Work out snow load instantly with clear inputs, formula shown and shareable results.
Roof snow load starts from the ground snow load and applies three modifiers: 0.7 for the general reduction from ground to roof, exposure for wind scour and thermal for heat loss through the roof. A slope factor then reduces the load further above 30 degrees, falling linearly to zero at 70 degrees as snow slides off.
Flat roof load
pf = 0.7 x Ce x Ct x pg
Sloped roof load
ps = Cs x pf, Cs = 1 - (slope - 30) / 40 for slopes above 30 degrees
Preliminary estimate only. Snow loads including drift, sliding and unbalanced cases must be established by a qualified engineer to the loading code in force.
pf = 0.7 x Ce x Ct x pg. Roof snow load starts from the ground snow load and applies three modifiers: 0.7 for the general reduction from ground to roof, exposure for wind scour and thermal for heat loss through the roof.
Yes. Snow accumulating against a parapet, a step in roof height or an obstruction can be several times the balanced load, and codes give specific drift surcharge shapes for it.
This calculator takes 4 inputs: Ground snow load, Roof slope, Exposure factor Ce, Thermal factor Ct. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.