Roof Joist Spacing

Spacing in exterior exposure.

Roof joist spacing.

Span calculator for wood joists and rafters also available for the. Joist spacing of 24 inches is allowed for spans between 16 to 20 feet using 2 inch by 10 inch lumber of these three grades. Dead load weight of structure and fixed loads 15 lbs ft 2. You should check with your local building department for construction requirements in your area.

Maximum rafter spans for a patio roof. If the roof is not completely square you can decrease the space between joists but never increase the space. Use these two tables for roof rafters with a slope of 3 in 12 or less. 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.

For example the highlighted cell below shows that a 2 x 6 southern yellow pine joist with a grade of 2 and spaced 24 apart can have a maximum span of 10 feet 0 inches 10 0 if you are designing your structure to support a plaster ceiling. Variations in ceiling construction nonparallel ceiling joist designs require additional support construction in the ceiling. So the space between rafters can be greater without reducing the maximum span. Various lumber size options 2 4 2 6 2 8 2 10 the maximum ceiling joist span based on the lumber size species grade and spacing used.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. The same concept holds true for roof trusses. 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. Joist span and spacing is set by your local building code.

A roof joist is always spaced no more than 16 inches apart from another roof joist. For additional species of lumber check out the rafter span calculator from the american wood council website. 1 ft 0 3048 m. 1 psf lb f ft 2 47 88 n m 2.

The above spans are based on american softwood lumber standard sizes. In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart. While most residential construction uses 2x8 joists with 16 inch spacing there are many other factors you need to consider when determining the proper joist span length. Ceiling joist spacing in inches 12 16 19 2 24 species and grade of lumber.

2 are indicated below.