Roof Joist Spacing

Use these two tables for roof rafters with a slope of 3 in 12 or less.

Roof joist spacing.

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. 2 are indicated below. Span calculator for wood joists and rafters also available for the. Live load psf dead load psf span calculator for wood joists and rafters available for the iphone.

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

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. Joist span and spacing is set by your local building code. The same concept holds true for roof trusses. In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart.

1 ft 0 3048 m. Dead load weight of structure and fixed loads 15 lbs ft 2. The above spans are based on american softwood lumber standard sizes. Spacing in exterior exposure.

Use these two tables for roof rafters with a slope greater than 3 in 12. You should check with your local building department for construction requirements in your area. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. 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.

Ceiling joist spacing in inches 12 16 19 2 24 species and grade of lumber. Maximum rafter spans for a patio roof. 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. So the space between rafters can be greater without reducing the maximum span.

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.