Ice Damming: Causes and Solutions

One major problem that many homes face during the winter months is ice damming. Although the weather has been unseasonal this year, the snow will soon be accumulating. Snow on your driveway is a pain the back, but snow on your roof can lead to leakage (even if your roof is new) due to ice damming.

What causes ice damming?

Heat loss from inside the house causes accumulated snow on the roof to melt in spots. Then the water runs down the roof until it reaches an unheated area at the edge of the roof. The snow then stops the water and it re-freezes. After a while, a dam of ice forms on the roof above exterior walls. The dam causes water to form a small pool that can back up under the edges of the shingles. Once under the shingles, the water can leak into the ceiling and walls, causing damage to structure and interior finishes.

Inspectors, appraisers and other building professionals can often get clues from the house about its ice dam history. Water stains on ceilings or around windows in rooms below valleys or other vulnerable areas and condensation stains or mold in the attic are both potential indicators of ice damming.

How to prevent ice damming

Keep the house warm and the attic cool: Keeping the roof cold enough to prevent the snow from melting is one of the obvious solutions.
Insulation: In a house with little insulation, heat loss will cause snow to melt. Luckily, upgrading insulation in attics and roof spaces is often easily done. Attic doors also need to be insulated and weather-stripped. Foam board and foam weather-stripping work well.
Heat registers: Ductwork that travels through an attic must not help snow on the roof. Attic ductwork should be air-sealed and insulated. For air vents in ceilings, the joint between the ducting and the ceiling should be caulked.
Ceiling fixtures: Ceiling mounted electrical devises like lights and bathroom fans should be sealed at their boxes. Be careful with this. Some electrical devises, such as pot lights, generate lots of heat and you don’t want to cause a fire. This is a job for a specialist.

The cost of taking these preventative measures – either by doing them yourself or hiring a professional – is relatively small in comparison to the potential water damage repair costs, especially if the problem re-occurs or results in a decrease in property value due to obvious water damage.

Once the warm air is kept inside the rooms where it belongs, the existing level of attic ventilation will often by sufficient to keep the attic and roof spaces cold enough to prevent ice dams.

Sources: http://www.slideshare.net/johnhelfrich/johns-nov-dec-2011-newsletter, http://desertluxuryrealty.com/december-2013-newsletter/, http://www.thisoldhouse.com/toh/article/0,,1131314,00.html