Expansion gap around upvc windows

9 Sep 2013
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United Kingdom
I am fitting a upvc window into a wooden dorma window frame which has had fiberglass coating over it and lipped around into the opening. The window and cill when in place are very tight. Is it necessary to have a gap at the top and bottom to provide room for expansion?
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It depends on the size of the window really. I believe PVC expands and contracts approx 1.6mm per linear meter in length.
Ideally its recommended to allow 5mm for expansion.
If the window is fairly small I wouldn't worry about it.
You could always cut the ribs off the side/sides of the window, They are only there to clip on addons which would give you 4-10mm.
Thanks . The window is little more than 500mm wide so should not be too much of a problem from what you have said. Useful to know the I can loose the edges off the frame that should allow me to get a bead of silicon around the edge.
Thank you that's helpful.

What tool would be best to take the edges off cleanly?
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