Flat Roof Framing Spans

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

Flat roof framing spans.

You can do this with a foam layer that exactly fits your roof. Flat roofs are always built at a slight incline at least 1 8 inch per foot. 1 ft 0 3048 m. Spacing your 2 4 shed rafters at 24 on center limits the width of your roof.

For pitched roofs flat roofs and ceiling joists. For heavy loads 2x4s can span up to 5. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. 1 psf lb f ft 2 47 88 n m 2.

Most roof framing is 24 on center and you can still build sheds up to 14 with 2 4 rafters at 24 on center. When framing a flat roof you will need to create a slight incline. 2 4 rafters can span up to 7. 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.

Surveyors span tables for designing roof rafters. Let s consider a basic gable wood roof framing design. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial. 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. 2 are indicated below. 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. Some roofs actually slope in several directions ensuring optimal water runoff.

The loads are based on adjusted roof snow loads from the governing building code. Dead load weight of structure and fixed loads 15 lbs ft 2. For light load roofs 24 o c. 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.

This will help you create a flat roof framing plan. Also available for the android os. Floor beam span tables of residential structural design we will now look at roof rafter and beam design. 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.

Rafter spans are tabulated for the most common roof loads. 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. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.