Last winter, the Boston area experienced one of the worst winters on record. A record amount of snowfall caused an unprecedented amount of ice dams and damage to homes across the area. As we are now in the middle of another winter, this guide should help you to prevent the damage caused by ice dams this year.
What is an Ice Dam?
Ice dams are ridges of ice that form at the edge of a roof that prevent water from melting snow from draining off of the roof. This happens when:
- Heat from the inside of the home warms the underside of the roof, and/or
- The accumulated snow warms and water runs down the slope of the roof. When the water runs down to the cold edge of the roof, it refreezes and causes an ice dam.
When an ice dam forms, it causes any additional water to find other pathways and is most often forced up and under the roof covering. The water that backs up behind the ice dam can cause leaking and damage to ceilings, insulation, walls and other areas of the home. When a roof doesn’t drain properly, snow, ice and water can also be trapped on the roof, adding significant weight and putting the roof at risk.
How Can You Avoid Ice Dams?
It is NOT recommended that you chip or try to break up ice dams as you could cause significant damage to the roof in the process. The best way to avoid the ice dams are to prevent them from happening by:
- Increasing ventilation in attic spaces.
- Insulate recessed lighting fixtures and other ceiling penetrations to reduce the amount of heat lost into the attic.
- Insulate and seal all attic penetrations, vents, plumbing stacks, access doors and mechanical or electric chases.
- Keep accumulating snow off of the roof with the use of a roof rake. If the roof height is too high, hire a roofing professional.
- Remove snow especially from flat roofs or flat sections of roofing. A roof without a pitch or slope can have significant problems in keeping water flowing into the roof drains.
- If ice dams form around roof drainage points, use heating cables on the drains to help to keep the water flowing.
How Can You Prevent Roof Damage?
Another concern other than ice dams is the weight of snow on the roof. In general, most residential roofing can support:
- 20 pounds of snow per square foot of roof space before they become stressed.
- For fresh snow, 10-12 inches of new snow is equal to one inch of water or about 5 pounds per square inch of roof space. The roof will become stressed usually after about 4 feet of new snow.
- For packed snow, 3-5 inches of old snow is equal to one inch of water or about 5 pounds per square foot of roof space. Anything more than 2 feet of old snow can be too much for a roof to handle.
- If there is ice on your roof, 1 inch of ice equals 1 foot of fresh snow.
Preparation is key to preventing ice dams on your roof and resulting water damage to the interior of your home. There are some easy steps that you can take before the snow falls, like sealing and insulating attic areas and having a professional survey of where potential heat losses may be in your home. Heating strips can also be installed in gutters to prevent the build up of ice during snow melts. If you don’t have a chance to prepare for the winter or if winter is already underway, be sure to keep your gutters and roof drainage clear from obstruction and be mindful of the accumulation of snow and ice on your roof. The good news is that Spring is only a few short months away!