Bearing Wall Wood

Numeric Parameters

 

Equations

 

There are several equations that are useful in determining properties and limits of wood members. The below equation can be used to find the beam size that is required to support a given load at a given span. 

 

 

 

 

 

 

The above equation can be manipulated to output the allowable span or the allowable load in the following ways.

 

 

 

 

 

 

 

The American Wood Council has provided many charts and tables for the purpose of determining the allowable spans and sizes of certain pieces of lumber. Typically, the distance between studs in residential wall construction is 16", joists and rafters follow this convention as well. The AWC also has several tools that can help determine the maximum horizontal span of a wood member when given parameters such as type of wood, size, grade, spacing, dead/ live loads, etc. and the conditions of a wooden connection in a frame or a truss. When an Eastern White Pine, construction grade 2 x 4 is subjected to 40 psf live load and 10 psf dead load, the maximum horizontal span according to the span calculator is 4' 11" (see results to to right).

 

For Pine lumber (most commonly used in construction) the Modulus of Elasticity is generally around 9 Gpa (1,300,000 psi) and the Ultimate Tensile Strength is about 40 Mpa (5,800 psi).