Wall Bracing

Limitations of the Material in this Section

The IRC presents many methods and complex rules for wall bracing. Wall bracing is best left to qualified engineers and architects. This section discusses a few common wall bracing methods and some general rules about how to install them. Refer to the IRC and to qualified professionals for more information about wall bracing.The material in this book applies to wall bracing for one and two family homes and for townhouses in seismic design areas A and B. The material in this book does not apply to wall bracing in:(a) wind speed areas110 mph, and (b) wind exposure categories C and D, and (c) the D series seismic design areas, and (d) large and complex homes such as homes with ceilings higher than 10 feet and homes with multiple angled exterior walls.

Wall Brace and Braced Wall Definitions

Braced wall: (braced wall line) A braced wall is a mostly straight interior or exterior wall that contains the required length of approved wall braces (braced wall panels). Most exterior walls and some interior walls are braced walls. A braced wall begins and ends where one braced wall intersects: (a) a perpendicular braced wall, or (b) an angled braced wall, or (c) an exterior wall. You may angle a braced wall either direction from the straight braced wall line if the angled wall is not more than () 8 feet long. You may off set a braced wall not more than () 4 feet either direction from the straight braced wall line.

Wall brace: (braced wall panel) A wall brace is a full height wall with no vertical or horizontal offsets that has approved wall bracing material attached. A wood structural panel (such as OSB) is an example of a common approved wall bracing material. Each braced wall must have an approved total length of wall braces. The total length of wall braces depends on: (a) the criteria described in the next section, and on (b) the type of bracing material such as wood structural panels and let-in bracing, and on (c) the story being braced, and on (d) the design wind speed, and on (e) the seismic design category.

Wall Bracing Methods

1. Use one of the approved wall bracing methods. Common wall bracing methods include wood structural panel sheathing that is at least () inch thick, hardboard panel siding that is at least () ₁₆ inch thick, let-in bracing, and portal frame braces that provide shorter length bracing near large openings and garage doors. Each of these methods is an intermittent bracing method. This means that individual wall braces are installed near the ends of each braced wall.

2. You may use a continuous sheathing wall bracing method. This means that all braced walls have sheathing such as wood structural panels applied continuously to the walls including above and below openings and on gable end walls. Refer to the IRC for requirements regarding panel lengths near openings and for panel installation and hold-down straps at the ends of continuously sheathed braced walls.

3. Refer to the IRC for information about other wall bracing materials and methods. Refer to manufacturer’s instructions for information about manufactured wall braces.

4. You may use different wall bracing methods within the same braced wall and you may use different bracing methods on different stories. Example: you may use let-in bracing at one end of a braced wall and structural panel bracing on the other end. Use the highest required bracing length in the table when using different bracing methods in the same braced wall. Refer to the IRC for some restrictions when mixing wall bracing methods.

Wall Bracing General Installation Requirements

1. Install a wall brace near the end of each braced wall.

2. Begin the wall brace not more than () 10 feet from the end of a braced wall.

3. Begin a wall brace not less than () 20 feet from the closest edge of the next wall brace in the braced wall.

4. Do not exceed () 60 feet between braced walls. Smaller distances between braced walls are required in the D series seismic design areas. Refer to IRC Table R602.1.3.

Wall Brace Length

1. Install at least () the minimum length (in feet) of wall braces in a braced wall as specified in Table R602.10-1 and as modified by Table R602.10-2. Example: the minimum wood structural panel wall brace length for a wall with no stories above in the 85 mph wind category is 5 feet per The minimum length for an individual wall brace in a 10 feet tall wall is 48 inches per Table R602.10-2. Two wall braces are required if the wall is not more than () 16 feet long. Two 48 inch individual wall braces are required per Table R602.10-2 even though Table R602.10-1 says only 5 feet of wall bracing is required.

2. You may use one wall brace that is at least () 48 inches long if the braced wall is not more than () 16 feet long. Use at least two wall braces if the braced wall is more than (>) 16 feet long. Install the minimum total wall brace length if the minimum length in Table R602.10-1 is greater than 48 inches. Example: the minimum wood structural panel wall brace length for a wall with no stories above in the 90 mph wind category is 5.5 feet per Table R602.10-1. A 12 feet long wall requires only one wall brace. You may install one 5.5 feet long wall brace or two 48 inch long wall braces to obtain the minimum wall brace length. You may make one of the wall braces a shorter length wall brace as described in #4 below.

3. You may interpolate when actual values fall between values in Table R602.10-1. Example: the actual distance between braced walls is 15 feet. When using wood structural panel sheathing in an 85 mph wind area the minimum wall brace length is (2+3.5)/2=2.75 feet.

