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Rain ingress through side of bay window

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18 Nov 2025
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Hi All,
We have had an issue in our living room with rain getting in to the side of the bay window. This started as a small leak with heavy rain and has gradually worsened.
Firstly we thought that it was an issue with the windows, so we have had them sealed and resealed. We have had the pointing replaced on the other side of the leak. We have had a brick taken out the external wall and a membrane put against the inside of the void. We have also had new felt put down on the roof above the leak. The leak remains.
Does anyone have any ideas what else could be the issue please? Any help would be grately appreciated.
Many thanks,
A
 

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Further pics are attached. Thanks
 

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Has it got worse since you had fiber installed and do you get water pooling on the inside cill by the black stain on the corner. It looks to me like you may have more than one problem. Does the top gutter around the bay overflow during heavy rain as the pipe going to the hopper looks a bit small. Is the hopper full of leaves from that climber growing up the wall, or elsewhere, and overflowing during heavy rain.
 
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I can see pipes going into the wall from the outside, what are they for?

The wall looks very wet in the pics. If this is the case, it suggests a pipe leak rather than a water ingress.
 
Has it got worse since you had fiber installed and do you get water pooling on the inside cill by the black stain on the corner. It looks to me like you may have more than one problem. Does the top gutter around the bay overflow during heavy rain as the pipe going to the hopper looks a bit small. Is the hopper full of leaves from that climber growing up the wall, or elsewhere, and overflowing during heavy rain.
I would say it probably has got worse since we switched to Vodafone about a year ago. Before that there was a very small leak. Not sure about it overflowing, but the gutters and hopper are clear at the moment as we have recently had them cleaned. I can usually hear a fizzing/trickling noise under the window sill during heavy rain.
 
I can see pipes going into the wall from the outside, what are they for?

The wall looks very wet in the pics. If this is the case, it suggests a pipe leak rather than a water ingress.
Pretty sure they both relate to the Broadband, one of them is an Openreach line. There was a leak in the downpipe in the neighbours garden, this has been patched up now but the leak remains.
 
Your neighbour has added a larger diameter pipe to feed into hopper , might be worth you doing same .
If you can hear rain hitting sill suggests problem is high level .
 
As I said I think you have more than one problem, as Foxhole says thre is a possibility that water is getting into the cavity from somewhere higher up, possibly the roof of the bay area, and running down the cavity. Secondly I wonder if the fibre cable has perhaps been drilled slopping downward and carrying water across the cavity. I would suggest having a look inside the Openreach white box in the corner and see if ther is moisure in it. Or better still get it removed all together. You could also ask Vodaphone to come and check their instalation for moisture in the boxes.
 
Thanks very much for your replies. A couple of things to think about there so I will look into them.
 

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