Everyday
Roof Snow Load Calculator
Measure the snow on your roof, pick its condition, and the page works out the load in pounds per square foot, the total weight on the roof, and how that compares with the design load in your permit record, so you can decide whether to shovel.
How it works
Behind the numbers
The load comes from depth times density. A foot of settled snow at 20 pounds per cubic foot puts 20 pounds on every square foot, so 20 inches works out to about 33 pounds per square foot. An ice layer counts separately at 57 pounds per cubic foot, which is why a single inch of ice adds almost 5 pounds per square foot on its own. Multiply by roof area for the total weight: 33 pounds per square foot over 1,500 square feet is close to 50,000 pounds, or about 25 tons.
The result is judged against the design load you enter, which defaults to 30 pounds per square foot. Under 50 percent of it, the roof is well within range and monitoring is enough. From 50 to 80 percent, the load is getting heavy and removal is worth planning before the next storm adds to it. From 80 to 100 percent, removal should happen soon, and past 100 percent it should happen promptly, with a watch for sagging, leaks, sticking doors, or cracked members.
This is a homeowner decision tool, not a design estimator. Pro tools work from ground snow load tables and code factors to size a new roof; this one starts from snow you can measure on the roof you have, and answers whether to shovel. The design load in your permit record or local code is the authority, and the page is a planning estimate, not a structural assessment. Clearing is ground work: a roof rake, in sections, never a climb onto an icy roof.
FAQ
Questions, answered
How much does snow weigh on a roof?
It depends on depth and condition. Fresh powder weighs about 7 pounds per cubic foot, settled snow about 20, wet snow about 30, and ice about 57. So 20 inches of settled snow puts about 33 pounds on every square foot, while the same depth of wet snow puts about 50 pounds per square foot.
How do I know if my roof has too much snow?
Compare the load with the design load in your permit record or local code. Under 50 percent of it, the roof is well within range. From 80 percent up, removal should happen soon, and past 100 percent it should happen promptly. Sagging, leaks, sticking doors, or cracked members are warning signs; if you see any of them, call your local building official.
Should I shovel snow off my roof?
If the load is near or above the design load, yes. Clear it from the ground with a roof rake, working in sections so the weight comes off evenly. Never climb onto an icy roof, and never clear one side only while the other side stays loaded.
What is a typical roof snow design load?
Older permitted structures are often designed for 20 to 25 pounds per square foot, and manufactured homes for 30 pounds per square foot. The number that matters for your house is the one in your permit record or local code, which is why the page lets you change the default of 30.
Does ice on a roof weigh more than snow?
Yes. Ice weighs about 57 pounds per cubic foot, against about 20 for settled snow. One inch of ice alone adds almost 5 pounds per square foot, so a thin ice layer under the snow can push a load that looked safe well past the design limit.