Ask a roofer in Barrie what destroys more roofs and interiors than any storm, and the answer is the ice dam. It doesn't arrive dramatically — it builds quietly along the eaves over a few cold weeks, then sends water into ceilings and walls that were perfectly dry all fall. The good news: ice dams are a heat problem, not a weather problem, and heat problems can be fixed.
How Ice Dams Form
- Heat escapes into the attic through an under-insulated ceiling and unsealed gaps, warming the roof deck from below.
- Snow on the upper roof melts, even in deep cold, because the roof surface above the heated attic is warmer than the air outside.
- Meltwater runs down toward the eaves — where the roof extends past the house wall and has no heat under it.
- The water refreezes at the cold eave, building a ridge of ice a little higher with every cycle.
- Water ponds behind the dam and backs up under the shingles, which are built to shed running water, not hold standing water.
The Damage They Do
Ponded water finds every seam and nail hole above it. It leaks into the attic and walls, soaking insulation until it loses its insulating value — which makes the heat loss, and the dams, worse. It feeds mold inside wall cavities, rots roof decking and fascia, and the ice itself tears at shingles and bends gutters under its weight. Most of the damage is hidden until a ceiling stains, which is why dams cost far more than the prevention ever would.
Prevention: Insulation, Sealing, Ventilation
- Insulate the attic to R-60. A properly insulated ceiling keeps the roof deck cold and the snow on it frozen.
- Seal the attic air leaks. Top plates, pot lights, plumbing stacks, wiring holes, and the attic hatch leak warm air straight onto the roof deck. Sealing them matters as much as the insulation itself.
- Ventilate the attic properly. Working soffit and roof vents flush out any warmth that does get in, keeping the whole roof one even, cold temperature.
- Keep gutters clear. Clear gutters don't prevent dams on their own, but clogged ones give meltwater a frozen head start at the eave.
If You Already Have Ice Dams
Don't climb up and chop at them — hacking at ice damages shingles and is genuinely dangerous; and don't throw rock salt on the roof, which harms shingles and everything the melt runs onto. Work from the ground with a roof rake to pull snow off the lowest section of roof, so less is available to melt. For an active dam, fill a stocking with calcium chloride and lay it across the dam — it melts a channel through the ice for water to escape. Serious dams with active leaks call for professional steam removal, which clears ice without touching the shingles.
The pattern to notice: every real prevention on this list is about the attic, not the roof. Fix the heat loss and the dams stop forming, winter after winter. Call Concepts Construction at (705) 330-2911 for a free estimate on ice dam prevention in Barrie and Simcoe County. We're available Monday to Friday, 8:30 AM to 4:30 PM — and if ice has already damaged the roof, that's roof damage repair we can assess at the same visit.
