Maine Weather
What causes ice dams and how do I prevent them?
Short answer
Ice dams form when heat escaping into the attic melts snow on the upper roof, the water runs down to the cold eave and refreezes, and the resulting ridge of ice backs water up under the shingles. The fix is air sealing, insulation and ventilation — not a better shingle.
The mechanism
Warm air leaks from the living space into the attic through recessed lights, top plates, chimney chases and hatches. It heats the underside of the deck, the snow above melts, and the meltwater reaches the overhang, which is outside the heated envelope and stays at ambient temperature. It refreezes there and builds a dam that holds standing water on a roof designed to shed it.
What actually prevents them
- Air seal the attic floor — this is the highest-value fix
- Bring insulation up to a consistent, adequate depth
- Balanced soffit intake and ridge exhaust so the deck stays cold
- Keep gutters clear so meltwater has somewhere to go
- Ice-and-water shield at the eaves whenever the roof is replaced
What doesn't fix them
Chipping ice with a hammer damages shingles and often the gutter. Heat cables melt a channel but leave the underlying problem in place and add running cost. Rejuvenation doesn't prevent ice dams either — what it can do is help an aging shingle stay flexible through the freeze-thaw cycling that ice dam season imposes.
See if your roof qualifies
Six quick questions about your roof, and an honest read on whether rejuvenation is likely to be a fit for it.
2-minute self-check
Answer six questions from the ground.
This won't replace an on-roof inspection, but your answers shape the recommendation you'll get at the end — including when rejuvenation isn't the right call. "Not sure" is a fine answer.
1.Is your roof roughly 8–25 years old?
2.Do you have any active leaks or interior water stains?
3.Are there shingles missing, cracked through, or hard-curled in sections?
4.Do you see granules collecting in gutters, or fading and dry-looking shingles?
5.Do any roof planes sag, or does the decking feel soft?
6.Does the roof have more than one layer of shingles?
0 of 6 answered — your personalized result appears when you finish.
Before you replace — see if you qualify.
A free roof assessment tells you whether your asphalt shingles still have serviceable life. If they don't, we'll say so and point you to a roofer we trust.