Tony Bryer wrote:
On Mon, 22 Oct 2007 13:19:17 +0100 Brian G wrote :
That's all a UPVC frame is - a hollow, extruded lump of plastic
that comes in various shapes and sizes - have a look at the profile
here http://www.qualplas.co.uk/windows.html

Larger ones do have metal reinforcement in the cavity, but the
opening lights are held square by the glass, thus the need for
accurate placement of spacers.

Tony,

Agreed with your comment on spacers, but I have also been involved with the
manufacture and installation of 'plastic' windows where reinforcing was
necessary in sashes (opening lights) due to their size - albeit some years
ago now.

This reinforcing is generally not used to keep the frames square, but to
stop/reduce long, individual stiles etc from bending over their length.

Brian G