2Wood-framed wall components include studs, plates, headers, trimmer studs, sills, cripple studs, and corner posts. Exterior walls are commonly covered with structural panels such as oriented strand board or plywood.Wood‑framed walls consist of structural parts referred to as wall components or framing members. Components of a wood-framed wall include studs, plates, headers, trimmer studs, sills, cripple studs, and corner posts. See Figure 43‑1. For some applications, diagonal braces may also be required. Each component has a special function within the total wall structure
3Corner posts are constructed wherever a wall ties into another wall Corner posts are constructed wherever a wall ties into another wall. Straight studs are used to frame corner posts. When an inside corner is constructed using a block laid flat, a carpenter must insulate the U-shaped cavity before exterior wall sheathing is applied. When metal clips are used, the wall cavity can be insulated after exterior wall sheathing is appliedCorner posts, also called corner assemblies, are constructed wherever a wall ties into another wall. Outside corners are at the ends of a wall. Inside corners occur where a partition ties into a wall at some point between the ends of the wall. Three typical designs for corner posts are shown in Figure 43‑2. All corner posts should be constructed from straight studs and should be well nailed.
4Rough door and window openings must allow for the finish frame and a required clearance around the frame.The rough opening for a door is framed with a header, trimmer studs, wall studs, and, in some cases, cripple studs. The rough opening for a typical window includes the same members as for a door, plus a rough sill and bottom cripple studs. See Figure 43‑3.
5Various methods are used to construct door and window headers. Headers may be solid pieces or may be built up of two pieces with 1/2″ spacer blocks between them. Spacer blocks are needed to bring the width of the header to 3 1/2″, which is the actual width of a 2 × 4 stud wall. A built‑up header is as strong as a solid piece. However, it involves extra labor to construct a built-up header. Another type of built‑up header is made of two planks, such as 2 × 10s, with a 2 × 4 piece nailed at the bottom. For 2 × 6 walls, a solid piece of lumber (for example, a 6 × 12) may be used as a header. Another common header for 2 × 6 walls consists of two 2 × 10s with a 2 × 6 nailed to the bottom. See Figure 43-4.
6Header size is determined by the width of the opening and load bearing down from above. For example, a 4 × 6 Douglas fir header can be used for an opening up to 6′‑0″ wide.The required header type and size are shown on the prints. Header size is determined by the width of the opening and the load bearing down from the floor above. See Figure 43‑5.
7A 12″ wide solid header can be used to accommodate a 6′-8″ door in an 8′-1″ standard-height wall. For standard-height door openings in standard-height walls, cripple studs are not necessary if a 12″ wide header is placed directly below the top plate. The distance between the bottom of the 12″ wide header and the subfloor allows for the 6′‑8″ door height, thickness of the head jamb, clearance above the head jamb, and required clearance below the door. See Figure 43‑6. The clearance below the door varies with the thickness of the finish floor material.
8When a header less than 12″ wide is installed, cripple studs are installed between the top of the header and top plate.Header‑cripple stud construction is usually used only where walls are more than 8′‑1″ high. For walls higher than 8′-1″, a 12″ wide header placed directly under the top plate would result in a rough opening that would be too tall for standard doors. Cripple studs must be used to provide a rough opening of the correct height. See Figure 43-7.
9Corner braces may need to be installed in rough openings for installation of oval or round windows. The framing for the rough openings of oval or round windows may require corner bracing so that the finish window frames can be secured from all sides. See Figure Some oval, round, or irregularly shaped windows have bracing and other framing members in place when they are delivered. The window units are installed in the rough opening and fastened in place.
10T-shaped metal braces fit into saw kerfs in the studs. Two diagonal bracing systems are metal wall braces and 1 × 4 let‑in braces. Metal wall braces are 16 ga to 22 ga L- or T-shaped metal pieces that are installed in a saw kerf running diagonally across a wall section. See Figure 43‑9. A diagonal line is snapped diagonally across the wall section and a saw kerf is made along the line. A metal wall brace is placed in the kerf and secured to the top plate. The wall is squared and the brace is secured to the studs it crosses.
