header construction. The header above the window on the left is solid dimensional lumber, and the one on the right is laminated veneer lumber.

Figure 9-63 shows an example of a long double LVL micro lam header over a garage door.

Estimating the Door and Window Headers

You will need to add the cost of door and window headers to your estimate. In order to do this, you will need to know the type of headers that you will be using. Once you have determined this, it is simply a matter of determining how much of each header type you will need and the cost of the types of headers you will be using.

Specialty Framing Subsection

The special framing subsection is for estimating the cost of specific framing items not covered in other subsections. These are often count and list items, which can vary widely depending upon the specific job requirements.

Specialty Framing Materials

Several items that are placed in this section for the example project include the front porch posts, LVL beams and framing connectors. Figure 9-68 shows the front porch framing. The finished porch will have decorative stone and wood posts that cover the 4 × 4 wood posts that are the support for the roof. The posts also support a LVL beam that wraps around three sides of the porch to support the roof trusses and other roof soffit and fascia framing.

The dimensions of the front porch are determined from the plans, sections, and details as shown in Figure 9-69.

Porch Posts

The height of the posts can be determined from an elevation view at a little under eight feet. This will be rounded up to the full eight-foot increment and two eight-foot 4 × 4 posts will be used in the estimate .

LVL Porch Beams

The center to center placement of the posts is at 9′ 8″. The LVL beam at the top will need to extend at least to the outside of the post or an additional 3½ inches for a total of 9 feet, 11 inches, which will be rounded up to the next two-foot increment of 12 feet. The LVL beams on the side of the porch will need to extend to the outside edge of the post. In addition, the beams will need to extend inside of the wall framing to be supported with at least one trimmer stud. This would add an additional three inches to the length for a total of 5′ 10″, which would be rounded up to the next two-foot increment of six feet. Added together, the total length would be

6 ft + 12 ft + 6 ft = 24 ft

The 1¾ inches of LVL material is doubled up to form the 3½-inch wide beams, so the 24-foot total would be doubled resulting in a total purchase of 48 feet. This will be used in the estimate .

Porch Hardware

Each post will be anchored to the concrete porch and to the top LVL with a post cap. These will be included in the estimate .

Stair Framing

Often, the structure for stairways is constructed during the framing process. Some of the finished parts of a stairway are installed during the framing process, but it’s possible that they do not get installed. The discussion will begin with a review of standard stair construction terms and methodology.

Stair Framing Terms

Figure 9-70 shows the essential parts of stair framing including total run, total rise, unit run, unit rise, tread, riser, length of the stairwell, and headroom.

It is not uncommon for residential house plans to provide only minimal information about stair framing. The construction estimator would be required to determine the necessary elements of the stairway to be estimated. This will require an understanding of minimum stair building code requirements.

Unit Rise

The unit rise is the vertical distance that the stair will rise for each step. The building code requires that residential stairways have a maximum unit rise of seven and three quarters of an inch. In commercial construction, the maximum rise is seven inches. The actual unit rise is determined by dividing the total rise by the number of risers.

Total Rise

The rise is the total height of the stairway calculated from finished floor to finished floor. One common example would be for stairs from the first floor to the basement of a residence. An example of typical construction is shown in Figure 9-71. The foundation height is eight feet and the basement floor thickness is four inches. The wood floor system consists of a 1½-inch mudsill, 11⅞-inch rim joist, and three quarters of an inch OSB subfloor. The calculation for the finished floor to finished floor height would be

(96″ – 4″) + 1-1/2″ + 11-7/8″ + 3/4″ = 106-1/8″

Calculating Unit Rise

To calculate the unit rise, first divide the total rise by the maximum desired unit rise.

106-1/8″ ÷ 7-3/4″ = 13.69

Since there cannot be a fraction of a riser, the 13.69 is rounded up to the next whole number or 14 inches.

106-1/8″ ÷ 14 = 7.58″

Unit Run

The unit run is the horizontal length of each step. The building code requires that residential stairways have a minimum run length of 10 inches. In commercial construction, the minimum run length is 11 inches.

Total Run

The total run is determined by multiplying the unit run by the number of treads. The example shown in Figure 9-69 shows 13 ten-inch-wide treads. This would result in a total unit run of

13 treads × 10 inches = 130 inches

or

130 inches ÷ 12 inches/ foot = 10′ -10″

The combination of the unit rise and unit run work together to make a stairway more or less comfortable to use. Generally, as a rule, as the unit rise increases, the unit run decreases within the limits of the maximum unit rise and minimum unit run required by the building code.

A common formula that is used in determining the ratio of the unit rise to the unit run is to multiply the unit rise by two and add it to the one-unit run. The three together should equal 25 inches with a variance of plus or minus one inch. For example, if a stairway had a unit rise of 7½ inches and a unit run of 10 inches, the formula would be as follows:

This would be well within the required 25 inches plus or minus one inch.

In the example from Figure 9-69, the unit rise was calculated at 7.58 inches. To determine an idyllic unit run, subtract the total of two multiplied by the unit rise by 25 inches as follows:

25 inches – (2 × 7.58″) = 9.84″

However, this would be below the minimum run requirements of 10 inches. A run of 10 inches would work, and the total together would equal 26.16 inches, which would be in the plus or minus one-inch range.

Stairwell Length

It is possible to have a stairwell length that is shorter than the total run. If this is the case, another variable also must be taken into account, which is the minimum headroom height.

Headroom

The code requires that the minimum headroom distance is 6′8″ or 80 inches. The length is a vertical distance measured along the slope of the front of the treads to the floor or ceiling above.

Stair Framing Elements

Stair framing usually requires several elements that could be broken into the stair’s components and the landing.

Stair Component

The stair component comprises the stair stringers, sleepers, stringer spacers, stringer hanger, and temporary treads (Figure 9-72).

Stair Stringers

Stair stringers are the support elements of the stairway. Stringers can be called stair jacks or stair carriage. Traditionally, stringers were constructed of 2 × 12-inch framing lumber. This can be the case, but they are more often made from engineered lumber such as laminated strand lumber (LSL) or laminated veneer lumber (LVL). These can be purchased in widths from 9½ inches to 14 inches and have a thickness of 1¾ inches. A stair run will have a minimum of two stringers, but it could have three or more depending upon the width of the stairway and the needed strength.

The length of the stringer is determined by calculating the slope length of a triangle formed from the total run and total rise of the stair (Figure 9-73).

The previously determined total rise of 106 1/8 inches and total run of 130 inches will be used. In this case, the stringer ends one-unit rise or 7.58 inches below the finished floor, so that will be subtracted from the total rise for a total stringer rise of 98.55 inches. The slope length will be calculated by using Pythagorean’s theorem. The decimal lengths inputted into the formula are as follows:

130 in² + 98.55 in² = C²

or

or

or

163.13 inches

This would be rounded up to 164 inches or 13½′. Framing lumber is usually sold in increments of two feet, and the total will be rounded up to a purchase length of 14′. This would be multiplied by the number of stringers.

