Ice Damnation
February 4, 2015 6:20 AM   Subscribe

I have an ice dam on my roof, on a high dormer I can't reach (or really rake very well, but I'm going to give it another go!). The thing is, though, everyone on my block has ice dams, many that are proud and terrible cataracts of frozen majesty that put my small ice dam to shame. But no one seems to be doing anything about it. What gives?

My dormer is maybe about 40' long, now all ice and icicles. The dam behind it looks like it's maybe 6 inches. It seems to have developed maybe yesterday or over the weekend. Not long ago.

All up and down my street, though, other houses have big dams going three or four feet up the roof and colonies of icicles that themselves are two feet around. It's a crazy sight. But no one seems to be doing anything about it, and those icicles and dams have been hanging around from, in some cases, weeks and weeks ago. I also seem to be one of only a couple people on the street who raked their roof at all--and the other guy has a bunch of ice, too.

What's the deal? Obviously, if everyone else jumped off a bridge I wouldn't jump too, but the blasé approach to these dams perplexes me.

My roof is relatively new and in good shape otherwise. We don't have any leaks into the living space (yet), but I haven't been into the attic (ever; it's just a crawlspace). We're planning on getting closed cell spray blown in this spring and we'll see what else we can do long term.

So: I will try to pull down snow above the dam with my rake (from the ground), I will try the stocking with calcium chloride gambit, and pray for no more snow (prayers the forecast is already ignoring). Is that what the seasoned and prudent homeowner would do, or should I be calling in reinforcements to climb up to the roof and do a full thaw and clear? Fwiw, a friend in the town over just had to pay $600 to get a guy to come out to fix his dam; maybe there's better deals to be had, but there's a lot of markup given the demand (and the relatively pricey towns). Cheaper than fixing after a big leak, but that was also going to be my snowblower money! Thanks!
posted by Admiral Haddock to Home & Garden (8 answers total) 4 users marked this as a favorite
A new roof should have a membrane down near the eaves for just this situation. As long as the ice dam does not allow water to accumulate above the membrane then you should be fine. I have one area on my house where a gutter from a higher section of the roof dumps onto a lower roof with a large eave. I get a large ice dam here sometimes if I fail to pull off the accumulated snow. Ice dams on the rest of the roof never seem to get big enough for me to worry about them. For the big ice dam, a little salt generally creates a channel through which the water can drain. I just dump it on the roof because I can reach it from a step ladder but some people put the salt into a stocking and toss it up to the ice dam.
posted by caddis at 6:35 AM on February 4, 2015 [2 favorites]

Long term if improved insulation (and ventilation) doesn't prevent a dam at this spot you can heat trace this section of roof. Even if you forget to turn it on when ice is forming it'll still instantly create a channel for water to drain after the dam is there.

I had a north facing valley that was constantly icing up on my old place (directly over my entrance door to boot) and I just put the heat trace on a timer to come on for a while every day during the winter.
posted by Mitheral at 6:46 AM on February 4, 2015

Good advice so far. Leave it as is this year. Next year, improve your insulation, and if that doesn't work, go to heat cables.
You must have a story and a half house. They get ice dams easily.
Unless the ice dam is causing serious water damage, don't have it removed. Those guys can cause more damage than the ice dam.
posted by littlewater at 7:27 AM on February 4, 2015 [3 favorites]

Ice dam salt pucks that you fling up there somehow are evidently a thing for strategic melting.
posted by travertina at 8:20 AM on February 4, 2015

Seriously, physically messing with ice dams can damage your roof and your gutters. So unless damage is actually happening (leaks in the walls, sagging gutters, anything like that) I'd not go that route.

Be really careful with the roof rake, both of falling ice and snow, but also of accidentally dislodging any shingles.

On the east side that gets morning sun ice dams are pretty much inevitable given the temperature differential, regardless of roof insulation. Salt pucks are a very good strategy for problematic spots. I live in a house with a mansard, so we just lean carefully out the windows and drop them in the gutters. The real solution is those heated strips, but not until spring.

I'd take this bad year as a chance to evaluate your roof for spots that show evident problems. You can then budget and figure out what the best course of action is after this horrid winter is over.
posted by lydhre at 9:16 AM on February 4, 2015 [3 favorites]

With damming that serious I would worry about what is heating up the edge of the roof. It could be a major bypass (conditioned air leaking from the interior).
posted by werkzeuger at 1:03 PM on February 4, 2015

I've been ignoring mine since I replaced the roof because I had an impermeable membrane installed on the dormers (and because I'm lazy and can't effectively handle the roof rake). Since they no longer cause actual leaks as they did in the past, I'm hoping for the best.
posted by metasarah at 2:54 PM on February 4, 2015

I had a bad ice dam one year. I was skeptical, but I threw up two full boxes of those salt pucks (80 pucks). A couple hours later, there was a MASSIVE THUMP that shook everything in the house, and a solid block of ice the entire length of the house had fallen down -- must've been a couple of tons. So those things do at least have the potential to work if you're lucky.
posted by miyabo at 12:31 PM on February 10, 2015

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