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What you need to know about ice dams

March 6, 2023

Icicles hanging along the edge of a roof may look pretty, but they’re a sign of a problem.

This is a sign of ice dams - they can tear off gutters, damage your roof, loosen shingles or cause water to back up into your house. They can also cause soggy insulation in the attic, which loses R-value and becomes a magnet for mould and mildew.

How do they form?

The best way to combat ice dams is to understand what they are and how they happen. An ice dam is a buildup of ice that traps melting snow on your roof. They are formed when the heat rises to the attic from your home. Poor insulation and ventilation allow the warm air to escape and heat up your roof. The snow melts on the warm roof, runs down and freezes on the cold eaves. As more snow melts and freezes in the same place, the buildup of ice gets larger, forming an ice dam that prevents water from running off into your eavestroughs.

The meltwater from the warm roof then backs up behind the dam, and flows under the shingles and into the house. The leaking water can damage your ceiling, walls and even warp floors. In severe cases, mould can begin to develop. It can cause structural damage too – they can bend, twist or even tear the gutters right off the home.

The most common areas for ice dams to form are:

  • At the eaves of the roof (most common)
  • In valleys of the roof
  • On low-angle roofs
  • Around chimneys and skylights

Tips on preventing ice dams

  1. Add Insulation. More insulation on the attic floor keeps the heat where it belongs. Seal any gaps in your attic floor to stop warm air from seeping in. Consult with a professional about the best type of insulation.
  2. Ventilate your attic. While it might seem strange to add insulation for warmth but allow cold air to come in through the vents, some airflow is needed to remove moisture from the attic and keep the roof cool enough to prevent ice dams.
  3. Install heat cables. Also known as heat tape, they are heated cables that can be attached with clips along the roof’s edge in a zigzag pattern. They melt channels through already-formed ice dams to minimize buildup and allow water to drain off your roof rather than pooling behind the dam. This may help prevent water from seeping into your home. They are especially useful for limited problem areas and are best to install before bad weather hits.
  4. Do some caulking. Seal around electrical cables, vent pipes and chimneys in the attic with a fire-stop sealant. Look for any spots where the light shines up from below or the insulation is stained black by the dirt from passing air.
  5. Exhaust to the outside. Make sure ducts connected to the kitchen, bathroom, and dryer vents all lead outdoors through either the roof or walls, but never through the soffit.
  6. Keep snow off the roof. A roof clear of excess snow is the first step toward prevention. However, climbing up on the roof to clear it away isn’t safe. Consider using an extendable roof rake from the ground. Look for a rake with small rollers or bumpers at the bottom of the blade and follow the manufacturer’s instructions. Your roof can collapse if ice and snow build up to a dangerous weight. For extreme cases, call in professionals who have the proper safety gear.
  7. Forget the tools. Never use a hammer, pickaxe, or other sharp tools to chip away at the ice on your roof. This can damage your shingles and allow for more leaks.
  8. Invest in an ice and water shield. If you’re in the market for a new roof, consider asking a professional roofer to add this protective barrier that can help keep water out of your home even if it has already made its way through your shingles.

Will insurance cover the damage?

Most home insurance policies cover damage caused by ice dams. After you pay your deductible, the insurer could support you through any necessary repairs and provide additional living expenses if you have to move out of your home while they are done.

Keep in mind, however, as a homeowner you are required to keep your roof in good repair. If it is nearing its life expectancy, the insurer may limit coverage to the depreciated value.

Always speak with your broker to be sure of what your policy covers.


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