Open Mike: Ice Dams! (OT)

Icicles hanging off a snow-covered roof in the winter are picturesque, but what you might be seeing is something that can ruin a valuable house as surely as a three-alarm fire. It's a dreaded term in the north: ice-dams.

Here's a great explanation of how ice dams form and why. If some of those illustrations don't make you wince, I'm guessing you're not a homeowner.

As the fellow in the video says, "water always wins."

The pool shed
The pool-table shed I bought last year immediately preceded a serious downturn in my economic fortunes, never robust in the first place, and if I had it to do over again I definitely wouldn't. It turned out to be very bad timing. However, since it's done and dusted, I'll say it's one of the best things I've ever bought for myself in my life. Second only to the used Miata I had for three years starting in 2010. I've really enjoyed it.

Of course, I rank a lot of things more highly that I've done for others, including paying for my son's college education and digging deep to pay for my late dog Lulu's TPLO operation even though I was desperately poor at the time. I'm proud of certain charitable donations too. In 2006 I had pneumonia, and received some expensive medical care from a local free clinic for the uninsured. After I got more prosperous I donated $500 to that clinic every year for a number of years. It's satisfying to repay such a debt. But I digress.

The pool table shed has been a steady source of pleasure. In the 13 months I've had it, not including when I'm traveling, I've missed a day only about twice. On a normal day I probably go out there four times, sometimes for just ten minutes, occasionally for as long as an hour. Longer when friends come over to play.

I won't be playing any pool today, however. The reason: ice dams! I saw a leak inside the pool table shed for the first time yesterday. Oh no! Gotta protect my investment.

Perfect storm?
The conditions are perfect for ice dams. There's a lot of snow on the roof, which supplies the water. And it's been cold, so I've been pumping a lot of heat into the shed. Two inches of spray foam insulation on the ceiling, it turns out, isn't enough to keep the heat away from the shingles. So water forms under the snow and then trickles down to the unheated edge of the roof, where it promptly freezes. Repeat indefinitely and before you know it there's a ridge of ice three inches thick. Behind that ridge, water builds up and works its way back up under the shingles. Water always wins.

Last week on a warmish day I got up on a ladder and removed all the ice dams by hand. And just as soon as the temperature plummeted they were back with a vengeance. It was 40°F on Monday, and I got all the ice dams removed again (carefully) using a spade. But as long as it's below freezing, I plan to leave the temperature in the pool shed at 35°F, just above freezing, to try to minimize the problem.

By the way, you'd think it would be easy to just get up on the roof and shovel the snow off, but, apart from the risk to my not-so-nimble self, I'm not really sure the roof can support my weight. I think I'd break the adhesion between the rafters and the insulation on the inside, weakening the structure.

Billiard hall at Paul Smith's casino, Adirondack Mountains, 1905. Courtesy Shorpy.

Of course, the best thing to do would have been to build a better building in the first place. But we're all bound by budgets. Most of us, anyway.

Fixes
Here's what I'll do today—a temporary fix. Ice-Melt in nylon stockings (now where in the world do you buy nylon stockings? I don't have the first clue) to create channels through the ice for the trapped water to escape. As soon as I can, I'll try to install a better solution: heated de-icing cables for the roof.

The best solution would be more insulation under the roof. My rafters are 2x6's, so there's still room for more insulation—Rockwool, maybe? Unfortunately there's an impediment: the pool table. With the pool table already in place, it's no longer convenient to get to the ceiling above it.

The biggest problem with the heated de-icing cables? I don't really trust myself to install them by myself, and it's such a small job that I'm unlikely to be able to entice a tradesman to help me. Around here, the trades are in high demand, so they're pretty picky about what jobs they'll take on. I already have several jobs around my property that are too big for me to do alone but too small to hire anyone to help me with. As Roseanne Roseannadanna used to say, it's always something.

Anyway, beware icicles! When the weather is just right, or rather, just wrong, icicles are a big warning flag for possible damage to your house.

Mike

Book o' the Week:

Ernst Haas: New York in Color 1952–1962. "When Haas moved from Vienna to New York City in 1951, he left behind a war-torn continent and a career producing black-and-white images. For Haas, the new medium of color photography was the only way to capture a city pulsing with energy and humanity. These images demonstrate Haas's tremendous virtuosity and confidence with Kodachrome film and the technical challenges of color printing."

This book link is a portal to Amazon.

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(To see all the comments, click on the "Comments" link below.)
Featured Comments from:

Ronny Nilsen: "Getting the snow of the roof can be done without climbing by using a snow roof rake."

Mike replies: A lot of people have suggested that, and it would be a good suggestion, except that one side of the shed roof is pretty much right next to the barn wall. So there'd be no room on that side to use a roof rake.

I have a friend coming out tomorrow to give me a quote on installing those zigzag heated cables. I know they use a lot of electricity, but I'd really only need them a few times a year.

Comments

[James]

Nylon stockings, those were the days.
Anyway, each pair of tights cuts down to two stockings.

[Speed]

Mike wrote, " ... so there's still room for more insulation—Rockwool, maybe?"