4. Make each wall brace at least as long as required in Table R602.10-2. You may use shorter length wall braces as allowed in Table R602.10-3, but shorter length wall braces count toward the total required wall brace length only as described in Table R602.10-3. Example: a 36 inch long wall brace in an 8 feet tall wall counts only 27 inches toward the minimum wall brace length required in Table R602.10-1.

Wall Bracing Length Adjustment Factors

1. You may need to adjust the minimum wall brace length specified in Table R602.10-1 when these factors are not within the indicated ranges: (a) the mean roof height above grade () 30 feet), or (b) the height from the eaves to the roof ridge (() 10 feet), or (c) the height of each wall (() 10 feet), or (d) the seismic design area (A B, and C), or (e) the wind exposure category (B), or (f) not more than() two parallel braced walls connected to one perpendicular braced wall. Refer to the IRC when these factors are not within the indicated ranges.

2. Increase or decrease wall brace length requirements when factors (a)-(f) are not within the indicated ranges. The indicated ranges in factors (a)-(f) will accommodate many homes in most areas of the continental United States. Any increases or decreases in wall brace length are cumulative. Example: the wall brace adjustment increase for a 1 story home in wind exposure category C is 1.20. The wall brace adjustment increase for a 12 feet tall wall is 1.10. A home subject to both of these adjustments would have its wall brace length from Table R602.10-1 increased by 1.20 x 1.10 = 1.32.

3. Use the wall bracing prescriptive requirements in the IRC only when braced walls are straight and are parallel or perpendicular to each other and when braced walls are angled or off set within the specified limits. An engineer must design bracing for other types of walls.

Fastening Wall Braces

1. Fasten wall bracing material to framing according to the fastening schedules in Section R602.3 or according to the brace manufacturer’s instructions.

2. Fasten vertical joints at panel sheathing edges to studs. Fasten horizontal joints to at least () 1 ½ inch thick blocking. Refer to the IRC for some uncommonly used exceptions.

3. Use fasteners and uplift connectors as required to connect rafters and trusses to wall braces and connect the wall braces to framing in stories below as described in Section R602.3.

4. Connect wall braces to wood framing as described in the following illustrations. Connect wall braces to concrete and masonry foundations using bolts or straps as described in Section R403. Refer to the IRC for other options.

5. Install at least () ½ inch drywall as required in Chapter 7 on the interior side of wall braces. You will need to increase the wall brace length by 1.40 if drywall is omitted. Space drywall fasteners not more than () 8 inches on center at panel edges when using let-in wall braces.

Supporting Wall Braces

1. You may use cantilevered floor joists to support wall braces if the cantilevered joists comply with the requirements in Section 502.3.3.

2. Build masonry stem walls that are not more than () 48 inches long and not more than () 48 inches tall according to the following illustration.

3. Build concrete stem walls that are: (a) not more than () 48 inches long, and (b) more than (>) 12 inches tall, and (c) less than (<) 6 inches thick according to the following illustration.

4. Build concrete and masonry stem walls that are not described by 2 and 3 above as foundation walls as specified in Chapter 4. Refer to the IRC for more support options and for more information.

5. Do not attach a type PFH wall brace to a masonry stem wall.

Simple Wall Bracing

1. You may use a less complex wall bracing method for certain homes that are basically rectangles with insets and pop-outs. The home must comply with all of the following to qualify for this less complex method: (a) wind speed area () 90 mph, and (b) wind exposure category is A or B, and (c) dimension of the long side not more than () 60 feet with a long side to short side ratio not more than () 3 to 1, and (d) wall height not more than () 10 feet, and (e) seismic design category A, B, or C for one and two family homes, and (f) not more than () 2 stories above a concrete or masonry foundation or basement wall, and (g) cantilevered floors extend not more than () 24 inches beyond the bearing point, and (h) roof eave to ridge height not more than () 15 feet, and (i) at least () ½ inch drywall installed on the interior side of all exterior walls, and (j) no cripplewalls allowed in 2-story homes.

2. Use either wood structural panels that are at least () inch thick or structural fiberboard sheathing that is at least () ½ inch thick as the wall bracing material. Fasten wood structural panels according to Table R602.3-2. Fasten fiberboard sheathing using at least () 1 ½ inch galvanized roofing nails spaced at 3 inches on center at the edges and at 6 inches on center at intermediate supports. You may not use both wood structural panels and fiberboard sheathing on the same story.

3. Build bracing units as full height walls with no openings and no vertical or horizontal offsets. A bracing unit must be one fully sheathed vertical wall segment.

