Question about fitting upvc window sill

9 Jul 2013
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United Kingdom
Hi people,
I will be fitting a upvc window and sill but I have seen two ways of fitting the sill and am not sure which is the best way or if one of them is wrong?

The first way I have seen is to secure the sill in position and then place the window onto the sill.

The second way I have seen is to screw the sill from underneath to the bottom of the window first and then fit the window.

Are both methods correct and is one method better than the other?

Thanks in advance.
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If you're a novice then I'd advise you to cut the sill in, fix down, then put the window in and fix window to the sill.
Run a bead of silicone in the corners and along the sill before the window sits on it.
Many of the ready made ones seem to have a "N" section upstand on the sill which locates into a similar recess on the window frames.

Often supplied already screwed or glued together.


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