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When temperatures plummet and snow starts falling, many of us reach for the shovel or snowblower. Smart homeowners, though, remember to look up too -- and check their roofs for ice. Ice dams are accumulations of ice on the edge of the roof -- and they mean Big Trouble for you and your home, so be on the lookout.

What's the big deal, you ask? Ice dams result in water seepage, which can rot roofs, destroy insulation, flood attics and ruin gutters. Moisture damage can extend far inside the home, damaging ceilings, paintwork and belongings. The dampness encourages mold, too, which can trigger nasty allergies.

You may have heard that gutters cause ice dams by providing a place for water to collect. Wrong! You may also have heard that installing heating cables along the gutter line is the best way to prevent ice dams. Wrong again! Yep, there's a lot of misinformation out there. Let's look at where ice dams really come from.

How Ice Dams are Born
In poorly insulated homes, warm air escapes through the ceiling and into the attic. If ventilation inside the attic is also inadequate, all that warm air has nowhere to go. Result: the roof's temperature starts to creep up higher than the outdoors air temperature, causing accumulated snow on the roof to begin melting.

Water then trickles down the slope of the roof until it once again hits a cold patch, usually the gutter. There it refreezes, gradually forming a dam that prevents runoff. Additional melting snow, having nowhere to go, starts seeping inside the house -- and that's where the homeowner's headaches begin.

A Cool Solution: Insulation and Ventilation
The only way to permanently eradicate ice dams is not to warm your roof up (with heating cables) but to cool it down with better insulation and attic ventilation. Until then, you'll go right on experiencing ice dams in severe weather. Any other strategy will provide a temporary fix, at best.

In northern states, attic insulation should be at least 12 inches deep. Make sure it is installed correctly, without any gaps between sections, and in conjunction with a vapor barrier. While you're at it, check that attic heating ducts are located as far as possible from the roof.

Also check around light fixtures, chimneys, bathroom fans and anywhere else heat might escape upwards. If you discover small holes, seal them up with caulk, spray foam or weather-stripping.

Next, evaluate your attic's ventilation system. Are there adequate inlet and outlet vents? If not, look into installing a continuous soffit and ridge ventilation system. Here's how it works: a vent is installed that runs the entire length of the roof at its apex.

We all know hot air rises, right? In this case, the hot air now has somewhere to go, naturally flowing up and out through this new attic vent.

Meanwhile, that draught of air upwards and outwards creates a vacuum, sucking cold outdoors air into the attic via soffit vents, further cooling down your trouble zone. The beauty part is there are no fans or wires or anything else to be maintained. Nature does all the work for you!

Help! There's An Ice Dam on My Roof. Now What?
Your best strategy is to sit tight and wait for the ice to melt away. Later you should focus on preventing future dams by making the improvements described above.

Before you decide to manually chip away at an ice dam, know that it's not recommended, and best left to a professional. For one thing, you could seriously injure yourself. (Never, ever climb up on an icy roof. If you must inspect the ice dam up close, use a ladder and beware of falling debris.) Second, forcibly dislodging chunks of ice could easily damage your roof and gutters, worsening your leakage problem.

If you really, really can't stand just waiting it out, here's an ice-melting tip courtesy of This Old House: Cut the legs off a pair of pantyhose, fill with calcium chloride ice melter and lie them down the slope of the roof so that each leg crosses a section of ice and the toes dangle over the edge of the gutter. This should melt small channels in the ice, allowing runoff to occur.

See also:
Fast Fixes for Ice Dams
How to Fix a Broken Gutter in a Storm


  • Darin Rohead

    While I can agree with your observation that many homes are poorly insulated and have areas were heat loss from the home causes problems and should be focused on to remedy, there are many factors as to whether a COLD ROOF will stop ice dams. With so many architectural challenges by poor designs, dormers, gables, cathedral ceilings, getting to a cold roof via ventilation can be difficult and extremely costly. Your article does not address a basic fact of Mother Nature… THE SUN. What do you do about radiant heat from the sun everyday? Most homes will see some sun exposure during the day. That heat melts snow and creates moisture on the roof, typically following the slope to the eaves and valleys. Then the temperature drops and the melt refreeze. If this happens over a couple of days... ICE DAM! Even on a well vented cold roofs like you have described. Keeping valleys, eaves and gutters clear can only be achieved by keeping the refreeze from occurring by keeping the melt liquefied and allowing it to get off the roof and then too the ground. There are products out on the market that can prevent ice dams and keep them from forming. Checkout www.thermaltechusa.com and see them in action.

    Reply
  • Cam Carey

    i agree, with your comments, temperature fluctuation, i am vented up the wazu, and i have ice jams. Since i pulled my ice filled gutters my problem has been reduced alot.

    Cam


  • Barry A Clarke

    I agree with you. I live just south of Chicago and have an R60 insulation factor and my attic is vented up the wazo. The problem is the dark multi color brown roof and the afternoon sun which melts snow and when the sun sets, bingo, an ice dam around the chimney and vallies of the dormers at the gutters that gets worse each day. This article is not very informative to the average person who does not know better than to believe everything they read.....


  • susan

    Does anyone have any thoughts or advice about installing snow guards on a standing seam metal roof? Snow-magedon is doing a number on our gutters, so we were thinking about having snow guards installed to protect the gutters in the future. But would snow guard increase the risk of ice dams? Also, what is the risk/benefit bottom line of the snow guards' keeping the extra weight of the snow ON the roof versus saving gutters from damage?


