Ice Dams on Your Roof: How to Prevent Them

Icicles hanging from the edge of a residential roof
Ice dams cause some of nature’s most beautiful sights — icicles — but they also wreak havoc on your home. (DepositPhotos)

If you’re fortunate enough to live in the Sun Belt or some other balmy region, chances are you’ve never heard of — or at least experienced — ice dams.

However, in New England and other areas, every winter, ice dams are as common as frostbite and sub-zero temperatures.

Ice dams on house in winter
Ice dams lead to icicles. (DepositPhotos)

Ice Dams: Beautiful, But Problematic

Ice dams are often responsible for one of the most beautiful and iconoclastic of all winter images: glistening crystal-clear icicles hanging from gutters and eaves.

It all starts with a roof blanketed in snow. The snow layer sitting directly on the roof begins to melt, and water runs down the roof under the blanket of snow.

When the water hits the overhanging eave of the house, it begins to freeze. Some water drains into the gutter, where it freezes as well.

As the snow continues to melt and water freezes at the eave, ice eventually builds up along the roof, forming a thick ridge or dam.

Then, as water runs down the roof, it’s blocked by the ice dam, and forced up the roof.

It seems to defy all laws of physics, but water will actually flow up the roof, working its way under the shingles.

House surrounded by ice in the winter
Ice eventually melts, and soon, that can cause damage. (DepositPhotos)

Why Ice Dams Should Concern You

Roofs are designed to shed water that runs down the shingles, not up. However, when ice dams form, over time, water will work its way beneath the shingles and the underlayment, and into the seams between the plywood roof sheathing.

From there, water drips into the attic, where it soaks through the insulation and drywall ceiling, before dripping into the room below. If not detected immediately, the damage can be difficult and expensive to repair, especially if it ruins the floor, walls or furnishings.

The science behind this phenomenon is much more complicated, but if you go back to the beginning, you’ll find a clue to solving this problem.

The entire process starts when snow sitting on the roof begins to melt. Ideally, you want the interior attic temperature to be as close as possible to the outside air temperature. That’s why there’s usually only insulation on the attic floor, not between the roof rafters.

However, if the attic floor isn’t properly insulated or if heated air is leaking through the ceiling via cracks, crevices, ductwork and light fixtures, then the attic will become warm.

And it doesn’t take much heat to raise the attic temperature enough to melt the snow on the underside of the roof sheathing.

And since the overhanging eave extends past the house, it remains cold, which is why the water freezes when it hits the eave.

Man wearing a mask and gloves while installing mineral wool insulation in the attic
Adding insulation to your attic is part of the plan to prevent ice dams. (DepositPhotos)

Ice Dam Prevention

So, now you’re probably wondering what you can do to prevent ice dams.

First, use caulk, insulation and weatherstripping to seal all upstairs ceilings to stop heat from flowing into the attic.

Next, measure the depth of the insulation on the attic floor, and add more, if necessary. Call a building inspector or licensed contractor to find out how much insulation is required in your area.

Confirm that the attic ventilation system is operating properly. Most homes have soffit vents and ridge or gable-end vents, which allow air to flow into the attic along the eaves and out the attic at the ridgeline or gable walls.

Be certain the attic-floor insulation isn’t blocking the soffit vents. And never staple plastic or anything else over attic vents. Remember, you want the attic temperature to be as close as possible to the outside air temperature.

Finally, once the roof is covered with snow, use a snow rake to pull as much snow as possible from the lower portion of the roof. That’ll at least remove the source of water, which will greatly reduce the chance of an ice dam forming.

If your home already has ice dams, there’s not too much you can do about it. Avoid installing electric cables or any other device to melt the ice.

Those products don’t solve the problem that’s causing the dams to form in the first place.

Further Reading


  1. We have a flat roof only over my office in our home.We had a leak so we had a copper roof put on they said it will never leak,guess what it does and the roofing compancy will not do anything about it. It only leaks when it snows or when ice melts then it come from the celing and drips into my office.It’s a ice dam. We have know attic its just a flat roof.My husband has gone out on the roof and shovel the ice off he can’t keep doing this he is 71 years old.
    What can we do next if anything?
    We do not get your show. so can you email me and tell us what to do if anything.

