Dealing with Mitre gaps in the Window Sills

[Yetty]

I have these hardwood window frames, south facing, with various mitres at the sills that like to open. Presumably the mitre gaps change as the wood dries in summer heat and soaked in winter. With the current warm weather, I'm about to treat the window frames to an overdue sanding followed by Sikkens base and top coats.

Any ideas on how to fill these 'moving' mitre gaps to prevent water damage?

Here's a couple of pics:

 

[NickWelford]

Putty?

 

[Woody2Shoes]

I might be tempted to open them up slightly - into a V profile, say 4 to 6 mm wide - e.g. with a chisel - then prime/seal the freshly cut surfaces and then fill the V-shaped gap with low-modulus silicone (you can get it in brown, I think) or with sulphide mastic (which is used for sealing expansion joints and between timber/masonry, but is trickier to work with) and tool it flat(ish).

Cheers, W2S

 

[HOJ]

I have used this to repair several rotten sash frames, may be worth a look, most decorators merchants stock it.

http://www.repair-care.co.uk

 

[kostello]

+1 for repair care epoxy......

mightons do similar ones......

 

[Myfordman]

+1 for a flexible filler. Anything that hardens will fail as the wood moves with the seasons.

 

[Yetty]

Lots of ideas and just what I was hoping. Thanks for all the replies, appreciated.

 

[JonnyW]

I've used the repair kit as mentioned above in similar circumstances. That was last year and it worked a treat.

Jonny