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Posted at 11:00 AM ET, 02/ 7/2010

Watch out for those ice dams!

By Don Lipman

*** More snow Tues/Wed, are you kidding?: Full Forecast ***

* Detailed look at next snow threat: SLCB | A mess to be reckoned with *
* NWS snow totals (WaPo map) | Report snow to CWG (see reports) *
* Power outage maps for Dominion Electric | Pepco | BG&E *
* Outside now? Radar, temps & more: Weather Wall *
* News, traffic & storm coverage: Local home page | Get There *

Note to readers: We will be running fresh post-storm content throughout the day and an update on the Tues/Wed storm this evening, which is looking more and more significant. Keep checking back every 3-4 hours for fresh posts...

With all of the media's precautionary advice about how to deal with our HUGE storm and its immediate aftermath, I haven't seen any information about ice dams, which are a potentially significant and expensive problem for many homeowners, particularly owners of Dutch colonials. Take it from me, as I lived in a Dutch colonial for many years. Despite my best efforts, ice dams, which are masses of ice that form in gutters, usually appeared after major snowstorms.

ice-dam.jpgIce dam.

Here's how ice dams form: The warmth from within the dormers as well as the high solar insolation (on a sunny day) melts the snow from the dormer roofs. In the subfreezing air, icicles then form, which get longer and longer until they reach the gutter below. Once that happens, the ice continues to build, both horizontally and vertically, possibly deforming and even breaking the gutters and backing up under the shingles, eventually causing a ceiling leak somewhere in the house. This is what happened in my case, and what may happen to many unlucky homeowners in the post-"Snowmageddon" days ahead.

Keep reading for more on the danger of ice dams...

Fortunately, not all Dutch colonials are as prone to ice dams as others. As it turns out, three big factors lead to the worst cases:

  • The dormers are not well insulated. Mine weren't. (A tell-tale sign of poor insulation is massive icicles hanging from the dormers.) In fact, walking down the street, you can easily spot well-insulated homes from others.
  • The dormers face toward the south, where solar insolation is greatest. (My rear dormers did face south and that's where I repeatedly experienced severe ice dams. My front dormers, however, were less affected.)
  • A stretch of at least 1-3 days of sub-freezing weather occurs after the storm, which is what we expect.
dormer-windows.jpgDormer windows.

What can be done to prevent these destructive ice dams? Before the fact, better dormer insulation would help, and gutter heating cables would probably prevent them altogether. But the cables, although available in our area, are almost never installed by builders unless requested and are seldom installed by homeowners because, I suppose, most people believe they would rarely be needed.

After a storm like the one we just had, the best thing you can do, if at all possible without risking injury, is to remove the snow from the dormers. In general, it's best to limit snow and ice build-up on every roof because, to some extent, they're all vulnerable, particularly the flatter ones and those with more than one layer of shingles.

We've already seen stories of some homeowners in trouble as well as several commercial and private roof collapses. And, of course, the mother of all Washington snowstorms--the famous Knickerbocker Storm of January 28-29, 1922, which unloaded a record 28 inches of the white stuff -- was named after the five-year old, flat-roofed theater whose roof collapsed, killing almost 100 people. (For you weather history buffs, that storm was a meteorological bomb very similar to our "Snowmageddon," and for you general trivia buffs, that night--January 28, 1922--the theater was showing the movie, "Get-Rich-Quick Wallingford.")

We'd like to hear from you. If you've had ice dams, how have you dealt with them and, in general, handled removing snow from your home's roof?

By Don Lipman  | February 7, 2010; 11:00 AM ET
Categories:  Education, Lipman, Snowmageddon  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: More snow?... Are you kidding?
Next: Measuring Snowmaggedon's snow depth


ICE DAM is a great name for an 80s heavy metal hair band group.

Posted by: SWester2010 | February 7, 2010 11:06 AM | Report abuse

Any comments on road conditions? Namely, main roads in Gaithersburg, Germantown, Rockville area? Am I crazy to go to someone's house tonight for Super Bowl since we lost our cable?

CWG, any recommendations on driving today?

Posted by: derrickd | February 7, 2010 11:12 AM | Report abuse

Is there a FedCast for Monday?

Posted by: soprano87 | February 7, 2010 11:14 AM | Report abuse

so, I am stuck on the west coast...any ideas on whether my expected 9:45 PM flight into National has a snowball's chance? take the shot and end up spending the night in Sky Harbor or just hunker down and miss more work? (yes, my employer will be open tomorrow)

Posted by: joshuaostevens | February 7, 2010 11:19 AM | Report abuse


FedCast is three Capitol Domes for now. Apparently, OPM is going to announce its decision on Fed Gov status prior to the SuperBowl... so we'll update at that time.

