I have recently done this... Replaced 600mm of rotten sill around a corner of a 1930s bay - solid as a rock, no fixings and can't see the joins!
Rot also sets in at join line between sill and any vertical members and also on lower parts of any opening windows. Solution...
Use Dry-Flex and Dry-Fix products. They are two part epoxy resin products. Cut out all rotten timber to dry wood. Paint with two-part primer stabiliser wait 30 min.
Fill with two-part flexible resin filler up to 50mm. Or use resin as a glue/filler to fix new wood. Leave at least 4mm between components. Wait to dry (16 hrs) and plane, sand, paint as for normal wood.
Sticky (wear vinyl gloves) and expensive - my two 8 section bays, ground and first floors cost £300 to refurbish but far less costly than new windows. My 2m length of harwood sill was £30 - paint and sundries £90 and the resin (I used quite a lot) £180.
Call the UK distributor for outlets in your area...
http://www.window-care.net/
See excellent descriptions here...
http://www.countyconchem.co.uk/OLDSITE/index.html#Nelson
This stuff is magic - hardly runs at all - can fill verticals without any slump - makes windows as good as new - saves windows and sills that would otherwise be scrapped! You can tell I'm a bit bullish about it.
Answer here if require e-mail for more info - I have no pecuniary interest in this repair system.
Look at the second URL first and be amazed.
Peccavi, October 2008
