I've just started to replace my windows and doors with UPVC. The new
exterior cills are much thicker than the old ones were so they are now
visible above the internal cill. I need to raise the internal cills by about
10mm but I was thinking of replacing them anyway with UPVC. Is there such a
thing as a replacement cill approx 10-15 mm thick which fits on top of the
existing wooden cill ??
This would save me a fair bit of work/mess.