Wet around edge of interior window sill - uPVC

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Hi,

We have a uPVC window in a dormer, and we've recently had the roof of the dormer changed, along with the tiling on the side cheeks. We also had the interior replastered, and since then I've noticed that when we have heavy rain, the interior window sill gets very wet at the edge. I'm not 100% if it's a new issue, or was always there and never noticed.

Either way, I contacted the roofing company, and they came back and checked the new roof, and added sealant all around the exterior window frame, and where there was a gap at the ends of the window sill, but the issue still seems to persist, and I'm a bit perplexed where the water could be coming from.

A couple of notes:

* It seems they added sealant around the exterior window sill - I guess they shouldn't have done that since that would be the drainage area for the frame?
* There is quite a bit of water inside the frame when it rains - not sure how that gets there but from what I read its expected and should go through the drainage holes?
* Theres an area of lead flashing under the window sill which has gaps, but the gaps dont align with where I see water on the interior, and I dont think water should be able to get up under there anyway?
* I did recently sand the interior window sills and a lot of the interior seleant that was old came away - would that be a source of an issue? My view was that water shouldn't be on the inside anyway?

Thanks in advance
 

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I can't see any external drainage on that frame. There should either be drainage holes ( with cover caps ) on the front face OR base drainage which drains onto the upvc cill and then drains between the gap between frame and cill ( which looks sealed with very thick white sealant ). The other thing , which you'd never be able to tell without taking the window out , is if the ends of the cill are sealed so water can't track off the cill into the building, ( basically bottom left and right of frame where it joins cill.). You should be able to run water through the drainage holes you can see when you open the window, and it should appear somewhere on the outside....if not , and the watercdisappears , your frame is draining into the cavity, along the top of the cill, and possibly causing your problem
 
The flashing under and to sides looks like it will collect rain rather than deflecting it.The point of entry can be metres away from where it shows internally.
 
Last edited:
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I can't see any external drainage on that frame. There should either be drainage holes ( with cover caps ) on the front face OR base drainage which drains onto the upvc cill and then drains between the gap between frame and cill ( which looks sealed with very thick white sealant ). The other thing , which you'd never be able to tell without taking the window out , is if the ends of the cill are sealed so water can't track off the cill into the building, ( basically bottom left and right of frame where it joins cill.). You should be able to run water through the drainage holes you can see when you open the window, and it should appear somewhere on the outside....if not , and the watercdisappears , your frame is draining into the cavity, along the top of the cill, and possibly causing your problem

There was previously a gap between the frame and the cill, but the roofers sealed that, along with all the other edges of the frames when I complained to them about the water ingress. I can try and remove that seal at the bottom of the window and then do a water test to check if the drainage is working properly.

The flashing under and to sides looks like it will collect rain rather than deflecting it.The point of entry can be metres away from where it shows internally.

Is it likely that water would be able to enter under the cill where the flashing is not tight to the cill? Seems like rain would need to be driven at quite an angle to get under the cill there? I'll get a mallet though and try and make it a bit more flush. Regarding the flashing on the side you mentioned - which bit is that specifically?
 

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