R802.8

Section R802.8 is titled 'Lateral support' and covers the requirements for providing structural bracing for wood roof-ceiling framing members. The minimum size roof-ceiling framing member which requires lateral support, and clarification for how to apply this section to adjacent rafters and ceiling joists is established. The purpose of this section is to prevent structural failure, water intrusion, and gaps in the thermal envelope.

The model shows a partial roof section with rafters which are provided with lateral support blocking, and a separate section with a rafter that is not laterally supported. Notice the unsupported rafter slowly twisting.