Ice Dam Prevention
If you are up a ladder with a roof rake every February, the roof is not the problem. The ceiling underneath it is.
How an ice dam actually forms
- Warm air escapes from the house into the attic.
- That warmth reaches the underside of the roof deck and melts the snow sitting on top of it.
- The meltwater runs down the roof until it reaches the eave, which overhangs the wall and stays at outdoor temperature.
- There it refreezes. Repeat for a few days and you have a ridge of ice with a pond of water backing up behind it.
- That water works its way under the shingles, and it comes out on your ceiling.
The dam is a symptom. Heat cables, roof rakes and re-shingling all manage the symptom, and they all have to be done again next winter. A cold roof deck cannot melt snow, so there is nothing to run down and refreeze.
Making the roof cold
The fix is to stop the heat getting up there in the first place, which means sealing the ceiling plane properly - not just laying more insulation on top of what is already failing. Air moves through gaps around wiring, plumbing, light fixtures, the attic hatch and the top plate, and none of those are things a batt was ever going to seal.
Spray foam expands into all of them and hardens. See the attic page for how that job runs.
Worth knowing before you re-roof
If you are already planning to strip the roof, that is the cheapest time to deal with the insulation underneath it, because the deck is open. It is worth a phone call before the roofer starts rather than after.
Stop Fighting the Same Ice Dam Every Winter
(207) 452-2930Call and talk to us. If you would rather write it down, use the form and we will call you back. Mon-Fri 7am-5pm.