1707.3.3 Blocking Attachment to Lateral Braces
Where ceiling joists or truss bottom chords are deeper than 6 inches (152 mm), an anchor block shall be installed in each space between ceiling members along the length of the lateral brace except for the space next to the gable end wall.
Anchor blocks shall be fastened to lateral braces with a single row of 8d common nail, 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 fastener 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 three per anchor block made of nominal 2-inch thick lumber. For nominal 2-inch thick lumber anchor blocks, the number of fasteners need not exceed three fasteners per anchor block.