Avoid Ice Dams on Your Roof


Ice dams can build up on roofs. An ice dam is a pile of ice that blocks water from running off of the roof. As snow melts water will build up behind the ice dam into a pool. Roofs on a house are not designed to protect against standing water, they are designed to facilitate water running off the roof. The standing water that builds up behind an ice dam can do considerable damage to a house if it is not removed quickly.

What is an Ice Dam?

When snow accumulates on a roof a cycle of melting and refreezing can occur. The snow melts on the surface of the roof as heat escapes from the attic through the roof. As the water runs down the roof it refreezes near the edge of the roof where heat escape is less and the surface of the roof is colder. This refreezing gradually builds up a ridge or heap of ice commonly referred to as an ice dam. The ice dam blocks the flow of melting snow, causing water to pool up behind the ice. When the ice dam reaches a certain size the water behind it will seep under the roofing, through the roof causing damage to the roof, attic, insulation, ceiling and walls inside the house. This situation can cause a lot of damage to a house and damage can occur quickly, especially as spring approaches and mild days cause water to pool up quickly.

How can Ice Dams be prevented?

The main cause of ice dams is an overly warm attic. To facilitate ice dam prevention, lowering the temperature of the attic is essential. This can be accomplished by installing additional insulation on the attic floor. There are limits to the value of this procedure, at a certain point more insulation will not help reduce the temperature any further. The next thing to do is to install weather stripping and /or insulation on attic stairways or hatchways, and attic floor mounted ventilation fans. Some recess light fixtures and vent fans are not meant to be covered so be careful to find this out from the manufacturer before covering them over.

Ventilation is very important for regulating the attic temperature. Without adequate ventilation there will be heat buildup in the attic no matter how much insulation and weather stripping is used. Soffit vents along with a ridge vent is ideal, the cold air entering through the soffits will move up the roof to the ridge vent and exit removing excess heat and moisture. If you can’t install soffits a ridge vent will still help a great deal. The ultimate goal is to keep the temperature inside the attic as close to the temperature of the outside surface of the roof as possible to prevent snow from melting and refreezing.

What can be done to the outside of the roof to prevent Ice Dams?

Even if you do everything right ice dams can still form under certain conditions. However, a properly installed roof will prevent most of the damage. A properly installed roof in snowy regions will have the following components: proper flashing, ice and water barrier installed on the edges of the roof and over all valleys, rolled asphalt underlayment (tar paper) over the entire roof, and high quality roofing shingles with the proper overlap.

Other preventative methods

Physical removal of the ice dam could be dangerous. If you have a flat roof shoveling the snow off is possible. If your roof is not flat you can use a snow rake to scrape as much snow as possible off, this will slow the buildup of the ice dam. Another possibility is to chisel grooves into the ice dam to allow water to drain from behind the ice dam.

As spring approaches damage from ice dams can occur quickly so beware of this situation and be ready to take action to prevent damage to your home. Whatever physical method you try use extreme caution to avoid falling or having sharp pieces of ice fall on you. Consider hiring a professional, the cost may actually save you a lot of money.