Lumber Roof Loads

Too often builders gang together 2 inch dimension lumber to support roof and floor loads without considering other options.

Lumber roof loads.

Use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size. For example if building is 24 x 24 and has trusses and the load on the roof will be for 30 lb snow load and a ceiling with no storage will total out like this. The dead load is constant and is estimated as 10 pounds per square foot for wood framed construction. Let s start by taking a broad view.

The structural goal of a house is to safely transfer building loads weights through the foundation to the supporting soil. The live load depends on the maximum snow load in your area. For roof live loads of 12 psf or 16 psf. 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.

These numbers are for roofs supporting light loads of 20 pounds for square foot. The loads are based on adjusted roof snow loads from the governing building code. Wood screws withdrawal forces allowable withdrawal load force wood species moisture content and weight weight of green and air dried fire wood wood panel and structural timber products mechanical properties density fibre stress compressive strength and modulus of elasticity of clear wood panel and structural timber products. A complete analysis of wood s mechanical properties is complex but understanding a few basics of lumber strength will allow you to size joists and rafters with the use of span tables.

The dead load of a typical asphalt shingled wood framed roof is about 15 pounds per square foot. Live load psf dead load psf span calculator for wood joists and rafters available for the iphone. Span calculator for wood joists and rafters also available for the android os. Roof rafter span use this table to determine the maximum lengths of roof rafters based on species and grade of lumber spacing dimensions load and slope.

The load on an outside wall with clear span trusses is exactly half the load on each wall. Determine the load per square foot that the roof must support. Spf 2 6 rafters can span 8. A clay tiled roof may have a dead.

If you place the 2x6s at 16 o c then syp can span over 16 and spf can span 14. The load increases with the use of heavier roofing material. You can t beat sawn lumber for most small window headers but as spans and loads increase stronger materials are a better choice. An spf roof at the same spacing and lumber size will span 11.