11Fireblocking is required in concealed spaces to cut off vertical and horizontal draft openings and to form a barrier between stories.Fireblocking requirements are different for residential and commercial construction, and vary from jurisdiction to jurisdiction. Always consult the applicable local building code for specific fireblocking requirements. In general, fireblocking is required in the following locations for residential construction:• stud walls and interior partitions at the floor and ceiling level• junction between concealed wall spaces, such as those at soffits, coves, or drop ceilings. See Figure• concealed spaces between stair stringers at the top and bottom of the stringers• concealed spaces around fireplace and chimney openings• openings around ducts, pipes, and vents at the floor and ceiling level
12Fireblocking caulk is applied to joints or openings in walls or structural members to inhibit the spread of fire, smoke, and fumes.Fireblocking caulk is commonly used to seal holes drilled through walls or structural members. See Figure
13Wood-framed walls may be assembled while they are lying on the subfloor. Wall components are assembled on the subfloor. The components are nailed together and the completed wall is raised into place. Figure 43‑12 shows a partially assembled wall lying on the subfloor of a building under construction.
14Lines are snapped to indicate the exact locations of walls, and top and bottom plates are cut to length and tacked next to the chalk lines.The first step in wall layout is to snap chalk lines on the subfloor to indicate the exact locations of walls. The locations are determined from the measurements provided on the floor plan. See Figure
15The top and bottom plates are tacked next to the snapped chalk lines before laying out the wall components.After the lines are snapped, the top and bottom plates are cut to length and tacked next to the chalk lines. See Figure 43‑14.
16Framing members are nailed where the plates are marked. The plates are then marked for corner posts and regular studs, as well as for studs, trimmer studs, and cripple studs for rough openings. All framing members must be clearly marked on the plates for carpenters to frame the wall efficiently. Figure shows a wall with framing members nailed in position according to layout markings.
17Stud-and-block corner posts are constructed with full-length studs and blocks. A procedure for marking outside and inside corners for stud-and‑block corner posts is shown in Figure 43‑16.
18If the first stud of an exterior wall is placed 15 1/4″ from the corner and other studs follow 16″ OC layout, the edges of standard-size panels will fall over the stud centers.A procedure for laying out studs for the first exterior wall is shown in Figure 43‑17. In this common layout method, plates are marked for the first stud from a corner post by measuring 15 1/4″ from the end. Subsequent studs follow 16″ OC layout. This layout method ensures that the edges of standard wall sheathing or gypsum board panels fall on the centers of the studs. Cripple studs are laid out to follow the stud layout.
19When the second exterior wall is laid out, the 15 1/4″ mark is measured from the outside edge of the panel on the first wall. The corner of the first panel on the second exterior wall will align with the edge of the first wall panel. The opposite edge of the panel will fall on the center of a stud.A procedure for laying out studs for the second exterior wall is shown in Figure 43‑18. The plates are marked for the first stud to be placed 15 1/4″ from the outside edge of the panel on the first wall. This layout allows the corner of the first panel on the second wall to align with the edge of the first panel on the first wall. In addition, the opposite edge of the panel on the second wall will break on the center of a stud.
20On partitions, the 15 1/4″ measurement ensures that standard-size gypsum board or interior finish panels will fall over the center of a stud.A procedure for laying out studs for partitions is shown in Figure 43‑19. If wall panels are placed on the exterior wall first, followed by the partitions, wall plates for the partition are marked for the first stud to be placed 15 1/4″ from the edge of the panel on the exterior wall. If panels are to be placed on the partitions before they are placed on the exterior wall, then the wall plates of the interior wall are marked for the first stud to be placed 15 1/4″ from the unpaneled exterior wall.
21The finish door opening is the width of the door and the distance from the head jamb to the floor. The rough door opening is the distance between the trimmer studs and the height from the floor to the header.Dimensions for the widths of rough door and window openings must also be marked on the wall plates. Rough openings are calculated based on door or window width, finish frame thickness, and 1/2″ shim clearance at the sides of the frame. See Figures 43‑20 and 43‑21.
