I am planning to replace the roof in this year. I want to know
something about the features that I should look for in order to avoid
water leak from ice-dam:
- I know that I should avoid low-pitch roof. I should improve the
insulation in the top floor, and improve the ventilation in the attic.
What other things that I should look out for?
- I am planning to have a gutter in the roof. But I am wondering
what will happen if we have rain and the gutter is filled with ice and
snow. Where will the water go to? Will the water go over the edge of
the gutter and drop to the ground (this I think will be acceptable)?
Will the water somehow go between the roof and the gutter and end up
inside the house? Will I have to use one of those heating cable to
melt the ice and snow from the gutter and the downsprout?
Thanks in advance for any input on this issue.
You may want to call your city to find out what is required under local
code in replacing a roof. For instance, the code may require applying
ice dam barrier material to the roof before shingling. The barrier is a
waterproof, adhesive-backed membrane that is rolled out and stuck to the
roof deck. Local code where I live specifies that it must extend from
the edge of the roof overhang to at least 3 feet up beyond the line
where the exterior wall and roof meet.
This stuff doesn't cost a whole lot more than ordinary tar paper, but
provides better protection against moisture incursion from ice dams.
Thanks for the suggestion. I saw its use in several This Old House TV
shows. I will definitely keep this in mind.
How's about the issue with gutter that is filled with snow and ice? Do
you think using heating cable around gutter and downsprout is a good
If you insulate the ceiling and ventilate the attic, then the roof will stay
cold and there will not be any runoff water to ice up in the gutters. When
the water melts on the roof, it will be above freezing anyway, so it will
still not ice up. Well that's the theory anyway.
You may still want to put a membrane on the last few feet near the edge, to
be on the safe side.
This sounds reasonable. I guess I should replace the old roof with a
higher pitch roof that has better insulation and ventilation, and with
the membrane that you have recommended. And see what will happen.
If I still get leak caused by ice and snow in the gutter, I will put
heating cables. Otherwise, I will not put them on the gutter, and save
the money and the trouble.
There can be periods when melting can occur, not because of heat lost
through the roof, but due to solar heating. Don't scrimp on the
membrane it's easy to add more before you put shingles on.
I see many people putting heating cables in gutters. The run them up
the down spout and along the inside of the gutter. I prefer not to do
it but it seems to work.
If solar heating is happening, the conditions will continue
to exist for the water to keep being liquid instead of frozen.
Plain and simple, any heat that gets into the attic needs to be
gone before it can heat the roof from the underside. Peak
venting and plenty of soffit openings, unobstructed by insulation.
That's the ticket.
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