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Ice Dams - Its that time of year again

posted Jan 11, 2016, 8:38 AM by Christopher Kidd   [ updated Feb 5, 2016, 9:12 AM ]

The Problem?

An ice dam forms when the roof over the attic gets warm enough to melt the underside of the layer of snow on the roof. The water trickles down between the layer of snow and the shingles until it reaches the eave of the roof, which stays cold because it extends beyond the side of the house. There, the water freezes, gradually growing into a mound of ice.

The flatter the pitch of the roof, the easier it is for an ice dam to get a grip. Gutters at the eaves can also trap snow and ice. If snow and ice build up high enough in the gutter, it can provide a foundation for an ice dam.


The Result!

When an ice dam gets big enough, melted water backs up behind it and seeps underneath the shingles. Eventually, it will drip into the insulation and down into the ceilings and exterior walls beneath the eave, ruining sheetrock and paint. If the ice dam breaks free, it can pull shingles and gutters off with it, and if the roof sheathing stays wet, it can form mildew and start to rot.


Dealing with what has already happened.

1. Remove the ice dam by breaking it up into small chucks. Do not use anything sharp because you could cut through the shingles. This is slow, dangerous work, so hire someone experienced at roofing. Even if you do it safely, the chunks of ice can take pieces of shingle with them.

2. Clear out gutters and downspouts. Again, this is ladder work and an easy way to damage either plastic or metal gutters and downspouts.

3. Melt troughs through the ice dam with ice melt. Do not use rock salt! It will damage paint, metals, and plants beneath the eave and wherever the salty water drains.

Preventing it from happening again in the short term.

You can scrape snow from the roof whenever it falls, using a snow rake from below or a broom or plastic shovel from above. 

Fixing the problem.

The only way to truly fix the problem – is to prevent it in the first place:

1. Seal all points where warm air leaks from the living space into attic.

2. Insulate the attic well enough to prevent the conduction of heat through the ceiling of the living area.

3. Properly vent the space between the attic insulation and the roof sheathing, so any heat that leaks through is carried away.