Flat Roof Rafter Spacing

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.

Flat roof rafter spacing.

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 your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. 1 ft 0 3048 m. Live load is weight of furniture wind snow and more.

2 are indicated below. 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. 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.

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. Dead load weight of structure and fixed loads 15 lbs ft 2. The size of rafters for a flat roof depends on the horizontal span of the building the type and grade of timber used and the load on the roof. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.

The rafters in a flat roof serve as ceiling joists for the space below. They are nailed securely to exterior wall plates and to each other.