Will A Metal Roof Avoid Ice Dams?

February 11, 2010 | Filed under: Ice Dams and Metal Roofing, Misc, Roofing Answers

This time of year I often get asked whether a metal roof can help someone avoid wintertime ice dams and the resulting damage to their roofs and homes. Generally, the answer to that question is “yes” but there are several things to keep in mind.

First, any time you re-roof your home, it is an opportunity to install an ice and water shield type of membrane around the bottom edge of the roof. Required by code in many places, this rubber or asphaltic membrane will help guard against water intrusion inside of your home if ice damming occurs. However, it does not help keep your shingles from being damaged.

Next, if you have interior damages from ice damming but in the spring your shingles look okay, that does not mean they do not need to be replaced. Some ice damage can be small cracks which, though barely visible, leave your roof extremely vulnerable to water intrusion and further damage.

Third, metal roofs due to their smooth surface and heat handling characteristics, tend to shed snow quickly. This helps avoid ice damming.

The interlocking nature of most metal panels also helps avoid problems due to ice dams.

Finally, if your home is prone to ice dams, when you re-roof is the time to see if you can increase your attic ventilation as well. Keeping your attic at a similar temperature to the outside will go a long way in keeping ice dams from occurring.

25 responses to “Will A Metal Roof Avoid Ice Dams?”

  1. Darin Rohead says:

    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 metal roof 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 http://www.thermaltechusa.com and see them in action.

  2. WE have a 33 year old two story home in Minnesota. the roof on our home needs replacing and we are wondering about a metal roof. The roof line is steep and an area attaching the house to the garage that collects a fair amount of snow. Would a metal roof be a good choice for this application? I love the looks of metal, the stability of metal and the fact that the life span may be longer for a metal verses asphalt roof. Looking forward to your reply!

    • toddmiller says:

      A metal roof is a good choice I feel for almost any home and roof design. However, it is still improtant to think about details and the exact roof being done.

      It sounds like you have a “blind valley” area that catches snow. I have the same thing where the garage attaches to my house. This area won;t change much with metal. In fact, some snowguards above the area may help hold the snow and prevent it from converging and packing quite to hard in this area. I would also suggest looking at increasing attic ventilation in the area (which may be very difficult) and perhaps some sort of heating system to help melt the compacted snow.

      I hope this helps.

  3. Jack Johnson says:

    We have a low slope roof. Last winter we had severe interior and roof damage due to ice dams, and are now considering a metal roof. With a metal roof do we still have to have rain gutters/eaves troughs? Do we need to take any measures, such as heating the lower portion of the roof? We already had a waterproof membrane under the current shingles, and it still leaked in. Also, what sort of cost are we looking at for metal roofing?

    • toddmiller says:

      Metal roofing will be 2 – 3 times the cost of traditional shingles. Most metal roofing customers are homeowners who intend to stay in their home through at least one re-roofing cycle.

      Metal roofing does not eliminate ice dams. Its smooth surface can help and the way that the panels interlock can reduce damage from ice dams but there is nothing magical about metal that eliminates ice dams. Many folks give out false information about this fact.

      Ice dams are most often the result of inadequate ventilation and insulation in the attic. Addressing those things is the most sure way to end ice dams.

      There are a couple of articles here on my site which I have written about this subject.

  4. Andrew says:

    I have a metal roof on my house. Recently I have had some Ice Damming where two shed roofs form a valley over a heated sunroom. The roof has 4:12 slope, a rubberized asphalt roofing underlayment (Ice & Water Shield), a heat trace line that runs up the valley. The furnace failed and was off for a week, the pipes froze and the ice dam occurred. The insurance company will cover pipes, filters and other damages related to the plumbing system but will not cover the claim related to the Ice Dam. The roof faces south and the snow melts and forms ice as it gets closer to the eaves. I have had the house for seven years and there is nothing different this year than years past, in terms of weather. Is there a diagram that you can direct me to that would explain what phenomenon happened in my case.

  5. If there is some ice damming on a steel roof, does that increase the risk in any way of water seeping through and damaging the sub-roofing or interior of the house?

  6. Lucinda Rettke says:

    Dear Mr. Miller,
    I recently wanted to have a steel roof put on my house and the contractor stated that the Ice would be worse with the house vs shingles. I found this hard to believe. But he stated the angle of the roof was not steep enough to stop damming of the ice.

    • toddmiller says:

      In most cases the root cause of ice damming is inadequate insulation on the attic floor and inadequate attic ventilation. A metal roof’s smooth texture can sometimes help a tiny bit but certainly it will not end an ice dam problem that existed in the past.

