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Old 01-30-2009, 05:24 AM   #1
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Damp issues under bay window

I have a bay window in upstairs front bedroom, with serious damp/mould issues underneath window, mostly in corners. Having recently tried to re-decorate, after cleaning off mould with commercial "mould killer", I added 2 coats of Dampseal and then 2 coats of emulsion. However, the wall gets so wet that the emulsion runs off the wall before it gets a chance to dry. I believe it to be a condensation prob, as I had a similar experience in my porch until i added an airbrick. But upstairs wall is pebbledashed, and airbricks are never placed in bedrooms, are they(?). I have a gas radiator on the affected wall, but i`m not sure if leaving the heating on to dry the wall out is doing more condensation harm than good. The windows are double-glazed, i leave the top window open when practical to aid ventilation, but this negates any effect the radiator may be having of course. Please can anyone advise?


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Old 01-30-2009, 06:37 AM   #2
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are you sure its not leaking from above?Missing or loose flashing could be alowing water to get in.Or it could be missing insulation and vapor barriers at the head or seat.Some pictures from the inside and out would help.
Whats a air brick?


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Old 01-31-2009, 05:55 AM   #3
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Is the gas appliance vented to the outside?? Gas appliances can put out water vapor that could condense on cold or poorly insulated surfaces. But I suspect, as above, that you have a leak. What you describe sounds like a lot of water, and water does not always appear where the leak is located, it travels. Close inspection around the window, by someone that knows what they are looking for, is needed.
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Old 02-01-2009, 02:08 PM   #4
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It could also be that the space above the bay window wasn't properly insulated and the cold air is condensing on the warm top board.
Second the question about the, "air brick".
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Old 02-02-2009, 03:12 PM   #5
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Geoff the guys have given some good pointers.There is only one thing to do to find out whats going on here and thats to get up there and find out.
You say the house is double glassed and pebble dashed which came first?
I ask this because the dash could be covering the capillary grove on the out side window cill and any rain hitting the window would be directed behind the rendering and onto the brick work trapping it there.
Something else to look at pebble dashing usually has a bell cast above the fist floor window and this can be cracked also trapping moister on the bricks. OK the air brick is a ventilation brick fitted to allow the exchange of air from inside to out and vis a vis.
I have seen seen air bricks fitted in bedrooms but a much better solution would be to to fit vents at the top of each window frame.
CONDENSATION what is it? When cold meets warm this is the dew point and each person releases moister into the air and when this point reaches over load the moister is deposited on a cold surface.
What to do?Insulate the cold surfaces or remove the water?
May be both, if you have cavity walls look into cavity wall insulation and buy a dehumidifier.Any way geoff let us know how you get on and then we will all learn something.Hope this helps billy.

Last edited by billy d; 02-02-2009 at 03:30 PM.
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condensation , damp

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