Blocking Between Roof Trusses

Where required by this section blocking between rafters or roof trusses shall be attached to top plates of braced wall panels and to rafters and roof trusses in accordance with table r602 3 1.

Blocking between roof trusses. A new provision in the 2009 irc and carried through to more recent versions is the use of blocking panels between roof trusses to connect the trusses to the braced wall panels below if the heel height is greater than 9 for trusses with heel heights less than 15 this blocking can be made of solid sawn dimensional lumber as shown in figure 1a. And often in a humid environment. Some may call these wood members blocking and deem them as optional. Roof trusses shall be supported laterally at points of bearing by solid blocking to prevent rotation and lateral displacement.

Truss heel blocking can function as perimeter blocking of the roof diaphragm however the adequacy of this connection depends on multiple factors the building designer may not assume that prescriptive heel blocking will perform adequately as perimeter blocking for the roof diaphragm. A continuous band rim or header joist or roof truss parallel to the braced wall panels shall be permitted to replace the blocking required by this. 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 or boundary member.

For low pitch roofs building codes may require larger dimension rafters. For instance if your roof has a steep pitch you may be able to use 2 inch by 4 inch rafters but if your roof has a low pitch building code may require that you used 2 inch by 6 inch or 2 inch by 8. Roof rafters and ceiling joists shall be supported laterally to prevent rotations and lateral displacement when required by section 2306 7. Preventing rotation is typically accomplished by installing full depth solid blocking along wall top plates between rafters and ceiling joists.

As roof pitch is lowered the weight burden on the rafters increases.