Residential Roof Framing Spans

The rafter spans in this guide are based on the horizontal.

Residential roof framing spans. Let s consider a basic gable wood roof framing design. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Rather the span is based on the rafter s horizontal projection. For roof live loads less than 20 pounds per square foot psf rafter spans and required e values tabulated for 20 psf shall be permitted to be adjusted in accordance with the fol lowing table.

The international codes i codes are the widely accepted comprehensive set of model codes used in the us and abroad to help ensure the engineering of safe sustainable affordable and resilient structures. Rafter spans can be extended slightly beyond what the rafter tables suggest when there is a cantelever extending beyond the supporting wall. Ceiling joists 15 hanging beams member16 underpurlins 17 strutting beams 18 roof beams 20 verandah beams 22 garage roof. Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size.

This is known as prescriptive framing. Span calculator for wood joists and rafters also available for the android os. Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. The provisions for prescriptive roof construction are found in chapter 8 of the irc and in section 2308 of the ibc.

The loads are based on adjusted roof snow loads from the governing building code. Pitching beams 23 common installation details 25 notches cuts and. The international code council icc is a non profit organization dedicated to developing model codes and standards used in the design build and compliance process. Contents general 2 terminologybe used for specification where alternate 3.

The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. Rafter spans are tabulated for the most common roof loads. Span guide for. Fully supported by.

So consider a simple gable roof on a 24 foot wide ranch framed with 2 6 exterior walls and a 1 1 2 ridge. Prescriptive roof construction the international residential code irc and the international. This is the horizontal distance from the inside surface of the supporting wall to the inside surface of the ridge board. Continuing on from part 3.

Here we have a wood framed gable roof.