Snow Load Calculator

Different snow conditions pack dramatically different amounts of water into the same depth -- fresh powder is mostly trapped air, while settled, packed, or icy snow has been compressed or partially melted and refrozen into a much denser mass. This calculator assigns each Snow Type its own density, so the same Snow Depth can produce several times more load as ice than as fresh snow.

No -- not below 30 degrees. This calculator uses the ASCE 7 roof slope factor Cs for a warm, non-slippery roof (asphalt shingles, wood shakes), which holds at 1.0 for any pitch up to 30 degrees because snow does not reliably slide off those surfaces at shallow angles. A 10-degree roof and a 25-degree roof therefore carry the same calculated load. Above 30 degrees the factor drops linearly to zero at 70 degrees, so from there on a steeper roof does show a lower load. Slippery surfaces like standing-seam metal or slate begin shedding at shallower angles than this curve assumes.

% of Typical Capacity compares your calculated Load per Sq Ft against a general 30 PSF figure representative of many residential roof designs, not your specific building's actual engineered load rating. It's a rough screening comparison -- check your building's actual structural documentation for a load rating you can rely on for a real safety decision.

Yes, holding Snow Type and Roof Pitch fixed -- Load per Sq Ft is directly proportional to Snow Depth, since the weight of a given snow type scales linearly with how deep it has accumulated. Doubling Snow Depth doubles the calculated load per square foot before any pitch adjustment is applied.