Sleeper

The sleeper is a length of framing lumber that is inserted at the bottom of the stairway. Its purpose is to provide a means of solid attachment of the stringers to the floor. If the bottom of the stair is resting upon concrete, the sleeper will need to be of pressure treated lumber or other rot resistant material. The sleeper will also need to be firmly anchored to the floor and may require anchor bolts into a concrete floor. The length material needed is the same as the width of the stairway (Figure 9-74).

Stringer Spacer

The stringer spacer is usually a length of 2 × 4 material attached to the bottom of the stringer. The purpose is to hold the stringer a distance away from the stud wall framing. This is so that drywall can be slipped down past the top of the stringer and attached to the wall studs, so it will not have to be cut around the stair shaped stringer. The length of the stringer’s spacer board is usually the same length as the stringer (Figure 9-74).

Stringer Hanger

The purpose of the stringer hanger is to support the top of the stairway as it rests against the floor system. Several methods could be used including a hanger board and hanger hardware. A hanger board is a piece of OSB that is attached to the top of the stringer and also attached to the floor system. The hanger board becomes, in essence, the riser for that stair, so to keep the stair run consistent the thickness of the hanger board (usually 3/4″) is cut off of the stair tread length. This is shown in Figure 9-75.

Another method of attaching the top of the stringer is to use framing anchors to attach it to the floor framing as is shown in Figure 9-76. In this case, stringer hangers are count and list items.

Temporary Treads

If the stairway is to be used during the construction project, temporary treads will need to be installed. Often, if the finished treads are such that they will not be exposed and have a covering, such as carpet, the finished treads will be installed during the framing phase, but it will be priced later during the interior phase of construction. If temporary treads are installed, they will need to be priced at this time. Current safety regulations prohibit the former practice of installing a single 2 × 4 or 2 × 6 to be used as a temporary tread. The temporary treads need to be of the same width as the finished treads. This means that they will likely need to be constructed of 2 × 10 or 2 × 12 material. This material can be costly and should be added to the estimate. Calculating the quantity is done by determining the width of each tread and multiplying that by the number of treads to establish a lineal footage of material needed (Figure 9-77).

Stair Landings

Stair landings are used when it is desirable to provide for a change of direction in the stairs. They do take up valuable floor space, but they also allow for stairs to fit into some spaces they otherwise would not. In addition, building codes require that landings be installed at every 12 feet of vertical rise in a stairway. Landings are usually framed like small floors with joists and subfloor, and they are often supported by surrounding walls. Figure 9-78 shows a stair landing framed with 2 × 10 floor joists.

The landing is sized at 37 inches by 48 inches. There are three joists 34 inches long and two rim joists 48 inches long. In addition, four corner framing anchors and four 2 × 10 joist hangers installed. The floor is covered with 3/4-inch OSB sheathing.

Closed Sides

An additional consideration when estimating stair framing is the number of closed sides. Stairways can be constructed so that all of the sides of the stairway are enclosed by walls as shown in Figure 9-79.

Stairways can be constructed so that no sides are enclosed by walls, or so that any combination of closed and enclosed such as the example in Figure 9-80 which shows the stairway with three enclosed walls and one open side.

Stair Material

Figure 9-81 shows the view of the floor plan that details the stairway. In this instance, the stairway is L-shaped with a landing halfway along the stairway. Residential house plans may provide more detail than this about the stair construction, or they may not. Using the information from this view and finished floor to finished floor height, the stair construction can be determined.

The view shows six treads from floor level down to the landing level. Four more treads are shown from the landing down to the base of the stairway, however, there are two additional treads covered by the floor and wall above it.

Stringer Hanger

The stringer hanger utilized in this instance will be three quarters of an inch thick OSB material. Each stringer hanger will need to be as long as the width of the stairway, which, in this case, is three feet. The width of the stringer spacer will need to be at least as wide as the height of two risers. The riser height was previously calculated at 7.58 inches and doubled would be 15.6 inches. This will be rounded up to an even increment of 16 inches. One stringer hanger will be needed for each stair, so two will be needed for the project. Even though it is not usual to purchase a portion of a sheet, smaller scraps left over from making the OSB risers could be utilized.

Temporary Treads

Temporary treads will not be used on this project because the finished OSB treads will be installed at the time the stairway is framed. The OSB tread quantity will be calculated later during the interior finish phase.

Stair Landing Materials

The stair landing material will be manually calculated using methods that have already been discussed.

Landing Joists

Figure 9-78 shows the stair landing which is 48 inches long and 36 inches wide. It is constructed of 2 × 10 inch material spaced 16 inches on-center. In addition, there are two rim pieces 48 inches long. The total would be as follows:

4 PCS × 4 ft. + 2 PCS 4 ft. =

or

16 ft. + 8 ft. = 24 ft.

Landing Subfloor

The landing subfloor will be three quarters of an inch OSB material. The finished size including overhangs for the tread nosing at the landing is approximately 38 inches wide by 48 inches long. This equals approximately one half of a sheet.

Framing Anchors

Figure 9-77 shows the stair landing and a couple of the framing anchors. The end of each 2 × 10 floor joist is supported by a 2 × 10 “U” type joist hanger for a total of four for the job. Each corner of the landing is also reinforced with a corner framing anchor. There will be four on the job.

Roof Framing

There are many styles of residential roofs; however, most are primarily built using one of two systems: the traditional roof framing system, which is also known as rafter framing or stick roof framing, and the other main roof framing system, which is also known as truss roof framing. Traditionally, almost all framing was done using rafter framing, however, the majority of contemporary house framing utilizes truss roof framing. Some roofs are also framed using a hybrid of both systems such as truss framing for the majority of roof elements, but many of the details and small particulars are still stick framed. An effective construction estimator will need an understanding of both systems. Regardless of the system used, a basic understanding of basic roofing terms and principles is important.

Common Roof Framing Terms and Principles

Important roof framing terms to understand include total span, total run, total rise, unit rise, unit run, slope, line length, and pitch. Figure 9-82 shows an example of the basic roof framing terms.

Total Span

The total span is the distance of the roof from the outside of the bearing wall to the outside of the other bearing wall. Most often, this is the width of the building, but the span could also be from an outside bearing wall to an interior bearing surface.

Total Run

The total run is usually one half of the total span, however, there are some roof styles in which the run is longer on one side of the roof than the other.

Total Rise

Total rise is the distance of vertical rise of the roof. The amount of rise is determined by the distance of the run and the steepness of the roof. Steeper roofs will have a greater vertical rise than ones that are shallower.

Slope Length

The slope length, also known as the line length, is the angled distance of the roof edge. It is determined by finding the length of the hypotenuse of the triangle that is formed by the total rise and the total run.

Unit Run

Unit run is a fixed unit of measurement that is always 12 inches in the English measurement system. Any measurement in the horizontal direction is always expressed as the run.

Unit Rise

Unit rise is the vertical distance of rise of the roof for every unit run or 12 inches of the total run. Typically, it is expressed in inches.