22The finish window opening width and length is the frame-to-frame dimension. The rough window opening is the distance between the trimmer studs and the height from the rough sill to the header.Dimensions for the widths of rough door and window openings must also be marked on the wall plates. Rough openings are calculated based on door or window width, finish frame thickness, and 1/2″ shim clearance at the sides of the frame. See Figures 43‑20 and 43‑21.
23When laying out the width of a door or window rough opening at the corners of intersecting walls, allowances must be made along the corner assembly for the trimmer stud, side jamb thickness, and shim clearance.Door and window schedules found on prints may provide rough opening dimensions. When rough openings are not included on schedules, carpenters must know how to calculate the rough openings. The procedure for calculating rough openings is shown in Figures 43‑22 and 43‑23.
24When laying out the width of a door or window rough opening, the center of the opening is first laid out. One-half of the rough opening width, side jamb thickness, and shim clearance is laid out on each side of the centerline.Door and window schedules found on prints may provide rough opening dimensions. When rough openings are not included on schedules, carpenters must know how to calculate the rough openings. The procedure for calculating rough openings is shown in Figures 43‑22 and 43‑23.
25Floor plans provide information to properly lay out walls Floor plans provide information to properly lay out walls. Information on this floor plan is used in the layout calculations for Figures 43‑25 through 43‑28.A completely laid out wall plate includes markings for corner posts, rough openings, studs, and cripple studs. A procedure for laying out walls according to the floor plan shown in Figure 43‑24 is shown in Figures 43‑25 through 43‑28. First, wall plates are laid out and chalk lines are snapped. The corner posts are then laid out and properly marked to indicate studs and blocking. Next, the 16″ marks for the studs and cripple studs are marked. Finally, rough openings for doors and windows are laid out and marked.
26Wall plate locations are laid out and chalk lines are snapped. A completely laid out wall plate includes markings for corner posts, rough openings, studs, and cripple studs. A procedure for laying out walls according to the floor plan shown in Figure 43‑24 is shown in Figures 43‑25 through 43‑28. First, wall plates are laid out and chalk lines are snapped. The corner posts are then laid out and properly marked to indicate studs and blocking. Next, the 16″ marks for the studs and cripple studs are marked. Finally, rough openings for doors and windows are laid out and marked.
27Outside and inside corner posts are laid out and studs are laid out 16″ OC. A completely laid out wall plate includes markings for corner posts, rough openings, studs, and cripple studs. A procedure for laying out walls according to the floor plan shown in Figure 43‑24 is shown in Figures 43‑25 through 43‑28. First, wall plates are laid out and chalk lines are snapped. The corner posts are then laid out and properly marked to indicate studs and blocking. Next, the 16″ marks for the studs and cripple studs are marked. Finally, rough openings for doors and windows are laid out and marked.
28Studs are commonly laid out 16″ OC. A completely laid out wall plate includes markings for corner posts, rough openings, studs, and cripple studs. A procedure for laying out walls according to the floor plan shown in Figure 43‑24 is shown in Figures 43‑25 through 43‑28. First, wall plates are laid out and chalk lines are snapped. The corner posts are then laid out and properly marked to indicate studs and blocking. Next, the 16″ marks for the studs and cripple studs are marked. Finally, rough openings for doors and windows are laid out and marked.
29Rough door and window openings are located and stud, trimmer stud, and cripple stud locations are marked.A completely laid out wall plate includes markings for corner posts, rough openings, studs, and cripple studs. A procedure for laying out walls according to the floor plan shown in Figure 43‑24 is shown in Figures 43‑25 through 43‑28. First, wall plates are laid out and chalk lines are snapped. The corner posts are then laid out and properly marked to indicate studs and blocking. Next, the 16″ marks for the studs and cripple studs are marked. Finally, rough openings for doors and windows are laid out and marked.
30Rough door and window opening dimensions may be obtained from the door and window schedules on the prints.Figure 43‑29 shows a typical wall section view and door and window schedules. The wall section and door and window schedules provide information needed to lay out a story pole.
