Lumber Roof Size

Dimensional lumber and modern building.

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. This tells you the size of the beam needed to support the porch s roof. 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. Live load is weight of furniture wind snow and more.

Last updated july 15 2018. There are several variables to consider when determining the proper rafter size. 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. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt.

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. This calculator matches up with 90 of the applications in the 2012 international residential code book. This sizing guide for roof rafters will help determine what you need for your small project. In the example d calculates to 7 75.

2 are indicated below. For a porch roof the beam needs to be. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Douglas fir maximum horizontal roof rafter span for lumber grade selected structural and no.

1 psf lb f ft 2 47 88 n m 2. Most interior beams need to include the roof load. Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter. Pitched roof timber sizes.

1 ft 0 3048 m. This means the example porch would need a 6 inch by 8 inch beam. The dead load is constant and is estimated as 10 pounds per square foot for wood framed construction.