Prevent Ice Dams Before They Start

The time to think about ice is before the winter sets in and temperatures in the Lower Mainland plummet on a daily basis. In particular, now is the time to work to head off “ice dams” that may form on your roof this winter and cause significant and expensive damage.

An ice dam forms when the roof deck of your Vancouver area home is warmed by the sun or heat rising from your home’s interior. This melts the snow covering your roof from the bottom up. The melted snow runs down to the edge of the roof where it is again exposed to frigid air and refreezes, either on the roof edge or in a clogged gutter. This is what forms an ice dam.

When an ice dams forms, the additional snowmelt that runs down your roof has no place to go except to be forced back up and under your roof shingles and into the home. Once water gets into your home it can travel anywhere — along the rafters, across ceilings, down walls and even into the basement. The damage can be extensive and expensive, including rotted wood, mold, mildew, stains and cracked foundations.

The cause of ice dams is not actually the roof, but the attic that lies beneath. If your attic gets too warm it heats up the roof deck and causes the snow to melt. The secret to preventing this is to lower the temperature in your attic to match that of the roof.

There are two ways to do this, and we recommend using both of them. The first is to install a full-length ridge vent along the peak of your roof. This allows air to circulate under the roof deck and not only prevents freezing, but also helps to avoid the build up of moisture in the attic.

The second step is to install adequate insulation on the floor of your attic. The insulation should not be directly attached to the underside of the roof deck. Good insulation will keep warm air from your home from rising up to the roof and heating the roof deck, thus causing the accumulated snow to melt. There is an added bonus, as insulation can also help reduce your heating costs.

The best time to take these steps is before the first snow falls here in Vancouver. Ice dams can form without you even knowing it and may not become obvious until the damage is done.