Flat Roof Framing Spans

The loads are based on adjusted roof snow loads from the governing building code.

Flat roof framing spans.

2 4 rafters can span up to 7. 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. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. 1 ft 0 3048 m.

You can do this with a foam layer that exactly fits your roof. Span calculator for wood joists and rafters also available for the android os. Some roofs actually slope in several directions ensuring optimal water runoff. For light load roofs 24 o c.

When framing a flat roof you will need to create a slight incline. 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. Let s consider a basic gable wood roof framing design.

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. Dead load weight of structure and fixed loads 15 lbs ft 2. Also available for the android os. Live load is weight of furniture wind snow and more.

This will help you create a flat roof framing plan. 2 are indicated below. For pitched roofs flat roofs and ceiling joists. 1 psf lb f ft 2 47 88 n m 2.

Rafter spans are tabulated for the most common roof loads. Flat roofs are always built at a slight incline at least 1 8 inch per foot. 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. 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.

Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center. 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. Continuing on from part 3. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.

Spacing your 2 4 shed rafters at 24 on center limits the width of your roof. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. Surveyors span tables for designing roof rafters.