Flat Roof Framing Spans

The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.

Flat roof framing spans.

Flat roofs are always built at a slight incline at least 1 8 inch per foot. 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. Here we have a wood framed gable roof. Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

For pitched roofs flat roofs and ceiling joists. 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. 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. Live load is weight of furniture wind snow and more.

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. Let s consider a basic gable wood roof framing design. Surveyors span tables for designing roof rafters. Span calculator for wood joists and rafters also available for the android os.

Floor beam span tables of residential structural design we will now look at roof rafter and beam design. 2 4 rafters can span up to 7. When framing a flat roof you will need to create a slight incline. 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.

For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. Continuing on from part 3. For heavy loads 2x4s can span up to 5. 2 are indicated below.

Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. 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. This will help you create a flat roof framing plan.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. For light load roofs 24 o c. 1 ft 0 3048 m. Dead load weight of structure and fixed loads 15 lbs ft 2.

Also available for the android os. 1 psf lb f ft 2 47 88 n m 2. You can do this with a foam layer that exactly fits your roof.