Slope

Slope is the ratio of unit rise to the unit run. It would be expressed in terms such as 6:12 slope or a 6/12 slope, which means that the vertical rise of the roof is 6 inches for every 12 inches of horizontal run. The higher the slope the steeper the roof is. A roof slope of 12:12 would represent a roof with a 45-degree angle of slope. It is possible with very steep roofs to have a slope greater than 12 inches, such as a 16:12 slope.

Pitch

Pitch is the ratio of the unit rise of the roof over the unit span. According to a US government document written in 1993, pitch constitutes the following:

“Pitch is the ratio of unit of rise to the unit of span. It describes the slope of a roof. Pitch is expressed as a fraction, such as 1/4 or 1/2 pitch. The term pitch is gradually being replaced by the term cut. Cut is the angle that the roof surface makes with a horizontal plane. This angle is usually expressed as a fraction in which the numerator equals the unit of rise, and the denominator equals the unit of run (12 inches), such as 6/12 or 8/12. This can be expressed in inches per foot.”

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The term cut is also usually no longer used and has been replaced by the term slope. In contemporary usage, the term pitch is still common, however, the terms slope and pitch are used interchangeably to mean the ratio of the rise of the roof over the run of the roof.

Calculating the Rafter Roof Slope Length

With the total run and the roof slope known, both the total rise and the roof sloped length can be calculated (Figure 9-83).

Calculating the Total Rise

The total run and the roof slope can be used to calculate the total rise of the roof. For example, if the total run of a roof were 12 feet and the roof slope was given as 6:12, then the following formula could be used to calculated the total rise:

Total Rise: Total Run × Roof Slope

Calculating the Roof Slope Length

With the total run and rise known, the roof slope length can be calculated using the Pythagorean theorem of A2 + B2 = C2. The roof slope length would be as follows:

A² + B² = C²

or

12 ft² + 6 ft² = C²

or

144 ft² + 36 ft² = 180 ft²

or

or

13.42 ft.

Total Run and Rise Including Overhangs

The total run, rise, and slope length calculated so far are for a simple triangle. Most roof framing also includes a roof overhang. The roof overhang should be included in the roof calculations. Figure 8-84 shows a roof with a more realistic layout including the roof overhang.

Figure 9-84 also shows that the rise is measured to the center of the rafter. When calculating the total run, total rise, and sloped length, the dimensions are calculated using a triangle that is formed from the center of rafter as is shown in Figure 9-85. This is also known as the line length.

The dimensions shown in Figure 9-84 are used to calculate the actual slope roof length as follows:

Total Run = 13′0″

Total Rise = 6′6″

13 ft. 0 in² + 6 ft. 6 in² = Slope Length²

14.53′

Rafter Length Charts

Traditionally, carpenters used a rafter length chart to calculate the length of roofing members. For convenience, rafter charts are printed on framing squares that can be used to lay out roofing members. The scale for laying out rafter lengths includes a multiplication factor aligned with each slope. For example, the number aligned with the 6 on the blade of the square is 13.42 (Figure 9-86).

This represents the length of slope in inches for every one foot of horizontal run. In use, the total run in feet is multiplied by the slope factor to obtain the total sloped length in inches. The total inches are divided by 12 to obtain the slope length in feet. The previous example had a roof with a 13′ total run. Multiplying that length by the slope factor of 13.42 will result in the following:

Common length factors for the different roof slopes are shown in Table 8-1.

Table 9-1 Rafter length multiplication factor

Common Rafter Length Factors
Roof Slope	Length Factor
2:12	12.16
3:12	12.37
4:12	12.65
5:12	13.00
6:12	13.42
7:12	13.89
8:12	14.42

Rafter Framing Terms

Framed rafter roofs are formed of several components including common rafters, ridge boards, hip rafters, valley rafters, hip and valley jack rafters, and cripple jack rafters. Figure 9-87 shows an example of the various roof framing components.

Common Rafters

Common rafters span from the ridge board to the wall. They are the type most often used in rafter framing and become the basis point for all other roof framing elements. The top of the common rafter is cut plumb and ties into the ridge board. The bottom of the rafter has a bird’s mouth cut that rests upon the top of the exterior wall, and the rafter tails extend out past the walls and form the roof overhang.

Ridge Boards

Ridge board forms the peak of the roof and ties the top of the rafters together. Because the top of the rafter is a vertical plumb cut, ridge board needs to be wider than the rafter material. The width of the ridge board is dependent upon the slope of the roof. The steeper the roof, the wider the ridge board needs to be (Figure 9-88).

Hip Rafter and Valley

The hip rafter forms the intersection of two roof sections. They are formed at 45-degree angles to the wall plates and cross the corner of two walls. They form a ridge in the roof. The jack rafters that tie into the hip rafter are also cut with a plumb cut. The hip rafter is wider than the rafters that tie into it.

The valley rafters also form two intersections of the roof planes; however, they meet in a valley of the roof instead of a ridge. Like the ridge board and hip rafter, valley rafters are wider than the intersecting rafters.

The length and layout of hip and valley rafters are identical and determined by the following formula:

Run Length² + Common Rafter Length² = Hip Rafter Length²

Using the roof example in Figure 9-84 with a total run length of 13′ and a common rafter length of 14.53′, the length of a hip or valley rafter would be calculated as follows:

13 ft² + 14.53 ft² = Hip Rafter Length²

or

169 ft² + 211.12 ft² = 380.12 ft²

or

or

19.50 ft.2

Slope factor charts can be used to calculate the length of hip and valley rafters. Figure 9-90 shows a graphic of a framing square with the slope factor for hip and valley rafters highlighted.

Using the length factor for the previous roof with a 13-foot total run would result in the following calculations:

Common lengths for hip and valley rafters are shown in Table 2.

Table 9-2 Hip and valley rafter multiplication factor.

Hip and Valley Length Factors
Roof Slope	Length Factor
2:12	17.09
3:12	17.23
4:12	17.44
5:12	17.69
6:12	18.00
7:12	18.36
8:12	18.86

Jack Rafters

Jack rafters are cut shorter than common rafters and at least one end lands upon a hip or valley rafter. Three types of jack rafters are hip jack rafters, valley jack rafters, and cripple jack rafters. Hip jack rafters have a birds’ mouth cut at the bottom similar to a common rafter, but the top of the hip jack rafter has a compound angled cut to tie into a hip rafter. Valley jack rafters have an angled cut at the top similar to a common rafter, but the bottom of the valley jack rafter has a compound angle cut to tie into a valley rafter. Cripple jack rafters have compound angle cuts at both the top and the bottom of the rafter and tie into a hip rafter at the top and a valley rafter at the bottom.

Each jack rafter on the side of a roof is cut at a different length than the adjacent rafter, and the jack rafters get longer or shorter as they move up or down the slope of the roof. The change in length between each rafter is a consistent amount based upon the slope of the roof and the spacing of the rafters. Framing squares also have tables on them that identify the amount that each jack rafter changes based upon the roof slope and spacing factors. Figure 9-91 shows a graphic of a framing square with the rafter differences in length highlighted.

The table shows that for a rafter with a 6:12 slope, each jack rafter would vary in length by 17.88 inches if the rafters were spaced at 16-inch centers and 26.81 inches if the rafters were spaced at 24-inch centers. Figure 9-92 shows a rafter framed roof with the three types of jack rafters highlighted.

