R802.9

Section R802.9 is titled 'Framing of openings' and covers the requirements for framing openings in roof and ceiling framing. The method for framing based on the size of the opening and distance from the bearing point, and attachment methods where members exceed a minimum span is established. The purpose of this section is to prevent structural failure. The code language regarding 'sufficient cross section' implies that shorter depth members, relative to the roof or ceiling framing, could be used for the opening framing, but this is rarely if ever done.

The model shows 2 framed ceiling openings. The 1st shows an opening with a header joist span less than 4', which is being supported by a single trimmer, which is allowed because each header is less than 3' from the trimmer's bearing point. The 2nd shows an opening with a header joist span greater than 4', which requires the headers and trimmers to be doubled. The model does not show headers exceeding 6', which would require they be attached to the trimmers with hangers, nor does it show tail joists exceeding 12', which would require framing anchors or a ledger strip at the connection to the header.