Sizing up window aperture for UPVC double glazing

Well, the frame has to go *under* the lintel - there's no two ways about that. You can't start chopping bits off the frame so that some goes under and some doesn't.

If you don't want to fill the gap between the frame and the brickwork with silicone, there are a couple of other possibilities. If you rake out some of the existing mortar, you may be able to re-point it, with some new mortar which extends from the top of the frame to the underside of the brickwork. Alternatively, you may be able to stick a length of uPVC beading along the top of the frame to cover the gap.

When ordering the window, make it a few mm less the the actual aperture in both width and height - plus a bit more if the angles of the aperture are out of square - otherwise, you'll never get it in!

If you can see that the brickwork is excellent, plumb and level, get it made to measure otherwise allow a quarter of an inch height and width, to allow for scew. Tell the maker what you have done.

If it goes pear shaped it is down to you. If they measure it, it is down to them. You can plane some off a plastic window. Not like you can with a wooden one though.

I thought I'd just ask a local none chain glazer to come round and measure so I could compare the cost of DIY and not DIY. He took one look at it and said it's a 1050 by 600 so the extension must have been built with standard sizes in mind. After he left I re-measured the existing wooden frame and it is actually 1050 by 631* which is indeed a standard size of casement window sold by the likes of M@gn*t et al. Why I didn't do this to start off with I don't know?

Out of interest the window will cost approx. 140 and I've had a couple of quotes to fit ranging from 230 to 260, so I guess they estimate about 3 to 4 hours work.

Cheers

Ross

• sizes are actually 5mm less but quoted as above - I wonder why?