Other Exterior Rafter Framing Components

Other components used in rafter framing include sub-fascia, barge rafters, lookouts, and gable end framing. Each of these are important components used in the completion of the exterior roof elements.

Sub-Fascia

Sub-fascia is a horizontal framing member that attaches to the rafter tails that are used to attach the finished fascia material. Sub-fascia is sometimes called false fascia or rough fascia. The sub-fascia is often constructed of 2 × 4 material, but 2 × 6 or wider material is also commonly used depending upon the style of the roof. Calculating the quantity of sub-fascia material is a matter of calculating the horizontal length of the roof edge. On hip style roofs, this would include all of the roof edges, however, the angled edged members of gable roof ends are usually calculated as barge rafters.

Barge Rafters

Barge rafters are the angled edge members of a gable end roof that forms the overhang of the roof on the ends. Barge rafters are also called fly rafters or rake rafters. They are similar to common rafters with the exception that they do not have a birds’ mouth cut at the bottom to sit on the bearing wall. Usually they are made using 2 × 4 material, but 2 × 6 and wider material is sometimes used. Barge rafters are typically the same length as the common rafters. Calculating barge rafters is usually a matter of calculating the number of barge rafters by their length. They are supported in the roof structure by the gable end lookouts and the gable end framing.

Gable End Lookouts

Gable end lookouts are framing members that extend from the common rafters to the barge rafters and support the barge rafters, which form the overhang of the roof on the gable ends. The lookouts can be either long or short depending upon the style. Shorter gable end overhangs of 12 inches or less often use lookouts that attach to the end rafter and the lookout as shown in Figure 9-93.

Some lookouts extend back into the roof framing and attach to a common rafter. They rest upon and cantilever past the gable end framing to support the barge rafters. This is typically the case for roofs with longer gable end overhangs as shown in Figure 9-94.

Calculating gable end lookouts is a matter of determining the length of the lookouts and multiplying by the number of lookouts. The length of the lookouts can be calculated by first determining if the lookouts are long or short. If the lookouts are short, their length is equal to the overhang distance. If they are long, the lengths are determined by adding the overhang distance to the rafter spacing. For example, if the rafters were spaced 16 inches on-center and the overhang distance were 12 inches, the total length of each lookout would be

16 in + 12 in = 28 in

The number of lookouts is determined by the sloped roof length (Figure 9-85) and the lookout spacing. For example, if the sloped roof length were determined to be 14.53 feet (Figure 9-85) and the spacing were 24 inches (2′) on-center, the number of gable end lookouts would be

14.53 ft ÷ 2 ft = 7.265

This would be rounded up to eight gable end lookouts on each roof slope. The total lookout quantity would be

8 × 28 in = 224 in

or

Gable End Framing

Gable end framing is the studs that are installed to fill in the angled portion of the wall created by the gable roof. Several methods can be used to fill in the gable end framing. The example Figure 9-94 shows a small rake wall framed in the gable end. This would be common in installation where the gable end lookouts cantilever over the rake wall, and it is used to support the cantilevered lookouts. Calculating this type of framing would include determining the length of the bottom plate, two angled top plates, and the individual studs cut at an angle at the top. Each stud would vary in length a consistent distance based upon the roof slope and the stud spacing. For example, the gable end framing shown in Figure 9-95 has a total run of 12′ and a total rise of 6′, and a slope angle length of 13′5″. The king stud is 6′ long and each adjacent stud is eight inches shorter than the preceding stud.

The gable end framing would include the following:

Bottom Plate: 1 pcs. 2×4 × 24′ 0″

Angled Top Plate: 2 pcs. 2×4 × 13′ 5″

King Stud: 1 pcs. 6′ 0″

Stud 1: 2 pcs. 5′ 4″

Stud 2: 2 pcs. × 5′ 0″

Stud 3: 2 pcs. × 4′ 8″

Stud 3: 2 pcs × 4′ 0″

Stud 4: 2 pcs. × 3′ 4″

Stud 5: 2 pcs. × 2′ 8″

Stud 6: 2 pcs. × 2′ 0″

Stud 7: 2 pcs. × 1′ 4″

Stud 8: 2 pcs. × 0′ 8″

Total Length = 104′ – 10″

A simpler method of calculating this gable end wall framing would be to visualize the gable end as a rectangle with a width equal to the total run and the height equal to the total rise with each stud equal in length to the king stud. The king stud would be counted once, and the angled cut studs counted as one king stud (Figure 9-96). The calculations for this would be

Bottom Plate: 2 pcs. 2×4 × 12′ 0″

Angled Top Plate: 2 pcs. 2×4 × 13′ 5″

King Stud: 9 pcs. 6′ 0″

Total Length = 104′ – 10″

Another method would be similar to the example shown in Figure 9-97. This example uses short lookouts attached to common rafters at the gable end. Vertical 2 × 4’s are notched into the gable end rafters and attached to the top plate of the wall. The calculation for this wall type would be similar to the previously calculated gable end framing with the exception that the top and bottom plate are eliminated.

Interior Rafter Framing Components

Interior rafter framing components include ceiling joists, collar ties, rafter bracing, and ridge beams. Rafter framed roofs require one of these elements to make the roof structurally sound. In addition, they serve other functions such as providing support for the ceiling material.

Roof framing has to support two types of loads: live loads and dead loads. Live loads are the result of non-stationary forces, such as is caused by wind and snow. Building code requires roofs to be built to withstand the typical maximum live loads that a roof in a geographic area is subjected to. Dead loads are the result of stationary forces such as the weight of the roof framing and roofing material. Without the additional framing elements such as ceiling joists, rafter bracing, collar ties, or ridge beams, the downward live, and dead load forces can cause the building walls to bulge outward as is shown in Figure 9-98.

Ceiling Joists

The most common method of tying the roof framing together is with the use of ceiling joist. In addition to providing a structure for attaching the ceiling finish such as the ceiling drywall, the ceiling joist ties the roof structure together. The ceiling in narrower rooms can be made from a single piece of material, however, it is also common for ceiling joist to be attached together over a load bearing interior wall (Figure 9-99).

In situations where two ceiling joists meet, the building code requires that either the joists lap each other or a fastening plate tie each joist together. Where the ceiling joists lap, the code mandates a minimum lap distance of three inches and a maximum lapping distance of 12 inches.

Estimating ceiling joist is a matter of determining the length of the joists and the number of joists needed. The length of joist material is equal to the span of the roof plus any additional length needed to meet the code mandated lapping requirements. The number of ceiling joists is determined by the rafter spacing, usually 16 or 24 inches on-center as each rafter should be tied together with a ceiling joist.

Rafter Bracing

Rafter bracing can be used to support and brace the roof to diminish the size of rafter material required by the building code. Factors that contribute to the material size include the live and dead load requirements, the type of lumber used, and the span of the roof.

Live load requirements are usually based upon the local weather conditions. Areas that receive a heavy snow load in the winter have a larger requirement for live load than those that receive little or no snow. The specific requirements for a geographic area would be specified by the local building department.

