Ice Dams

Ice Dams: Removal and Prevention

Ice dam removal by steam, now, then fixing the attic insulation and ventilation that caused it, so next January in Wisconsin is different.

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The Answer

Ice Dam Removal In Wisconsin: Steam Now, The Attic Fix After

Ice dam removal in Wisconsin is low-pressure steam — never picks, hatchets or pressure washers — followed by the fix that stops it coming back: air-seal the attic, open and baffle the soffits, then insulate. An ice dam is an attic problem that presents as a roof problem; the roof is rarely the fault.

The icicles hanging off the gutter are the visible symptom; the dam behind them is the damage, and the reasons a Watertown eave ices up are below, in order.

The Cause

The Mechanism: A Warm Attic, Melting Snow, Refreezing At The Cold Eave

Heat escaping into the attic melts snow high on the roof. The meltwater runs down to the eaves, which are cold because there is no house underneath them, and refreezes. The resulting ridge of ice traps the next lot of water, which backs up under the shingles and into the house. The icicles hanging off the gutter are the visible symptom; the dam behind them is the damage.

Chipping the ice off solves this January. Air-sealing the attic and balancing the ventilation solves it permanently, and it is why ice dams on a roof in Watertown are one of the few roofing problems where the roof is not really the fault. The ventilation page is the other half of this one.

The Work

The Real Fix Is Ventilation And Insulation

Steam removal

Low-pressure steam melts the dam without damaging shingles. Never ice picks, hatchets or pressure washers, all of which we get called to repair in the spring.

Find the heat source

Recessed lights, bath fans venting into the attic, gaps around the chimney chase, missing insulation over the top plate. Usually several at once.

Air-seal and insulate

Sealing the leaks matters more than adding depth. Insulation slows heat; air sealing stops it.

Balance the ventilation

Cold intake at the soffit, exhaust at the ridge. A cold attic does not melt the snow above it, and SPS 322.39 sizes the openings.

Ice barrier membrane

At the next replacement, membrane at the eaves means a future dam backs water onto a waterproof layer rather than into the ceiling. The code requires it on low slopes; we fit it on all of them.

Heat cable, sometimes

On a few problem geometries — a north-facing valley over a porch — cable is the pragmatic answer. It is a management tool, not a fix.

The state code requires ice dam protection at the eave only on roofs of 4:12 or less — a membrane from the edge to at least 30 inches up the slope and at least 12 inches past the inside face of the wall, under SPS 321.28(4), which the replacement page quotes in full. On steeper roofs the code is silent, and plenty of roofs in this county have no membrane at all. We fit it on every replacement whatever the pitch, because a Watertown eave ices up regardless of what the code assumes.

The Damage

What An Ice Dam Does If It Is Left

Under the shingles

Water backs up behind the ice and over the top of the course below, into the nail holes. Once it is past the underlayment it is in the house.

The gutter

Ice weighs a great deal. A gutter full of it pulls its hangers out of the fascia, and the fascia behind rots where water sat against it all winter.

The ceiling and wall

The stain appears at the top of the exterior wall or along the ceiling edge, usually in a thaw. Behind it the insulation is saturated and the drywall is failing.

The shingles themselves

Freeze-thaw under the dam lifts and cracks the eave courses. A roof that had five years left loses them at the edge first.

Straight Answers

Ice Dam Questions

Please do not. Every winter someone takes a hammer to a dam, breaks the shingles underneath, and turns a seasonal nuisance into a spring replacement — and no policy covers damage the homeowner did with a hatchet. Falls off icy ladders are the bigger risk. If water is coming in tonight, the emergency page has what to do inside; the roof can wait for daylight and steam.

Interior water damage from an ice dam is often covered as a sudden loss. The cost of removing the ice, and of fixing the insulation and ventilation that caused it, usually is not, because those are maintenance rather than damage. Check your policy — this varies more than most coverage — and photograph the dam and the interior stain before anything is removed. The claims section covers how to document a loss.

Different attic. A well-sealed, well-ventilated attic keeps the roof deck close to outside temperature, so the snow on it does not melt in the first place. Look at the two roofs after a snowfall: the one that stays white for days is the cold attic, and the one with a bare stripe along the ridge and icicles at the gutter is losing heat. The ventilation page explains what to do about it.

Rarely. Blowing more insulation over unsealed light fixtures and duct penetrations slows the heat loss without stopping it, and blown insulation pushed into the eaves blocks the soffit intake — which SPS 322.39 forbids and which makes the attic warmer, not colder. Air sealing first, baffles at the eaves, then insulation. Done in that order it is the cheapest fix in this trade.

No, though they get blamed. A full gutter gives the ice somewhere to build and makes the icicles bigger, but the melt is caused by heat in the attic, not leaves in the trough. Clean gutters are still worth having — the gutter page explains what they actually protect — and the FAQ covers what else gets blamed on the roof unfairly.

All roofing services

Replacement, repair, storm work, inspections, ice dams and ventilation, and how they fit together.

Roofing services

The questions we get asked

Cost, timing, permits, insurance and warranties, answered plainly on one page.

Roofing FAQ

Attic ventilation

The permanent fix. Intake and exhaust sized to the ceiling area, and the soffits actually open.

Ventilation

Roof replacement

Ice barrier at every eave, whatever the pitch, is part of every roof we put on. What else is in the scope.

Replacement

Winter Work

Ice Backing Up Under Your Shingles?

We will steam it off, then tell you what in the attic caused it.

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