Ice dams are one of the most common winter roofing problems in Calgary, especially when temperatures swing between freezing and thawing. While they might look harmless on the outside, ice dams can quietly cause major damage inside your home.
What exactly is an ice dam?
An ice dam forms when heat from your home escapes into the attic and warms the underside of the roof. Snow on top begins to melt, and the water runs down to the colder roof edges. There, the water refreezes, creating a ridge of ice.
As more snow melts, water gets trapped behind that ridge. With nowhere to drain, it can back up under your shingles.
How ice dams damage your home
Ice dams may start small, but the consequences can be serious:
Leaks into your attic
Melted water can seep under shingles and soak the roof deck, insulation, and attic space.
Stains and damage inside your home
Water can make its way into ceilings, walls, and light fixtures, causing stains, bubbling paint, and mould growth.
Shingle deterioration
Repeated freezing and thawing can lift shingles, break their seal, and shorten their lifespan.
Insulation damage
Wet insulation loses its effectiveness, making your home less energy-efficient and more expensive to heat.
Why icicles are a warning sign
If you’re seeing icicles forming along the edges of your roof, it may look like a winter postcard — but it’s also a red flag.
It often means that:
- Warm air is escaping into your attic
- Your roof isn’t venting or draining properly
- Hidden ice dams may already be forming under the snow
- Catching this early can prevent hundreds or even thousands in repair costs.
How to prevent ice dams
You can reduce the risk of ice dams with the right maintenance and upgrades:
- Improve attic insulation
Good insulation prevents warm indoor air from reaching the roof deck and melting snow unevenly. - Fix ventilation issues
Balanced roofing ventilation keeps your attic cold in winter, helping snow melt evenly and drain properly. - Clear gutters and downspouts
When gutters are clogged with leaves or ice, meltwater has nowhere to go and begins to back up. - Schedule a winter roof inspection
A professional check can catch problem areas — like poor airflow, blocked vents, or shingle damage — before they turn into leaks.
When to call a professional
If you’ve noticed icicles, water stains, or uneven snow melting across your roof, it’s time to take action. Addressing ice dams early can save your shingles, prevent interior water damage, and protect the overall structure of your home.
Niko Roofing offers winter roof assessments and ice dam prevention solutions tailored for Calgary homes.