Dead load requirements are usually determined by the weight of the framing and roofing material. For example, a traditional slate or concrete tile roof weighs considerably more than one roofed with asphalt shingles and would have a higher dead load requirement.

Figure 9-100 shows a view of two rafter span tables based upon a 24 on-center spacing with different live load requirements. The first table shows a span table based upon a live load condition of 20 pounds per square foot, and the second shows the span table based upon a live load (ground snow load) condition of 50 pounds per square foot. In addition, each table has two options for dead load, one for 10 pounds per square foot, and one for 20 pounds per square foot.

Number two grade Douglas fir-larch framing material is highlighted, with the spans for 2 × 6 material emphasized in both tables. The first table shows a maximum spacing for the material at 10 pounds per square foot at 11′9″. The second table shows a maximum spacing for the material at 20 pounds per square foot at 7′4″, a difference of span of about 4½ feet for the same material.

The 2 × 6 material spaced at 24 inches on-center would not work in a situation with a roof span of 24′. The 12′ run of the roof would be longer than the maximum span of 11′9″ allowed for the minimum live and dead load requirements shown. The rafter spacing could be decreased from 24 inches on-center to 16 or 12 inches on-center to increase the span, or a wider rafter material like a 2 × 8 could be used. Another option would be to provide bracing for the rafter. The bracing could extend from the center of the rafters down to a load bearing wall in the center (Figure 9-101).

The braces cut the distance of the run to 6′ (half its original distance), which would meet the span requirement of the 50 pound per square foot live load and 20 pounds per square foot dead load.

The length of the braces would be calculated by using the roof slope of 6/12 and the 6′ run length of the braces. The rafter length multiplication factor from Table 9-1 shows a multiplication factor of 13.42 inches per lineal foot of horizontal run.

or

Two braces would be needed for each rafter pair.

Collar Ties

In circumstances where it is desirable to have a ceiling that is higher than the exterior walls, or situations where a vaulted ceiling is preferred, collar ties can be substituted for ceiling joist. A collar tie is a form of ceiling joist that ties the rafters together at a plane that is higher than the bottom of the attic space. The building code requires modifications to the allowable span for rafters when collar ties are used instead of ceiling joists. The modifications are based upon a ratio of the distance that the collar ties are above the plane at the bottom of the attic and the total rise of the roof. Figure 9-102 shows an example of an installation where the collar tied is raised 16 inches above the top plate of the supporting walls.

The total rise of the roof is approximately 72 inches high. The ratio is determined by dividing the distance above the top plate by the total rise.

Table 9-3 shows the adjustment requirements for rafter size when collar ties are used.

Table 9-3 Rafter span adjustment when using collar ties.

https://books.byui.edu/-WLYL

Collar Tie Adjustment Table
Collar Tie Height to Total Rise Ratio	Rafter Span Adjustment Factor
1/3	67%
1/4	76%
1/5	83%
1/6	90%
1/7.5 or less	100%

The ratio of 0.25 is equal to 1/4 (.25) and the adjustment factor of 76% will be used.

The maximum span allowed for the rafters will only be 76% of the maximum allowed by the code. Figure 9-103 shows an example from Table R802.5.1 (5) of the 2015 International Residential Building Code (IRC).

Based upon a roof live load of 20 pounds per square foot and a dead load of 10 pounds per square foot, the maximum span allowed for #1 Douglas Fir/Larch lumber is 12′6″ for a 2 × 6 rafter. Using this table shows that a 2 × 6 rafter would be sufficient for a building with a 24 foot span (12 foot run) if standard ceiling joist were used. However, using collar ties spaced up 18 inches above the top plate would require the allowable span to be reduced to 76 percent of the 13′6″ maximum span. In this case, the span would be reduced to

12 ft 6 in x 0.76 = 9 ft 6 in

This would be insufficient for the project. The next largest size of 2 × 8 lumber has a maximum span of 15′10″. Using the same formula, the maximum span in this situation would be

The 2 × 8 rafter material would meet the code requirement (Figure 9-104).

The size of the collar tie will be determined by the building code. Figure 9-105 shows a portion of the 2015 IRC Table R802.4(1) for sizing ceiling joists with the #2 2 × 8 Douglas fir/larch lumber highlighted.

Based upon the live and dead load requirements for this situation, 2 × 6 Douglas fir-larch lumber can span a maximum distance of 18′9″.

The length of the collar tie is determined by the roof slope and the collar tie offset distance. The roof is a 6/12 slope, and the distance above the top plate is equal to 18 inches.

First the roof slope and the distance above the top plate is used to determine the length that is subtracted from each side of the collar tie. The slope of 6/12 means that for every six inches of vertical rise of the roof, the horizontal run of the roof is 12 inches. The 18-inch distance of the collar tie above the top plate is divided by the six-inch vertical rise of the roof.

18 in Vertical Rise ÷ 6 in Slope Rise = 3

This number is multiplied by the 12-inch horizontal run.

3 x 12 in Horizontal Run = 36 in

This is the amount that is subtracted from each side of the roof span to calculate the length of the collar tie.

or

24 ft Span - (2 x 3 ft) = 18 ft

Estimating the number of collar ties is a matter of counting the number of rafter pairs. The number of collar ties would be equal to the number of rafter pairs as each rafter pair would be joined with a collar tie.

Collar ties are limited by the building code to a vertical rise of no more than 1/3 of the total rise of the roof. When a higher ceiling is desired on a rafter framed roof, a ridge beam will be needed.

Ridge Beams

Ridge beams are structural beams that are used in place of a ridge board to support the roof structure. They are structural beams that typically support half of the load of the roof. Ridge beams, like floor girders, can be constructed of a number of materials, including solid lumber, built-up framing lumber, or engineered materials such as glulam lumber, LVL lumber, or parallel strand lumber. The size of the beam is determined by the roof load, both live load and dead load, the span of the roof, the length of the beam, and the carrying capacity of the beam material. Ridge beams can be installed below the rafters to carry the load (Figure 9-106).

Glulam beams may be installed flush with the rafter and in this case hangers will be required to attach the rafters to the beam (Figure 9-107).

Span charts (Figure 9-108) can be used to determine the size of a required beam based upon the loads, beam length, and building width. Using the example of a building that is 24 feet wide and has a live load requirement of 30 pounds per square foot and a dead load requirement of 10 pounds per square foot, a single glulam beam constructed of number two Southern Pine lumber would need to be a minimum of 3½ inches wide and 11¼ inches tall to span a clear opening distance of 16′.

Estimating ridge beams is usually a count and list process where the beam quantity, size, and cost are calculated individually.

Truss Roof Framing

Since the development of the metal-plate connector truss system in the 1950’s, truss roof framing continues to increase in popularity, and it is estimated that currently 80 percent of new residential construction utilizes pre-manufactured roof truss systems. Truss roof framing has several distinct advantages of conventional stick framed roofs.

