Snow Load Roof Calculator
Calculate roof design snow load using ASCE 7. Determine structural requirements by ground snow load and pitch with reinforcement cost estimates.
How It Works
Enter location
Select your climate zone or enter the ground snow load (Pg) from ASCE 7 maps.
Input roof parameters
Set roof slope, exposure category, thermal condition, and occupancy type.
Get design snow load
Receive the flat roof snow load (Pf) and sloped roof load (Ps) per ASCE 7 methodology.
Frequently Asked Questions
How do you calculate roof snow load?
Use the ASCE 7 formula: Ps = 0.7 × Cs × Is × Pg. Where Ps is the sloped roof snow load, Cs is the roof slope factor (decreases as pitch increases above 5/12), Is is the importance factor (1.0 for residential), and Pg is the ground snow load for your location. A roof with 6/12 pitch in a 40 psf ground snow load area has a design load of approximately 20–28 psf.
What is the maximum snow load a residential roof can handle?
Most residential roofs are designed for 20–40 psf (pounds per square foot) of snow load depending on local codes. Fresh snow weighs 3–7 lbs per sq ft per inch of depth. Wet, packed snow weighs 20+ lbs per sq ft. If snow accumulation reaches 2–3 feet of wet snow, it can exceed the design load on roofs in high-snow areas. Consult a structural engineer if you are concerned about your roof's capacity.
Should I remove snow from my roof?
Remove roof snow if accumulation exceeds your roof's design load, if you hear cracking sounds, see visible sagging, or notice doors and windows sticking (indicating structural stress). Use a roof rake from the ground — never walk on a snow-covered roof. Remove snow in sections from the edge upward. Ice dams (ice buildup at eaves) are a separate concern and require professional removal.
How do steep roofs handle snow better than flat roofs?
Steeper roofs shed snow more readily due to gravity — pitches above 6/12 self-clear much more effectively than low slopes. ASCE 7 allows snow load reductions for roofs above 5/12 pitch. Flat roofs (under 2/12) require the full ground snow load in design calculations and need careful drainage for snowmelt. Metal and smooth surfaces shed snow better than textured materials.