-
You can't 'lock' a uPVC window frame into masonry.
The uPVC will react much more quickly to temperature changes, the frame will expand and contract, as you can see in your picture by 2-3-4mm.You need to apply an elastomeric sealant, one that can accomodate the movement you can see.
The best elastomeric sealants claim '25% movement accomodation factor', in total.
This means you need for a durable waterproof seal, to apply a bead 16mm wide, and around 8-10mm deep between the masonry and the uPVC frame.
Soudal Fix All High Tack Adhesive & Sealant, (Toolstation 84704) comes in white,
so you save the painting you envisaged.
mespilus-
Thank you! This makes sense, I was wondering how it would initially be fixed into the opening - would there be screws from the frame into the brick?
-
Just wanted to get back and say thanks for this tip,
Bought the Soudal sealant and went at it this weekend by opening up the gap a little and getting it all down in there, worked really well - window frame is now fixed in place and the outside noise has been reduced massively!
Actually surprised how easy it was... thanks!
who22
related to windows and frames above,
Any idea on what I should do about this internal window frame? There's a crack that runs all the way around the sides of the frame and if you open the window it wobbles a bit, it's leting in a draft and noise currently. Old old UPVC frames, but the renovation budget hasn't yet stretched to replacing them all yet - so a shorter term fix with filling and painting is planned
Scrape anything loose out and try and fill with expanding foam to lock it in place, or is this a job for a professional?