Flat Roof Rafter Spacing

Dead load weight of structure and fixed loads 15 lbs ft 2.

Flat roof rafter spacing.

The rafters in a flat roof serve as ceiling joists for the space below. Common spacing for trusses on this type of building is often between 2 and 4 feet but trusses built with advanced designs may allow spacing as great as 8 or 12 feet. 1 ft 0 3048 m. The same concept holds true for roof trusses.

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. 2 are indicated below. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. They are nailed securely to exterior wall plates and to each other.

Live load is weight of furniture wind snow and more. 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. 1 psf lb f ft 2 47 88 n m 2. An essential part of planning a patio roof or gazebo project is determining the number size and spacing of rafters beams and posts according to the loads they will carry.

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. 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.