  2. Dear Gloria, I’m sorry to hear about your roof leak. Flat roofs are notorious for leaking, which is why you see very few of them. The first suggestion is to please keep your husband off the roof. That’s no place to be, especially when it’s wet and/or covered with snow and ice. It’s hard to give specific advice without seeing your roof, but I suspect it doesn’t leak during a rain storm because the rain runs off. But snow and ice sits up there and melts slowly, where it gets a chance to seep through seams and joints between the copper roof panels. The problem isn’t with the roof itself, but the way it was installed. Any roof system will leak if improperly installed or damaged. Your only option is to call a professional roofing contractor and have them inspect the roof for punctures or ill-fitting joints. The contractor should also closely inspect flashing or vent pipes, if there are any. Another common place for leaks is where one roof meets another roof or the side wall of the house. Sorry I can’t be more specific, but an experienced contractor will certainly be able to locate and fix the leak. Thanks for writing and good luck.–Joe T.

  3. Thanks for providing great information for us home owners. We just moved into a 40 year old home with lots of leaks. I noticed today the ice dam on and around the gutters. I know we lack enough insulation. I have watched the other videos on how to instull and how much. I think I am not ready to tackle this job. Appreciate the easy and simple use of this website too. blessings from Grove City Ohio

  4. Hey Tim, Glad you like the website and found the information on ice dams useful. Hope all is well in Grove City. As you mentioned, the lack of attic insulation is likely the main cause of your ice dams. And when you do add insulation, be sure you don’t place it in too close to the eave. You must leave space for outside air to flow through the soffit vents, up between the rafters, and out the ridge or gable-end vents. Maintaining an efficient attic-vent system is the best way to combat ice dams. Thanks for writing and good luck!–Joe T.

  5. We have just survived the Great Blizzard of 2013 here in R.I. and today it is raining! Thank you for your great article on ice dams & how to prevent,plus your information on insulating the attic. Plan on being very busy; can’t wait for spring.

  6. Hi, can you tell me the better choice for insulation in the attic?
    My brother is pushing me towards blown in, where we buy the packages and get the blower from the home store. Sounds easy, less stress on us to crawl around placing rolls or batts in the attic.

    I think we lay down our exacts with rolls or batts, meaning I buy R30, lay it down and there we go,

    I can not tell price-wise which is saving me money. My sq ft is 910 I need covered, any help is very much appreciated

    thanks, tim helsel in Ohio

  7. Hi Patricia, I feel your pain. I live in Connecticut and we’ve gotten a ton of snow this winter–with more to come, I’m sure. Glad you liked the article on ice dams. Increasing attic ventilation is key, but it’s also helpful to remove snow from the edges of the roof with a roof rake. I bought a roof rake online that has an extra-long handle, which allows me to pull off the snow while standing safely on the ground. Good luck, Patricia and hang in there, spring is coming!–Joe T.

  8. Hi Tim, I am not familiar with insulation costs in Ohio, but it’s typically cheaper to buy fiberglass batts and lay them down yourself, as opposed to renting a blower and buying blow-in insulation. Of course, as you mentioned, it is much more work to cut and lay down each individual batt than to simply blow in the insulation. Regardless of which type of insulation you install, be sure you don’t block the air flow from the soffit vents, assuming you have soffit vents. It’s important to allow fresh air to enter the attic at the eaves and exhaust out the ridge vent or gable end vents. Sorry I couldn’t be of more help. Good luck.—Joe T.

  9. I have used a snow rake the past 10 winters with great success, but prior to using the snow rake I have had ice dams . The ice dam caused water to leak into my kitchen windows and wall. I cut the legs off of pantyhose and filled the legs with granular salt, tied off the open ends of the leg section and left a 10′ long rope handle. I toss the filled leg a few feet above the edge of the roof. Then I pull the rope handle to position the filled leg perpendicular to gutter to melt a narrow trough for the water to travel off the roof. I also placed a small salt filled leg section on the gutter right above the downspout connection. Thought this worked in an emergency to avoid major damage to the wall and windows. Never miss the show, great content.

    Lee Nuzzo Crown Point, In

  10. We replaced our roof and added insulation in the attic but still get ice dams at the soffits.. There were’nt any baffles so we added some but that hasn’t helped. .I noticed that the lousier have been covered with siding is this the reason? We added a roof ridge when we replaced the roof. HELP!