Truss roof components are assembled in manufacturing facilities using automated equipment. Their assembly requires less time and skill than cutting and assembling stick framed components on the job site. Manufactured trusses can be made using smaller and cheaper pieces of lumber, yet they are very strong and able to span larger distances than conventional framed roofs. This allows for more open design and eliminates interior load bearing walls. Less time is usually needed on the job site for the roof framing, which helps the contractor get the roof completed and the building weather in faster.

Disadvantages of truss roof framing can be the size of the truss members, which may require the assistance of large equipment and cranes on the job site. In addition, there may be longer lead times required for ordering trusses and having them delivered to the job.

The development of computer truss design software has also increased significantly the type and styles of trusses that are available and allows for almost unlimited possibilities for truss roof design.

Truss Styles

Dozens of basic truss styles and designs are available to meet specific project needs. General category types would include standard gable roof style trusses, modified interior ceiling trusses, specialty roof style trusses, and service trusses.

Standard Gable Style Roof Trusses

Standard gable style roof trusses include Fink, Howe, fan, king post, and queen post trusses as well as modified versions of each of these. Figures 9-109 and 9-110 show examples of standard and modified standard truss configurations.

Standard style trusses are also available in modified styles that provide additional structural support (Figure 9-110).

Modified Interior Ceiling Type Truss Configurations

Trusses can be designed for interior ceiling configurations such as cathedral or sloped ceiling. These include scissor, cambered, cathedral, and studio type ceilings. Figure 9-111 shows some examples of these truss configurations.

Specialty Truss Configurations

Specialty truss configurations are available in different shapes and styles. Some common specialty types include girder trusses, gable end trusses, hip trusses, mono pitch trusses, and jack trusses.

Girder trusses are used to carry the load of other trusses. Examples of girder truss usage includes where trusses meet to form intersecting valleys. They have larger bottom plates and other heavier components to carry the load of the supporting trusses. Often multiple girder trusses are placed together to increase the carrying capacity.

Gable end trusses are used on the gable ends for attaching wall sheathing and exterior finishes. Gable end trusses, which have only vertical web members, are not considered load bearing trusses; the walls supporting the trusses require load bearing headers above all openings. Special gable end trusses can be manufactured with angled web members to make them load bearing. In addition, gable end trusses can be manufactured with top chord lowered down a distance so that gable end lookouts can cantilever over the top of the gable end truss to support the barge rafter.

Hip trusses are used in conjunction with other specialty trusses such as mono pitch trusses to construct hip style truss roofs. Jack trusses are used to complete a roof that forms intersecting gable roofs. Each truss in a package of jack trusses is consistently smaller in size to form the valley of the roof.

Truss Plans and Drawings

Truss designers use sophisticated computer software to design truss roof systems. The advancement in the ability of computer software and systems has contributed to the increasing popularity of truss roof systems and the ability to design and deliver more complex truss roof systems. Using the software, the designer is able to design the roof and test that it will be able to withstand the needed loads. The truss designer will prepare a number of drawings and details outlining the specific truss design and placement for each project. Figure 9-113 shows a truss plan with six truss configurations. It also shows the location and placement of each truss.

Figure 9-114 shows the cover sheet of a truss plan. Information about the project is included on the sheet. Each truss for the project is identified both with a name and small graphic. Specific details about each truss size is also included.

Each truss configuration will also have a detail sheet that shows the specific construction details for each truss, including specific size and engineering information like the load carrying ability of the truss. An example of a Fink truss configuration is shown in Figure 9-115.

Roof Truss Overhang Framing Members

In addition to the individual truss members, truss roof framing typically requires additional onsite overhang framing members including sub-fascia, barge rafters, and gable end lookouts.

Sub-Fascia

The horizontal sub-fascia is installed at the base edge of the roof, similar to the installation with conventional framed roofing. When an overhang is desired along the horizontal roof edge, the truss members are usually fabricated so that the top chord of the truss extends past the building edge with a tail to form the horizontal roof edge. A sub-fascia piece is attached to truss tail. The sub-fascia members are commonly made from 2 × 4 material, but 2 × 6 and wider material can also be used.

Barge Rafters

If a roof overhang is wanted on the gable end of the building, barge rafters will need to be installed. The sizing and construction of barge rafters in truss roof construction is the same as with conventional stick framed roof construction. The layout of the rafter and the angle of the cuts are determined using mathematics, a framing square, or a rafter length multiplication factor based upon the slope and total run of the roof, as has been previously discussed. The barge rafters are typically supported by gable end lookouts, the same as is done with conventional stick roof framing.

Gable End Lookouts.

The gable end lookouts are horizontal roof members that extend from the trusses to the support for the barge rafters. Lookouts may be long or short depending upon the overhang of the gable end. Short gable end lookouts are attached directly to the gable end rafter in a fashion similar to conventional roof framing. Gable ends with longer overhang often use longer lookouts that are attached to the first truss inside of the gable end truss. The gable end truss is fabricated, with the top chord lowered down the width of the lookout material, and the lookouts rest upon and cantilever past the edge of the gable roof. The barge rafters are attached to the lookouts. Estimating gable end lookout is a matter of determining the length of the lookouts, either long or short, and multiplying by the number of lookouts.

Truss Roof Bracing

Truss roof framing requires bracing to strengthen and support the roof. A minimum amount of bracing typically requires three types of bracing, which includes top chord bracing, bottom chord bracing, and diagonal bracing (gable end bracing) (Figure 9-118).

Top Chord Bracing

The solid roof sheathing made of either plywood or OSB often can satisfy the top chord sheathing requirement. When a roof does not have sheathing such as could be the case when sheet metal roofing is installed, horizontal bracing will need to be installed along the top chord of the trusses.

Bottom Chord Bracing

Bottom chord bracing is often provided by attaching a horizontal ribbon of framing material attached across the top of the bottom chord of the truss. This type of bracing is frequently called the “catwalk.” This can be made from 2 × 4 or 2 × 6 framing lumber.

When the length of the catwalk requires multiple pieces of lumber, the pieces are joined by lapping over each piece by at least the distance of one rafter spacing interval. Bottom chord bracing is usually spaced at 8′ to 10′ intervals across the roof width. Figure 9-118 shows roof truss construction with catwalks along the length of the main house and two catwalks along the length of the garage.

Diagonal Bracing

Diagonal or gable end bracing is attached at an angle from the gable end of the roof to a point inside of the roof. The diagonal bracing can attach to vertical truss chord members, or it can be attached at an angle across the web bracing of the trusses. The diagonal bracing can be installed at a single sloped angle or in an X fashion. The height and width of the trusses determine the length of the diagonal brace. Typically, a 12′ to 16′ length of lumber will suffice for each diagonal brace. Figure 9-117 shows a roof with six diagonal braces, each approximately 14′ long. Figure 9-119 shows a truss roof installation with diagonal X bracing and a catwalk.

Truss Roof Overbuild

On occasion, truss framing roof construction will require additional roof framing or roof overbuild framing. A specialty set of jack trusses can be made to fill in overbuild sections, however, contractors often elect to stick framing in the overbuild section rather than purchase additional small trusses. These trusses can be quite expensive for their size as they take time and effort to make multiple one-off truss instances of trusses. Figure 9-120 shows a truss roof with a couple of small roof overbuilds.