  7. Michael Forman says:

    Low slope…brand new roof..ice and water shield over entire surface..ice dam with severe damage to interior. Our house has cathedral ceilings with poor insulation. Thinking of strapping it and putting down steel. Logically it seems like this would give me more protection from future damage. Concerned that ice might form between new steel and old roof. Is this likely? Thanks..Mike

    • toddmiller says:

      I believe that any sort of airgap will help. I would recommend actually cross-battening. Put down vertical battens first followed by horizontal battens and then ventilate the resulting vertically oriented chambers.

      You could also consider putting down rigid urethane foam insulation before the battens.

      Make sure that the metal roof you use is approved by its manufacturer for your roof pitch and also for installations over battens.

      You should not get ice beneath the metal roof unless you have leaks through the metal or a real whopped amount of moisture coming up from the living space.

      Also, try to seal any possible sources of air leakage from the living space to the roof assembly — around can lights, pipes, vents, etc.

  8. Brian says:

    Can you elaborate on that bit about ventilating the resulting vertical chambers? Does this mean the metal roof has it’s own mini ventilation? Also putting down rigid foam first sounds interesting to me. I have a “hot roof” now meaning I’ve insulated right up the the roof decking (extruded polystyrene) and it seems to actually have less ice damning than it used to with a “cold roof” probably because the insulation is better now than it used to be. Adding rigid foam would basically be connected to my interior insulation increasing my overall R-value.
    My concern isn’t really with the ice damns as much as letting humidity get out. Without venting if any humidity ever gets through my insulation and to the roof decking where it is cold, it will freeze, then later melt and become water. (I think this is a more important reason for venting than ice damns is.)
    What I’m trying to decide is what would be best for me and these different options seem interesting.
    A self-venting metal roof would sort of give me a cold roof outside of my hot roof.
    Would cross-battening, or leaving chambers would increase the noise?

    • toddmiller says:

      Thanks Brian. What I was referring to was putting down sleepers vertically in line with the roof rafters, and then putting decking over that. the resulting air chamber can be ventilated. This, combined with your current insulation, should be very effective.

      An airspace is also a good sound dampener as it actually does not transmit sound the way that packed insulation can.

      I hope this helps.

  9. dorothy finnemore says:

    I have a metal roof on my garage . I have a door way that is on the side that the snow falls from it I would like a shield of some sort to stop the snow from getting in front of my door ,can you tell me what i could get thank you

  10. Jamie R. says:

    I have a 3/12 low slope roof. We experience some serious ice damming on both the east and west side. Now it is an older house and attic insulation and ventilation arent very good. Two years ago i had the attic topped up with cellulose but due to the attic being so shallow (only about 3-4 feet of space at center the insulation guy had to crawl on belly — i doubt he could insulate everywhere evenly. I also discovered many soffits werent opened nor baffles being used.
    My intent is to have the new crew suck out all the old insulation, hopefully patch any visible holes on the attic floor, then blow in new cellulose (they wanted to lay down batts but i just dont see how that covers every angle). I will also have them open all soffits and install baffles. I will also add a ridge vent for exhaust ventilation.
    I live in Ontario Canada. Is the above sufficient for preventing ice damming OR should i look into having a “cold roof” installed overtop my existing decking to add a air gap — the crew could due it with shingles or a low slope membrane layer.
    Your thoughts?
    Thx

    • toddmiller says:

      There is no way to predict this with 100% certainty but what you describe (air sealing, good insulation, good intake and exhaust ventilation) works well for many homes to avoid ice dams.

  11. Jon Ash says:

    Hot Edge roofing system is recommended for metal roofs with ice dam problems. What are your thoughts? Thanks…Jon Ash

    • Todd Miller says:

      Thanks. The hot edge systems I am familiar with do not retrofit well onto an existing metal roof. In regards to the idea of a hot edge system on a metal roof, it can be helpful. However, on a building with a deep overhang, it likely will not transfer heat high enough up the roof. So, the ice dams still build, just higher on the roof. Try to do all you can to address the situation with insulation and ventilation.

  12. Maggie says:

    We purchased an old bungellow that has a finished attic. There is no insulation on the ceiling of the finished attic space. We get huge icicles in the winter.
    We are looking to resolve this issue from the outside. We are considering two options. Create ventilation chambers by installing battens perpendicular to the ridge and install a new roofing deck over that and shingles.
    The other option is to install battens parallel to the ridge every 24”, install 1.5” thick foam boards in between and then install a new metal roof over that.
    In your opinion which methode will work best to eliminate the icicles.
    Thanks.

    • toddmiller says:

      I definitely suggest the vertical battens and vented air space. However, if you were to use 2 x 4 battens and add 2″ of poly-iso insulation between the battens and then still have 1.5″ of vented air chamber, that would be even better.

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