Snow Load Calculator

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.

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.

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.

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.

Yes, once the slope is steep enough for snow to slide. On non-slippery surfaces such as asphalt shingles the reduction starts above 30 degrees; on slippery surfaces such as metal or membrane it starts above 5 degrees. Both curves reach zero load at 70 degrees, where snow cannot accumulate.

For roofs sloped under 15 degrees, ASCE 7 requires a minimum load of I x Pg when Pg is 20 psf or less, or 20 x I psf when Pg exceeds 20 psf. This prevents under-design of low-slope roofs, where a rain-on-snow surcharge and uniform accumulation are most likely.

No. Drift loads on lower roofs, unbalanced loads on gable roofs, and sliding snow loads require separate checks beyond this simplified balanced-load method. Consult ASCE 7 Chapter 7 or a structural engineer for complex roof geometries.

This is a planning estimate using the ASCE 7 simplified balanced-load approach. Structural design requires a licensed engineer stamping calculations for your specific building.