31A story pole is marked to indicate the lengths of studs, trimmer studs, and cripple studs. The example shown here is based on information in FigureFigure 43‑30 shows a procedure for laying out a story pole using information obtained from the wall section view and door and window schedules.
32Some prints provide only finish opening dimensions. Prints may only provide finish opening dimensions in the wall section views and door and window schedules. If only finish opening dimensions are provided, additional information must be obtained from detail drawings and the finish schedules to lay out the story pole. Figure 43‑31 shows a wall section view that provides finish dimensions, parts of door and window schedules, and detail drawings.
33The story pole being laid out here is based on information found in Figure 43-31. Figure 43‑32 shows a procedure for marking a story pole based on the information provided in Figure
34A bench is useful for making up large quantities of corner posts A bench is useful for making up large quantities of corner posts. The material should be held tightly against the fence and end block when pieces are nailed together.For improved productivity, corner posts for a building can be constructed at one time using a bench as shown in Figure
35Outside and inside corner posts are commonly assembled prior to wood-framed walls being assembled. Before nailing, align the ends of the studs.Figure 43‑34 shows a procedure for assembling inside and outside corner posts. Blocks should be held slightly back from the ends of the studs. Before nailing, ensure the ends of the studs align with each other.
36Door openings are assembled before assembling the rest of the wall Door openings are assembled before assembling the rest of the wall. In this example, cripple studs are required over the header.Many carpenters prefer to frame door and window openings before assembling the rest of the wall. Figure 43‑35 shows a typical procedure for framing a door opening. In this example, cripple studs are required over the header. To frame a door opening with a 4 × 12 header in a wall no more than 8′‑1″ high, the procedure is the same except that cripple studs are not needed.
37The procedure for framing window openings is the same as framing door openings. A rough sill and bottom cripple studs are then added. Cripple studs follow the stud layout (usually 16″ OC).For window openings, a rough sill is added to the bottom of a window opening. Cripple studs that follow the stud layout (usually 16″ OC) are nailed between the sill and bottom plate. Cripple studs are also placed under each end of the sill. The procedure for framing window openings is the same as the procedure for framing door openings, and then a rough sill and bottom cripple studs are added. See Figure
38A wood-framed wall is nailed together on the subfloor after corner posts and door and window openings are completed.After corner posts and door and window openings have been constructed, the entire wall is nailed together on the subfloor. Position top and bottom plates on the subfloor at a distance slightly greater than the length of the studs. See Figure 43‑37. Position corner posts and rough openings between the plates according to the plate layout. Place studs in position with crown side up. Nail the plates into the studs, cripple studs, and trimmer studs.
39Joints in plates should occur over a full header or at the center of a stud or cripple stud. On long walls, breaks in the plates should occur over a stud or cripple stud. If a 4 × 12 header without cripple studs is used, breaks in the plates should occur over a stud or over the header. See Figure 43‑38.
40The topmost plates of a double top plate overlap the plates below them at all inside corners. A top plate may be doubled while the wall is lying flat on the subfloor or after all walls have been raised. The topmost plates are nailed so they overlap the plates below them at all corners to tie the walls together. See Figure 43‑39. All top plate ends are fastened with two 16d nails. Between the ends, 16d nails are placed every 16″ OC (over the studs) so that it is easier to identify stud locations when attaching sheathing. Butt joints between the topmost plates should be at least 4′ from any butt joint between the plates below them.
41A framed wall is often squared while it is lying on the subfloor A framed wall is often squared while it is lying on the subfloor. Temporary braces must be attached to keep the wall square while it is being raised. Wall sheathing may also be applied while the wall is lying on the subfloor to keep the wall square when raising it.A framed wall is often squared while it is lying on the subfloor. Walls are squared and braced. Braces and structural panels or other exterior wall sheathing is nailed in place to keep the walls square while being raised. See Figure 43‑40.
