Flat Roof Framing Spans

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.

Flat roof framing spans.

1 psf lb f ft 2 47 88 n m 2. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. 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. Flat roofs are always built at a slight incline at least 1 8 inch per foot.

Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. 2 4 rafters can span up to 7. This will help you create a flat roof framing plan.

Dead load weight of structure and fixed loads 15 lbs ft 2. 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. 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. Rafter spans are tabulated for the most common roof loads.

Here we have a wood framed gable roof. 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. 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. The loads are based on adjusted roof snow loads from the governing building code.

1 ft 0 3048 m. 2 are indicated below. For pitched roofs flat roofs and ceiling joists. Also available for the android os.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Let s consider a basic gable wood roof framing design. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. Continuing on from part 3.

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 light load roofs 24 o c. Live load is weight of furniture wind snow and more.

Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. Some roofs actually slope in several directions ensuring optimal water runoff. Surveyors span tables for designing roof rafters.