Ice Dams and How To Prevent Ice Damming

excessive ice dam

Ice dams in Massachusetts are an ongoing nuisance and are causing extensive damage to soffit cavities, fascia boards, roof sheathing, gutters, and to the most outer portion of living area walls. This ice build-up can absolutely be alleviated, but every house tends to have a different situation as to why this ice dam is there in the first place. First, I'd like to explain how this massive ice mound forms on the most outer edge of your roof...


It snows and your roof surface will continue to accumulate this falling snow and the temperature (outside) of your home drops to below freezing.

1.) The temperature inside your attic is above freezing (warmer), due to the heated living area (below the attic) allowing heat to infiltrate the attic cavity, thus raising the temperature of your roofing material to above freezing.

2.) Because of the temperature differential and the warmer roofing material, the snow on top of the roof starts to slowly melt and gravity takes over. The melted snow (now water) starts to cascade down the roof (underneath all the accumulated snow) in an attempt to drain off the roof or into your gutters.

3.) As soon as the water reaches the outer edge of the roof (where the outer roof edge will not be as warm as the attic cavity) it gets exposed to the freezing air. The cascading water now freezes into an ice mound (that literally clings to your roofing material) along the edges of your roof and the gutters (if applicable).

4.) As more and more melted snow (water) continues to cascade down your roof, it continues to freeze behind and on top of the previously frozen run off, forming a much larger ice dam. Once this ice dam takes shape, it will literally trap any water that is attempting to drain down and off the roof. Now, all the melting water is dammed and has nowhere to drain to, so it builds up. This accumulating water is simply backing up and is forced right under your roofing material and into your attic or soffit cavity (and then gravity takes over once again), and this water infiltration simply drips down into your living area wall cavities, causing the nuisance staining and damage that may be observing throughout your walls.

ice dam at edge of roof

When the heavy snow on your roof field becomes excessively uneven, this is indicative of heat infiltrating your attic and melting the snow on your roof, in turn causing ice dams.

roof ice dam at edge of roof

Preventing this ice from forming on the edge of your roof in the first place is absolutely preventable. Many homeowners are continuously researching articles on “HOW TO PREVENT ICE DAMS” and they learn that proper insulation and ventilation is necessary to prevent these ice dams. That’s fine, but after most homeowners obtain their education on “HOW TO PREVENT ICE DAMS” they may attempt to correct their ice dam situation, but are still baffled and are unable to figure out exactly where any improvement is needed. That’s why they call me in to access their situation.

thick ice dam at roof edge

Your solution to alleviate your ice dam issues is the use of Infrared technology. My infrared inspection is a brilliant method of providing you with an instant snapshot of any active heat loss through the most outer portion of your walls and ceilings of your home. Deficient insulation is a poor insulator, which allows it to now become a great conductor of your conditioned air, and this is what enables me to easily detect the inefficient insulation applications throughout your home. Infrared imaging will visually show thermal mapping of any improperly insulated ceiling and wall cavities that are causing the ice dams at the outer roof edges of your building.

Take a look at the images below and see how easy Infrared detects uninsulated/problematic cavities where ice dams were occurring...

infrared line

Infrared clearly detects cold air (blue color) infiltrating the living area

infrared detects moisture from ice dam

infrared line

Infrared detects missing insulation at all outer ceiling cavities

insulation missing causes ice dam

infrared line

Thermal imaging detects cold spots from improperly installed soffit vents

conducive conditions for ice dams

infrared line

Infrared detects insulation issues above this bathroom ceiling.

excessive insulation voids


The brown ice clinging to this particular siding is caused from ice dams at the eave area combined with excessive mice activity in the attic. The brown color of mice excrement mixes in with the ice accumulation (at the eave area) and when this ice starts to melt, the brown mess will seep out from the eave area and behind the siding material


ice dam brown

Note how this brown mess will follow the contour of the building.

brown ice on siding

You can see how this brown ice seeps out from behind the clapboard siding.

brown ice dam

This church had ice dams with signs of mice activity below the belfry.

brown ice

brown icing

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Tags: Damming, Dams, Ice, Prevent


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Comment by David Valley on November 22, 2010 at 12:01pm
Yes Ed, nice catch.

I find many ice dam indicators in attics in the summer months. Most of the time, I can tell if an attic has problematic ice damming simply from inspecting the insulation and ventilation. Most of the time the rafter tails have moisture stains at the eave area.
Comment by Ewald Schwarzenegger on November 22, 2010 at 10:03am
I evaluated a old farm home which was having problems with their siding and paint job. Blistering was taking place in the summer on the south and west side with small amounts on the east side (Greene County, NY). After a meeting with my client on winter I noticed the excessive buckets in the house at each window sill catching water. I asked if I could visit the attic only to find that there was probably 100% humidity in the attic and water, water everywhere. The insurance claim went from $7,000 to 48,000 (back in the 90’s) after my report. But long story short, the sun was driving the vapor out of the wall in both directions, only to get caught behind the paint bubbles. With the cold summer evenings this vapor would condense and after a while would be full of water (in the summer). Interesting how Ice Damning can affect things long after the snow is gone!
Comment by David Valley on November 12, 2010 at 8:18am

Ice Dams are everywhere in Massachusetts. The only problem is...Homeowners are purchasing heat wires and those cheap aluminum roof edges in an attempt to melt these problematic ice dams away. I'm attempting to educate homeowners on "how to properly alleviate ice dams" without getting ripped off on those gimmicks. They need to know that ice will not accumulate in the first place if the underside of the roof (attic) is properly conditioned.
Comment by Michael Stuart on November 11, 2010 at 6:44pm
You may be the only person that I have ever heard of who is looking forward to ice dams! LOL! ;-)
Comment by David Valley on November 11, 2010 at 1:59pm

Thanks. I'm really looking forward to the upcoming winter months and the ice dams that occur constantly in my area. I'll post the newer Infrared images as I get them.
Comment by Michael Stuart on November 10, 2010 at 6:48pm
David, nice post... and I love the diagram and photos as well!


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