Blocking Between Roof Rafters

In my experience traveling across the country observing wood framed construction it was apparent that east of the rocky mountains structural wood members in line with supporting walls between roof framing cease to be installed.

Blocking between roof rafters.

Some may call these wood members blocking and deem them as optional. Blocking or boundary member. Inches 387 mm or less blocking between rafters or roof trusses shall be provided above the braced wall panel in accordance with figure r602 10 8 2 1. Each block is 2x4 or 2x6 depending on the size of the rafters and is secured to the top plate.

Preventing rotation is typically accomplished by installing full depth blocking along wall plates between rafters and ceiling joists. Rotation loads on rafters occur when the roof sheathing is resisting lateral loads perpendicular to the rafter because these loads are actually trying to move the top edge of the rafter sideways. Where the distance from the top of the braced wall panel to the top of rafters or roof trusses exceeds 151 4 inches 387 mm the top plates. Rafter blocking is an essential part of the roof framing process in that the blocks provide a stop for ceiling insulation and a continuous surface for the roof sheathing to be edge nailed to.

This load path is shown in figure 6 4. The blocking panels will provide additional connections between the roof trusses and the top plate of the wall. That blocking is then nailed to the wall top plate with three 8d nails per rafter space as prescribed in irc table 602 3 1. A truss to top plate connection consisting of three 16d box 3 long x 0 135 diameter nails is allowed to resist up to 200 pounds of uplift force per irc section.