An ice dam is a ridge of ice that builds up along the bottom edge of a roof, often right in the gutter. It starts in the attic, where heat from the house melts the snow on the roof.
The gutters are where most people first see the ice, so they get the blame. The fix for the ice itself starts in the attic.
What is an ice dam?
An ice dam is a band of ice at the roof edge that blocks melting snow from draining. The water pools behind it, up on the shingles.
Shingles shed water that flows down the roof. Pooled water can work its way under them and leak into the attic, the ceilings and the walls.
Why does an ice dam form?
Three things have to line up. There is snow on the roof, the air outside is below freezing, and the upper part of the roof is above freezing.
Warm air from the house leaks into the attic and heats the roof from below. The snow on top melts, and the water slides down toward the edge.
The lowest part of the roof hangs out past the walls, over no heated space. That edge is as cold as the outside air, so the water freezes there.
The ice often starts in the gutter. Each melt adds a new layer, and the ridge grows up the roof. Chicago winters bring plenty of sunny days near freezing followed by cold nights.
What stops an ice dam?
Less heat reaching the roof. Warm air leaking into the attic through gaps in the ceiling is the usual source.
These steps cut that heat loss:
- Seal the gaps where warm air gets into the attic, around light fixtures, pipes and the attic hatch.
- Add insulation on the attic floor so less heat passes through the ceiling.
- Vent the attic so cold outside air moves under the roof deck.
Check that bathroom and kitchen fans blow outside, and not into the attic. An insulation contractor does this attic work. Our team works on gutters, so if the attic is the cause, we will tell you that first.
Once a dam has formed, some homeowners pull snow off the lower edge of the roof from the ground with a long roof rake. Never climb onto an icy roof, and never chip at the ice with a hammer. Chipping tears shingles and dents the gutter.
Do heat cables work?
Heat cables are electric wires clipped in a zigzag along the roof edge and laid in the gutter. They melt a path so water can drain through the ice.
They can help at one bad spot. The cables do nothing about the warm attic, so ice can build up on the roof above them.
They also need power every time it snows. We do not sell or install heat cables.
Do guards on your gutters cause ice dams?
No. An ice dam comes from heat loss in the attic, and a guard does not change that.
In a hard winter, snow and ice can build up on top of a guard. The same snow and ice would build up in an open gutter.
Guards help in one way. Wet leaves in an open trough freeze into a plug, and that plug is often where the first ice forms. The gutter guards we fit are Raindrop, and they take the leaf pack out of the trough.
What does ice do to a gutter?
Ice is heavy. A gutter packed with it pulls down on every hanger along the house.
Over a winter, that weight can bend the trough and pull the hangers loose. The gutter then tips away from the house, and water gets behind it to soak the fascia board.
After the thaw, walk around the house and look for sags, gaps at the corners and paint peeling in a band under the gutter. Our list of common gutter problems shows what each sign means.
When are the gutters the part to replace?
Replace them when they are bent, split or pulling away, or when the wood behind them is soft. Fixing the attic stops the next dam, and it does nothing for gutters the last one broke.
Our seamless gutter installation uses .032 inch aluminum. We screw QuickScrew hangers into the fascia board every 24 inches.
We fit gutter apron flashing on every install, so water coming off the roof edge goes into the gutter and not behind it. The only seams are at the corners and downspouts, and we seal those with GeoCel.
Our standard size is a 6 inch gutter, with 5 inch available. Every system comes with a lifetime warranty on materials and workmanship.
If ice bent your gutters last winter, call us at (866) 488-7776 or ask for a free estimate. We install and replace gutters, and we do not remove ice, rake roofs or put up heat cables.
