Damp patch...

23 Aug 2016
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United Kingdom
Recently had our old kitchen gutted and re-plastered ready for a new kitchen to be fitted. After heavy rain on the weekend, this patch appeared at the bottom corner of the window (see pic).
Its a UPV frame, sat on a stone cill. The exterior cill is approx 3/4" below the interior upvc cill.
So far as I can see, all exterior seals look in good condition with no obvious gaps. When window is opened, the interior of the frame seems quite dry, but there is a lot of water around the trickle vent in the same corner as the damp patch.

I've heard that a poor cill seal can cause this, but given that the exterior cill is 3/4" below this damp patch, should I look for other causes?

many thanks.


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Hi, thanks for the reply. Yes, there were Pvc trims. The walls are solid stone/rubble with face bricks surrounding the Windows. The walls had scratch render applied right up to the window frames before plasterboard and skimming. So there's no wall cavity that could have been bridged by the new render. What do you think?
Thank you.
Can you post a pic of the outside of that corner and the whole window from outside?
Its not just the cavity being bridged that can cause this but also a vertical DPC, Although its unlikely that you had those in that type of wall.

It most likely is to do with the end of the cill not having been sealed up. But unlike the other chap if you have brick around the window it should be a fairly easy half day job to remove seal and refit the window.
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Thank you. I'll take some exterior pics when I get home this evening and post them here. Grateful for your advice
Sorry for the delay! Here are some photos. Included another interior view. The internal cill is a separate pvc profile, not integral to the frame. The new plaster board reveals sit on top of this cill. The exterior stone cill is approx 3/4" lower and slopes away from the wall.



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Well you haven't got a PVC cill so it wont be the same problem as the other guy.

First thing I would do other than thinking about a new window (sorry its a bit old and mucky plus externally beaded) is take those trims off and either clean them up or get a new length of 30mm trim from Eurocell for about £5 along with a couple of tube of clear silicone.

I would then clean the window (Silicone sticks best to clean surfaces) and reseal the edges of the window. I would get it fully water tight before putting the trims back on and then seal them too.

Hopefully that will sort your problem otherwise its a water penetration issue. In which case a pot of Tompsons water seal coated onto the bricks and mortar around the window.
Thanks. A closer inspection revealed some suspect pointing around the brick arch over the window that may be to blame. Have resealed the window, sealed all surrounding brickwork and will sort the pointing. Fingers crossed one of them will sort it!

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