42Diagonal metal braces may be used to provide additional wall stability Diagonal metal braces may be used to provide additional wall stability. A shallow kerf is required for T- and L-shaped braces.When installing metal braces, lay out and snap lines on the studs to show the brace location. See Figure 43‑41. Shallow kerfs are cut in the edges of the studs to allow for metal braces. A brace is installed in the kerfs and fastened in place. Metal braces should be placed at the corners of walls and approximately every 25′ in longer walls.
43Wall plates and studs are notched for wood let-in braces Wall plates and studs are notched for wood let-in braces. The braces are tacked in place when the wall section is lying on the subfloor. After the wall is raised and the brace adjusted to its final position, the nails are driven in.When installing wood let-in braces, the studs are marked and notched for the brace. See Figure 43‑42. Tack the brace to the studs while the wall is lying on the subfloor. Tacking instead of nailing allows for some adjustment after the wall is raised. After any necessary adjustment is made, the nails can be securely driven in.
44Wall jacks can be used to raise walls when small carpentry crews are working on a job site. A minimum of two wall jacks must be used when raising a wall. The number of wall jacks used depends on the wall length, height, and overall wall structure. The general procedure for raising walls using walls jacks is shown in Figure Always follow manufacturer instructions when raising walls using wall jacks. When walls are being raised, no workers should be allowed directly below the wall or on the opposite side of the wall.
45A plate level is used to plumb a wall corner. Plumbing of corners is performed after all walls are raised. Plumb the outside corners first and then securely brace for stability. Most framing material is not perfectly straight; therefore, a plate level or straightedge and a hand level should be used to plumb walls. See Figure 43‑44. A straightedge is ripped out of plywood or a straight 2 × 4. Blocks 3/4″ thick are nailed to each end of the straightedge to accurately plumb the wall from the bottom plate to the top plate. Walls should not be plumbed by placing a short hand level directly against the end stud.
46After the corners are plumbed, the tops of the walls are straightened using a line and 3/4″ blocks. Wall tops are straightened (aligned) after all corners have been plumbed, but before floor or ceiling joists are nailed to the tops of the walls. A string is attached to the top plate at one corner of the wall. The string extends to, and is fastened to, the top plate at the opposite end of the wall. Three small blocks are cut from a 1 × 2. One block is placed under each end of the string so the line is clear the entire length of the wall. The third block is used as a gauge to check the wall at 6′ or 8′ intervals. See Figure 43‑45. At each check point, a temporary brace is fastened to a wall stud.
47Powder-actuated fasteners are often used to fasten bottom plates to concrete slabs. Often the basement or ground floor of a wood‑framed building is a concrete slab. Bottom plates must be bolted to the slab or secured to the slab with powder-actuated fasteners. See Figure 43‑46. Bolts for attaching bottom plates must be accurately set into the slab when the concrete is placed. Bolt holes are laid out and drilled in the bottom plate when the wall is framed. The wall is slipped over the bolts as it is raised and secured in position with washers and nuts.
48Metal framing angles attach wall studs to plates and concrete slabs. Metal connectors strengthen wood‑framed wall connections by providing additional support between framing members and the concrete foundation. See Figures and
49Stud plate ties secure wall studs to plates. Metal connectors strengthen wood‑framed wall connections by providing additional support between framing members and the concrete foundation. See Figures and
50Seismic or hurricane ties are required in areas that experience earthquakes and high winds. Seismic or hurricane ties are required in areas that experience earthquakes and high winds. See Figure Wood-to-wood ties, such as floor ties and plate ties, are attached to the framing members with galvanized nails. Wood-to-masonry (or concrete) ties are attached to the masonry or concrete with self-tapping screw anchors. Refer to the local building code to determine metal connector and fastener requirements.
