Ice Dams in Minnesota: Causes, Fixes and What Not to Do

Checked against the official sources below on November 12, 2026. By Twin Ports Contractors.

Short answer: An ice dam is mostly a heat problem, not a roofing problem. Warm air leaks from the house into the attic and melts the snow. The water refreezes at the cold roof edge. Seal the attic air leaks first, then consider more insulation. The Minnesota Department of Commerce warns against heating cables, chipping the ice and adding roof vents.

What an ice dam is

An ice dam is a ridge of ice at the edge of a roof. It stops melted snow from draining off. Water pools behind the ice. It can get into the house and damage walls, ceilings and insulation.

Wet areas can also grow mold and mildew. Dry any wet part of the house right away.

Why ice dams form

University of Minnesota Extension lists three things that must happen at the same time:

There is snow on the roof.
The upper part of the roof is warmer than 32 degrees F.
The lower edge of the roof is colder than 32 degrees F.

Extension means average temperatures over a sustained period.

Snow melts on the warm part. The water runs down, reaches the cold edge and freezes. The ice grows as more water arrives.

The heat comes mostly from the house, and only rarely from the sun. The Minnesota Department of Commerce puts it plainly: the main cause of ice dams is attic air leaks. Warm, moist air rises through holes around plumbing vents, electrical wires and chimneys. People once blamed the roofing or the attic vents. The state now says the cause is warm air in the attic.

Extension names other heat sources too:

A kitchen or bathroom exhaust that ends just above the roof.
A chimney, when a wood stove or fireplace is used often.
Ducts in the attic that leak or have too little insulation.

Extension also says some features make ice dams more likely: recessed lights, skylights, a complex roof design and heating ducts in the attic.

If water is coming in right now

Stay off the roof. Extension warns that anyone on a roof in winter, or working on it from below, risks injury and can damage the roof. It says to call professionals for this work.
Have the trapped water let out. Extension says that in an emergency, channels made through the ice dam let the trapped water drain. The only method it gives is hosing with tap water on a warm day, working up from the lower edge. Do not chip at the ice. This is a short-term fix. The channel stops working within days.
Have the snow removed. Snow is one thing an ice dam needs. Extension says a roof rake or push broom can remove it, but either can damage the roofing. Its injury warning covers this work too, even when it is done from below. It says to contact professionals.
Dry the inside. Dry wet ceilings, walls and insulation right away to head off mold.
Wait to repair. Do not fix the ceiling or walls until they are dry. Fix the heat loss at the same time, or the damage will come back.

What not to do

These warnings come from the Minnesota Department of Commerce:

Don’t install heating cables. They shorten the life of your roof and cost money to run.
Don’t break up the ice with chippers, chemicals or heat. These can damage shingles, gutters and other parts of the house.
Don’t add roof vents to cure it. More vents, including powered ones, will not get rid of ice dams and often make things worse.

Extension agrees on powered vents. It says mechanical attic ventilation is not a recommended fix in Minnesota. It can cause moisture problems in the attic and can pull the air pressure in the house too low.

The fix that lasts

Extension gives two steps, in this order:

Seal the ceiling. Make it airtight, so no warm, moist air gets from the house into the attic.
Then look at insulation. After the leaks are sealed, consider more insulation in the ceiling or roof.

The Department of Commerce says spray foam or caulk can seal the leaks, and that doing so saves energy and prevents nearly all ice dams. It also says insulation alone is not enough. Leaking air can even soak the insulation you have, and wet insulation does little.

Two cautions from Extension:

Snow load. Once the fix works, the snow stays on the roof, so the roof carries more weight. A house built to current codes should have no structural problem. If you are unsure about your roof, a professional engineer should be able to evaluate it.
Air for your appliances. When a house is sealed tighter, fans, vents and fuel-burning appliances still need enough air to run safely. Ask your contractor how they check this.

Who to hire for what

The job	Who does it	What to ask
Find and fix the heat loss	A weatherization contractor	Do you run a blower door test? Do you use an infrared camera?
Repair shingles and roof damage	A roofer	What is your state license number?
Repair ceilings and walls	A remodeler or drywall contractor	Will you wait until everything is dry?

Extension says weatherization contractors are professionals who can deal with the heat problem behind ice dams. The contractor should run a blower door test to see how airtight your ceiling is. They may also use an infrared camera to find where heat escapes.

This directory has no weatherization category. Use it to find roofers for roof damage and general contractors for interior repair, and ask each one who will fix the cause. The Department of Commerce brochure points to its home energy pages at mn.gov/commerce/home-energy.

Licenses for this work

These rules cover a person or company that contracts directly with the owner of a home of one to four units. The state lists a few exceptions.

Roofing. Roofing work takes a Minnesota residential building contractor, residential remodeler or residential roofer license.
Gutters, soffit and fascia. A roofer license covers roofing only. A licensed roofer cannot also contract for gutters, downspouts, soffit or fascia under it.
More than one kind of work. Work in more than one of the state’s special skill areas takes a building contractor or remodeler license.
One kind of work only. A specialty contractor with a single skill, other than roofing, does not need a state license.

Ask each contractor which of these applies to them. See what licensed, registered, bonded and insured mean, then check the license before you sign.

Questions to ask before you hire

Will you find and seal the air leaks before you add insulation?
Will you run a blower door test?
How will you make sure my furnace, water heater and fans still get enough air?
Do you hold a state license? What is the number, and what type is it?
Will you put the work and the price in writing?

Common questions

Do roof vents stop ice dams?

No. The Minnesota Department of Commerce says adding roof vents, including powered vents, will not eliminate ice dams and often makes the problem worse.

Will more insulation alone fix an ice dam?

No. The Minnesota Department of Commerce says insulation alone is not enough. University of Minnesota Extension says to seal the air leaks first, then consider more insulation.

Are heating cables a good fix?

The Minnesota Department of Commerce advises against them. It says heating cables shorten the life of your roof and cost money to run.

Can I rake the snow off my roof?

University of Minnesota Extension says a roof rake or push broom can remove snow but may damage the roofing. It warns that anyone on the roof in winter, or working on it from below, risks injury, and it says to contact professionals.

Sources

Every rule, number and deadline in this guide comes from these official pages, read on November 12, 2026. Rules change. The source is always the final word.

This guide is general information, not legal advice.