Posted by: Jason-CapitalWeatherGang | February 7, 2010 11:24 AM | Report abuse

Great. Not. I'm in a dutch colonial with icicles too. But they appear to be falling off with the sun and the roof slop is steep enough that I don't think there was a great snow buildup on top of the roof anyhoo. I'll keep my fingers crossed.

Posted by: HokieAnnie | February 7, 2010 11:28 AM | Report abuse


I would call your friend and ask about conditions around his house. My understanding is that crews are making progress on main roads and most are passable, but neighborhoods will take longer and vary significantly by the area.

Posted by: Jason-CapitalWeatherGang | February 7, 2010 11:29 AM | Report abuse

We have a Dutch Colonial and ice dams have formed on the shaded side of the house, and we have some leaking coming in between the window frame and the house. These storms have been a learning experience!

If you have ice dams, look up ice dam socks. .. I made them during last week's storm and they were very helpful at creating a channel for water to flow off the roof. Hopeful they will work today too.

Posted by: lrw2a | February 7, 2010 11:30 AM | Report abuse

never mind, the airline finally called it

Posted by: joshuaostevens | February 7, 2010 11:39 AM | Report abuse

The easiest way to prevent an ice dam is to keep your attic cool. I had an attic fan in my roof for summer ventilation that was on a thermostat for heat. I installed a 3 position switch in my wall that could turn it on manually during ice dam conditions. The fan draws cold air through the soffit vents and out the roof above the insulation. This prevents the snow from melting higher up on the roof and then refreezing at the overhang/soffit of your roof which is where the ice dams forms.
Worked like a charm!

Posted by: joepar703 | February 7, 2010 11:57 AM | Report abuse

Hey, CWG you are now internationally famous. I read an article about the snow today from the "Diario de Yucatan" in which you were quoted.

Posted by: celestun100 | February 7, 2010 12:12 PM | Report abuse

My 1950's rambler has a very nice set of icicles on the north-facing back gutter. One in front of my dining room window looks to be about 30 inches long. So far, the south-facing front gutters are clear, although in these really heavy snow, I often get an ice dam there too.

Another reminder that I really, really have to beef up the insulation in the attic.

Posted by: magicdomino | February 7, 2010 12:18 PM | Report abuse

Lotta' empty seats at the Caps game; wish I was down there, despite the current score.

Let's get 10 more inches of snow, break the all-time Washington snowfall record, get CWG "Swowmaggedon 2010" tees printed and distributed, and start thinking about the weather for cherry blossom snow (petals, not flakes).

Posted by: JerryFloyd1 | February 7, 2010 12:27 PM | Report abuse

I would characterize driving right now as being in Adams Morgan on a Saturday night: slow, sloppy, and there's no where to park

Posted by: artandcarly | February 7, 2010 12:36 PM | Report abuse

What if you live in a condo and they won't be unclogging drains etc? The drain outside my bedroom window is frozen solid - would a blow dryer on it getting it moving again or cause it to bust as the ice turning to liquid will expand? I can see the snow dome on top of the drain but no way to reach it.

Posted by: hereandnow1 | February 7, 2010 12:40 PM | Report abuse

reposting from previous thread. MoCo school are closed Monday and Tuesday. Administrative offices and facilities are also closed on Monday and all activities cancelled.

Posted by: soleil2000 | February 7, 2010 12:42 PM | Report abuse

Hereandnow, Water contracts going from ice to liquid so I don't see that as a problem. However, it may take a while with a blowdryer to clear it out, though it would be amusing to see...

Posted by: Brian-CapitalWeatherGang | February 7, 2010 12:54 PM | Report abuse

Please people... just whatever you do for ice dams and other frozen areas DON'T use a blow torch!! :-)

While this might seem common sense, when I lived in MS and got hit with a MAJOR cold spell one year, a number of people used blow torches to thaw their frozen water pipes.

Needless to say, there were more than a few houses that burnt down that morning.

Dad used a hair dryer to heat up the joints and water flowed nicely after that.

Good Luck all! :-)

Please be safe! :-)

Posted by: aquarnnr | February 7, 2010 1:07 PM | Report abuse

Ended up getting cleared out...had to take a sledge hammer to some of the ice built up due to the plow...a solid 2 inches..and I do mean solid.

Cleared off a small part of the roof for drainage while also clearing off the sat dish so I can watch TV. LOL.

Man am I beat.

I am NOT looking forward to Tues/Wednesday. I might not stop aching before then!

