Flat Roof Rafter Spacing

Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center.

Flat roof rafter spacing.

Use these two tables for roof rafters with a slope greater than 3 in 12. Rafter spacing is based on the width of the metal roofing panels. Builders aren t bound by standard rafter spacing measurements. Span calculator for wood joists and rafters also available for the.

Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. Spacing in exterior exposure. 2 are indicated below. Boarding to be fastened on top of flat roof joists with a depth to width ratio greater than 4 the allowable clear spans have been calculated in accordance with bs 5268 2 2002 structural use of timber part 2.

Dead load weight of structure and fixed loads 15 lbs ft 2. 1 psf lb f ft 2 47 88 n m 2. Code of practice for permissible stress design materials and workmanship and bs 5268 7 2 1989 structural use of timber section 7 2. Live load psf dead load psf span calculator for wood joists and rafters available for the iphone.

2 4 rafters can span up to 7. Wider panels allow for greater spacing between rafters. 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. 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.

Rafter span tables use these two tables for roof rafters with a slope of 3 in 12 or less. But they do tend to space rafters in one of several industry standard increments typically either 12 16 or 24 inches apart. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. For heavy loads 2x4s can span up to 5.

1 ft 0 3048 m. 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. The rafters in a flat roof serve as ceiling joists for the space below. It is always better to have a large rafter rather than be concerned with a sagging roof.

A metal roof must also allow for some overlap on each side of the panels which will reduce the effective width of the panel. The above spans are based on american softwood lumber standard sizes. They are nailed securely to exterior wall plates and to each other.