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.
1. 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.
2. 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.
3. 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.
4. 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).
5. 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.
6. 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.