Questions and Answers

Common engineering questions answered by our professional engineers.

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). (more…)

A: The purpose of the corbel block is to support the load carried by the truss. Corbel blocks attach directly to the posts usually with a combination of bolts and hot dipped galvanized nails.

A: Purlin size, grade and spacing are affected most by bay spacing and snow load.

A: The most common purlin size in the Northwest is #2 DOUG-FIR or HEM-FIR 2×6 spaced at 24″ o.c.

A: Girt size, grade and spacing are affected most by bay spacing and wind loading due to wind speed and wind exposure.