Checking for Ice Dams on Your Roof During a Chinook

There are few things more familiar in Calgary than a chinook arch over the mountains. The temperature can climb fast in a few hours and snow that seemed settled in for the season can disappear in a day. The break from the deep cold feels good, but the sudden thaw also puts a bit of pressure on a house. It is a natural stress test for the roof, and one of the main trouble spots it can reveal is ice dams.

An ice dam is simple in principle. It is a ridge of ice that forms at the edge of a roof and stops melting snow from draining off. The water that backs up behind the dam can leak into the house and damage walls, ceilings, and insulation. The thaw and freeze cycle that a chinook brings can create or worsen these dams quickly, so it is a useful time to watch what is happening.

Spotting the Problem from the Ground

You do not need to get on your roof to know you might have an ice dam forming. The most obvious signs are visible from the safety of your driveway or backyard. Look for a thick, solid band of ice along the eaves, often with large icicles hanging from the gutters or soffits. Some icicles are normal in winter, but the ones connected to ice dams tend to be larger and heavier, built up from water that has pooled and refrozen many times.

Another clear sign is water staining on your exterior siding, just below the roofline. This shows that water has gotten behind the gutter and is running down the wall. If the problem has been going on for a while, you might even see signs inside. Watch for damp spots or discoloration on the ceiling of your top floor, or bubbling and peeling paint on the upper part of exterior walls. These are strong indicators that water has breached the roof deck and is making its way into the structure of the house.

The Cause is Inside the House

While the ice is on the outside, the problem almost always starts on the inside. Ice dams usually point to a warm attic. In a roof system that is working as intended, the attic stays almost as cold as the air outside. When heat escapes from the heated living space into the attic, it warms the underside of the roof sheathing. This warmth passes through the roof and melts the snow from the bottom up.

This meltwater runs down the slope of the roof until it reaches the eaves. The eaves, which extend past the exterior walls of the house, are not warmed by the attic. They stay at the outdoor temperature. As the water hits this cold surface, it refreezes. Over time, this process builds a ridge of ice. A chinook speeds this up by melting the snow from the top down as well, sending a lot of water down to the cold edge in a short period.

I recall walking through an attic in a bungalow in Canyon Meadows. The owner could not figure out his ice dam problem. The insulation looked deep enough, but when I pushed it aside, I saw the bathroom fan was not vented to the outside. It was just blowing warm, wet air directly into the attic space. Every shower was feeding the ice on his eaves.

Safe, Temporary Measures

If you see a significant ice dam forming, it is natural to want to do something right away. Safety comes first. Never get on a sloped roof in the winter. It is extremely dangerous. Swinging a hammer or axe at the ice is also a bad idea. It is very easy to damage shingles or gutters and turn a nuisance into a larger repair.

The safest immediate action a homeowner can take is to use a roof rake. This is a tool with a long handle that allows you to stand on the ground and pull snow off the lower portion of the roof. By removing the snow, you remove the source of water that feeds the dam. Clearing even the first few feet of snow from the eaves can help and may ease the immediate problem. It is a short-term measure, not a cure.

Permanent Fixes for a Warmer Attic

To stop ice dams for good, you need to address the heat loss that causes them. This means looking at attic ventilation, insulation, and air sealing. A cold, well-ventilated attic is the aim. Ventilation, with vents at the soffits for intake and near the peak for exhaust, allows outside air to move through and keep the roof deck cold.

Insulation is the next piece. The attic floor should have a thick, continuous blanket of insulation to the level specified by the current Alberta building code. This slows the transfer of heat from the living space below. A well insulated attic works together with a properly maintained heating system, and you can read more about how to get your furnace ready for our cold season on this blog.

Finally, and often missed, is air sealing. Even with deep insulation, warm air can leak into the attic through gaps around light fixtures, plumbing stacks, attic hatches, and wiring. Sealing these gaps with the appropriate caulking or foam limits this movement of warm, moist air. Addressing these three areas often calls for a professional, but that is how to prevent ice dams rather than just dealing with the results. Making significant upgrades to your home's energy performance can be a real investment, and it is wise to understand how such improvements are viewed. You can learn more on the City of Calgary assessment pages about how property characteristics are documented.

When the next chinook rolls in, take a quiet walk around your property. Watch how the melting snow moves on and around your roof and attic. It is a good time to catch a problem early and set a clear goal for more permanent work when the weather allows.