  11. Lee,
    what type of salt did you use to keep it from freezing? My neighbors have ice shows every winter, and most are elderly, although maybe insulation would help too.

  12. ice dam on roof at bottom of shingles about 4 inches thick and 4 inches wide.. I have removed the gutter and use roof rake to clean the roof off.. but I am still getting water into my bow window.. how can I get this ice off the roof to stop the leak without contacting professional contractor as we are living on social security and have limited it safe to use ice melt ?? when the temp gets to be about 30 degrees that’s when the problems start.. PLEASE HELP.. thank you for your time

  13. This is an absolutely terrific article on ice dams written in layman’s terms. What caught our attention is the focus on PREVENTION. Once you have ice dams it is to late to avoid them. The article also re-enforces our position to avoid electric cables and other melting devices on your roof. Thank you..

  14. I have watched your shows for many many years. Even when your daughter was starting as a single gal on limited shows. Now I can not get your shows since I switch from Dish to Charter tv.
    Questiong: I am 74 and have always lived in stick or brick built homes. We moved from Wisconsin to Florence,Or R. in a 55+ Manufactured
    “Florentine Estates “Gated community. We need info to do home repairs around our homes inside as well as outside. Can you advise or help? We own our homes and our Lots?

  15. Check with your local hardware store for snowmelt which will be safe for use on your roof. It is made especially for roof, most concerns is the salt that is in most of the stuff you pay. Because it can cause roof damage itself at the worse, sometimes even stain your shingles, some home owners have used salt. Placing some in a used nylon stocking and laying it across the worse ice buildup on the roof, cheaper and last longer. Just make sure the salt is safe for your roof, cheap and fast like I said.
    Sometimes you can buy the snowmelt at large retailers like Home Depot,…etc. It does work, but it is only a bandage for a problem with your attic, I have turned off my registers near my worse spot and it helps, along with removing the snow. Like the article says, do it from the ground and be safe.
    Think Spring and God Bless.

  16. We have a ridge vent and soffit vents. There is an hvac unit for the second floor, in the attic which generates heat enough to melt the snow on the roof. How can we isolate this unit from allowing the heat into the attic? Should we put insulation underneath the roof to prevent this? If this unit was not in the attic, I believe we wouldn’t have this problem. It also appears that the venting isn’t adequate.

  17. Also…I pour hot water in the downspout to give the water a place to go.
    Now this year, I need to figure out a way to do this without a ladder. Maybe a new, unused, pressurized insect sprayer with a bent tube, 6 feet long? (I live in a ranch home. Easy to do).

  18. Hi Joe,
    The family room in our house has a raised ceiling. The house was built in ’95. There is no access to examine the area. We have had ice dams in the past. Your article states that we should not install electrical devices to melt the ice as this will rectify the cause of the ice dam. Besides doing some shoveling with those extension devises you suggest, the only thing that works while we are gone is the electrical heating wire. It does work well. On a heavy snow, the heating wire will create a snow tunnel (if you will). When the snow melts, the water will continue down the drain, as the gutter contains the heating wire as well. Would you have any suggestion for our raised ceiling? It is the only place where this has occurred in our house.

    • Hi, Mike. We’re always looking for homeowners to call into our radio show and ask questions directly to Danny and Joe. We’ve reviewed your question and shared it with our radio show’s producer.
      Thanks for writing! 🙂

  19. I have had ice dams in two of the three homes I have lived in. The house I grew up in was a Cape Cod with no attic or if the second floor was considered the attic, that’s where the bedrooms were. The angled ceiling of the roof was right above our heads. We had ice dams. The second house I lived in had two stories but had a full attic above it. There, the attic was cold and the insulation was on the floor, or the ceiling of the second floor bedrooms. No ice dams. The house I’m in now is a jumbo Cape Cod and again, no attic. The second floor bedrooms are the attic. The slanted roof is literally the ceiling in these rooms. Had major ice dams. Water leaked into the kitchen right after we remodeled it. I’m not sure what to do. I go on the roof and shovel the snow off. I have a roof rake but cannot reach all of the roof because of a sunroom. I thought of getting electric wires. Not sure what else I can do.

    • Thanks for sharing your thoughts with the community, Thomas! Try installing some soffit vents and eave vents. This will circulate the warm air underneath the roof and prevent the ice dam from forming.


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