I have a bay window which has been replaced by a PVC one some time ago :( When it was done the internal window sill was hacked about and is appx 5cm too narrow so there is a gap between where the new window is and the old sill.
Would it be best to remove the old sill and replace it with one that fits properly (if so how) or try and cover the gap over with some kind of trim / bead?
Replacing the sill shouldn't be too difficult. From the description I doubt it's going to be held in by very much at all. Try levering one end out and see if it moves. Chances are that it will, in which case lever each end in turn and slowly work the sill out. Take it slow and you'll see what needs to come out in what order to minimise any damage. You'll knock a few bits off the plaster in the process, but nothing a bit of polyfilla won't fix. You may need to widen the gap at each end if the new sill is thicker than the old one. If you still have a small gap then tack a bit of beading to the back of the new sill.
You could simply stick a bit of wood over the gap, but it's gonna look a bit odd!
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