Internal windowledge extension/replacement

[darrengreen]

I live in a 1930's solid brick property which consequently has
very narrow windowledges, approx 80mm depth. I want to install
a Venetian blind in the living room which will take up much of this usable
depth but the missus is insistent that the cat still needs to be able
to sit on the ledge!! Consequently I also need to extend/replace the
ledge. As it is imbedded in the plasterwork at the sides and I'm not
sure how it's fixed to the double glazing, I though extending with 20mm thick timber (the same as the ledge) may be easier than replacing with a deeper ledge? I thought I could affix with screws through the new timber into the existing ledge, make good any gaps with filler, sand and paint. Any other suggestions out there?!

 

[foxhole]

I would sit a 9mm mdf on top to full new width, screwed down to original, if you want it to appear thicker add a baton to front bottom edge, less work than all that filling and more secure.

 

[darrengreen]

Thanks Foxhole, great idea! I hadn't considered an "overboard" but makes perfect sense and should, as you say, be alot more secure and hopefully a better finish.
Thanks for the advice!