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Question DetailsAsked on 2/19/2018

Two up stairs windows leak sporadically when temperatures are very cold. These windows are under a dormer roof.

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1 Answer


I presume you mean water leak, not air - if air leak is what you meant, I would be looking at whether the latch pulls the window into the frame snugly, ofor worn or torn or missing weathstrip on the window unit, missing outer caulk, or the gap between window frame and rough opening studs not being sealed with foam or backer rod.

If water leak, if coming in through the window itself ditto to above. If coming in from above (may need to remove interior top trip piece to check for this), then I would be looking at water coming into the attic from the dormer roof - either from leaking flashing, missing/damaged roofing, or ice damming from freezing up of roof runoff and snowmelt/rain water backing up behind an ice dam and getting under the roofing, then down into the top of the wall and down in the wall to the window where it breaks to free surface.

Also - sometimes a roof leak further upslope, especially if a relatively small leak, can stick by capillary force and run down the underside of the sheathing or the bottom side of rafters until it hits something that makes it drop free - commonly a top of wall or an insect screening or such at the outer walls.

Certainly checking the attic/underside of roof sheathing (if accessible) for wetness should tell if coming from the roof. Also, obviously if they are leaking and it has not been raining for some time then the water pretty much has to be coming from above.

Two other possible cause, fairly rarely - a leaking attic water heater or HVAC drain vent which is normally carrying water but freezes up when it gets cold in the attic, causing overflow which then trickles down into the top story. Easy to check out.

Another cause, normally only forming when below about 10-15 degrees or so outside, is frost or condensation buildup in the attic insulation or on the underside of the roof sheathing from excess moist interior air leaking to the attic - then when the sun shines on the roof or it gets warm enough outside, the attic goes above freezing and the frost melts, causing wetting of attic insulation and in heavy cases dripping down into house. Again, if attic is accessible, easy to check for wet framing and sheathing, or wet insulation.

If unable to check these out yourself, if happening without recent rain then Roofing would be the normal Search the List category to find well-rated and reviewed contractors for this type work - and normally you will also see (during the cold weather) icing building up inches thick on the roof eave and sometimes gutters.

If happening only with rain, could be roof or window - Handyman can commonly handle exterior caulk and weatherstrip issues, not normally so competent on roofing but could check out the attic and help tie down most likely source of water.

Answered 2 years ago by LCD

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