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Leaking Roof or Ice Dam?

Updated: Feb 4

We've had a very cold January and ice dams are becoming more common. Just look up as you walk through your neighborhood. Can you see an inch of ice below the snow on the roof? Can you see icicles forming? Ice dam-in-waiting...



What is an ice dam?


An ice dam occurs primarily due to lack of attic sealing, insulation, and/or ventilation. When warm air is able to sneak into the attic, it will slowly melt the snow that has accumulated on the roof. Icicles forming is the first step towards an ice dam.


As the snow melts on the roof, it gradually flows down to the edge, just over the eves. When the melted snow (that is now water) reaches the edge, it will freeze in the open air. As we know from leaving a water bottle in our car overnight in January, water expands when it freezes. The expansion in this case leads to a slightly lifted roofing shingle. As this happens each day, the accumulated ice allows water to climb under that lifted shingle until it reaches the top of the base layer of shingles, like an overflowing tub. Now the water has a clear pathway to get into the house. Eventually, a leak will be visible on the ceiling of your top floor, typically close to the outside wall.


How do I stop an ice dam from forming?


  • Sealed Attic Bypasses: This, in our opinion, is the first thing to work on. An attic bypass is any hole or access to the attic that may allow warm air to easily move into an attic space. Attic hatches, ceiling lights, and bath fans are the most common. Seal the attic hatch with weather stripping and screen door latches. Insulate and seal the ceiling lights from above so warm air can't sneak up there. Same with bathroom fans. Typical fiberglass attic insulation is no match for flowing air.


  • Improved Insulation: After the attic bypasses have been sealed, adding insulation to the attic is a simple and relatively inexpensive solution. Not only will you stop ice dams from forming, you'll save on your energy bills. Many use blown fiberglass insulation as they have DIY solutions for this. Blown insulation has greater success insulating the entire space. Strips of insulation will have gaps between them.


  • Proper Attic Ventilation: Talk to a roof specialist about your attic ventilation. If inadequate, warm air that accumulates in the attic cannot escape as it should, leading to more melting and more ice dams. On a side note, poor ventilation is a big reason for mold accumulation in attics and shortened life of roof coverings. Not good.


  • Roof Raking: The quickest and cheapest solution is to rake the roof. Raking snow off the last 3-4 feet of your roof (over the eves) allows the melted snow to become exposed to the sun on a dark roofing shingle to evaporate. The water will disappear before it causes an ice dam. This is easier said then done as many have two story homes that are not easy to rake. In that case, call in a roofer to help. DON'T do it yourself unless both feet are planted firmly on the ground.


A roof after roof raking - exposed shingles allows the ice to melt and evaporate.



Ice dams are most common during January and February when its coldest, particularly when we're having long stretches of cold like January 2022. They are helpful to help you become aware of an issue with your home that could be harmful in other seasons (or next winter), so don't forget about it once March comes around.


Thanks for reading!


Matt & Matt

Square One Home Inspections, LLC

Serving Maine Since 2014

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