When the water is already in the house
Start inside. Move the furniture away and place containers under the drips. Then call a roofer equipped for ice removal, and notify your insurer.
Three things not to do
- Hitting the ice. An axe or a hammer breaks the frozen shingles along with the ice.
- Climbing on the roof or up a ladder, to remove ice or snow. An icy slope is dangerous. This work belongs to an equipped company.
- Relying on heating cables. They trace a path for the water, but they do not correct the cause and they use electricity.
Where this ice comes from
The cause is often under the roof: heat is escaping from the house. The solution lies in insulation and attic ventilation far more than in the shingles.
An ice dam needs three conditions: snow on the roof, freezing temperatures outside, and a roof warmer at the top than at the bottom.
Heat passing through the ceiling warms the deck above the living spaces. The snow melts at its base, even in freezing weather, and the water runs down under the blanket of snow. The overhang extends past the walls and nothing warms it. The water freezes there. The ridge grows with each melt cycle, and the water that follows collects behind it.
A shingle roof is not a tub
Shingles overlap like scales. Water passes from one course to the next without meeting an opening, as long as it runs downhill. The roofing is not sealed for all that.
Behind a dam, the water stops running down. It collects, its level rises, and it slips under the edge of the shingles, against the slope. It then reaches the nail holes and the joints of the deck.
The role of the eave membrane
On a recent roof, the bottom of the slopes is covered, under the shingles, by a self-adhesive membrane. This membrane tightens around the nails and blocks backed-up water.
The membrane is a protection, not a cure. Ice still forms. And if the dam climbs above the membrane, water gets through despite it.
Keeping the roof cold from end to end
A roof that stays cold over its whole surface generally does not produce a dam. The work is done in a precise order, by contractors.
- The ceiling first. Warm air leaks around the hatch, light fixtures and pipes often warm the attic a lot. They are sealed first.
- The insulation next. It is topped up, especially above the exterior walls, where it is often thin.
- The air last. We restore the airflow so the cold air entering through the soffits runs along the underside of the deck.
Frequently asked questions
Are icicles on the gutter already a dam?
Not necessarily. Small icicles after a sunny afternoon are nothing abnormal. Massive icicles that re-form all winter, under a thick band of ice above the gutter, signal a roof that is losing its heat.
Is damage caused by ice insured?
It all depends on the policy. Ask your insurer what it covers and under what conditions. Keep photos of the ice, taken from the ground, and of the damage inside.
Does redoing the roof put an end to ice dams?
Not on its own. A new roofing, with its eave membrane, better resists backed-up water. As long as heat escapes, the ice often comes back. Re-roofing is a good opportunity to correct the ventilation at the same time.