Replacement UPVC window damp/condensation issue

[Iggy]

Hi all,

 

Can someone please help & advise me of the best way forward.

About 2 years ago I had new UPVC windows fitted & due to a noisy street location, I had acoustic double glazed glass. I elected to have no air vents, as this sort of conflicted with the reason for acoustic glass.

In pouring rain, I have zero leaks or water ingress.

The window fitter used a 2'' section of plastic trim where the inside of the new window meets the plasterboard.
However, the bedroom when it is cold outside the obvious condensation appears on the inside of the glass. I expected this on the glazing, which is fine. However, where the 2'' plastic trim ends in the reveal, I noticed the painted plaster board was discolouring all along the edge of the plastic trim 'as if wet/damp' in the morning & damp in both bottom corners, with the paint peeling off & signs of damp spots in the bottom corner.

I could only assume that there was condensation building up actually on the inside section of window frame and leaching on to the plasterboard reveal, if this is even  possible??

As this happens when it hasn't been raining & hadn't been, so no concern over water ingress/leaking. So can only assume it's condensation!?!

After now removing the 2'' plastic trim & cutting out a section of the plastoerboard where it meets the UPVC window, I can see there is nothing between the window frame and the external layer of house brick, pictures below. It actually feels markedly cooler in this area & it has been pouring with rain this last week or two & the inside is bone dry. It just feels cooler in the void.

My house is approx 20 years old & built by Taylor Wimpy I believe.

I know the window fitter sealed the external sections where the UPVC meets the brickwork, with silicone sealant. But should he have also used some expanding foam for between the UPVC & brickwork which I would then see from the inside, as nothing can be seen in the pictures?

 

Searching on this forum, I think I need to use some expanding foam in the small gap (it does appear very small) between the window frame & brickwork on the inside. Would I then need to use some vapour tape round the whole join between frame & brickwork & then fill the entire gap/void, before re-plastering?

Also, what should I use to fill this gap, it looks like there is some form of cement covering the insulated gap between outer/inner bricks & a DPM?

Thanks for any expert advice.
Iggy

[Redbeard]

I cannot promise 'expert' advice in this particular field but I can sigh on your behalf, and that of many dozens of clients over the years who have suffered from the dreaded 'plastic plank syndrome'. Many clients have given me permission to get out my pen-knife and peel off the offending trim only to find a great yawning chasm behind. The worst we ever had was an arched section of said 'plank' in a 100-year-old arched opening. It was a bit 'flappy', so I agreed to take it off and re-bed it. Behind it was... the outside world! Nothing had been done on the outside at all. There was 5-6mm of uPVC as 'insulation' and 'weather protection.

 

To deal with your particular issue, probably air-tight expanding foam to fill the void (Illbruck FM330 is not cheap but really good). If you mist-moisten and start near the frame you will deal with the small gap as part of the 'whole'. It sounds too small to actually try to gun foam into the gap itself. Let the foam 'over-expand' then trim it back so it (and the edge of the frame) is a 'bed' for the placcy plank. 

[Iggy]

Hi Redbeard, and thanks for your reply.

 

So from what you're saying, I should just fill the entire void with FM330?

Trim off any over expansion, level with the reveal plasterboard & then re-trim to cover up?

 

I shouldn't need any vapour seal tape covering the UPVC & brickwork joint no?

[Dave Jones]

cold bridge and dew point in action.

 

Not thats its any help to you, but its why new build regs windows have to be sat in the cavity at least 70% so they form part of the insulation envelope of the building and then issues like yours are moot.

[Iggy]

At least new house building is getting better!!

 

That's exactly what I thought was the issue, being that it's cold in the void area & with the warm moister air inside my bedroom that area was accumulating condensation & making my plaster walls damp.

 

What is the best & safest way to cure this & fill the void.

I'm not a builder... far from it but do quite a bit of DIY.

 

As above, do I need to vapour barrier tape of as much of window frame brick wall joining point & then fill the void with FM330 or similar, then re-trim & seal corners with CT1?

I just don't want to cause any other issues by bridging this gap.

 

Thanks in advance.