Flat Roof Rafter Span

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 span.

Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. Input the rafter span on the flat eave overhang and pitch of the roof. The above spans are based on american softwood lumber standard sizes. 2 are indicated below.

1 ft 0 3048 m. Use these two tables for roof rafters with a slope greater than 3 in 12. 1 psf lb f ft 2 47 88 n m 2. For light load roofs 24 o c.

The lengths and sizes of joists vary depending on the species and quality of the lumber used. Also available for the android os. 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. Dead load weight of structure and fixed loads 15 lbs ft 2.

Span calculator for wood joists and rafters also available for the android os. The imposed uniformly distributed live load in the main span. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. 2 4 rafters can span up to 7.

Live load 20 lbs ft 2 956 n m 2. Wood beam calculator american wood council website rafter and joist span faq. For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine. 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.

Click the button to calculate the stock size needed for this job. The 1 grade. Live load overhang kpa. Live load is weight of furniture wind snow and more.

1 in 25 4 mm. The rafters in a flat roof serve as ceiling joists for the space below. Rafter stock size calculator. Input the rafter span on the flat eave overhang and pitch of the roof.

Click the button to calculate the stock size needed for this job. This is set by the roof use you selected in the previous screen and cannot be modified. For heavy loads 2x4s can span up to 5. Loads are calculated in accordance with table 3 1 of as nzs 1170 1 2002.

The tables below give maximum spans for rafters and beams. This calculator is to be used as an estimating tool only. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements.