CG1234

Dave, thank you so much! Really, really appreciate your insight. Will do the above.

I have just checked and the others have like an indent running along them, a 10mm or so from the edge - I assume that is what this main one should have too? I assume what you are suggesting is too essentially create our own but with sealant, and convex not concave? Also how would you go about patching up the interior? Will it need a patch of replastering?

Thanks Dave - photos below!

Thanks for your replies. Attached are photos of the outside. Assume its a case of sealing around the side/underside of the sill externally, and then patching up inside? The wall is a little damp inside, post rain...would you wait for it to dry before sealing externally? Thanks again for your help! Really appreciate your knowledge!

Hi all, we have sash window, with a radiator below it. It has been cracking and paintwork chipping a bit over the last few years, but recently it has got worse, and today, rainwater appeared (it was a violent storm tbf). I suspect the main cause is the heat of the radiator/cold from outside. But presumably there is more to this? Can anyone help me by guiding me through what is probably happening? And any advice re fixing the gap which the rain got through, and making presentable again? We are pretty strapped for cash at the minute, so any DIY, low cost advice very gratefully received. I have zero building experience so i may have not used the right terms to describe! Thank you!