Lumber Roof Size

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.

Lumber roof size.

Pitched roof timber sizes. Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter. It has been my experience to never use a beam smaller than a two ply 2 x 8. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt.

This calculator matches up with 90 of the applications in the 2012 international residential code book. Dimensional lumber and modern building. 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. Last updated july 15 2018.

In the example d calculates to 7 75. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. The term dimensional lumber came into popular use around the beginning of the 20th century to distinguish lumber cut to pre determined sizes from other types of wood such as corded wood for fireplaces during this period the building industry sought to control costs and minimize waste by developing standard sizes and grades for building timber.

There are several variables to consider when determining the proper rafter size. 1 psf lb f ft 2 47 88 n m 2. Before lumber companies began selling osb the standard choice for sheathing a roof with a 24 inch rafter spacing was 1 2 inch cdx plywood the letters cdx indicate that it is construction grade. If there is are any questions about anything else then you should contact your supplier or an engineer.

Live load is weight of furniture wind snow and more. This means the example porch would need a 6 inch by 8 inch beam. This sizing guide for roof rafters will help determine what you need for your small project. 2 are indicated below.

This tells you the size of the beam needed to support the porch s roof. 1 ft 0 3048 m. For a porch roof the beam needs to be.