Thursday, February 10, 2011

ICE DAMS

 A reminder to make sure you remove ice damns after a heavy snow.An ice dam, on a smaller scale, is a problem of house and building maintenance in cold climates. An ice dam can occur when snow accumulates on the slanted roof of a house with inadequate insulation and warm air leaks into the attic at penetrations for plumbing stacks, wiring, chimneys, attic hatches, recessed lights, etc. These warm air leaks are known as attic bypasses. Heat conducted through the insufficient insulation and warm air from the attic bypasses warms the roof and melts the snow. Meltwater flows down the roof, under the blanket of snow, onto the eave and into the gutter, where colder conditions on the overhang cause it to freeze. Eventually, ice accumulates along the eave and in the gutter. Snow that melts later cannot drain properly through the ice on the eave and in the gutter. This can result in:

  • Leaking roof (height of leak depends on extent of ice dam).
  • Wet, ineffective insulation.
  • Stained or cracked plaster or drywall.
  • Rotting timber.
  • Stained, blistered or peeling paint.


Under extreme conditions, with heavy snow and severe cold, almost any house can have an ice dam, whereas a house that is poorly insulated with attic bypasses will have ice dams during a normal winter weather. Giant icicles hanging from the eave are one indication of a poorly insulated attic with many attic bypasses.

Although high snow levels along with extreme cold weather is generally considered the highest potential risk conditions for ice dams to accumulate, standing snow is not even a required prerequisite for ice dams to form. It takes very little actual moisture to form ice dams.

22 comments:

  1. useful and practical with the weather we have been having in the northeast. thanks!

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  2. always sun where I live never had problem with snow haha

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  3. Glad I don't have to deal with any of that. Go Florida haha

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  4. It annoys me how our country stops dead with the snow =/

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  5. I'll have to check my roof now, thank you for the warning!

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  6. Being new to Idaho, and under a lot of snow, I found this extremely useful.

    Just checked my roof and I'm good, but at least I know to check on it now and then!

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  7. Thanks! Im about to check my roof for these...

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  8. I live in an apartment building. I'll keep this in mind when I buy a house in a couple of years!

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  9. i hope its not going to snow again and thx for the warning never thought that such thing can happen

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  10. We don't have that problem in Portugal!

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  11. Oh a business log, interesting. New one for me!

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  12. I only use Purdy brushes. They're a little more expensive, but totally worth it.

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  13. good to know some theory behind why snow on roof tops is bad...

    i'm helping a buddy out with a snow removal off rooftops job.

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  14. This is very useful tip. Fortunately it doesn't snow where I live, but this is still good to know.

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  15. I've been reading through your blog and I really like it, I'll be following :)

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  16. Good advice, however this surely wouldn't be a problem in an energy efficent house with minimal heat loss from the roof?

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  17. Good tip, will keep it in mind for when I have my own roof ;)

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