Ice Dams

1/23/2021 (Permalink)

Ice Dam on a Roof

It looks like we have a winter storm moving into NJ this week.  At SERVPRO this means we will likely receive calls for water leaking through the ceiling.  The most common cause during winter storms is Ice Dams.

Ice dams form when the snow melts, runs down your roof and refreezes near the edge or in a valley. This only occurs when the roof has colder and warmer spots which allow the water to melt and then refreeze.  Where the water refreezes it masses and creates a ‘dam” which pushes the water back up the roof.  This water pushing/flowing against the usual force of gravity helps it to find openings to penetrate the roof and ceiling below. 

Typically, heat escapes through ceilings into the attic and warms the wood and shingles directly above it. Although the outdoor temperature is below freezing, the snow melts over the warmed section of roof. Ideally, you should not see the snow melting on the roof if the temperature is below freezing.  This means sufficient heat is escaping from your home’s living spaces to provide enough warmth to melt the snow.  You should also not see uneven melting as evidenced by bare shingles next to patches of snow.  The melted areas show where the strongest heat loss is occurring.

If you see these warning signs on your roof you should take steps to prevent an ice dam from occurring.  The overall strategy is to keep the roof cold which also makes your home more energy efficient and comfortable.  Three steps to consider are:

1. Look for openings which may be causing heat loss such as gaps around pipes and air ducts which can easily be filled with spray foam.
2. Make sure the attic floor is properly insulated with insulation rated at R-40 or higher. Look for areas where insulation has been removed or pushed aside such as bathroom exhaust fans or other modifications.
3. Make sure your roof is properly ventilated, based on the type of roof you have.

A technician from SERVPRO can perform an inspection for you using a thermal imaging camera to view and photograph areas where heat is escaping.  This needs to be done on a cold day.

If these measures don’t work you might consider installing a heating coil in the affected area with a thermostatic switch which turns on the heating coils when the temperature drops below freezing.  For worst case scenarios, safely remove the snow and ice manually with a shovel and/or broom until a long term solution can be found.