Roof Rafter Size Requirements

Here appear the numbers 12 7 1o which is the rafter length required and which represents 12 feet 7 inches and 10 12 of an inch.

Roof rafter size requirements.

Input the rafter span on the flat eave overhang and pitch of the roof. Be sure to use rafter clips on every rafter not nailed into a ceiling joist. Dead load weight of structure and fixed loads 15 lbs ft2. The rafter length is 16 11 6 or 16 feet 11 6 12 inches.

Live load is weight of furniture wind snow and more. 12 feet 7 10 12 inches. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. Live load 20 lbs ft2 956 n m2 maximum span ft in nominal size.

They are written as follows. In some regions however local. Building code for roof rafters. 1 psf lbf ft2 47 88 n m2.

Click the button to calculate the stock size needed for this job. A roof with a 1 2 pitch or a rise of 1 2 the width of the building and a run of 12 feet. 1 ft 0 3048 m. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.

For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2. Maximum rafter spans for a patio roof in areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot. If you re building rafters and aren t sure where to start when determining the length of your lumber you re in the right place our rafter stock size calculator shows you how long your rafters should be so you ll know what you need in terms of framing lumber dimensional lumber studs and more. The tables below give maximum spans for rafters and beams.

Rafter span table and 2012 irc requirements these rafter spans are for 2 lumber a ground snow load of 30 psf the ceiling not attached to rafters and a dead load of 10 psf. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. Just enter the dimensions of the roof rise and run to get started.

All other data can be found in the 2012 international residential code rafter spans. This calculator is to be used as an estimating tool only.