If you've lived through a Michigan winter, you've probably seen thick ridges of ice along the edges of roofs, often with icicles hanging below. Those ridges are ice dams, and they can cause leaks inside your home.
How ice dams form
Ice dams start with heat. Warm air from the living space leaks into the attic and warms the roof deck. Snow on the upper roof melts, and the water runs down toward the eaves. The eaves hang past the warm walls of the house, so they stay cold. When the water reaches them, it freezes.
Over time, the ice builds into a ridge. Meltwater backs up behind it and can work its way under shingles, where it may drip into the attic, walls or ceilings.
Signs you may have a problem
- Large icicles along the gutters, especially with ice building on the roof edge
- Water stains or damp spots on ceilings or exterior walls during or after winter
- Wet insulation in the attic
- Peeling paint or damage near the roofline
The long-term fixes
The most effective way to prevent ice dams is to keep the roof deck cold:
- Air sealing: close gaps where warm air leaks into the attic, such as around light fixtures, plumbing stacks, chimneys and attic hatches.
- Insulation: enough attic insulation keeps heat in the living space.
- Ventilation: a balanced attic ventilation system with intake at the eaves and exhaust near the ridge helps keep the attic close to outdoor temperature.
Roofing details that help
When a roof is replaced, a waterproof ice barrier membrane is installed along the eaves in cold climates. It goes under the shingles and helps keep backed-up water from reaching the roof deck. It doesn't stop ice dams from forming, but it gives important protection where they cause the most trouble.
What not to do
Avoid chipping ice off the roof with hammers, shovels or picks. It's dangerous, and it can damage shingles and gutters. Clearing snow from the lower roof with a roof rake while you stay on the ground can reduce buildup. If ice dams are causing leaks, have the attic and roof assessed so the cause can be fixed.
See how we plan roof replacements for Michigan weather.
