School me on ice dams

[mclasser]

I took a walk around the neighborhood to enjoy all the snow we got over the weekend. I live in a condo (more like a townhome since it's not multistory but they call it a condo). I noticed many of my neighbors' roofs had ice dams. Mine does not any.

I'm curious as to why. Is my unfinished attic better insulated? Pretty sure none of the neighbors have finished attics. Am I running the heat more / less than them? When I moved in, I believe my roof had been recently replaced. I don't know anything about ice dams other than they aren't good for the roof.

 

[Rob_Roy]

Your attic may be vented better, and/or have less exposure to the sun.

 

[64bawagon]

Ice dams are typically from poor/inadequate insulation, lack of ventilation and improperly routed bathroom vents. Some are a combination of all three.

 

[The_Jeff]

You're supposed to have a cold attic, put the insulation on the floor/ceiling and not up in the roofing joists. Open soffits for ventilation. Cold attic means the snow can't melt to any appreciable degree. This causes water which levels off if you don't have enough of a roof pitch. It keeps other water that melts higher up from dripping off the roof, it catches the ice and becomes part of it.

If you're somewhere where you get a good melt after every snow fall, it's not really a big deal. Roofers put rubber "Ice & water shield" under the lowest three feet of shingles to keep the ice dam from finding a nail hole and finding its way into the house.

 

[joekingcorvette]

No problem at all here but you can buy roof rake to help remove the snow. I have one and have used it on a couple years when there has been extensive snowfall on the roof. You can also buy heating elements to help melt the snow and move it down the gutters.

 

[AZjeff]

I took a walk around the neighborhood to enjoy all the snow we got over the weekend. I live in a condo (more like a townhome since it's not multistory but they call it a condo). I noticed many of my neighbors' roofs had ice dams. Mine does not any.

I'm curious as to why. Is my unfinished attic better insulated? Pretty sure none of the neighbors have finished attics. Am I running the heat more / less than them? When I moved in, I believe my roof had been recently replaced. I don't know anything about ice dams other than they aren't good for the roof.

Ice dams happen when heat in the attic melts the snow, the water runs down and hits the cold eve and freezes over and over building up. It's odd that other units in the same townhouse complex have ice dams and you don't. Maybe some units have upgraded insulation?

 

[Lubener]

Is my unfinished attic better insulated?

Yes.

I always look around at my neighbor's roofs during the winter. You can always tell the homes which are better insulated than others by the amount of snow which remains on the roof over a period of time. Ice dam damage is not as common as it used to be. Most building codes now require atleast three feet inward beyond the outside wall of ice guard under the shingles on a new roof installation. After a heavy snow, I use a snow rake to clear the snow a few feet up and to the gutters. Synthetic under layments used today offer much better protection than the old tar paper used years ago.

Icicles aren't too bad a thing as long as they aren't allowed to get too big and pull down your gutters.. They do show lack of insulation but they allow the melted snow to go over the gutters towards the ground instead of backing up under the shingles.

 

[rszappa1]

You're supposed to have a cold attic, put the insulation on the floor/ceiling and not up in the roofing joists. Open soffits for ventilation. Cold attic means the snow can't melt to any appreciable degree. This causes water which levels off if you don't have enough of a roof pitch. It keeps other water that melts higher up from dripping off the roof, it catches the ice and becomes part of it.

If you're somewhere where you get a good melt after every snow fall, it's not really a big deal. Roofers put rubber "Ice & water shield" under the lowest three feet of shingles to keep the ice dam from finding a nail hole and finding its way into the house.

Thats what they put on my new roof that was installed in 2023 here in Louisville....

 

[Kestas]

It's worth mentioning that raking the snow off your roof, or at least the lower part of the roof, is another way to prevent ice dams... unless you live in a two-story home.

 

[opus1]

Ice dams are typically from poor/inadequate insulation, lack of ventilation and improperly routed bathroom vents. Some are a combination of all three.

Or a builder who decided that the fix to get combustion air into a small room housing the furnace, water heater, and washer/dryer is to punch a hole in the ceiling to draw air from the attic and put a return-air grill over the hole to make it pretty...and then when called on it the builder responds that it "meets code". Ask me how I know...

 

[Donald]

The roof should have ice and snow shield on the plywood for the first 3 or 4 feet. Then synthetic felt underlayment. Gone are the days of black felt or tar paper.

I think most companies installing insulation do a poor job of installing the proper insulation baffles to allow for proper venting from the soffit.

 

[repairman54]

2nd winter in my current home. Last year I had an ice dam issue, I'm in a lake effect snow zone. Problem has been corrected this winter by me installing gable vents to vent the attic better. House has a ridge vent, useless in a snow zone. Snow covers and blocks the vent with only a few inch's. There are air baffles in place to the eaves, short eaves as that is a snow country must.
I also added foam board insulation to the attic access hatch, 2 layers of 2'' R19 foam board. Perforated soffit vinyl around the perimeter up to the peak was not enough venting. Raking the roof edge helps but too warm of an attic still lets melt water drain down to the edge.
I'll add it got a new roof the first summer so I know there is plenty of ice shield on it.
A cold roof is a happy roof. Just had 3-4 feet of snow shoveled off it, not happy to pay but I'm too old to be shoveling roofs now.