4. Use bracing units that are at least () 3 feet long when the walls are continuously sheathed with the wall bracing material. Continuously sheathed means all wall areas have structural sheathing applied including above and below openings and at gable wall ends. Use bracing units that are at least () 4 feet long when the walls are not continuously sheathed.

5. Begin a bracing unit not more than () 12 feet from a wall corner. Make the distance between adjacent bracing units in the same wall not more than () 20 feet. Place at least () 1 bracing unit in any wall more than (>) 8 feet long.

6. Determine the length of exterior walls as shown in the following illustration. Do not include open structures such as porches, decks, and carports. Determine the number of bracing units in each exterior wall according to Table R602.12. Interior walls do not count as braced walls.

7. You may count bracing units that are wider than the minimum width as multiple bracing units. Divide the width of the bracing unit by the minimum bracing unit width to determine the number of bracing units. Example: a bracing unit is 7 feet wide. The wall is not continuously sheathed, so the minimum bracing unit width is 4 feet. The 7 feet wide bracing unit counts as 1 ¾ bracing units (7/4 = 1.75).

8. Do not count sheathed wall segments that are narrower than the 3 or 4 foot minimum lengths as bracing units. Refer to the IRC for exceptions involving certain continuous sheathing methods at garage doors and large openings.

9. You may use the PFG and PFH methods as described in later sections. A PFG panel counts as ¾ bracing unit and a PFH counts as 1 bracing unit.

10. Refer to the Supporting Wall Braces section in this book when using masonry and concrete stem walls that are not more than () 48 inches long to support a PFG panel.

Let-in Wall Bracing (LIB)

1. Install let-in wall bracing using a continuous wood 1×4, or an approved metal strap, cut into the studs diagonally from the top to the bottom plate at an angle at least () 45 degrees and not more than () 60 degrees from horizontal.

2. Secure wood 1×4 bracing to each stud using two 8d common nails or three 8d (2 ½ in. x 0.113 in.) nails. Secure metal strap bracing according to the brace manufacturer’s instructions.

3. Space studs in the wall brace at not more than () 16 inches on center.

Wood Structural Panel Wall Bracing (WSP)

1. Install wood structural panel wall bracing using 4×8 or 4×9 panels that are at least () ³inch thick (span rating 24/0). Refer to Table R602.3-2 for different requirements for home located in high wind areas and in the C and D wind exposure areas.

2. Install panels that are at least () 48 inches wide and cover at least () 3 stud bays for studs spaced 16 inches on center. You may install the panels horizontally or vertically.

3. Secure³inch thick wood structural panel bracing to studs using at least () 6d common nails spaced not more than () 6 inches on center at panel edges and 12 inches on center at intermediate supports. Secure ₁₆ inch thick panels (span rating 24/16) using 8d common nails and using the same spacing previously described.

4. Install solid blocking where panel joints occur between studs to maintain fastener spacing. Use at least 1 ½ inches thick wood for blocking. The blocking is usually the same dimensions as the studs. Example: 2×6 blocking is normally used with 2×6 studs, although 2×4 blocking is acceptable.

Hardboard Panel Siding Wall Bracing (HPS)

1. Install hardboard panel siding wall bracing using 4×8 or 4×9 siding panels at least () ₁₆ inch thick and at least () 48 inches wide.

2. Secure hardboard panel siding to studs using nails with at least () 0.092 inch diameter shank and at least () 0.225 inch head. Space nails not more than () 4 inches on center at panel edges and at not more than () 8 inches on center at intermediate supports when hardboard panel siding is used as wall bracing. Nails should penetrate studs at least () 1 ½ inches.

3. Space studs in the wall brace at not more than () 16 inches on center.

Garage Door Header Wall Bracing (PFG)

1. You may use the following method to build a PFG type wall brace for a garage door header that supports a roof or that supports one story and a roof. You may install this PFG type wall brace on one or both sides of the garage door depending on how many feet of bracing are required in the wall. You may use approved engineered designs or commercially available products instead of this method. You may use alternate bracing methods described in the IRC.

2. Build the PFG type wall brace not more than () 10 feet tall. You may increase the total wall height to not more than () 12 feet by adding a pony wall.

4. Install wood structural panel(s) at least () ₁₆ inch thick vertically (long dimension vertical) on one side of the PFG type wall brace. Extend the panel(s) to cover the header any pony wall. Attach the panel(s) to studs, plates, and to the header using at least () 8d common nails or galvanized box nails spaced at 3 inches on center. Install double blocking at panel joints, if any, to maintain nail spacing. Locate any panel joints within 24 inches of the wall brace center.

