Posted 01-12-2004 at 10:05:28
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Seems like a number of people here in No. Va. had ceiling stains, and insulation damage from ice daming above their gutter line, then melting and backing back up into the attic. The water runs down into the attic insulation and then onto the backside of the ceiling, staining the ceiling, and in some cases causing the drywall to buckle, and pop nails.
This is preventable. Usually does not require any roofing repair. If you are having similar promblems with your ceiling, and gutters freezing solid, etc. look into your attic. That will usually be the culprit.
Warm air escapes the house into the attic, finding it's way to the upper reaches of the roof slope. Then it melts the snow above. That melted snow will run down into the gutter, and subsequently refreeze. The frozen snow melt will then begin to build upon itself with future snows adding depth to the dam.
Making sure that heat does not escape into the attic is part of the solution. You can do this by caulking holes that wires and pipes lead through, laying an insulation blanket over your attic access, and trapping air under more insulation. Be careful with recessed lighting. Most of these fixtures require insulation to be a certain distance from the fixture. This creates a large heat sink in the winter months. You give up a lot of heat this way.
In some houses the insulation runs all the way to the eaves. Big mistake. This inhibits any natural flow of air between any overhang vents (soffit vents) and the upper vents in the roof structure. These upper vents are usually on the gable ends in older house, and ridge vents in newer houses and additions. I've gone into customers attics to find vents covered over with plastic and duct tape. Usually the same house will have restricted lower vents too. The ice daming in the gutters build all winter, then if we get a good thaw followed by heavy rain folks have water stains suddenly and often blame the problem on their gutters, or shingles.
A general rule of thumb is 1 square foot of combined roof venting for every 150 foot of ceiling space on the uppermost floor.
So- before you look into spending your hard earned cash on gutters, roofing membrane, and shingles, look into how well your attic ventilates warm air. Your A/C will thank you for it too.
I hate to see people get caught up in spring time roofing hustles based on ice daming woes, when usually the problem is a matter of controlling the movement of air, rather than by attempting to control the movement of water.