51Wall sheathing panels can be placed with the grain running vertically or horizontally. Wall sheathing panels are typically placed with the long edges in a vertical position, although the long edges may also be placed horizontally. If panels are placed horizontally, nailing blocks should be installed between the studs. Building codes may require nailing blocks along the long edges of horizontal panels. Joints at panel edges should be staggered so no joints are aligned. A 1/8″ space should be allowed between the panels to prevent buckling, which may result from panel expansion. See Figure
52After placing wall sheathing panels and securing them at the corners, snap vertical chalk lines locating the intermediate studs before installing nails or screws.When placing wall sheathing panels, ensure the first panel is plumb along its vertical edge and level along the horizontal edge. Secure the panel with nails, screws, or staples at the corners. Snap vertical chalk lines locating the intermediate studs before installing nails or screws. See Figure Some wall sheathing panels are available with factory-painted lines at 16″ and 24″ OC.
53Weather barriers, such as housewrap, prevent water and air penetration into a building while allowing moisture vapor and gases to escape. Housewrap for the prefabricated panels forming the exterior walls of this house is applied at the manufacturing facility. Housewrap that is folded back at the corners and along the joists will be laid into position and fastened.Housewrap is a common weather barrier used over panel sheathing. Housewrap is a translucent spun plastic sheet material that is tightly wrapped around a building to prevent air and water infiltration. See Figure Housewrap allows a building to “breathe” by allowing water vapor and gases from a building interior to move outward without trapping moisture in the wall cavity. Housewrap is available in 3′ to 9′ rolls. The 9′ wide rolls, which are more frequently used, should be installed by two workers.
54Housewrap must be properly applied and overlapped to prevent moisture from infiltrating the building envelope.The general procedure for installing housewrap is as follows:1. Start the lowest course of housewrap at a building corner. Place a roll of housewrap vertically and extend the housewrap 2′ to 3′ past the corner. See Figure Position the housewrap so the bottom edge sill plate and approximately 1″ of the foundation wall are covered. Wrap the housewrap entirely around the house, keeping it level and tight. Make tight inside corners by holding a 2 × 4 in the corner. Overlap the beginning of the housewrap approximately 6″. Each subsequent row of house-wrap should overlap the row below by approx-imately 6″ to 12″.…see complete procedure for installing housewrap on page 404.
55An inverted Y cut is made in the housewrap, and the flaps are folded back and fastened to the inside of the rough opening. The top flap is folded up and tacked to the exterior side of the wall. The flap will be folded down and secured after the window or door is installed in the opening.The general procedure for cutting window and door openings in housewrap is as follows:1. Make an inverted Y cut in the middle of the window opening. See Figure2. Fold back the flaps at the two sides and bottom of rough opening and fasten to the inside of the rough opening using nails or staples spaced 6″ apart. If a sill pan is to be installed, the side flap may remain loose until the pan is installed. The flaps are then folded into the rough opening and secured.3. Make angled cuts at the top of the rough opening and fold the flap up. When the window frame is in place, the flap will be folded down and secured over the frame.
56A rainscreen wall is a method of preventing moisture vapor from accumulating between the exterior finish material and weather barrier.Oriented strand board or structural plywood sheathing provides lateral strength against high winds, earthquakes, and other natural forces. Moisture trapped between the exterior finish material and sheathing will cause fungal growth, physical deterioration of the sheathing, and possible loss of structural capabilities of the sheathing. One method for preventing moisture vapor from accumulating between the exterior finish material and weather barrier is using a rainscreen wall. A rainscreen wall is a moisture-management system that incorporates a vented or porous exterior finish, an air cavity, a drainage plane, and an airtight interior support wall. See Figure Moisture vapor or moisture entering the wall cavity is properly drained away and air is allowed circulate within the cavity to maintain dryness within the wall cavity.
57Structural insulated panels (SIPs) are composed of two outer panels and an insulating foam core. A structural insulated panel (SIP) consists of two outer structural panels (skins) with a thick inner foam core. See Figure The outer panels are commonly OSB, but plywood may also be used. SIPs are available in many standard sizes ranging from 4′ × 6′ to 8′ × 24′. The foam core is usually expanded polystyrene (EPS) or polyisocyanurate rigid foam, although other foam products such as extruded polystyrene and polyurethane are also used. Foam for the core has high insulation values and keeps its shape permanently. SIP construction is an environmeatally responsible alternative to standard platform framing.