Kim in Manassas

Posted by: ksrgatorfn1 | February 7, 2010 1:10 PM | Report abuse

Once more, here are the videos and pictures that I took of the Carlyle neighborhood in Alexandria near in between the Eisenhower Ave & King St. Metro stations.

Posted by: joelhousman | February 7, 2010 1:18 PM | Report abuse

Random question. Montgomery County was not included in the Blizzard warning. Can I still claim I went through the Blizzard of 2010? If so, this will be my second blizzard. I survived one in the late 70s in Michigan. We lived on a dirt road, two WEEKS without power or able to get out. But we were prepared.

Posted by: epjd | February 7, 2010 1:47 PM | Report abuse

Man, I thought I would get toasted for suggesting more snow. You guys are really civilized (or, else, exhausted)!

No question that these heavy snowfalls inconvenience a lot of people, sometimes dangerously so. But I suspect the crime rate drops, there are fewer accidents, etc. The ice damming is a real bummer so I hope everyone gets this resolved.

I also hope someday bus service is resumed where I live and sidewalks are fully cleared this week(dream on!!) in my Glover Park neighborhood.

For now, it's back to watching sucky Caps-Pens match (the rink now appears to be filled) and later today, it's Who Dat! time.

Have a great Super Bowl everyone.

Posted by: JerryFloyd1 | February 7, 2010 1:50 PM | Report abuse

@ksrgatorfn1, aka Kim in Manassas: You used a sledgehammer to clear your driveway of accumulated ice, then you went up and cleared ice off your roof? You're my hero!

Posted by: --sg | February 7, 2010 2:26 PM | Report abuse

We dealt with a nasty ice dam after the storm of 95-96 by Fleeing the area. Have been in California ever since.

Posted by: nellie4 | February 7, 2010 2:47 PM | Report abuse

For most people clearing snow off the roof isn't a very good option. Leaks are better than slipping and falling off your roof.

Apart from upgrading your insulation so the attic stays cool, you can also be sure you've cleared your gutters of leaves from the fall season. Lots of times leaky spots are also the spots where it's hard to reach the gutters so they don't get cleaned out as often as they should.

Posted by: RedBird27 | February 7, 2010 4:32 PM | Report abuse

I live a DC row house with no capability to put insulation in. There are just mere inches between our ceiling and the roof. We had a leak after the snow storm in Dec and again today. As the roof has warmed up from heat in the house, a pool has formed. Because of the ice dams, it has nowhere to go but under the flashing that needs repair (which unfortunately can't happen until warmer weather). Our solution was to turn off the radiator and open the windows in the room where the leak occurred. It worked. The leak has stopped.

Posted by: pookchop1 | February 7, 2010 5:47 PM | Report abuse

I had some HUGE icicles hanging off my roof. I hit them down with snowballs today just in case they fell on somebody.

Posted by: SkinsFan132 | February 7, 2010 7:59 PM | Report abuse

I lived in D.C. for 40 years...still have a house there and never had ice dams. But most of the year I live in New Hampshire, and after years of ice dams and water in several rooms I gave up on shingles and switched to a metal roof this past fall. It's more expensive, and an acquired taste (though they come in a wide range of colors), but the snow melts/slides off quickly and the roof will last 30-50 years. And ice dams are history.

Posted by: snowbird25 | February 8, 2010 12:24 AM | Report abuse

Can anyone recommend a contractor in the DC area (particularly Montgomery County) for removing/dealing with ice dams? We've got an ice dam problem, and it's causing leaks in our windows, ceiling stains, and a wet spot in our carpet. I don't have a tall enough ladder to remove the dam myself. Even if I did, I'd probably also injure myself and damage the roof in the process.

Posted by: rg42 | February 8, 2010 8:26 AM | Report abuse

rg42, I hope you found someone by now. Otherwise I can give you the name of the contractor we use for work around the house.

Posted by: RoseVA | February 8, 2010 11:46 AM | Report abuse

I got a real quick education in ice damming today, but can't get on the roof to clear anything (it's a 3-story townhouse). Since the problem is caused by a warm attic and colder eaves, I turned off the heat for a while and opened a 3rd floor window (it's only 1 foot below the the gutter. It seems to be working somewhat, as water is now dripping to the ground in that area.

Later I am going to try to turn the heat back on but close all the vents on the 3rd floor.

Posted by: reston3 | February 8, 2010 12:21 PM | Report abuse

RoseVA, I did find someone in my area who does ice dam removal. Hopefully they'll be able to address the problem. I really appreciate your response and will let you know if I still want your recommendation.

For those of you in a similar situation, you can search ["ice dam removal" loc: your city/state] in Google maps for businesses that can remove ice dams and snow off your roof. Doing it oneself (or with the help of an inexperienced contractor) apparently has its risks and benefits.

