A: Corbel block size (width) is affected by truss bearing area. The length of the corbel is affected by snow loading. Corbels are usually 2x boards that are the same width as the post. The area required to support the truss heel will be specified by the truss engineer on the truss drawings. Determine the bearing area of a corbel block by multiplying the width of the corbel by its thickness (Bearing area of a 2 x 6 = 1.5″ x 5.5″ = 8.25 square inches).

Corbel blocks must also be sized for length to accommodate bolts and hot dipped galvanized nails. The bolts and nails must be correctly and accurately installed in the corbel block to insure compliance with the National Design Standard for Wood Construction (NDS).