What an ice dam is
An ice dam is a ridge of ice at the roof edge. It blocks melting snow from draining. Water backs up under the shingles and leaks into walls and ceilings.
Grand Rapids sees about 75 inches of snow in a typical year. Lake-effect storms add more. Freeze and thaw cycles run through the winter, so conditions for dams show up often. The National Weather Service in Grand Rapids posts local forecasts and winter data.
How they form
- Heat leaks from the house into the attic.
- The warm roof deck melts snow from below.
- Meltwater runs down to the cold eave.
- The water refreezes into ice at the edge.
- More melt backs up behind that ice and seeps under shingles.
The root cause is attic heat, not the roof covering. A new roof on a hot attic can still form dams.
Roof details that help
Ice barrier
A sticky membrane seals under the shingles at the eaves. If water backs up, it cannot reach the deck. Michigan code calls for it to reach 24 inches inside the exterior wall line.
Intake and ridge vents
Cold air enters at the soffit and exits at the ridge. That keeps the deck near outdoor temperature.
Baffles
Plastic or foam baffles keep insulation from blocking soffit vents.
Proper flashing
Sealed chimneys and walls leave no easy path for water.
Fixes inside the attic
These steps cut the heat that feeds dams.
- Seal air leaks. Gaps around lights, plumbing, and attic hatches let warm air in.
- Add insulation. The U.S. Department of Energy lists high attic insulation levels for cold climates like Michigan's. Check the current numbers for your zone.
- Vent bath fans outdoors. Do not vent them into the attic.
- Keep ducts out of the attic. Or seal and insulate them well.
Do this work before or with your new roof. Your roofer can often check attic conditions during a roof inspection. See our installation process.
What to do when a dam forms
- Use a roof rake from the ground to pull snow off the edge.
- Do not chip or pick at ice. That can damage shingles and cause falls.
- Call a pro if water enters the house. Some use steam to cut channels safely.
- Take photos of any damage for your records and your insurer.
Ice dam or roof leak?
The two look alike inside the house. Both leave stains on ceilings and walls. Timing helps tell them apart.
- Ice dam: stains appear during or after a thaw, with ice along the eaves.
- Roof leak: stains appear after rain, often below a vent, chimney, or valley.
Both can exist at once. An inspection finds the source. A roofer checks the attic for frost on nails, wet insulation, and daylight at the eaves.
Common myths
"Heat cables fix ice dams."
They melt channels, but they do not cure the cause. They also use power. Treat them as a short-term aid while you fix airflow and insulation.
"Rock salt is a safe fix."
Salt and ice melt can damage shingles, metal, and plants. Skip them.
"A bigger gutter stops dams."
Gutters do not control ice dams. Attic heat does. Clogged gutters can make things worse, so keep them clear.
Older homes need extra care
Many Heritage Hill and Eastown homes date from before 1939. They often have little insulation and plank decking with gaps. Those conditions make ice dams more likely. We inspect the attic on every job. See our notes on Grand Rapids neighborhoods.
Where code fits in
The ice barrier rule is one part of the picture. Read our full Michigan roofing code guide for ventilation and flashing rules. Compare materials on our asphalt and metal pages.
Plan ahead
If you see icicles, wet ceilings, or frost on attic nails, book an inspection. Contact Northline Roofing and we will check the roof and attic together.