Figure 9-121 shows an example of the stick framed portion of the front porch roof. The portion of the truss roof underneath the overbuild is covered with roof sheathing and the overbuild built on top of it.

Seven individual pieces make up the overbuild framing. Six jack rafters and one ridge board. The truss plans in Figure 9-122 show the front porch section of the roof with a span of 11′10 ½″ wide, which could be rounded up to 12′ and a run of 6′. The ridge board would be equal to the 6′ span, and the length of the longest rafter would be based upon the rise and run of the 6′ span and 6 in slope. 

The rise would be equal to 36 inches, and the rafter length could be calculated using the run and the slope factor of 13.42 from Table 9-2.

Rafter Length = 72 in. × 13.42 ÷ 12 = 80.64 in.

The difference in length of rafter space 24 inches apart from Figure 9-91 is given as 26.81 inches. Each jack rafter would decrease in size by that amount for a total of

Jack Rafter 1: 2 pcs 80.64 in.

Jack Rafter 2: 2 pcs. 54 in.

Jack Rafter 3: 2 pcs. 27.16 in.

Framing Connectors

Each project will require different truss anchors, depending upon the truss style. Framing anchors are often identified on the plans using a framing connector legend that identifies framing connectors by type using a standard symbol with the connecter identified on the plan by the symbol. Figure 9-121 shows an example of a framing connector legend. Often, the connector legend will be a standard architectural detail identifying a number of common framing connectors, not all of which are used on that specific project. In addition, the framing connector may be identified by annotations or notes on the plans, such as is the case in Figure 9-123 that shows a small section of a roof framing plan that contains several structural framing tags and annotations. Framing connector 7 represents a Simpson ST22515 Strap tie; framing connector represents a Simpson H2.5 hurricane anchor. There is also an annotation explaining that a Simpson H2.5 framing connector is located on the end of each truss. The abbreviation “Typ.” suggests that this is a common detail on each truss end. This annotation eliminates the need to tag every H2.5 framing connector, as this could make the drawing over-cluttered.

It is the construction estimating professional’s responsibility to identify the framing connectors on the project from the plans and specifications and make an accurate count of the connectors required. Several types of metal truss anchors are usually required with truss roof installation. Common examples of required anchors include hurricane anchors, U type hangers, and strap anchors.

Hurricane Anchors

Hurricane anchors are the most common type of roof truss anchors that are required. A hurricane anchor attaches the roof truss to the top plates, studs, and the wall framing. There are multiple types of hurricane anchors that can be used; some are more applicable than others in a given situation. Figure 9-124 shows an example of two common types of truss anchors: H1 and H2 truss anchors. Hurricane anchors are typically required on each truss, as it is attached to the exterior supporting walls.

U Type Hangers

U type anchors are typically required when one truss is supported by another truss, such as when a girder truss has trusses attached to it. Several types of U type hangers can be required, such as single U type hangers, double U type hangers, or angled hangers. Figure 9-125 shows an example of two types of U type hangers: a single 2 × 4 U type hanger and an angled U type hanger.

Strap Tie Anchors

Strap tie anchors are used in high wind or earthquake areas to tie framing elements together such as floors and the walls or the roofs and the walls. Figure 9-126 shows an example of strap tie anchors placed between the exterior walls and the gable end trusses.

Roof Sheathing

Roofs are commonly framed with plywood or OSB sheathing material. Thickness of 7/16 inch, 1/2 inch, or 5/8 inch are most often used. Thicker sheathing can be used on some roofs with heavier roof loads or wider truss spans. Figure 9-127 shows one half in OSB sheathing delivered to the job site in preparation for installation on the roof.

Roof sheathing typically calculated by the square footage of sloped roof area. The slope roof area can be determined by multiplying the square footage of flat roof area by the roof slope factor. Figure 9-128 shows a roof with the first layer of OSB sheathing installed. Figure 9-129 shows the roof sheathing completed.

Soffit Ledger

Soffit ledger boards are installed on the exterior wall level with the horizontal fascia. They are used to attach the exterior finish soffit material, particularly wood soffit finish. Soffit ledgers are also commonly used to support the Soffit J Channel when installing aluminum or vinyl soffit. Estimating soffit ledgers is a matter of counting the lineal foot of horizontal material. Figure 9-130 shows an example of a 2 × 4 soffit ledger.

Soffit Lookouts

Soffit lookouts are also horizontal members installed to support the exterior finish soffit material. They are installed between the soffit ledger and rough fascia. They are usually spaced using standard framing on-center spacing. The length of the soffit lookout is determined by the width of the soffit. For example, a 12 inch soffit overhang would have lookouts calculated at 12 inches long. Soffit lookouts are estimated by calculating the number of soffit lookout pieces by the length of the soffit lookout. Figure 9-131 shows an example of soffit lookouts. Lookouts are often not installed with aluminum or vinyl soffit material.

Truss Roof Framing Examples

Truss roof framing can be very basic or very complex. Figures 9-132 through 9-144 show examples of various truss roof configurations, both simple and complex.

Estimating Truss Roof Framing

It is apparent from the truss installation examples in Figures 9-132 through 9-144 that there are endless numbers of variations in truss roof framing possibilities. For this reason, estimating the cost of truss roof framing presents some challenges. The truss construction details will need to be engineered before any price can be established, and the actual cost of the truss package will need to be provided by the truss manufacturer. The contractor should anticipate using the actual truss price from the manufacturer whenever possible.

In spite of the challenges of estimating the actual roof truss package, the estimator will often need to provide preliminary estimate numbers when preparing a construction cost estimate.

Estimating the Truss Material Cost

The NCE contains different prices for different basic truss types. The following is a guide to help you use the NCE to estimate truss material cost.

• Any standard style of trusses will be estimated using the Fink truss option. The price is estimated using a square foot cost based upon the square footage of the flat roof area, including roof overhangs.
• Any modified ceiling truss will be estimated using the scissor truss option. The price is estimated using a square foot cost based upon the square footage of the flat roof area, including overhangs.
• Any specialty type truss will be estimated using the specialty truss option. The trusses are estimated by the price per individual truss. These individual trusses are located within the square footage space of the standard and scissor truss areas. The specialty trusses are an addition to the square foot cost of the standard and scissor truss styles. In addition, the specific count of these specialty trusses is obtained using the following guidelines:
• Gable end and special gable end trusses are counted as one each.
• Trusses ganged together such as double girder trusses are counted as two trusses or more depending upon the number of trusses ganged together.
• Hip trusses, or girder hip trusses are counted as one each for each hip or hip girder truss.
• Groups of smaller trusses, such as those attached to a hip, or hip girder truss, are counted together as one specialty truss.
• Groups of smaller trusses such as a group of jack or valley trusses are counted as a single truss.

Completing the Truss Roof Framing Materials

Roof Sheathing

The quantity of roof sheathing is determined by using the square footage of sloped roof area. Information about the sheathing type can be found from the plans. Frequently, this information can be found on the detail section drawing, shown in Figure 9-145, which shows the roof sheathing as 1/2-inch OSB Sheathing.

