How to Prevent Ice Dams: What Your Gutters Have to Do With It

What an ice dam actually is

An ice dam is a ridge of ice that forms along the lower edge of a roof. Snow higher up melts, the water runs down under the snow, and when it reaches the colder eave it freezes again. Over days and weeks that ice builds into a wall, and new meltwater pools behind it.

That pooled water is the real problem. Shingles are made to shed water running downhill, not to hold back standing water, so it can work its way underneath them and into the roof deck, the attic insulation and eventually the ceilings and walls inside.

The main cause is heat, not gutters

It helps to be honest about this up front: most ice dams start in the attic. When warm air from the house leaks into the attic, it heats the underside of the roof and melts the snow on top, even on days that are well below freezing. The eaves, which hang out past the warm part of the house, stay cold, and that's where the water refreezes.

That's why the long-term fixes are usually air sealing, attic insulation and roof ventilation, which keep the roof deck cold and evenly cold. If your home gets ice dams every winter, it's worth having a roofer or energy auditor look at the attic. No amount of gutter work fully solves a heat-loss problem.

Where gutters come in

Gutters don't create ice dams, but they can make them bigger and more damaging. A gutter packed with wet leaves holds water instead of draining it. When that water freezes, the gutter becomes a solid trough of ice at the roof edge, which gives meltwater from above one more place to back up.

Weight is the other issue. A gutter full of soggy debris and then ice is very heavy, and that load can pull the hangers loose, bend the gutter or pull it away from the fascia board. Once a gutter sags or tilts the wrong way, it drains even worse the next winter.

Blocked downspouts cause a similar problem. If the downspout is clogged or its outlet is frozen shut, water that does reach the gutter has nowhere to go and refreezes in place.

What to do before the first hard freeze

Clean the gutters after the leaves are down. In the Chicago area that usually means a cleaning in late fall, once most of the trees over your roof have dropped their leaves. Cleaning too early in the fall can leave you with full gutters again by December.

Flush the downspouts and check where they drain. Water should run freely from top to bottom and come out far enough from the house that it doesn't pool and freeze against the foundation or across a walkway.

Look for sagging or loose sections. Gutters that pull away from the fascia, hold standing water or drip at the seams should be fixed before winter, while the work can be done safely. Gutter guards are also worth considering on heavily wooded lots, since they keep most leaves out of the channel through the late-fall drop.

Keep an eye on the attic. Frost on the underside of the roof sheathing, damp insulation or icicles that appear mainly over heated rooms are all signs that warm air is getting where it shouldn't.

If an ice dam has already formed

A roof rake with a long handle, used from the ground, can pull the bottom few feet of snow off the roof after a big storm and take away much of the snow that feeds an ice dam. Be gentle so you don't scrape the shingles, and stay well clear of power lines.

Don't chip at the ice with a hammer, shovel or ice pick. It's very easy to crack shingles or punch through the gutter, and working on a ladder against an icy roof edge is dangerous. If water is already coming inside, call a roofing contractor who handles ice dam removal.

Get your gutters ready for winter

EcoTouch Service cleans gutters and downspouts, repairs leaking and sagging sections, and installs gutter guards. Our gutter services start at $129, gutter guard installation starts at $499, and first-time customers get 25% off their first service. We'll give you a clear price before any work begins.

We work across Chicago and the suburbs, from our Crystal Lake base in McHenry County to the North Shore and western suburbs. Request a free quote and we'll get your gutters cleared and draining properly before the snow arrives.