Roof Snow Load Calculator

Calculate the snow load on a roof by entering the roof’s dimensions below along with the depth.



How to Calculate Snow Load

Snow load is the additional weight on a roof structure added by snow and ice buildup on the roof. Calculating the snow load is crucial to determining if the structure can handle the snow’s additional weight.

The ATC has a snow load hazard tool that can help you identify when a snow load presents a hazard to the structure.[1] You can calculate snow load in a few easy steps.

Step One: Calculate the Volume of the Snow on the Roof

The volume of snow on the roof directly relates to how much it will weigh. To find the snow volume, start by measuring the roof’s footprint.

Measure the Roof

We strongly recommend against walking on the roof to take these measurements for obvious safety reasons. Instead, measure the length and width roof from the ground to find the footprint; we’ll account for the pitch later. Keep all measurements in feet to simplify the formulas.

When you have the roof’s length and width as measured from the ground, multiply them together. This will give you the area of the footprint. Alternatively, you can also use a volume calculator to find this measurement.

Account for Roof Pitch

If you measured from the ground and did not measure the roof’s actual dimensions, then it’s time to account for the roof pitch. If you don’t know your roof pitch, then try our roof pitch calculator to find it.

To account for the pitch, you’ll need to multiply the area by the multiplier for the given roof pitch. You can find a list of multipliers on our roofing calculator. The calculator above applies this formula. If the roof is a flat roof, then this step is not needed..

Before moving on, multiply the area by the snow depth in feet to find the volume of snow on the roof.

Step Two: Find the Snow Density

Snow varies in weight depending on the density. Fresh powder weighs much less than wind-packed drifts. Check out our snow weight calculator to find the density of various types of snow.

Step Three: Calculate Snow Load

The final step in calculating the snow load is to multiply the volume of snow on the roof by its density. If you have a density range, then multiply the volume by each part of the range separately to find the minimum and maximum snow load.

You might also be interested in our snow to water volume calculator.

References

  1. ATC, Hazards by Location, https://hazards.atcouncil.org/