What the Snow on Your Roof Is Telling You

Go outside after the next snowfall

Snow on a roof is an insulation test. A properly insulated, properly ventilated attic keeps the roof deck close to outdoor temperature, so the snow sits there and melts when the sun and the air melt it — evenly, the same as your neighbour's. Anything else is heat escaping through your ceiling, and the pattern tells you where.

Reading the patterns

Even snow, melting slowly and uniformly

What you want. The attic is cold, which means the heat is staying in the house.

Bare roof while neighbours are still white

Heat is pouring through the ceiling across the whole plane. Usually shallow or missing insulation. This is the top rebate tier and the easiest job we do.

Melted stripes running up the slope

The warm lines are the rafters or truss chords and the snowy gaps between them are where the insulation is. Common where batts were laid between joists and have shifted or were never continuous. It means the framing is a thermal bridge and the coverage is not uniform.

Clear patch over one room

Almost always a bathroom fan ducted into the attic instead of through the roof, or a chase around a chimney or plumbing stack that was never sealed. A concentrated plume of warm wet air. This is the most useful pattern of all because it points at a single defect.

Melted middle, snow and ice at the eaves

The ice-dam signature, and the one to act on. Heat melts the snow on the warm part of the roof, the meltwater runs down to the cold overhang, refreezes, and builds a dam that pushes water back under the shingles. People call a roofer. It is an insulation and ventilation problem, and roofing alone will not stop it happening again.

Frost patches on the roof in the morning, none on next door

Counter-intuitive but good: frost forms on a cold surface. A frosty roof is an attic that is staying cold. Your neighbour's clear roof is the one with the problem.

Take the photograph

If you see any of these, photograph it from the street before it changes. It is genuinely useful on an attic check — it tells us where to look before we go up, and it is evidence of a pattern that a single day's inspection might miss.

Send it with a booking, or just tell us what you saw on the phone.