Sealant Under Cill?

[soapstar]

Hello,

 

We currently had some issues with one our windows letting rain water through, it only seems to happen in high winds - I know this as it happened soon as they were installed and was told it was rectified. Low and behold we just had very high winds and rain a year on after fitting and our carpet is soaked at two spots. These are gable windows on the first floor which are floor to ceiling height.

 

I am trying to determine where the water is finding it’s way in. Having a look today and noticed underneath the pvc sill they seem to have used some sort of mastic/putty (can anyone tell me what this is?). There seems to be a hairline crack between the pvc sill and the sealant, would water penetrate through here and inside? Or is it more likely to be the join/gap between the window frame on top of the pvc sill?
 

The water leak is not visible from the inside, it appears to be soaking the chipboard flooring below the carpet. Note this is not at the corners, only in the middle.

 

Thanks for any advice!

 

 

[craig]

This is highly likely to be your area of concern.

 

 

Run a bead of mastic along here, leave it to set and the hose test. Be specific at the location you're testing and don't just spray the door.  Do you also have a further out picture, it's difficult to see the full picture from the zoomed in picture.

[soapstar]

8 hours ago, craig said:

This is highly likely to be your area of concern.

 

 

Run a bead of mastic along here, leave it to set and the hose test. Be specific at the location you're testing and don't just spray the door.  Do you also have a further out picture, it's difficult to see the full picture from the zoomed in picture.

 

Excellent thank you for the confirmation, any sort of gap around a window seems suspicious to me. Can you recommend what type of sealant to use? The sealant/mastic/cement stuff which has been used underneath is not rock hard, it seems to be soft like a hard putty. The gap between the bottom of the PVC sill and concrete sill is around 3/4 inch.

 

I have always had my concerns on the fitment of the windows but as ever it slips your mind until the winter comes along!

 

I can get a wider photo later for more context.

Edited December 13, 2021 by soapstar

[craig]

Something like Silirub LM (colour matched if possible) would do the job.

[soapstar]

8 minutes ago, craig said:

Something like Silirub LM (colour matched if possible) would do the job.

 

Thank you. I keep hearing the product EverBuild 825 when researching sealing joints/pvc windows etc - Would this be the same?

 

Looking further into sealing windows this morning I now have concerns regarding the outer gap around the pvc window has been sealed with incorrect or inadequate sealant - I know from memory it was from the Soudal range - FixAll Crystal looks familiar, would this be adequate?

 

https://www.soudal.co.uk/pro/products/adhesives/bonding-and-construction-adhesives/fix-all-crystal

[craig]

2 minutes ago, soapstar said:

product EverBuild 825 when researching sealing joints/pvc windows

 

Haven't used it nor have experience with it. We usually stick to Soudal or Illbruck products.

 

3 minutes ago, soapstar said:

FixAll Crystal looks familiar, would this be adequate?

 

Yes, it can be used externally.

[SuperPav]

I'm confused by that image - that looks like a massive gap between the frame and cill - surely the sill gets mounted to the frame first so you shouldn't have that in the first place? 

 

And the gap in the sealant looks on top of what is a substantial thickness of sealant, + protected by a UPVC overhang - I'm amazed that much water can enter at that angle!

 

If you're saying that the leak is coming in from the middle, rather than the edges (more usual) then it's likely leaking through a poorly sealed fixing (screwhole in the sill)? Otherwise I'm not sure how it would track to the middle without getting to the edges. If that's the case then just sealing the bottom of the frame to the sill might not help, since the water might be coming in from around the sash (is it an opening window? flush casement or storm proof?) , and trickling down the frame.

 

Terrible drawing attached.

 

 

[craig]

7 hours ago, SuperPav said:

surely the sill gets mounted to the frame first so you shouldn't have that in the first place?

 

It should. That picture is not given the full picture if you pardon the pun. It actually looks like a stone cill and the window is sitting on that but not directly and maybe packed up a little. It doesn't look like a stub cill on the window tbh. Just not enough projection but again, not the full picture of what's happening.

Edited December 15, 2021 by craig

[soapstar]

@SuperPav thanks for your detailed response much appreciated.

I have attached a photograph of a typical window on our house to show the full layout.

 

As @craig mentions the window sits on the concrete sill and is packed underneath. I think the ‘weakest link’ is the gap as shown in the above photo attached previously now I look more into it. I have old cuts of the concrete sills which were us to get a better understanding of the profile. I will try get a photo and post up later.

[soapstar]

As above here is a photo of the sill, it has a lip at the back which I assume is where the sealant (or whatever it is) is packed against under the pvc sill.

[craig]

Sandstone mastic and you should be fine, just appears that they haven't applied any here.