What is the maximum span of 2"x8" Hem-fir #1 rafters spaced at 24" on center when subjected to a 50PSF ground snow load and a dead load of 20PSF?

To determine the maximum span of 2"x8" Hem-fir #1 rafters spaced at 24" on center under a load of 50 PSF ground snow and 20 PSF dead load, it's essential to understand how these loads interact and what factors affect the performance of the rafters.

The total load on the rafters, combining the dead load and live load (which in this case is represented by the snow load), gives a total load of 70 PSF (50 PSF + 20 PSF). When assessing the span capabilities of lumber, the design specifications often refer to span tables that indicate the maximum allowable spans for various load conditions.

For Hem-fir #1 lumber, span tables provide specific maximum span lengths based on the size of the lumber, spacing, and the total load conditions. The critical factor is that the lumber must not only support the total load but also deflect minimally under such loads to maintain structural integrity and performance.

In this scenario, the maximum span of 9 feet, 9 inches indicates that Hem-fir #1 rafters at this size and spacing can safely carry the imposed loads without exceeding the allowable limits for bending and deflection. This means that with a total load of