Flat Roof Framing Spans

Span calculator for wood joists and rafters also available for the android os.

Flat roof framing spans.

For heavy loads 2x4s can span up to 5. Also available for the android os. 1 ft 0 3048 m. Let s consider a basic gable wood roof framing design.

Flat roofs are always built at a slight incline at least 1 8 inch per foot. The loads are based on adjusted roof snow loads from the governing building code. 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. Here we have a wood framed gable roof.

Live load is weight of furniture wind snow and more. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. Continuing on from part 3. You can do this with a foam layer that exactly fits your roof.

For light load roofs 24 o c. Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center. Rafter spans are tabulated for the most common roof loads. Spacing your 2 4 shed rafters at 24 on center limits the width of your roof.

For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. For roof live loads less than 20 pounds per square foot psf rafter spans and required e values tabulated for 20 psf shall be permitted to be adjusted in accordance with the fol lowing table. Surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings. When framing a flat roof you will need to create a slight incline.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Surveyors span tables for designing roof rafters. For pitched roofs flat roofs and ceiling joists. 2 4 rafters can span up to 7.

Some roofs actually slope in several directions ensuring optimal water runoff. 2 are indicated below. 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. 1 psf lb f ft 2 47 88 n m 2.

Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. The 1 grade material is more expensive than the 2 grade but if you can use fewer or smaller 1 grade joists or rafters in your design you may actually save money.