How much does the snow on your roof weigh?

Worked example

Your roof has 20 in of snow. The city quick rule is S x 1.25, so 20 x 1.25 = 25 lb per sq ft, or 62.5% of a 40 lb per sq ft design load. Over a 1,500 sq ft roof that is 25 x 1,500 = 37,500 lb. If the snow is 25% moisture the calculator uses 0.25 x 5.2 = 1.3 lb per sq ft per inch, which gives 26 lb per sq ft. One inch of ice on top adds 5.2 lb per sq ft.

How it works

Depth x weight per inch. The City of Coeur d’Alene Building Department gives the quick check P = S x 1.25, where S is inches of snow and 1.25 is the weight in pounds of a square foot of snow for each inch of depth. That figure assumes about 25% moisture. The same document says saturated snow weighs about 20 pounds per cubic foot, moisture content can range from about 1% to 33% so snow can weigh from about 1 to over 21 pounds per cubic foot, and ice on the roof should be added at 5.2 pounds for every inch of thickness.

When you pick a moisture percentage, the calculator uses moisture x 5.2 pounds per square foot per inch (water is about 62.4 lb per cubic foot, so one inch of water covers a square foot at 5.2 lb). The 1.25 rule and 25% give nearly the same answer (1.25 vs 1.3). Structures built with permits are designed for a 40 lb per sq ft minimum roof snow load according to the same document, which also says older roofs may be of concern, manufactured homes were until recently designed for 30 lb per sq ft, flat roofs under a 3/12 pitch are more of a concern, heavy rain can raise the load quickly, and a licensed engineer should be consulted if the structure is in question. You can also weigh a 12 in by 12 in square of snow cut from the roof to check the real load.

Sources and basis: City of Coeur d’Alene Building Department, “Should I shovel the snow off my roof?” (PDF). Opened 2026-10-08. The city makes no recommendation on when to remove snow from roofs. Your local design load depends on location; ask your building department. Kilopascals use 1 lb per sq ft = 0.04788 kPa.

Planning guide only, not professional, medical or safety advice. Conditions, equipment and ability change real needs; use your own judgment and local guidance.

FAQ

How much does snow weigh on a roof?

A city rule of thumb is 1.25 pounds per square foot for each inch of snow, so 20 inches is about 25 pounds per square foot. It varies a lot with moisture: snow can weigh from about 1 to over 21 pounds per cubic foot.

How much does a cubic foot of snow weigh?

The City of Coeur d’Alene document says saturated snow weighs about 20 pounds per cubic foot and that snow can weigh from about 1 pound to over 21 pounds per cubic foot depending on moisture, which runs from about 1% to 33%.

What roof snow load is a house designed for?

The same document says structures built with permits are designed for a 40 lb per sq ft minimum roof snow load, with older roofs possibly below that and manufactured homes until recently designed for 30 lb per sq ft. Your local building department sets the figure for your area.

How does ice change the load?

Ice on the roof adds 5.2 pounds per square foot for every inch of thickness, so a single inch of ice is worth about four inches of the quick-rule snow.

Should I shovel my roof?

The source city does not make recommendations on when to remove snow and warns that shoveling or raking a roof can cause falls and injury from sliding snow. If you are worried about the structure, consult a licensed engineer.