Snow Load Calculator

Calculate design roof snow load per ASCE 7 from ground snow load, roof slope, roof surface, exposure factor, thermal factor, and importance factor.

Frequently Asked Questions

What is the design snow load for a 40 psf ground load, 6:12 shingle roof, normal factors?

Ps = 0.7 x 1.0 x 1.0 x 1.0 x 40 = 28 psf. A 6:12 pitch is 26.6 degrees, below the 30-degree threshold for non-slippery surfaces, so Cs = 1.0 and the design load is 28 psf.

How do I find the ground snow load for my area?

ASCE 7 Figure 7.2-1 maps ground snow load across the US. Your local building department will have the adopted value for your jurisdiction.

Does a metal roof reduce snow load?

Yes, if it can shed snow freely. Select the slippery surface option: the slope reduction then starts above 5 degrees (Cs = 1 - (slope - 5)/65) instead of 30 degrees for shingle roofs. A 20-degree metal roof gets Cs = 0.77.

What importance factor applies to a house?

Most single-family homes fall under Risk Category II, which uses I = 1.0 (normal). Structures with high occupancy or essential function use I = 1.1 or 1.2.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.