Ice Dams in Hermantown: Why They Form and How to Stop Them

If you've spent a winter or two in Hermantown, you've seen them: a thick band of ice along the edge of a roof, icicles as long as your arm, and sometimes a brown stain creeping across a ceiling near an outside wall. Ice dams are a common winter headache in the Northland, and a misunderstood one. Most people blame the shingles or the gutters. The real cause is almost always in the attic.

How an ice dam forms

An ice dam needs three things at once: snow on the roof, an upper roof warm enough to melt it, and a roof edge cold enough to freeze the water again.

Heat escaping from the living space warms the attic, and the attic warms the underside of the roof. Snow sitting on that warm section melts from the bottom up, even on a day that's well below freezing outside. The meltwater runs down the roof until it reaches the eave, the part of the roof that hangs out past the wall. There's no heated house under the eave, so it's as cold as the outdoors, and the water freezes again.

Every melt and refreeze makes the ice thicker. Before long there's a dam of ice at the edge of the roof with a pool of water behind it, and that water starts working its way under the shingles. Shingles are made to shed water running downhill, not to hold back a puddle, so the water gets through to the attic, the insulation, the walls and eventually the ceiling below.

Why Hermantown homes get ice dams

Hermantown sits higher than Duluth and farther from Lake Superior, so it misses the milder winter air the lake gives the shoreline. Winters run colder, and snow piles up and stays on the roof for weeks instead of melting off between thaws. A deep, long-lasting layer of snow is exactly what an ice dam needs. It also works like a blanket, holding the attic's heat against the roof.

The houses play a part too. Much of Hermantown was built from the 1970s on, and homes that age often leak more warm air into the attic than their owners realize. The usual culprits are gaps around recessed lights, bath fans, plumbing vents and chimneys, plus an attic hatch with no weatherstripping. Add insulation that has settled over the decades, and a lot of household heat ends up right under the roof, which is exactly what melts the snow.

Signs you have an ice dam problem

• Thick ice along the bottom edge of the roof, especially above heated rooms. If the roof over an attached garage stays clear while the roof over the house builds ice, heat loss is the cause.
• Icicles forming behind the gutter or under the roof overhang, not just hanging off the front edge.
• Water stains, peeling paint or bubbling drywall on ceilings, or high on the walls along the outside of the house.
• Bare patches on the roof on a cold day while the rest of the roof, or your neighbor's roof, is still covered in snow.
• Frost in the attic on the underside of the roof boards or on the tips of nails poking through, or damp, matted insulation along the attic's edges.

What to do if you have an ice dam right now

• Rake the snow off, from the ground. A long-handled roof rake can pull the bottom few feet of snow off the roof, which removes the snow most likely to melt and refreeze at the edge. Go gently, since scraping hard can damage shingles.
• Don't climb up and chip at the ice. A hammer or ice pick will damage the shingles, and an icy roof is a dangerous place to be. A fall is a far bigger risk than a leak.
• If water is coming inside, call an ice dam removal service. They use steam to melt channels through the dam so the water can drain, without damaging the shingles underneath.
• Don't count on heat cables. They can keep one trouble spot draining, but they don't stop ice from forming elsewhere, they cost money to run all winter, and they do nothing about the heat that's causing the problem.

How to stop ice dams for good

The lasting fix is to keep the attic cold, so the roof stays close to the outdoor temperature and snow can't melt from underneath. That comes down to three things, in this order.

1. Air sealing. Stop warm household air from getting into the attic in the first place. Sealing gaps around light fixtures, pipes, vents, chimneys, the tops of walls and the attic hatch is usually the single biggest improvement, and a home energy audit can show you exactly where your attic is leaking. The Minnesota Center for Energy and Environment calls air sealing and insulating the attic the best solution for ice dams.
2. Insulation. Once the leaks are sealed, enough insulation on the attic floor keeps the remaining heat in the house, where you're paying for it to be.
3. Ventilation. Vents under the roof overhang and along the peak let cold outside air move through the attic and carry off whatever heat and moisture still get in. Ventilation helps, but it can't keep up with an attic full of air leaks, so it works best after the first two.

You'll notice a new roof isn't on that list. A new roof over a warm attic will get ice dams just like the old one did. We made the same point in our post on roofing built for Duluth winter weather, and it's the most important thing to understand before you spend money on a fix.

Where the roof comes in

When a roof does need replacing, it's the right time to add protection for the winters that overpower even a well-sealed attic.

The most important piece is ice and water shield: a sticky, waterproof sheet that goes down under the shingles along the bottom edge of the roof and in the valleys where two slopes meet. That's where ice dams do their damage. It seals around every nail, so water that backs up under the shingles has nowhere to go. Minnesota's building code requires it along the bottom of the roof, and on low-slope roofs or homes with deep overhangs it's worth running it farther up than the minimum.

The second is ventilation. Every Covenant Builders roof replacement includes vents under the overhang and along the peak, either installed new or checked to make sure they're working, so the attic can breathe.

Finally, a good roofing estimate includes a look in the attic, not just at the shingles. A contractor who only wants to talk about colors hasn't figured out why you're getting ice dams. Our guide to vetting a roofing contractor covers the questions worth asking before you sign anything.

Do gutters cause ice dams?

No. Ice dams form with or without gutters, because the cause is heat escaping into the attic. Gutters do take a beating from the ice, though, and a gutter that pulls away under the weight can rip off the trim board it's mounted to. That's why, for gutter installation this far north, the hangers and how closely they're spaced matter as much as the gutter itself. We cover that in our post on protecting Cloquet foundations.

If you're seeing ice dams or ceiling stains this winter, or you're planning a new roof and want it built to stand up to them, call Covenant Builders at (218) 590-1293 or request a free estimate. We're based in Saginaw and work on homes throughout Hermantown and the surrounding area.