If you've lived through a Western New York winter, you've seen them: the thick ridge of ice along the edge of a roof, with icicles hanging off it like a curtain. They look like postcard winter. They're actually water damage waiting to happen.
How an ice dam forms
An ice dam forms when heat escaping from the house warms the roof. Snow on the upper roof melts, the water runs down to the colder edge over the eaves, and it freezes again. Do that for a few weeks and the ice builds a dam. The next meltwater has nowhere to go, so it backs up under the shingles and into the ceiling, the walls and the insulation.
The fix is mostly done before the first big snow, and most of it is cheap.
What to do before the snow flies
Clean the gutters after the leaves are down. A gutter packed with wet leaves freezes solid and gives the ice a head start. Clear them once the trees are bare, and make sure the downspouts carry water well away from the foundation.
Find where the heat is getting out. The real cause of ice dams is warm air leaking into the attic. On a cold morning after a light snow, look at your roof: bare patches or stripes where the snow has melted while your neighbors' roofs are still white are telling you where heat is escaping. Common culprits:
- gaps around attic hatches
- recessed lights
- bathroom fans that vent into the attic instead of outside
- thin insulation
Keep the attic cold and ventilated. A cold attic keeps the roof deck cold, so the snow stays snow. Air sealing and insulation stop the heat; vents at the eaves and the ridge carry away what gets through. Make sure insulation isn't blocking the soffit vents.
After a big storm
Get a roof rake, and use it from the ground. After a heavy storm, pulling the first three or four feet of snow off the roof edge removes the fuel for a dam. Stay on the ground, and keep away from power lines.
Don't chip at the ice. Hammers, shovels and ice picks break shingles and gutters, and ladders on ice are how people get hurt. If a dam has already formed and water is coming in, that's the time to call a roofer who does ice-dam removal.
A little attention in November is a lot cheaper than a stained ceiling in February.