Northwoods roofing guide

Ice Dams on Northwoods Roofs: How to Stop Them for Good

Ice dams are the number one cause of winter roof leaks in Tomahawk, Minocqua, Rhinelander, and Merrill. They are also almost entirely preventable. Here is exactly how they form on a Wisconsin lake home or cabin — and what actually fixes them.

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Why Northwoods roofs get ice dams

Northern Wisconsin gives ice dams everything they need: a deep, persistent snowpack that insulates the roof deck, long stretches below freezing, and sunny afternoons that melt the top layer. Add an attic that leaks heat and the snow melts from underneath, runs down to the cold overhang, and freezes into a ridge of ice at the eave.

Once that ridge is a few inches tall, meltwater pools behind it. Shingles shed water — they do not hold standing water — so it wicks up under the courses and finds the deck. The stain that shows up on your ceiling in February started as heat leaving your living room in December.

Cabins and seasonal lake homes are especially prone to it. Cathedral ceilings with almost no rafter cavity, additions built without soffit, and thermostats swinging between 50°F and 70°F on weekends all drive the melt-freeze cycle harder.

The five-step fix we use on Northwoods homes

1. Air seal the ceiling plane
Recessed lights, bath fans, attic hatches, chimney chases, and top plates leak warm air straight into the attic. Sealing them is the highest-return step and always comes first.
2. Bring insulation up to depth
Most older Northwoods homes and cabins sit well under R-49. Adding depth evenly — including out over the exterior walls without blocking the soffit — keeps the deck cold.
3. Balance intake and exhaust ventilation
Continuous soffit intake paired with ridge exhaust keeps outside air washing the underside of the deck. Baffles at each rafter bay stop insulation from choking the intake.
4. Detail the eaves for water that gets through anyway
Ice-and-water shield past the warm wall line, in valleys, and around penetrations means a dam that does form still cannot push water into your ceiling.
5. Fix the trouble spots that repeat every year
Dormer cheeks, cathedral ceilings, additions with no soffit, and unheated porch roofs off a heated wall are the usual repeat offenders. Each needs its own detail, not a blanket fix.

Warning signs to check before winter

Thick icicles hanging off the gutters or eaves
Bare stripes of melted roof while neighbors stay snow-covered
Water stains at the top of exterior walls or around window headers
Damp, matted, or frosted attic insulation near the eaves
Gutters pulling away or fascia rot on the north side
Peeling paint on soffits and overhangs

Ice dam questions, answered

What actually causes ice dams on a Northwoods roof?

Heat escaping the living space warms the roof deck, melts the snowpack above it, and that meltwater refreezes when it reaches the cold overhang. The ridge of ice that builds at the eave backs water up under the shingles. It is a heat-loss problem far more often than a shingle problem.

Will more attic insulation alone stop ice dams?

Rarely. Insulation slows heat loss, but without balanced intake ventilation at the soffit and exhaust at the ridge, the attic still warms up. The fix is almost always insulation, air sealing, and ventilation together.

Do ice dams mean I need a new roof?

Not necessarily. If the deck and shingles are sound, we can often solve it with air sealing, added insulation, and corrected ventilation. If the roof is already due for replacement, that is the moment to add ice-and-water shield well past the exterior wall line.

How far up should ice-and-water shield go on a Wisconsin roof?

Far enough to extend at least 24 inches inside the warm wall line — on low-slope roofs and deep overhangs common on Northwoods cabins, that often means two or three courses. We also run it in every valley and around every penetration.

Is raking snow off the roof a real fix?

It is a temporary one. Raking the lower few feet removes the fuel for the dam, but it does nothing about the heat loss that caused it, and it risks damaging shingles. Use it to get through a bad winter, then fix the cause.

Does homeowners insurance cover ice dam damage?

Interior water damage from an ice dam is often covered, while the underlying roof or insulation defect usually is not. Document everything with photos and call us for a written inspection before you file.

Ice dam help in your town

Seeing icicles or stains already? Call 715-453-4800 and we’ll get up there and tell you exactly what is causing it — free.