R602.12 Practical Wall Bracing
All buildings in Seismic Design Categories A and B and detached buildings in Seismic Design Category C shall be permitted to be braced in accordance with this section as an alternative to the requirements of Section R602.10. Where a building, or portion thereof, does not comply with one or more of the bracing requirements in this section, those portions shall be designed and constructed in accordance with Section R301.1. The use of other bracing provisions of Section R602.10, except as specified herein, shall not be permitted.
The building official shall be permitted to require the permit applicant to identify bracing on the construction documents and provide associated analysis. The building official shall be permitted to waive the analysis of the upper floors where the cumulative length of wall openings of each upper floor wall is less than or equal to the length of the openings of the wall directly below.
The following materials shall be permitted for use as sheathing for wall bracing. Exterior walls shall be sheathed on all sheathable surfaces, including infill areas between bracing locations, above and below wall openings, and on gable end walls.
- Wood structural panels with a minimum thickness of 7/16 inch (9.5 mm) fastened in accordance with Table R602.3(3).
- Structural fiberboard sheathing with a minimum thickness of 1/2 inch (12.7 mm) fastened in accordance with Table R602.3(1).
- Gypsum board with a minimum thickness of 1/2 inch (12.7 mm) fastened in accordance with Table R702.3.5 on interior walls only.
- Exterior braced wall panels shall have a minimum length based on the height of the adjacent opening as specified in Table R602.12.2. Panels with openings on both sides of differing heights shall be governed by the taller opening when determining panel length.
- Interior braced wall panels shall have a minimum length of 48 inches (1220 mm) when sheathing material is applied to one side. Doubled-sided applications shall be permitted to be considered two braced wall panels.
- Braced wall panels shall be permitted to be constructed of Methods ABW, PFH, PFG, and CS-PF in accordance with Section R602.10.4.
- Exterior braced wall panels, other than the methods listed in Item 3 above shall have a finish material installed on the interior. The finish material shall consist of 1/2 inch (12.7 mm) gypsum board or equivalent and shall be permitted to be omitted where the required length of bracing, as determined in Section R602.12.4, is multiplied by 1.40, unless otherwise required by Section R302.6.
- Vertical sheathing joints shall occur over and be fastened to common studs.
- Horizontal sheathing joints shall be edge nailed to 11/2 inch (38 mm) minimum thick common blocking.
BRACED WALL PANEL LENGTHS
|LOCATION||MINIMUM PANEL LENGTH (inches)|
|Wall Height (feet)|
|Adjacent garage door of one-story garagea||24||27||30||33||36|
|Adjacent all other openingsb||Clear opening height (inches)|
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
- Braced wall panels supporting a gable end wall or roof load only.
- Interpolation shall be permitted.
Required length of bracing shall be determined by circumscribing one or more rectangles around the entire building or portions thereof as shown in Figure R602.12.3. Rectangles shall surround all enclosed offsets and projections such as sunrooms and attached garages. Chimneys, partial height projections, and open structures, such as carports and decks, shall be excluded from the rectangle. Each rectangle shall have no side greater than 80 feet (24 384 mm) with a maximum 3:1 ratio between the long and short side. Rectangles shall be permitted to be skewed to accommodate angled projections as shown in Figure R602.12.4.3.
The required length of bracing for each side of a circumscribed rectangle shall be determined using Table R602.12.4. Where multiple rectangles share a common side or sides, the required length of bracing shall equal the sum of the required lengths from all shared rectangle sides.
REQUIRED LENGTH OF BRACING ALONG EACH SIDE OF A CIRCUMSCRIBED RECTANGLEa,b,c
|REQUIRED LENGTH OF BRACING ON FRONT/REAR SIDE|
|REQUIRED LENGTH OF BRACING ON LEFT/RIGHT SIDE |
|Length of Left/Right Side (feet)||Length of Front/Rear Side (feet)|
For SI: 1 ft = 304.8 mm.
- Interpolation shall be permitted; extrapolation shall be prohibited.
- For Exposure Category C, multiply the required length of bracing by a factor of 1.20 for a one-story building, 1.30 for a two-story building and 1.40 for a three-story building.
- For wall height adjustments multiply the required length of bracing by the following factors: 0.90 for 8 feet (2438 mm), 0.95 for 9 feet (2743 mm), 1.0 for 10 feet (3048 mm), 1.05 for 11 feet (3353 mm), and 1.10 for 12 feet (3658 mm).
- Where braced wall panels supporting stories above have been sheathed in wood structural panels with edge fasteners spaced at 4 inches (102 mm) on center, multiply the required length of bracing by 0.83.
- A floor level, habitable or otherwise, contained wholly within the roof rafters or trusses shall not be considered a floor level for purposes of determining the required length of bracing.
- A rectangle side with differing number of floor levels above shall use the greatest number when determining the required length of bracing.
- Exterior braced wall panels shall be assigned to the parallel rectangle side on which they are located or in which they face.
- Interior braced wall panels shall be assigned to the parallel rectangle side on which they are located or in which they face up to 4 feet (1220 mm) away. Interior braced wall panels more than 4 feet (1220 mm) away from a parallel rectangle side shall not contribute.
- The projections of angled braced wall panels shall be assigned to the adjacent rectangle sides.
The cumulative contributing length of braced wall panels assigned to a rectangle side shall be greater than or equal to the required length of bracing as determined in Section R602.12.4. The contributing length of a braced wall panel shall be as specified below. When applying contributing length to angled braced wall panels, apply the requirements below to each projection.
- The edge of a braced wall panel shall be no more than 12 feet (3658 mm) from any building corner or rectangle corner.
- The distance between adjacent edges of braced wall panels shall be no more than 20 feet (6096 mm).
- Segments of exterior walls greater than 8 feet (2438 mm) in length shall have a minimum of one braced wall panel.
- Segments of exterior wall 8 feet (2438 mm) or less in length shall be permitted to have no braced wall panels.