Ice Dams

[gillstone]

We've had some ice dam issues in the past few years and we're working on a few fixes but some won't happen until summer.  I've seen a number of options for ice dam removal or mitigation online but I can't get a straight answer on what actually works.  So, can anyone here let me know if using heat cable is effective at preventing dams (assuming proper install) and if the DIY trick of ice melt in a nylon works and if there is risk of damaging my asphalt shingle roof.

Thanks

[MDM]

Both can work.  The principle behind each is to "break the dam" and allow liquid water to run down and off the roof, instead of backing up under your shingles.

As it seems you understand, the better fix is to insulate and air seal the attic (and install ridge vent if not already there) so the attic stays cold and doesn't melt the snow on the roof in the first place.

[Jon Bon]

Both can work.  The principle behind each is to "break the dam" and allow liquid water to run down and off the roof, instead of backing up under your shingles.

As it seems you understand, the better fix is to insulate and air seal the attic (and install ridge vent if not already there) so the attic stays cold and doesn't melt the snow on the roof in the first place.

+1

Heating wire and ice melt will work, but I would not want to do it for more than a season. Neither can be good for your roof.

This is a case of treating the symptoms rather than the disease.

The disease is lack of insulation and ventilation in your attic, get more of that and forget about ice melt and heating wire.

[Yonco]

I live in an area where the houses (all alike in build) have a small overhang on the roof and heating ducts in the attic. Ice dams often cause water to get under the shingles and cause damage down the drywall. I didn't realize this when I moved in. Anyways, the way around it is prevention. In the future, buy a telescoping roof rake and pull off all the snow from the lower 15 feet of the roof. This helps from having all the snow at the bottom turn into a dam and you get zero icicles hanging from your gutters. Its worked for me and suggested by the neighbors who have been doing it for decades to prevent ice dams.

[BlueMR2]

My experience is the opposite.  We got massive ice dams and leaking into our ceilings when I raked the snow off.  Appears the snow was insulating and removing it just magnified the Sun melt/nightly freeze cycle.  If I leave the snow in place ice dams usually don't become an issue at all.

We've got massive amounts of insulation as well as good ventilation though, so we don't get much melt from the classic heat leakage.  It's basically all driven by the Sun.

[gillstone]

Thank you for the replies.  We have addressed the attic insulation and are hoping it's now adequate to deal with the furnace being up there.  We will move the furnace eventually, but it will involve a major reworking of the kitchen/dining room to create space. 

I had luck with the ice melt in the stocking, but don't want to repeat it because of the risk of corrosion and because my house is a split level and the dam was on the side that needs a either 20ft ladder to access or climbing up the ice of the other side and over the peak.   

We'll know how well our fixes in the attic have worked after the next storm.