  • bnbblades

    Darin

    You are 100% right, as the sun warms the roof, the water flows. When the sun moves away from the roof, the water freezes.


  • mitre619

    Please move to california sun shine every day !!!!!!!!!!!


  • jerry

    I don't disagree with your cold roof theory but I must say that the heat cables used correctly will for the perfect channel with the flick of a switch thus allowing the same water you are talking about to escape. It works the same way your stockings hanging off the roof will work without my wife wanting to kill me. We need to insulate correctly up here in the north but using the cables will always allow that channel to form under any circumstances.

    Reply
  • Charles Pedersen

    I absolutely agree with the use of ice melt cables. Properly installed cables channel water build-up into the gutter and downspout. You have to install the cables along the roof edge, along the length of the gutter and down the downspout. Don't try to do this when the ice dam is in place. This is a summer job. Read the instructions on the ice melt cable box for planning the layout. Measure carefully so you get the correct length of cable. You can't connect these cables together.


  • jenn

    As a roofer in Vermont for over 12 years(my boss has been roofing for over 40 years). We take more heat tape off then anything else followed by snowbelt. When you make water on your roof it will get into your house. We have taken off roof's less then a year old because of improper instalation. Spend money on underlayment it costs alot but bittathane is the best fix for this problem. Have drip edge and a proper overhang. All this stuff is actually printed on a shingle wrapper. If only people would read them.
    Also this article missed the fact that lots of"roofing" companies only use air guns to nail their shingles. Alot of times this put holes through the roof because of improper settings. Try hand-nailing it works wonders.


  • John

    What's all this global warming hanging from my roof? Must be algoresickles.

    Reply
  • vanesa

    Only a complete idiot would confuse the weather with the climate.


  • Carlos

    We just call 'em "Global Warming" Stalactites in these parts.


  • wayne

    roof rake is what we northerners use. Its a flat blade connected to a 18" aluminum pole. You reach up on the roof and pull the last 3 or 4 foot of snow off your roof so the gutters don't fill up with snow and cntinue to freeze. When the sun comes out the ice in the gutters thaw and you don't have to worry about the ice building up and going under your shingles.

    Reply
  • Dave

    I used to have problems with ice dams on the edge of the roof and the easiest way to prevent them without having to climb is to have a roof rake and after the snow or even during the snow, take the snow off the roof as far back on the roof as the rake will reach. I even bought an extra extension where I can almost take all the snow off the roof. If you have a two story house or above then then you might have problems doing it but with a normal one story home there should be no problems. Even with the two story you should be able to get a foot or two back which will help.

    Reply
  • Bill

    The area that the water gets in 9 out of 10 times is under your drip metal or at the front of dormers within a few feet of the roof edge. To resolve the problem when a roof is installed use a ice and water barrier at all eves and valleys. The water gets in where the plywood roof base and facia board meet under the drip edge. Forget the manufacturers install recommendations and run the ice and water barrier over the edge of the facia board 1.5 inches and stick it to the facia board ( cold weather use a heat gun ) placing drip metal over. In valleys run ice and water barrier over installed ice and water barrier and over top of drip metal. In front of dormers run ice and water barrier up wall and around corners of dormers where step flashing are installed folding in half and pressing before install to keep it tight to the inside corner closing all opening where roof meets wall. I've installed roofs for 25yrs. and been in business for 12yrs. I have never had 1 leak in any roof I've done.

    Reply
  • fred

    You nailed it Bill. You shoiuld have been the one to write this article in the first place. A couple diagrams for the lay person and you'd have it.


  • Matt

    There is a product called gutterglove ice breaker that will solve this problem. If anyone is interested, you can find it @ gutterglove.com

    Reply
  • Bill

    The area that the water gets in 9 out of 10 times is under your drip metal or at the front of dormers within a few feet of the roof edge. To resolve the problem when a roof is installed use a ice and water barrier at all eves and valleys. The water gets in where the plywood roof base and facia board meet under the drip edge. Forget the manufacturers install recommendations and run the ice and water barrier over the edge of the facia board 1.5 inches and stick it to the facia board ( cold weather use a heat gun ) placing drip metal over. In valleys run ice and water barrier over installed ice and water barrier and over top of drip metal. In front of dormers run ice and water barrier up wall and around corners of dormers where step flashing are installed folding in half and pressing before install to keep it tight to the inside corner closing all opening where roof meets wall. I've installed roofs for 25yrs. and been in business for 12yrs. I have never had 1 leak in any roof I've done. I live in CT and this is a common problem. I came up with this solution while I was working for a company here in CT. Ever since I came up with this idea it has been used by many companies in the area. When done properly you can have all the ice, snow or water on your roof and not have a probem.

    Reply
  • roofvents

    There is a big misconception about ridge vents. I get many phone calls daily from roofers, architects, and building professionals complaining that their ridge vents got covered by snow and are unable to function. Ridge vents are literally on the roofline, so when a ridge vent gets covered by snow, ice damming sets in and the vent is unable to function until the ice or snow melts off. A solution to this is, if you live in an area that can get four or more inches of snow, get a vent with a stack or collar. This will keep the vent above the snow thus enabling it to function properly no matter the weather condition. If you have any more questions please visit my website at www.roofvents.com or email me at roofents@aol.com

    Reply
  • jm

    My solution is to live in an old house where all the heat goes straight through the roof and there is no chance of ice or snow buildup! Everything just melts right away!

    Reply

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