Posted by: rg42 | February 8, 2010 12:38 PM | Report abuse

BTW, ice dams aren't limited to dutch colonials or the south side of the house.

All you need is a roof that's warm enough to melt snow and a gutter that's cold enough to freeze it, and then have more water back up on top of it. We have loads of icicles on a north-facing roof too, because the sun doesn't melt the water fast enough.

Posted by: ah___ | February 8, 2010 2:30 PM | Report abuse

I've spent many a miserable hour on a roof or on a ladder chopping at ice dams. Given the snow depth and predicted cold temperatures I was shoveling the drifts on our roof Saturday morning and cleared the whole roof Sunday. It was a ton of work, but if I had not done it, Thursday might have been a disaster, even with our well ventilated attic. Being careful, with the nature of this snow fall, I felt pretty safe on our 4x12 pitch roof, saving the last 3 ft to the edge for a push from the length of the shovel.

Posted by: ColoradoNative | February 8, 2010 6:51 PM | Report abuse

We have no dormers but had a snow dam a few years ago. I was able to reach the gutter and with a hammer and chisel (not a wood chisel!) break it up and remove it.

Since then we have replaced the insulation in our attic with blown in insulation rated at R-49. Significantly more than before, and we can tell the difference in the upstairs temperature. I have hopes that this might prevent future ice dams.

Side note: it has been interesting hearing what I think is water that drained and froze inside the downspout one evening and night, melting and tumbling down the gutter the next day. I don't think I've heard that noise before this year. I have no idea why not.

Posted by: stephen20 | February 8, 2010 8:07 PM | Report abuse

Pards, I got no probs with existing or future forecasts, but this one, according to some peeps I know of (and I'm sure others) that say this one is going to be 20-28". This is starting to be scary stuff. Remember, some folks haven't been out for groceries for 6 or 8 days. Not a big deal until you realize that 70% of the population doesn't store up for more than a couple or three or four days in "normal" times.

The people that haven't stocked up from the last storm need to get crack-a-lakkin! You folks with 4WD need to check with neighbors and see who needs help, especially old folks. Good luck with the difficult conditions..

Posted by: janicepappas | February 8, 2010 11:03 PM | Report abuse

I have huge ice dams and huge icicles hanging from all 4 sides of my house on both stories. Some are 3 ft long and wide lined up side by side. The house is over 100 years old and poorly insulated. I ordered some fiberglass insulation for the attic which I thought would help. Unfortunately it is sitting at the UPS because they cannot stop in front of my house without blocking traffic due to snow partially in the street by the tree box. I tried to move the ice snow mountain from the curb but it is too heavy and I am a senior citizen female. I did shovel out my sidewalks but it must not be enough for the delivery man. I dug out a place from the sidewalk to the street but it maust not have been wide enough. My arms and back and wrist are sore and now we are looking at more snow. There are no men in the area to help with shoveling. Anyone know how long UPS holds parcels due to the weather? Will I get the insulation delivered in the spring when the snow melts. Do they hold it that long? I cannot get through to them and no answer to e mails. Thanks

Posted by: peace4all2 | February 9, 2010 7:55 AM | Report abuse

I have Rambler whose roof (6 years old) starts about 10 Ft. off the ground and slopes up at a 20-30 degree angle. I have a long pole 15 feet with a curved reversed scooper at the end that enables me to pull a lot of snow off from low points of the roof.

I did that after the first Wash DC storm. I pulled it clean however I loosened the snow at the ends remaining which flaked off and froze. Now I had partial ice dams on my roof. The melting snow above hit them and backed up under the shingle to where the nail heads were. The water finds its way down that nail and drips into the attic. After time my ceiling was spotted and it found other crevices to where it dripped onto my kitchen floor.

I eventually went up on the roof and put black joe on the nail heads. I had trouble with big rains also. Somehow water is getting under the shingle and if it finds a nail you are going to get a leak. So I’ve had two problems with my relatively new roof but I digress.

If you are going to take the snow off the roof you better get it all off or leave it alone. I left it alone this time but got a foot and a half of snow up there and am concerned about the weight and this new storm.

Posted by: conrad031 | February 9, 2010 8:38 AM | Report abuse

While living in New England, I learned of ice dams as a somewhat different phenomenon. The ice builds up on the roof edge; the snow above it melts; the snowmelt sits on the roof and seeps into your house. It's explained here:

Posted by: michaelscalia | February 9, 2010 10:40 PM | Report abuse

Do not climb on the roof to remove ice dams and snow. You can remove snow from your roof while standing safely on the ground using a product called a roofrake. has several different styles that work with various roof types, solar panels and snow depth.

