Snow Load Calculator

What is my flat roof snow load?

psf
Thermal factor Ct

Flat roof snow load is

21psf

ASCE 7 formula pf = 0.7 Ce Ct pg for a slope of 5 degrees or less, importance 1.0 for homes. Check Ce in the ASCE 7 exposure table, since 1.0 is only a starting value. Slope factor, drifts and minimum loads are not included. Use a licensed professional for a design.

21 psf on the roof30 psf groundFlat roof load only. Depth drawn to a capped scale.
Ground snow pg30 psf
Ce1
Ct1
Snow weight per 100 sq ft2,100 lb

Convert a ground snow load from your building department into a flat roof snow load with the ASCE 7 formula.

How it works

pf = 0.7 × Ce × Ct × pg. Your local ground snow value and factors go in, and the flat roof load comes out.

Before you order

  • Get ground snow from your local building department or the ASCE hazard tool.
  • Sloped roofs, drifts and valleys need more work than this formula shows.
  • Hire a licensed professional for any structural decision.

Common questions

Is ground snow the same as roof snow?

No. Roof snow load is usually less because of wind and melting.

Does this give the load for a sloped roof?

No. It is the flat roof load only, before the slope factor.