Roof Problems · Ice Dams
Icicles look picturesque. The water they force back under your shingles is not. Here's why ice dams form and how to stop them for good.
An ice dam is a ridge of ice that forms along the eave edge of the roof. You'll see thick ice at the gutter line, large icicles hanging from the eaves, and — the telltale sign — water stains on exterior walls or interior ceilings that appear during a thaw, even when it hasn't rained.
In the attic during winter, look for frost on nail tips and sheathing, damp insulation near the eaves, and rusted nails. These are signs that warm, moist air is reaching the roof deck — the root condition behind every ice dam.
Ice dams are a heat problem, not a roofing problem. Warm air leaking from your living space into the attic heats the upper roof deck. Snow melts there, runs down to the unheated eave overhang, and refreezes. Meltwater then pools behind that ice ridge — and standing water on a shingle roof will find its way through, because shingles are designed to shed running water, not hold a pond.
The fix therefore has three parts, and only one involves the roof itself: sealing air leaks from the living space, bringing attic insulation up to current levels, and ensuring balanced intake (soffit) and exhaust (ridge) ventilation so the deck stays cold and uniform.
Common causes
If water is actively entering the house during a thaw, treat it as urgent — interior damage compounds daily. For ice dams without active leaking, schedule an assessment before the next major snow cycle.
Do not chip ice off the roof with tools — you'll damage shingles and gutters. Calcium chloride in a fabric sock laid across the dam can melt a channel as a temporary measure. Never use rock salt, which corrodes metal and kills landscaping below.
Ice dam damage repair usually means replacing waterlogged decking sections and shingles at the eaves, plus adding ice-and-water shield membrane — which Illinois building code requires at eaves on new work for exactly this reason. If your roof is due for replacement, a full tear-off is the opportunity to install proper membrane coverage, ventilation, and correct the conditions that caused the dams.
A few small icicles after a sunny day on fresh snow is normal. Thick ice build-up at the eaves, large icicles returning after every snowfall, or icicles forming behind the gutters (on the fascia or soffit) signal a heat-loss problem.
No. Ice-and-water shield membrane at the eaves stops the water that dams push back, but the dam itself is stopped from inside: air sealing, insulation, and ventilation.
They melt channels through ice but treat the symptom, cost money to run all winter, and do nothing about the energy you're losing through the attic. They're a reasonable stopgap for problem roof shapes while the insulation and ventilation work is planned.
Get a free, no-obligation inspection. We'll confirm the diagnosis, show you photos of what we find, and give you honest options.
Serving Chicago's Northwest suburbs. Licensed & insured. Written findings you can keep.
