Minimum Roof Rafter Size

This sizing guide for roof rafters will help determine what you need for your small project.

Minimum roof rafter size. Supporting low slope roof rafters cmhc advice. Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch. Rafter tied to joist every 1 2 m. Nominal ridge beam supported at 1 2 m 4 ft intervals by 38 89 mm 2 4 in.

Nominal vertical struts see figure 84. Rafters must be strong enough to hold the roof sheathing and the shingles. For rafters spaced 20 or more inches apart 1 2 or 5 8 inch plywood is recommended. For more information see our disclosures here.

A roof that slopes less than 1 3 should be vertically supported at the peak. If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16. Roof snow load kpa. Rafter tied to every joist.

Building width up to 9 8 m. Roof snow load kpa. Building width up to 8 0 m. Roof snow load kpa.

While this clearly establishes the horizontal seat cut s minimum length its maximum length varies according to the size of the rafter and the pitch of the roof. Typical rafter spacing codes will specify a minimum spacing of 16 inches 19 2 inches or 24 inches. Roof snow load kpa. 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.

There are several variables to consider when determining the proper rafter size. This can be accomplished by providing a 38 140 mm 2 6 in. If your local building authority has a rafter spacing code you may not space rafters wider than required by code. Minimum number of nails not less than 75 mm long.

Patio roof maximum beam rafter spans. The most common rafter spacing is 24 inches and 5 8 inch plywood is recommended for that. Building width up to 8 0 m. Homepage metal roof metal roof purlins spacing and rafter distance details by rooflast posted on june 29 2020 june 29 2020 during the roof installation or re roofing process after the roof sheets are prepared it is time to support their framework by installing purlins.

For example the irc allows the ends of rafters to be notched as much as one fourth their depth r802 7 1 but on a shallow pitched roof this can result in a seat cut that s wider. Building width up to 9 8 m.