Injected Foam Insulation may be your solution. A quick internet search turns up dozens of companies, large and small, happy to install it in exchange for some number of your dollars. I understand that it is appropriate for existing walls and roofs as well as new construction.

[DavidB]

I have gutter heating wires on the north-facing side of my house (no need on the south side) and they work well. I installed them myself on the first round (and had bruised and bloodied knuckles) but hired an electrician to re-install them when they reached their rated lifetime.

Almost everyone in our neighborhood has them.

[ASW]

Two inches isn't a lot of insulation. Some guick googling suggests that:
1) closed cell foam R-value = 6.7-7/inch
2) open cell foam = 3.8/inch
3) fiberglass batts = 2.9-3.8/inch
4) blown cellulose = 3.1-3.8/inch

So, assuming your spray foam was closed cell, you're around R-13 or R-14. Not great, which you have already figured out.

De-icing cables will help, but since your pool shed gets daily-use and is a long-term investment it would seem prudent to fully insulate your roof. Better in winter and summer. The easiest approach would be to complete your spray foam journey. I was going to suggest putting in a ceiling and going the blown cellulose route, but I recall some issues with the rafters and stringers from an earlier post. Still might be worth investigating.

As for the pool table being an impediment, if you protect the surface with blankets and tarps don't you have a large and stable step ladder?

[Tex Andrews]

Keep a sheet of 3/4 A/C plywood and some packing blankets in your stash. Very handy, always.

Packing blankets can protect the table when you lay the ply over it. Then rent a Baker scaffold and you can DIY your insulation. You can also rent the gear for blown-in insulation. It's not rocket science, and you seem fairly handy.

If you ever need space for some print evaluations or some such, you can use those blankets and ply on the pool table.

[Greg Heins]

Roof rake? We have a spot on our Boston 3-unit condo building where dams are prone to form. It's right above our small second-floor back porch and the solution is to drag the fresh snow off the roof at that point with a roof rake. It telescopes to about 20 feet long, so I'm guessing that you could pretty much clear your whole shed roof from the ground. No installation needed. Roof raking is the culminating event in our snowfall triathlon: sidewalk, driveway, roof. When I rake the roof there's no place for the snow to come but right down on my head, so that's why it's the final event.

[Jim Henry]

I used deicing wires one year but quit when I realized they were using 700 watts 24/7 all winter.

What I used after that was a plastic blade 30" by 15") on a long pole to pull the first 4 feet of snow off the roof when it snowed. I think you can buy them at Home Depot or Menards or Lowe's. The long pole comes in sections and you can use 2 or 3 depending on the height of the roof. It worked pretty well.

More insulation is better, of course.

[Ronny Nilsen]

Icicles is as you have found out, a sign that the roof is not insulated enough.

The cheapest way to solve this short term right now, is to lower the temperature inside the shed so no water melts on the roof.

Yes it sucks to have the shed cold some parts of the year, but that's the price to pay when not constructing a roof for the climate. :-(

[Greg Boiarsky]

Two words: roof rake. It's much cheaper and safer than mucking about with electricity or chemicals.

[Ed]

I have a roof rake. When the snow starts building up on your roof you rake it off so when it melts there isn’t enough water to cause ice dams. They’re fairly inexpensive, start at around $30 at hardware stores and building supply stores. They’ve worked well for me in Minnesota.

[Michael Coviello]

Mike,

Have you been using a roof rake to remove the snow that falls on the roof? They are of no use with ice storms and they require a light touch (lest you ruin the roof shingles), but they can save your roof.

[DB]

I’m in MN, Mike.

Roof raking after every significant snowfall.

Good exercise, too.

[Roger S]

2 inches of insulation, even closed cell phone, isn't code anywhere. "Flash and batt" and add another 20 inches or so of fiberglass or rockwool and you'll have a good performing room.

The electric cables use a lot of energy, can embrittle shingles and need to go on before the ice forms to have a hope of working.

[Rick Popham]

I can't remember how your roof system is set up, but is it possible to ventilate an "attic" space. We always tried to keep a cold roof/warm ceiling by allowing a space for cold air to enter through the eaves (above any insulation) and exit through a roof vent. That keeps the roof cold so ice won't form.

But if you've already sprayed foam against the roof sheathing at the eaves, ventilation won't be possible. In that case, the heat cables are your best bet. As you say, you only have to run them when the ice starts to form.

[John McMillin]

Foam insulation boards are one of the easiest ways to add R-value to a roof, but they usually require new sheetrocking, too. It's a day's job, with a helper. A 2" thick 4x8 board promises R-13 for $39. Thicker sheets are available, too. I used them to thermally isolate the cinder-block walls of my home office. Not being from the Northern Tier, I couldn't say how much thickness would solve your ice dam issue, but it has to help!

How about you skip the sheetrocking, which is certainly the hardest work, and string some sheets of fabric under the foam-foil ceiling panels? Make it look like a Mediterranean alleyway, or a French bordello. Portrait backdrops would give you an easily changeable color field look. How 'bout it?