An ice dam is a ridge of ice that forms at the edge of a roof when heat escaping from the attic melts snow on the upper roof surface, and that meltwater refreezes at the cold eaves. Once the dam builds, backed-up meltwater has nowhere to go except under the shingles, through the underlayment, and into the structure of the building. Ice dams are one of the leading causes of roof and interior water damage in the Gatineau-Ottawa region every winter.
Why Do Ice Dams Form on Quebec Roofs?
The fundamental cause of ice dams is uneven roof temperature: the upper section is warm (heated by escaping attic heat) while the eaves remain cold (unheated, exposed to outside air). When snow accumulates on a warm upper roof, it melts. As that water runs down toward the cold eaves, it refreezes. The cycle repeats with each snowfall, and the ice dam grows upward toward the warm roof zone.
Attic insulation and ventilation are the root variables. A properly insulated and ventilated attic maintains a roof temperature close to the outside air temperature across the entire surface — meaning snow melts uniformly or not at all. An under-insulated or poorly ventilated attic creates the temperature differential that triggers ice dams.
Clogged soffits, blocked attic vents, and inadequate vapour barriers are common contributors in older Gatineau-area homes. The problem is structural, not cosmetic — removing the ice dam without addressing attic conditions guarantees the dam will return next winter.
What Damage Do Ice Dams Cause?
Ice dam water infiltration typically causes: water staining and damage to interior ceilings and walls, insulation saturation (which permanently reduces R-value and promotes mould), deterioration of the roof deck and structural rafters, and rotting of soffit and fascia boards. In severe cases, the weight of the ice dam itself can tear gutters from the building.
The damage is often not visible immediately. Water may infiltrate in January and not appear as a ceiling stain until spring, by which time significant structural damage may have occurred inside the wall or roof cavity.
How to Prevent Ice Dams on Your Gatineau Roof
The permanent solution to ice dams is improving attic ventilation and insulation. A roofer or insulation contractor should assess the attic for the following: current insulation R-value (minimum R-50 is recommended for Quebec residential attics under current code), intake ventilation at the soffits, exhaust ventilation at the ridge or upper roof, and vapour barrier continuity between the living space and the attic.
At the roof level, ice and water shield membrane — a self-adhering waterproofing underlayment — installed at the eaves provides a critical secondary barrier. Under the Quebec Building Code, ice and water shield is required at the eaves of residential roofs. During any Cossette Roofing replacement project, ice and water shield is installed from the eave to a minimum of 600 mm inside the warm wall line.
Heating cables (electric trace heating) installed along the eaves are a remediation measure for existing homes where attic improvements are not feasible. They are maintenance-intensive and should be considered a secondary solution, not a replacement for proper insulation and ventilation.
Ice Dam Damage Repair: What’s Involved
Repairing ice dam damage involves three components: addressing the water infiltration damage inside the building (drywall, insulation, mould treatment where required), repairing the roof assembly at the affected area (replacing shingles, damaged underlayment, and rotted decking sections), and correcting the attic conditions that allowed the dam to form.
Attempting to repair only the interior damage without correcting the roof and attic is the most common and most expensive mistake homeowners make. The dam returns, the cycle repeats, and the cumulative damage is far greater than addressing all three components in the first repair cycle.
Cossette Roofing and Renovations provides full ice dam damage assessments for homes in Gatineau, Ottawa, Hull, Aylmer, and the Outaouais. Emergency roof services are available 24/7 at 819-777-7177 or at our website.
Frequently Asked Questions
What causes ice dams on roofs in Quebec?
Ice dams are caused by uneven roof surface temperature — the upper roof stays warm due to heat escaping from a poorly insulated or ventilated attic, while the cold eaves cause meltwater to refreeze. The resulting ice ridge backs up water under the shingles.
How do I prevent ice dams on my Gatineau roof?
The permanent solution is improving attic insulation (minimum R-50 for Quebec) and ensuring proper soffit and ridge ventilation to keep the roof surface at a uniform temperature. Ice and water shield membrane at the eaves provides a secondary barrier during any roof replacement.
Can I remove an ice dam myself?
You can use a roof rake from ground level to remove snow accumulation before it melts and refreezes, which reduces ice dam formation. You should not attempt to chip or pry ice from the roof — this damages shingles and flashing. A roofing professional or a contractor using low-pressure steam is the correct approach to removing an established ice dam.
Does my Quebec home insurance cover ice dam damage?
Most Quebec home insurance policies cover sudden water damage from ice dam infiltration if the roof was in good condition before the event. Damage resulting from long-term neglect or improper maintenance may not be covered. Review your policy terms and contact your insurer before beginning repairs.