Lumber Roof Size

Dimensional lumber and modern building.

Lumber roof size.

Most interior beams need to include the roof load. 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. 1 ft 0 3048 m. Last updated july 15 2018.

The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. This tells you the size of the beam needed to support the porch s roof. If there is are any questions about anything else then you should contact your supplier or an engineer. It has been my experience to never use a beam smaller than a two ply 2 x 8.

This calculator matches up with 90 of the applications in the 2012 international residential code book. For a porch roof the beam needs to be. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter.

Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no. The dead load is constant and is estimated as 10 pounds per square foot for wood framed construction. 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. Live load is weight of furniture wind snow and more.

Pitched roof timber sizes. This sizing guide for roof rafters will help determine what you need for your small project. This means the example porch would need a 6 inch by 8 inch beam. There are several variables to consider when determining the proper rafter size.

2 are indicated below. Dead load weight of structure and fixed loads 15 lbs ft 2. 1 psf lb f ft 2 47 88 n m 2.