Ice dam time again?

Fluctuating weather can mean a nasty bit of trouble with your roof

It’s Ontario, and it’s early spring, and that means the dance of sun and ice begins. Yesterday it was bitterly cold. Today it’s above zero, with beautiful, bright sunshine. Tomorrow the temperature will plummet again.

We love spring, but fluctuating weather can mean a nasty bit of trouble with your roof. The repetition of cold-warm-cold causes snow to melt and re-freeze. The buildup results in an ice dam.

An ice dam forms when the top part of your roof is warmer than the lower edge. Heat from inside your home can escape into the attic and warm the roof from underneath. If the middle of your roof gets warm enough, the snow on it melts. That water runs down the slope until it reaches the colder edge, usually over the unheated eaves. There it freezes again.

Over time, more meltwater runs down and freezes, growing a ridge of ice that stops water from flowing off the roof properly. Even a small cycle of melt-and-freeze can make an ice dam grow.

Ice dam damage

Ice dams are not just unsightly. They can cause real damage to your home. Water can back up behind the ice and work its way under shingles. From there it can leak into your attic or walls.

And that’s when it gets serious. Water leaks can lead to damaged insulation, wet ceilings, and even mold growth. The added weight of large icicles and ice can also strain gutters and eaves.

This is often a problem around skylights, simply due to the fact that there is a tremendous amount of heat loss. The thaw-freeze cycle can make water back up no matter how well the skylight and flashings are installed.

How to avoid ice dams

The best approach is to stop uneven roof temperatures before they start:

Improve attic insulation. A well-insulated attic keeps heat inside your home instead of letting it warm the roof surface.

Increase ventilation. Good airflow in your attic helps keep roof surfaces cold and closer to outdoor temperatures.

Seal air leaks. Warm air can sneak through gaps around lights, pipes, or vents and warm the roof. Sealing these gaps reduces that heat flow.

Clean gutters and downspouts. Clear gutters give meltwater a clear path away from the roof instead of allowing it to re-freeze at the edge.

Shovelling in progress with a roof rake

Use a roof rake. After snowfalls, a long-handled roof rake lets you remove snow buildup safely from the ground. Less snow means less meltwater to refreeze.

Note: Skylights are the exception. It’s so frustrating when water pours in around a skylight well. Yes, there might be opportunities to improve insulation and seal air leaks that will help. The best way is to clear the snow around the skylight (especially the bottom) to prevent the thaw-freeze cycle.

Also: Every home is unique. Sometimes the issue is not obvious. It could be a vent, vented into the attic, or into an eave. Even windows close to an eave (similar to skylights) can cause issues.  A trained professional will have the tools that can help assess root causes.

Some people install heated de-icing cables along the roof edges. These cables warm the edge slightly to melt ice and help water drain off. However, they don’t fix the root cause of ice dams. Often these are the last resort.

What to do about ice dams when they happen

It’s always best to call in the professionals. Otherwise, carefully remove snow with a roof rake, but avoid dangerous methods like hitting the ice with a hammer that damages the shingles or, of course, climbing onto an icy roof. Trained roofing professionals know how to remove ice without damaging shingles or risking injury.