California Residential Inspector Practice Exam

What is the maximum allowable span of a 2 x 8 Hem-fir #2 floor joist spaced 12 inches on center for a sleeping room with a dead load of 10 psf?

1. 12 feet, 0 inches

2. 14 feet, 6 inches

3. 16 feet, 0 inches

4. 18 feet, 4 inches

The correct answer is: 14 feet, 6 inches

The determination of the maximum allowable span for a floor joist involves several factors, including the type of material, the size of the joist, the spacing between the joists, and the loads acting on them, both live and dead. In this question, a 2 x 8 Hem-fir #2 floor joist spaced 12 inches on center is used in a sleeping room with a dead load of 10 pounds per square foot (psf). Hem-fir is a recognized material for residential construction, and the #2 grade specifies the quality of the lumber, which affects its structural capabilities. For a 2 x 8 Hem-fir #2 floor joist under a dead load of 10 psf, the governing factors allow for a maximum allowable span of 14 feet, 6 inches. This span is suitable for the dead load conditions presented in the question. The reason this answer is valid is because it adheres to the National Design Specification (NDS) for Wood Construction, which provides span tables that help determine safe load capacities based on various conditions. Lumber spans longer than this, such as options exceeding 14 feet, 6 inches, would not be able to safely support the loads specified. Thus,