Fascia Board

The fascia board can be determined from the lineal feet of roof edge from the basic takeoffs. The type of fascia material can be determined from detail section drawings as shown in Figure 9-145. Figure 9-116 shows a view of the roof overhang components. The fascia board is a combination of barge rafter and sub-fascia.

Catwalk

The catwalk installation shown in Figure 9-117 shows a view with catwalk installation. Three pieces of 2 × 6 lengths of catwalk are installed along the bottom of the trusses for the main building, and two pieces of 2 × 6 catwalks are installed along the bottom of the garage trusses. The main building catwalks would be equal to three times the length of the building and the garage catwalks would be equal to two times the length of the garage. The total would be equal to

Main Building Width: 36 ft. × 3 pcs. = 108 ft.

Garage Width: 20 ft. × 2 pcs. = 40 ft.

Total: 108 ft. + 40 ft. = 148 ft.

Diagonal Bracing

Diagonal bracing is required on all truss gable ends. The diagonal bracing is typically made from 12′ to 16′ lengths of 2 × 4 material. Figure 9-117 shows six diagonal bracing pieces, each at 14′ long.

Gable End Lookouts

Gable end lookouts include both long and short lookouts. Figure 9-116 shows a graphic of the roof overhang components, including the gable end lookouts. There are 41 long gable end lookouts that are shown in the project. Each long gable end lookout is equal to the length of one truss space and the roof overhang. Six short gable end lookouts are also shown on the front porch. The short overhang length is equal to the distance of the overhang or one foot. The total for gable end lookouts is equal to

Long Overhang: Truss Spacing 2 ft. + Overhang Distance 1 ft. = 3 ft.

Long overhang lookouts: 41 pcs. × 3 ft. = 123 ft.

Short Overhang: Overhang Distance = 1 ft.

Short Overhang Lookout: 6 pcs. × 1 ft. = 6 ft.

Total Gable End Lookouts: 123 ft. + 6 ft. = 129 ft.

Soffit Ledger

The 2 × 4 soffit ledgers will be installed on the wall parallel to the horizontal fascia boards as shown in Figure 9-143 to support the aluminum soffit J channel material. Estimating the quantity of soffit ledger is done by determining the horizontal length of fascia. Figure 9-116 shows the rough fascia board highlighted. The length can be calculated using the roof truss area graphic in Figure 9-141. The graphic shows the following horizontal roof lengths:

Back Edge: 58 ft.

Front Edge: 15 ft. 3-3/4 in. and 10 ft. 9-3/4 in.

Front Garage Edge: 20 ft.

Front Porch Edge: 2 pcs. 5 ft. 11-1/4 in.

The totals will be rounded up to the next half a foot.

Total Ledger: 58 ft. + 15 ft. 6 in. + 11 ft. + 20 ft. + 6 ft. + 6 ft. = 116 ft. 6 in.

Soffit Lookouts

There will be no soffit lookouts on this project as the soffit will be aluminum soffit material.

Nails

The building code requires that roof sheathing be fastened with nails placed at six-inch intervals along the edge and at 12-inch intervals along the framing supports in the middle of the panels. This calculates to approximately 60 nails per sheet of sheathing. The 8d Bostich framing nails are sold in a quantity of 2,000 nails per box. The 72 sheets of OSB on the roof multiplied by 60 nails per sheet equates to 4,320 eight penny nails (three boxes) for the roof sheathing installation.

The truss and truss framing will be installed using 16 penny framing nails. Estimate 25 nails for each truss and its associated rough fascia, catwalks, and diagonal bracing. There are 33 roof trusses for a total of 825 nails. The gable end lookouts will be installed using eight nails each. There are 48 pieces of ladder blocking for a total of 384 nails. The total nails for the installation will be 1,209. Sixteen penny framing nails are also sold in a box of 2000. One box will need to be purchased.

Completing the Truss Framing Anchor Materials

There are various different types of framing anchor materials that can be used. Figure 9-148 shows a copy of the roof framing plan with the framing connectors tagged and annotated. We will briefly discuss these materials.

2 × 6 U Type Hangers

The 2 × 6 U type hangers are typically used to support truss ends on a supporting load bearing girder truss as shown in Figure 9-139. This project has no girder trusses, and no 2 × 6 U type hangers will be used on this project.

2 × 4 U Type Hangers

The 2 × 4 U type hangers are typically used to support truss ends on a supporting load bearing girder truss as shown in Figure 9-123. This project has no girder trusses, and no 2 × 4 U type hangers will be used on this project.

Hurricane Anchors

The building code requires hurricane anchors to attach the end of the trusses as they are anchored to the exterior load bearing walls. One hurricane anchor is required at the end of each truss (Figure 9-122). There are 28 standard trusses in the project with a hurricane anchor on each end for a total of 56 anchors.

Strap Tie Anchors

The framing connector annotation symbol with a seven in the center represents a Simpson ST2215 strap tie (Figure 9-121). The annotations show six of these strap ties in the project, which is the quantity that will be used in the estimate.

Hanger Nails

Framing connectors usually require specific nails to meet the installation requirements. In addition, the requirement is typically for every nail hole to be filled. Information about the number of nail holes per fastener are usually readily available. The H2.5A hurricane anchors require six nails each for a total of

6 Nails × 56 Hanger = 336 Nails

The ST2215 strap ties require 20 nails each for a total of

20 Nails × 6 Strap Ties = 120 Nails

Total nails: 336 nails + 120 nails = 456 nails

The price of these nails can be found in the NCE.

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CITATIONS:

Automated Structures Inc. (n.d.). Truss FAQ. Retrieved from https://www.automatedtruss.com/truss-faq.html

Buza, J., BUCS (Ed.). (1993). Builder 2 & 3(Vol. 1) (United States, United States Navy, Professional Development and Technology Center). Naval Education and Training. Retrieved from https://www.constructionknowledge.net/public_domain_documents/Builder_and_2_vol_1_NAVEDTRA_14043_1993.pdf

Firszt, L. (2015, April 21). Why Roof Trusses Are More Popular Than Rafters. Retrieved from https://www.networx.com/article/why-roof-trusses-are-more-popular-than-r

GLOSSARY OF ROOF TERMINOLOGY - Residential Reports. (n.d.). Retrieved from http://www.residentialreports.com.au/wp-content/uploads/2015/03/Glossary-of-Roof-Construction-Terminology.pdf

Gromicko, N., & Gromicko, B. (n.d.). Structural Design Basics of Residential Construction for the Home Inspector. Retrieved from https://www.nachi.org/structural-design-basics-residential-construction.htm

Riverina TAFE Building & Construction. (2013, December 02). Retrieved December 04, 2018, from https://www.youtube.com/ watch?v=esI-BDeqa3I

Roof Trusses. (n.d.). Retrieved from https://www.sbcindustry.com/ education/topical-library/roof-trusses

The Benefits of Building With Roof Trusses. (2016, January 29). Retrieved from https://www.nisbetbrower.com/the-benefits-of-building-with-roof-trusses/