5. Install at least () a 3×11 ¼ inches glue laminated header or a site-built header made from at least two solid 2x12s. Extend the header to the outer (king) studs of the supporting walls. Make the header clear span at least () 2 feet and not more than () 18 feet. Do not use a steel header.

6. Install a tie-down strap of at least () 1,000 pound uplift capacity on the jack stud nearest to the opening on the PFG type wall brace. Install the strap on the side opposite the sheathing. Secure the strap to the stud, header and to any pony wall according to the strap manufacturer’s instructions. A larger capacity strap is required in many cases. Refer to IRC Table R602.10.6.4.

7. Install a tie-down strap of at least () 1,000 pound uplift capacity on the jack stud on the side of the opening opposite from the PFG type wall brace. Secure the strap to the stud and header according to the strap manufacturer’s instructions. A larger capacity strap is required in many cases. Refer to IRC Table R602.10.6.4.

8. Install at least () two foundation anchor bolts at least () ½ inch diameter in the PFG type wall brace bottom plate. Install the anchor bolts in the foundation according to Section R403. Install a ³₁₆ inch thick by 2 inches square washer between the bottom plate and the nut of each bolt.

9. Install foundation anchor bolts on the side of the opening opposite from the PFG type wall brace. Install the anchor bolts in the foundation according to Section R403.

10. Support the PFG type wall brace on a continuous foundation under the entire wall brace.

11. Secure the top plate of the PFG type wall brace to the header using 2 rows of 16d sinker nails at 3 inches on center.

12. Install the number of jack studs under the header on the side opposite from the PFG type wall brace according to Table R502.5-1.

Large Window and Door Header Wall Bracing (PFH)

1. You may use the following method to build a PFH type wall brace for a large window or door header that supports a roof or that supports one story and a roof. You may install this PFH type wall brace on one or both sides of the header depending on how many feet of bracing are required in the wall. You may use approved engineered designs or commercially available products instead of this method. You may use alternate bracing methods described in the IRC.

2. Build the PFH type wall brace not more than () 10 feet tall. You may increase the total wall height to not more than () 12 feet by adding a pony wall.

3. Build the PFH type wall brace at least () as wide as indicated in Table R602.10-5.

4. Install wood structural panel(s) at least () inch thick vertically (long dimension vertical) on one side of the PFH type wall brace. Extend the panel(s) to cover the header any pony wall. Attach the panel(s) to studs, plates, and to the header using at least () 8d common nails or galvanized box nails spaced at 3 inches on center. Install double blocking at panel joints, if any, to maintain nail spacing. Locate any panel joints within 24 inches of the wall brace center.

5. Install at least () a 3×11 ¼ inches glue laminated header or a site-built header made from at least two solid 2x12s. Extend the header to the outer (king) studs of the supporting walls. Make the header clear span at least () 2 feet and not more than () 18 feet. Do not use a steel header.

6. Install a tie-down strap of at least () 1,000 pound uplift capacity on the jack stud nearest to the opening on the PFH type wall brace. Install the strap on the side opposite the sheathing. Secure the strap to the stud, header and to any pony wall according to the strap manufacturer’s instructions. A larger capacity strap is required in many cases. Refer to IRC Table R602.10.6.4.

7. Install at least () two tie-down straps of at least () 4,200 pound uplift capacity on the studs at the PFH type wall brace. Embed the tie-down straps in the concrete footing and attach the straps to the framing according to the strap manufacturer’s instructions.

8. Install a tie-down strap of at least () 1,000 pound uplift capacity on the jack stud on the side of the opening opposite from the PFH type wall brace. Embed the tie-down strap in the concrete footing and attach the strap to the framing according to the strap manufacturer’s instructions.

9. Install at least () one foundation anchor bolt that is at least () inch diameter in the PFH type wall brace bottom plate. Install the anchor bolt in the foundation according to Section R403. Install a ³₁₆ inch thick by 2 inches square washer between the bottom plate and the nut of each bolt.

10. Support the PFH type wall brace directly on a continuous foundation, which is at least () 12 inches by 12 inches, under the entire wall brace. Install at least () one #4 reinforcing bar near the bottom and one near the top of the foundation. Lap bars at least () 15 inches.

11. Install the number of jack studs under the header on the side opposite from the PFH type wall brace according to Table R502.5-1.

Wall Bracing Discussion

Wall bracing helps the building resist movement during stress events such as high winds and seismic activity. This movement is called racking. During high wind events, roof framing and upper floors will be moved by the wind while the lower floors will remain more stable. During seismic events the lower floors will be moved while the upper floors will remain more stable. Without adequately braced walls that are secured to the foundation, this differential movement can tear a building apart.