-
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?
who22-
Quite possibly. Framing screws can just be driven in with a hammer once the hole is drilled. They are usually a rawlplug type sleeve with a ribbed nail that has a philips head on. So sloppy installation can lead to them having some movement. You can fit extra ones retrospectively.
-
As per @Airhead,
and,
there may be a couple of wooden wedges, (sometimes recycled from previous wooden window frame), and some expanding foam to quickly fill the irregular void between the uPVC frame and the masonry.
The foam then allows an inadequate thickness bead of sealant to be applied giving the impression of weatherproofness.
Airhead
mespilus
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.