Snow Load, Explained: Why Your Roof's Rating Depends on Where You Live

Snow load is the weight a roof structure needs to be designed to carry, and it's set using region-specific climate data — how much snow typically accumulates, how wet and heavy it tends to be, and how the local terrain and wind patterns affect drifting. Mountain and northern communities can see design loads several times higher than a coastal city with mild winters.

This is why a truss package or roof design from one part of the country can't simply be reused somewhere else without checking the local snow load value. It's also why flat and low-slope roofs, which don't shed snow as readily, get closer scrutiny — drift accumulation against a parapet or a taller adjacent wall can quietly exceed what the roof below was designed for.