We recently (a year or so ago) had new wooden sash windows fitted in bay windows. Where the sashes meet between the centre sash and the 2 outer ones the fitter put flat beading on each side to cover the gap. Unfortunately there is a significant draught coming through between the 2 pieces of beading, and when I pushed a piece of paper through the gap it was obvious that there are large gaps behind between the sashes. Can you recommend a suitable filler to fill the gaps? I assume some kind of expanding foam filler would be best. Does it need to be flexible to allow for movement in the wooden frames? I should be very grateful for definite recommendations, so we can get this done before the winter sets in!
TIA
TIA