1707.4 Alternative Installation
Where existing conditions prevent installation of lateral braces in accordance with Section 1707.2, lateral braces shall be permitted to be omitted for Retrofit Configurations A and B, as defined in Table 1704.1, provided all of the following conditions are met. This method is not allowed for Retrofit Configurations C or D.
- Lateral braces on each side of omitted lateral braces shall be 2 × 4 lumber placed approximately perpendicular to the attic-framing members and installed with their wide faces across attic-framing members. They shall be attached to a minimum of four (4) attic-framing members with attachment to the attic-framing member farthest from the gable end wall a minimum of 8 feet (2438 mm) from the exterior sheathing or siding on the gable end wall.
- The lateral brace on each side of an omitted lateral brace shall be fastened to each attic-framing member that they cross using three (3) 3-inch long fasteners. Fasteners shall be spaced a minimum of 1/2 inch (13 mm) from the edges of the lateral braces, a minimum of 23/4 inches (70 mm) from ends of lateral braces, and a minimum of 1 inch (25.4 mm) from adjacent fasteners.
- A retrofit stud shall be installed in accordance with Section 1706.4 at the location of the omitted lateral brace. This retrofit stud and both of the retrofit studs on either side of the omitted lateral brace shall be sized in accordance with Table 1704.1 for the largest of the retrofit studs required at any of the three locations.
- All three retrofit studs shall have their attic interior edges aligned such that they snuggly butt the strong back to be installed between the two lateral braces on either side of the omitted lateral brace.
- Retrofit studs adjacent to the omitted lateral brace shall be fastened to their corresponding lateral brace using straps in accordance with the L-bent strap method of Section 1708.1.1 except that a compression block is not required. The U-bent strap method of Section 1708.1.2 is not allowed unless U-bent straps are routed around the exterior face of primary studs.
- A strong back of minimum 2 × 6 lumber shall be installed parallel to the gable end and shall be located on and span between the lateral braces on the two sides of the omitted lateral brace. The strong back shall extend a minimum of 23/4 inches (70 mm) beyond the outer edges of the lateral braces and be snuggly butted against each of the three retrofit studs. The strong back shall be attached to each of the lateral braces on which it rests with four (4) 3- inch fasteners. The fasteners shall be placed a minimum 1/2 inch (13 mm) from all edges, a minimum of 2-inch (51 mm) spacing between fasteners, and a minimum of 23/4 inches (70 mm) from ends of the lumber members.
- The retrofit stud at the location of the omitted lateral braces shall be fastened to the strong back using a connector with minimum uplift capacity of 800 pounds (363 kg) as specified by the manufacturer for use with spruce-pine-fir or hem-fir lumber and installed such that this capacity is oriented in the direction perpendicular to the gable end wall.
- Lateral braces at ends of strong backs shall be permitted to be interrupted in accordance with Section 1707.4.2; but shall not be permitted to be shortened using the alternative method of Section 1707.4.3.
OMITTED LATERAL BRACE
Where existing conditions prevent the installation of lateral braces of required length in accordance with Section 1707.1, a splice member shall be permitted to be installed to bridge interruptions. Splice members shall be at minimum the same size lumber as the lateral braces they bridge. Although Figure 1707.4.2 illustrates the general methods that can be used where attic-framing members are spaced 24-inches (610 mm) o.c., the methods apply to other on center spacings. Splice members may extend beyond those shown and are allowed to be fastened to the main lateral brace segments farther than shown. Splice members shall be fastened at each end using the number of fasteners equal to the total number that would be required to be placed in total in that part of lateral braces more distant from the gable end wall. For a lateral brace that requires three fasteners at each roof framing members and installation across three roof framing members, the number of fasteners in the splice need not be more than nine fasteners if the interruption is between the gable end wall and the first attic-framing member; six fasteners if between the first and second framing members, and three fasteners if between subsequent interruptions. Fasteners shall be spaced 1/2 inch (13 mm) from the edges of lateral braces, 1 inch from each other, 1/2 inch (13 mm) from the edge of attic members, and minimum 23/4 inches (25.4 mm) from the ends of lateral braces and from the ends of splice members.
INTERRUPTED LATERAL BRACES
Where conditions exist that prevent installation of lateral braces in accordance with Section 1707.4.1 or 1707.4.2, lateral braces shall be permitted to be shortened, except where the brace is adjacent to an omitted lateral brace of Section 1707.4.1, provided all of the following conditions are met.
- The short lateral brace shall be installed across a minimum of two attic-framing members, be attached to an attic-framing member a minimum of 4 feet (1219 mm) from the gable end wall. Where lateral braces are 2 × 4 they shall be fastened to each attic-framing member over which they cross with three (3) 3-inch fasteners. Where lateral braces are 2 × 6 or wider they shall be fastened to each attic-framing member over which they cross with four (4) 3-inch fasteners.
- An anchor block shall be installed in each space between attic-framing members along the length of the lateral brace except for the space next to the gable end wall.
- Anchor blocks shall be minimum 15/32-inch plywood, 7/16-inch OSB, or nominal 2-inch thick lumber #2 spruce-pine-fir or better.
- Anchor blocks shall have minimum wide face dimension equal to the attic-framing members at the location where the anchor block is installed. Anchor blocks shall extend between attic-framing members and butt against them or their truss plates with a maximum gap of 1/8 inch (3 mm).
- Anchor blocks shall be installed on lateral braces with their wide face on the narrow face of lateral braces. Anchor blocks shall be placed on lateral braces with their attic interior edge flash with the attic interior face of lateral braces. They are permitted to be placed on different edges of lateral braces.
- Anchor blocks shall be fastened to lateral braces with a single row of 8d common nails, 10d common nails or #9 screws with minimum penetration into lateral braces equal to the thickness of the anchor block or 1 inch (25.4 mm) whichever is greater. The minimum number of fasteners shall be the maximum that can be placed in a single row with minimum 23/4 inches (70 mm) distance between fasteners and 23/4 inches (70 mm) distance to ends of anchor blocks except that the number of fasteners need not exceed seven per anchor block. For nominal 2-inch thick lumber anchor blocks, the number of fasteners need not exceed three fasteners per anchor block.