Ice Dams in Manitoba: What Causes Them and How to Stop Them

Icicles look nice.

What's happening behind them doesn't.

If you've spent a few winters in Manitoba, you've probably seen it: a thick ridge of ice along the edge of the roof, a row of icicles hanging off the eavestroughs, and maybe a brown water stain showing up on a ceiling sometime in March. That's an ice dam, and it's one of the most common calls we get once the snow starts flying.

Here's the good news: ice dams aren't bad luck. They have a clear cause, and in most homes they can be fixed for good. Below, we explain what's actually going on, the warning signs to check for this fall, and the fixes that work (and the ones that don't).

What is an ice dam?

An ice dam is a ridge of ice that forms at the edge of your roof and stops melting snow from draining off. The water backs up behind the ice, works its way under the shingles, and ends up in your attic, walls or ceilings.

How ice dams form

It starts in the attic, not on the roof:

1. Warm air from your house leaks into the attic through gaps around light fixtures, the attic hatch, plumbing stacks and bath fans.

2. That heat warms the roof deck and melts the bottom layer of snow, even when it's -20°C outside.

3. The meltwater runs down to the eaves, which hang out past the heated part of the house and stay cold.

4. It refreezes there. Every melt-and-freeze cycle makes the ice ridge bigger.

5. Eventually, water pools behind the dam and backs up under the shingles.

Manitoba winters are practically built for this: deep snow, long cold stretches, and those late-winter days where it's sunny and +2°C at noon and -18°C overnight.

Warning signs to look for

You can spot most of these from the driveway:

• Thick ice along the edge of the roof or packed into your eavestroughs

• Big icicles, especially with ice running down the siding behind them

• Bare or melted patches on your roof while the neighbours' roofs are still snow-covered

• Water stains or peeling paint on ceilings near exterior walls

• Frost, damp insulation or dark stains on the roof boards in your attic

• Eavestroughs that sag or pull away from the fascia after winter

If you're seeing any of these, get your roof and attic checked before the next big snowfall. Not sure if the damage goes deeper? Our post on signs you need a roof repair or full replacement walks through what to look for.

Ice dam fixes at a glance

Fix	What it does	Long-term solution?
Air sealing the attic floor	Stops warm air from leaking into the attic	Yes
Topping up attic insulation	Keeps heat in your living space	Yes
Balanced ventilation (soffit + roof vents)	Keeps the roof deck cold and even	Yes
Leak barrier at the eaves	Protects the roof deck if water backs up	Yes, installed with a new roof
Clean, properly sized eavestroughs	Lets meltwater drain instead of freezing in place	Yes
Raking snow off the roof edge	Removes the snow that feeds the dam	Short-term
Heat cables	Melts drainage channels through the ice	Short-term
Chipping or chopping the ice	Damages shingles and eavestroughs	Not recommended

Air sealing and insulation

This is the big one. If heat isn't getting into the attic, the snow on your roof doesn't melt from underneath, and there's nothing to refreeze at the eaves. Sealing the gaps comes first, then topping up insulation. A lot of older homes in Winnipeg, Winkler and Morden have far less attic insulation than homes built today, and it's often settled or packed down over the years.

Ventilation: soffit to roof

A healthy attic breathes. Cold outside air comes in through the soffit vents, flows up under the roof deck, and exits through roof or ridge vents. That airflow keeps the whole roof the same cold temperature so snow doesn't melt unevenly. One of the most common problems we find: soffit vents that are blocked by insulation, or older solid soffit with no venting at all.

Leak barrier at the eaves

When a roof is replaced properly in Manitoba, a self-adhering leak barrier membrane goes down along the eaves before the shingles. It seals around the nails, so if water does back up behind an ice dam, it can't get into the roof deck. It won't stop ice dams from forming, but it's your backup plan when one does.

Eavestroughs and downspouts

Eavestroughs full of leaves in October are full of ice in January. Clean them out in the fall, and make sure they're properly pitched and sized so water can drain away from the house. Seamless eavestroughs also mean fewer joints for ice to pry apart.

What about quick fixes?

Short-term fixes can buy you time, but they won't solve the problem:

• Roof rake: Pulling the bottom metre or so of snow off the roof from the ground removes the snow that feeds the dam. Stay off the roof itself.

• Heat cables: These can help in one or two problem spots, but they treat the symptom and add to your power bill.

• Don't chip the ice: Hammers, axes and ice picks crack shingles and dent eavestroughs. Rock salt is hard on shingles, metal and your flower beds.

If water is already coming inside, call a pro. Climbing an icy roof in a Manitoba winter isn't worth the risk.

Does a metal roof stop ice dams?

It helps a lot. Metal's smooth surface sheds snow much better than shingles, so there's less snow sitting at the eaves to freeze. But if heat is pouring into your attic, you'll still want to fix that, no matter what's on the roof. We compare both options in our asphalt shingle vs. metal roof guide.

Why ice dams are a whole-exterior problem

Ice dams form right where your roof, soffit, fascia and eavestroughs all meet. Fix one piece and ignore the others, and the problem usually comes back.

We've been doing exterior work across Manitoba since 1986. We have dedicated crews for roofing, soffit and fascia, and seamless eavestroughs, so each part of the job is done by people who do that work every day, and we make sure it all works together as one system. As a GAF Master Elite contractor, our roof installs are backed by our 24-month workmanship warranty on top of the manufacturer's warranty.

Frequently asked questions

-Does home insurance cover ice dam damage?

Many policies cover sudden water damage inside the home caused by an ice dam, but coverage for the roof itself and for long-term damage varies a lot. Check with your insurance provider about your specific policy.

-Does an ice dam mean I need a new roof?

Not always. Often the fix is in the attic: air sealing, insulation and ventilation. If the shingles or roof deck are damaged, or your roof is near the end of its life, replacement may make more sense. We'll give you an honest answer either way.

-When is the best time to fix ice dam problems?

Fall, before the snow builds up. Cleaning eavestroughs and checking your attic now can save you a lot of trouble in February. If you need a new roof, booking early helps you get on the schedule.

-Are heat cables worth it?

They can help with a stubborn problem spot, like a valley over a front entrance. But they don't fix the cause, and they need to be installed carefully to avoid damaging shingles.

-Do you service my area?

Yes. We work across Winnipeg, Winkler, Morden, Altona, Morris, Carman, Portage la Prairie, Emerson, Manitou and the Brandon area.

-Is financing available?

Yes. We offer 0% interest financing through Financeit on approved credit, with 3- and 6-month plans.

Get ahead of ice dams this winter

The best time to deal with an ice dam is before it forms. Book a free inspection and we'll check your roof, attic ventilation, soffit and eavestroughs, then tell you straight what needs fixing and what doesn't.

Call 1-800-287-5567 or request your free quote.