58A surface or dimensional lumber spline may be used to join SIPs together. Joining and assembly procedures for SIPs vary with the manufacturer. However, glue can be used in addition to nails and/or panel screws to fasten SIPs to the framework. Liquid expanding foam is usually applied at the joints to ensure airtight seals. Many manufacturers use spline connections at the joints. See Figure
59A pressure-treated sill plate is secured to the foundation wall, and SIP panels are lowered over and fastened to the sill plate.An SIP building must be constructed on and anchored to a solid foundation. A pressure-treated sill plate equal in width to the space between the SIP panels is secured to the foundation using anchors at a spacing specified by the manufacturer. See Figure The panels are then hoisted and lowered over the sill plates using a crane or other hoisting equipment, depending on the panel size. Smaller panels may be fitted into position by hand. Sealant should be applied as specified by the manufacturer. Nails are then driven through the lower edges of the panels and into the sill plates. The panels should be properly braced until the roof or floor framing for the next floor is complete.
60Top-flange joist hangers are used to support upper floors in SIP construction. Metal connectors are used to support floor joists for an upper floor of an SIP building. Top-flange joist hangers are fastened to the top plate of the SIP wall panels before the panels for the upper floor are placed and fastened into position. See Figure The joists can then be installed and fastened into position. Metal straps are fastened to the exterior panel faces to tie the wall panels together.
61The lateral direction of the shear load against the wall may cause uplift at the bottom of the wall, resulting in a downward force at the opposite end of the wall.The floors, roof, walls, and foundation of shear walls are tied together using specialized fasteners and anchors to provide the building with greater shear load and uplift resistance. Shear load is the lateral pressure against a wall. Two major contributing factors of shear load are high winds, such as winds generated in hurricanes, and seismic forces. Uplift occurs at the side of the lateral force, and is generally caused by forces generated during earthquakes. A downward force occurs at the opposite end of a wall experiencing uplift. See Figure
62Shear wall construction is similar to conventional wood-framed walls Shear wall construction is similar to conventional wood-framed walls. Additional shear anchor bolts and holddown anchors are installed at the ends of shear walls.As shown in Figure 43-61, shear wall construction is similar to conventional wood-framed walls, but there are several important differences, including the following:• additional shear anchor bolts in bottom plate• holddown anchors at the ends of shear walls• tighter sheathing nailing patterns• thicker sheathing• special fastening requirements at the top of shear walls• different lumber framing grades, species, and sizes
63Special anchors are required to secure sill plates of a shear wall system. Some anchors are embedded in concrete as it is being placed in the forms or CMUs. Other anchors are bolted to the foundation.Shear anchor bolts or holddown straps are embedded in the concrete or masonry foundation wall or footing. Holddown straps may also be bolted to the sides of foundation walls, and are commonly used when retrofitting a building. See Figure
64Holddowns are secured to anchor bolts embedded in the foundation Holddowns are secured to anchor bolts embedded in the foundation. Lag or carriage bolts are driven into the adjoining wall studs.When a shear wall panel is raised, the sill plate is properly positioned and fastened into position. Metal washers and nuts are used on intermediate anchor bolts, while holddown anchors are secured in position at the ends of shear walls. The holddowns are also fastened to the adjoining wall studs using lag or carriage bolts. See Figure
65In a one-story anchor tiedown system, a long threaded rod extends from the top double plates and is coupled with an anchor bolt embedded in the concrete.In one-story anchor tiedown systems, a long threaded rod extends from the double top plate and is coupled to a bolt embedded in the concrete foundation. See Figure The tension on the rod is adjusted by turning a nut positioned over a metal bearing plate, which rests on the double top plate.
66In a multistory anchor tiedown system, a threaded rod is tightened and secured to the next story with a take-up device.In multistory buildings, sections of threaded rod extend the height of each wall and are connected to one another using a take-up device. The take-up device is a heavy spring mechanism that compensates for wood shrinkage and settlement caused by dead loads. Connected anchor tiedown systems can extend up to five stories. See Figure