Internal Damp - uPVC Window

[Apophany]

Hi,

I'm getting damp at one corner of a uPVC window and trying to figure out where the water is coming from. We had a new roof installed above the window, and the roofers have been back twice to check that the water isn't coming from above and they confirmed it's all sealed. From what I can tell there might be two sources:

1. The roofers sealed the bottom of the window - I believe that's where drainage is meant to come out - but I tried (and failed) to remove the sealant!
2. The edge of the window cill isn't closed off or sealed - is it meant to be? I could see inside and it does look like water could potentially make its way in that way

Have attached some pics - Thanks!

 

[Wayners]

Mother in law had a similar problem.
I injected foam all around the window then applied new silicone which cured the problem for about 7 years then it started coming back.
She had a new window fitted which has cured the problem.
Fitters said original window had not been sealed in property.

 

[robinbanks]

Drill a hole here and see if the frame has water inside

Seems to me like your roofers don't appreciate how PVC frames work; they will always let water in, so drainage is arranged to let it out again. It either drains into the sill and then out the lip along the bottom outer edge, or it drains out of the base of the window frame onto the sill

For removing the sealant indicated in your blue lines you could try flexing the sill downwards while you run one of those extendable craft knives (the ones with the blade that you "sharpen" by snapping bits off them) along the joint

Alternatively, you may be able to drill a new drain hole into the sill, close enough to a corner that you can pick that expanding foam out of the way of the new hole, allowing the water into the sill, and then another hole on the underside outer edge of the sill

 

[ronniecabers]

The ends of the cill cap do ideally need sealing as that's a hollow.profile and potentially could let water in BUT all things considered that is unlikely.
The bigger issue is the silicone... unless you have drain caps ( or holes ) on the face of the bottom.of the frame then water had no way to escape as the frames would be base drain( concealed drainage) and drain on to cill and then run away. That silicone is preventing this, and I'm not sure why they would have sealed it up. You could drill a hole in the front to create face drainage but this would not work completely as water would still follow gravity and end up trying to come out the base of the frame, and have no where to go. Ideally you need to get that silicone out of that gap...find the lower front edge if the frame and run a blade through the silicone and then pry it out with a flat baded screwdriver and scraper . You may not get rid of all it , but along as water can drain out from on top of the cill.
I suspect the top of the cill has never been sealed at each end of the window in the cavity , and the trapped water is now starting to soak into your plaster as it can't escape any other way. Unfortunately this can only be rectified by removing the window but if it's never leaked before the gap between window and plastic cill was filled then just clear that silicone out