Ice Dams: Why They Leak Into Ceilings and How to Stop Them

After a big snow, a row of icicles can look pretty. But thick ice along the edge of the roof often means water is backing up under your shingles. If an ice dam is already leaking into your home, Laurel Dry Pros handles ceiling and drywall water damage repair in Laurel. This guide explains why ice dams form and how to stop them.

This is general information. Roof work is dangerous in winter. Hire a roofing professional for anything above the ground.

What is an ice dam?

An ice dam is a ridge of ice at the edge of a roof that stops melting snow from draining. As more snow melts above it, water pools behind the ice. Shingles shed water running down, but they don't hold back water pooled on them, so it seeps under the shingles and into the attic, walls and ceilings below.

How ice dams form

1. Snow covers the roof.
2. Heat escapes into the attic from the living space through air leaks and thin insulation.
3. The upper roof warms above freezing and snow on it melts.
4. Meltwater runs down to the eaves, which hang past the warm walls and stay cold.
5. The water refreezes at the edge and builds a dam.
6. More meltwater pools behind the dam and leaks into the house.

The University of Minnesota Extension explains that ice dams can be prevented by controlling the heat lost from the home. The problem starts inside, not on the roof.

Do you have an ice dam or just icicles?

Icicles hang off the roof edge. An ice dam is a thick ridge of ice on the roof itself, with water trapped behind it. Travelers Insurance notes that if icicles stay at the gutters with no water trapped behind them, a dam likely hasn't formed. Icicles can still be a warning sign, so keep watching after each storm. Stay out from under large icicles, since they can fall.

Warning signs of ice dams

• Thick ice along the gutters or roof edge
• Large icicles, especially with water dripping behind them
• Water stains or wet spots on ceilings near outside walls
• Peeling paint or wet drywall on upper outside walls
• Damp attic insulation or frost on the underside of the roof
• Water dripping inside window frames on the top floor

What to do if an ice dam is leaking

1. Catch the water. Put buckets and towels under drips. Move furniture and electronics.
2. Check the ceiling. If drywall is bulging, keep people out of the room. A small hole at the lowest point can drain it into a bucket.
3. Turn off power to light fixtures near the wet area at the breaker.
4. Remove snow from the ground. A roof rake can pull snow off the lower few feet of roof so less melts into the dam. Stay off the roof.
5. Don't chip the ice. InterNACHI notes that hacking at ice dams can easily damage the roof, and the homeowner too.
6. Take photos of the ice, the stains and the damage.
7. Dry the ceiling and walls fast. The EPA says wet materials dried within 24 to 48 hours usually won't grow mold.

How to remove an ice dam safely

Most homeowners can do this from the ground. Travelers Insurance describes this method:

1. Rake the snow. Use a roof rake to pull snow off the lower 3 to 4 feet of roof, from the ground.
2. Use calcium chloride ice melt. Don't use rock salt. It can damage the roof.
3. Fill a nylon stocking with the calcium chloride.
4. Lay the stocking across the dam, running up and down the roof, so it melts a channel for water to drain.
5. Cover plants below the gutters with a light tarp. Salty runoff can harm them.

If you can't reach the roof safely from the ground, hire a roofer. Some roofing pros remove ice dams with low-pressure steam, which melts the ice without hurting shingles. Never use a ladder on snow or ice, and never chip at the ice with a hammer or shovel.

The water damage ice dams cause

How to prevent ice dams

The goal is to keep the whole roof cold so snow doesn't melt unevenly.

1. Air-seal the attic floor first. The University of Minnesota Extension says to make the ceiling airtight so warm, moist air can't flow from the house into the attic. Common leaks are around light fixtures, plumbing and wiring holes, attic hatches and chimneys.
2. Add insulation. After sealing leaks, add attic insulation to cut heat loss. The U.S. Department of Energy notes that many older homes have little or no attic insulation and that a properly sealed and insulated attic can help prevent ice dams.
3. Keep vents clear. Natural attic ventilation, such as soffit and ridge vents, helps keep the roof deck at an even temperature. Baffles keep insulation from blocking soffit vents.
4. Fix heat sources in the attic. Leaky ducts, recessed lights and bath fans venting into the attic all add heat and moisture. The University of Minnesota Extension lists recessed lights, skylights, complex roofs and heating ducts in the attic as factors that raise ice dam risk.
5. Keep gutters clean before winter so meltwater can drain.
6. Rake snow off the lower 3 to 4 feet of roof after each big storm.
7. Add a membrane when you re-roof. A water-repellent membrane under the shingles at the eaves is an extra layer of protection if a dam forms.

The National Weather Service notes that winter sun has little effect on attic air temperature. Warm air from the rooms below is usually the cause. That's why the fix is in the attic. Heat cables are a short-term option at best. InterNACHI notes they rarely solve the problem, use electricity and can make shingles brittle.

Ice dams and insurance

Sudden interior water damage from an ice dam is often covered by homeowners insurance, while roof repair from wear and tear may not be. Report the leak quickly and document it. Our Maryland water damage insurance guide explains what's usually covered.

Local note: Older Cape Cods and ramblers in Bowie and Greenbelt often have shallow attics with limited insulation, which raises ice dam risk after a big snow. Some older homes in Silver Spring with finished attic rooms have the same issue.

Related reading: Before the first freeze, read what to do when frozen pipes burst, another common winter leak, and learn how long it takes mold to grow in a wet ceiling.

When should you call a water damage professional?

Call a pro when an ice dam leak has stained or soaked a ceiling or wall, when attic insulation is wet, when drywall is sagging, or when the same spot leaks every winter. Drying the ceiling and wall cavity quickly prevents mold.

Ice dam leak in Laurel? Call (301) 368-0221 to reach Laurel Dry Pros for drying and ceiling repair.

Frequently asked questions

Sources

1. University of Minnesota Extension: Dealing with and preventing ice dams
2. U.S. Department of Energy Building America Solution Center: Blown insulation in existing attics
3. InterNACHI: Ice dam hazards
4. U.S. EPA: Mold Cleanup in Your Home
5. Travelers Insurance: How to identify and help remove an ice dam
6. National Weather Service (Gaylord, MI): Preventing roof ice dams