Posted by: caal | February 10, 2010 2:05 AM | Report abuse

The best thing to do if your house tends to get ice dams in a certain area is to remove snow with a roofrake back about 6 feet from that area with every snow fall before the freeze thaw ice damming cycle starts. Just like you shovel your walks and driveways when it snows, get the roofrake out and pull off that first at least 6 feet of snow after every snowfall.

Posted by: caal | February 10, 2010 2:11 AM | Report abuse

Back in the big snow of 1996, I noticed my carport posts were bowing under the weight of snow. A neighbor and I set up a ladder, but the roof was too slick to get on it. So we took a 2x4 about two feet long, drilled a hole in the middle, put a rope through the hole and knotted it. Stood on the ladder and threw the board onto the roof, pulled it with the rope. The snow came off and the carport posts straightened. (They got replaced the next summer).

Posted by: SomersetNative | February 10, 2010 9:22 AM | Report abuse

Icicles hang from the gutters of my flat front federal style row house. I just replaced the front gutter, which faltered and bent under the ice after the the Christmas storm. I'm not comfortable climbing up on my roof so when the the storm ends I'm going to climb out from a second floor window to the front porch roof and knock the icicles off from below. That should help somewhat, right? Does anybody have any other suggestions? Is there a city agency that offers assistance? I wonder how helpful my homeowner's insurance will be if gutter repairs are necessary after this.

I heard that a Smithsonian building caved in - what were the circumstances there? I replaced my roof in 2007, but now the skylight in my bathroom is leaking.

Posted by: nikita67 | February 10, 2010 12:50 PM | Report abuse

I just found a great video on YouTube that shows the use of roof rake, homemade ice dam socks, and (a new one in my research)heated radiator fluid to remove ice dams.

BTW, I was able to buy roof rake (the "Snow Barber") at my neighborhood (Glover Park) hardware store on Monday. This model was highly recommended on Amazon, but is no longer being made.

Because our neighborhood has mostly flat roofs, roof rakes are not in big demand here. So, after the storm ends (assuming it does end), if you live in a peeked roof neighborhood and can't find a roof rake, try calling some hardware stores in the District.

Good luck!

Posted by: canzo | February 10, 2010 4:15 PM | Report abuse

It never occurred to me that the three- and four-foot icicles on the south side of my house could damage my (very expensive, no-clog) gutters...I just opened the windows near the worst offenders and knocked them down with a broomstick. Thanks CWG!

Posted by: gwynn898 | February 10, 2010 8:37 PM | Report abuse

I have had some problems with gutters that have pushed water into the house. My solution was to hook up the hose to the hot water heater and, with ladder, clear the gutter. Once the hot water gets flowing the gutter clears pretty quickly. I usually try to clear the snow on the roof near the gutters with the same hot water. Wonder if you couldn't clear your roof with a garden hose and spray attachment hooked up to the water heater or other source of hot water.

Posted by: carajillo | February 11, 2010 10:42 AM | Report abuse

I just wanted to clarify something. This YouTube:

was made to help and to learn from others dealing with ice dams. Windshield washer fluid (NOT Radiator Fluid) was warmed up in a microwave and then poured over the ice dam. It was better than hot water because it would not re-freeze. The combination of steps did clear the ice dam. The sun came out in a couple days and helped a lot!

Posted by: NEWHowToDIY | February 12, 2010 10:00 AM | Report abuse

We have ice dams all around our roof, but only one leaking. We filed an insurance claim and the insurance company, water remediation folks, etc., have all told us that at this point only one thing works - get the snow off the roof. We are lucky enough to have a contractor who is out here removing snow today and cutting channels in the ice dams to permit run off.

In the meantime, a trip to Home Depot and we were supplied with shop towels, a tarp for the floor and large orange buckets to catch the leaks thereby minimizing damage (hopefully). Roof rakes apparently can assist in removing snow from roofs, but the problem is that I can't find a store that carries them in the area. Home Depot had some large push brooms and a big squeegee that helped to pull some snow off the roof.

Good luck to everyone and I suggest that if you plan on filling a claim with your insurance co., do so immediately. They told us that they are already backed up with claims and it may be a week before an adjuster can make it out. That is a week when we can't even start repairs. So make the call now.

Posted by: lucillegrace | February 12, 2010 3:14 PM | Report abuse

ok, i've noticed some icicles hanging from my roof. I can't get u there to knock the snow off, so what do I do?????? HELP!!!!!!!

Posted by: garyolney | February 13, 2010 11:49 PM | Report abuse

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