An ice dam is a ridge of ice that builds up along the bottom edge of your roof. It forms when heat from the house warms the upper roof, the snow up there melts, and the water freezes again when it reaches the cold eaves. Water then pools behind that ice, works its way under the shingles and shows up as stains on your ceiling or walls. In western Pennsylvania, where snow often sits on roofs for days and temperatures swing above and below freezing, ice dams are one of the most common winter roof problems in Mercer, Lawrence, Butler and Beaver counties.
The good news: ice dams have a clear cause, and that cause can be fixed. Here is how they form, how to spot one, what to do (and not do) when you see one, and how to stop them from coming back.
How an ice dam forms
Three things have to happen at the same time:
- Snow on the roof. A few inches is enough.
- A warm upper roof. Heat escapes from the living space into the attic through gaps around light fixtures, attic hatches, plumbing pipes and thin insulation. That warms the roof deck above freezing, so the snow melts from underneath.
- Cold eaves. The roof edge hangs past the outside walls, so there is no heated space under it. When the meltwater runs down and reaches that cold edge, it freezes again.
Each day the ridge of ice grows a little taller. Meltwater keeps coming from above, gets trapped behind the ice and backs up under the shingles. Shingles are made to shed water running downhill, not to hold back standing water, so it finds its way through to the roof deck, the insulation and eventually your ceiling.
Our region makes this worse. A typical western PA winter brings snow, a thaw, then a hard freeze, often in the same week. The National Weather Service office in Pittsburgh, which covers Mercer, Lawrence, Butler and Beaver counties, posts winter storm watches and freezing forecasts that are a good early warning for ice dam weather.
Signs you have an ice dam
You can check for most of these from the ground or from inside the house:
- Thick icicles hanging from the gutters or roof edge. A few thin icicles are normal. A heavy row of them, or ice that has built up over the gutter itself, usually means water is melting and refreezing at the eaves.
- A ridge of ice along the bottom few feet of the roof, with snow still sitting on the roof above it.
- Water stains, peeling paint or damp drywall on ceilings or upper walls near the outside of the house. Ice dam leaks tend to show up along exterior walls, not in the middle of a room.
- Wet or matted insulation in the attic, or frost and water drops on the underside of the roof deck and nail tips.
- Gutters sagging or pulling away from the fascia. Ice is heavy, and a gutter full of it can bend brackets and loosen the boards behind it.
If you see water coming inside, treat it as a leak and act on it the same day. Our guide to roof leak detection explains why the stain is often a few feet away from where the water actually gets in.
What to do if you see an ice dam right now
The first rule is safety. Winter roofs are slick, ladders slip on ice, and a falling slab of ice can hurt someone. Here is what to do:
- Stay off the roof. Don’t climb a ladder onto an icy roof to deal with it yourself.
- Don’t chip at the ice with a hammer, ice pick or shovel. It is very easy to crack shingles, tear the gutter or punch a hole in the roof.
- Keep people and pets out from under heavy icicles, especially near doors and walkways.
- Catch the water inside. Put down buckets and towels, move furniture and electronics, and take photos of any stains or drips with the date on them.
- Call a roofer. If water is getting in, Big River Roofing offers same-day emergency tarping to protect your home, then a free inspection and written estimate for the permanent repair. Call (724) 877-7380.
Small ice dams often melt away on the next warm, sunny day. The ones to worry about are the ones that keep growing, or that are already putting water inside.
How to stop ice dams from coming back
Breaking up the ice only treats the symptom. The lasting fix is keeping the attic cold, so the snow on the roof melts evenly from the sun instead of from your furnace. That comes down to three things.
1. Seal the air leaks into the attic
Warm, moist air from the house rises into the attic through every small gap: around recessed lights, bath fans, attic hatches, chimneys and plumbing vents. Sealing those gaps is usually the most effective step. ENERGY STAR notes that proper insulation and air sealing keep attics cold in winter by blocking heat and moist air from below.
2. Add enough insulation
Insulation on the attic floor slows the heat that air sealing doesn’t stop. Thin or uneven insulation, especially near the eaves, leaves warm spots on the roof right where ice dams start.
3. Balance the attic ventilation
A healthy attic pulls cold outside air in at the soffits and lets it out at the ridge. That steady airflow keeps the underside of the roof close to the outdoor temperature. One common mistake is covering soffit vents with insulation, which ENERGY STAR specifically warns against. Big River installs roof ventilation and ridge vents, and our free roof inspection includes a look at the vents.
When a roof is being replaced, the eaves can also get a waterproof underlayment, often called ice and water shield, under the shingles. It doesn’t stop an ice dam from forming, but it gives the roof a second line of defense if water does back up. If your roof is near the end of its life, our roof replacement page explains what a full tear-off includes.
Do clogged gutters cause ice dams?
Not on their own. The main cause is heat escaping into the attic. But gutters packed with leaves hold water and freeze solid faster, which gives an ice dam a head start and adds weight to the roof edge. Cleaning gutters in late fall, after the leaves drop, is still worth doing. Our roof maintenance guide has a full fall checklist.
When an ice dam has already caused damage
After the ice melts, look for the same signs you would after any leak: stained ceilings, soft drywall, damp attic insulation and shingles that look lifted or cracked along the eaves. Gutters that were bent by the weight of the ice may need to be reset or replaced. If the decking stayed wet for a long time, it is worth having someone check for soft or sagging spots, which our structural roof repair team handles.
Many repairs are small. A section of shingles, a run of gutter, or a ventilation fix can be all it takes. Big River will give you an honest answer on roof repair versus replacement after a free inspection.
Frequently asked questions about ice dams
Are ice dams covered by homeowners insurance in Pennsylvania?
It depends on your policy. Coverage for the roof and for water damage inside the house can be treated differently, so read your policy or ask your agent before you file. The Pennsylvania Insurance Department has consumer guides on homeowners coverage, and Big River offers insurance claims assistance when storm or ice damage is covered.
Can I get rid of an ice dam myself?
Not safely from the roof. Chipping at the ice can crack shingles and damage gutters, and icy roofs and ladders cause serious falls. Small ice dams often melt on the next warm day. If one keeps growing or water is getting inside, call a roofer.
Does an ice dam mean I need a new roof?
Usually not. Most ice dams come from heat escaping into the attic, not from a worn-out roof. Fixing air leaks, insulation and ventilation often solves the problem. An inspection after the ice melts will show whether any shingles, flashing or decking need repair.
Will a metal roof stop ice dams?
A metal roof sheds snow faster than shingles, which leaves less snow to melt and refreeze at the edge. It does not fix a warm attic, though, so air sealing and ventilation still matter. Our metal roofing page covers how metal handles western PA winters.
When is the best time to fix the cause of ice dams?
Before the snow arrives, ideally in the fall, so the attic is ready for the first freeze. If you are already dealing with one, call for help with any leaks now and plan the attic and ventilation work for the next dry stretch of weather.
Get your roof checked before the next freeze
If you had ice dams last winter, or you’re seeing icicles and stains this year, a free roof inspection is the quickest way to find out why. Big River Roofing serves Hermitage and homeowners across Mercer, Lawrence, Butler and Beaver counties from our office at 2404 E. State Street in Hermitage. Call (724) 877-7380 or request your free estimate online.
