A builder put in a new window-sill in our kitchen a year or so ago, and I just noticed that there is a large gap - up to 1 inch at one end - underneath the sill, and there is a strong draught through this space on windy days.
I'm wondering what is the best way to fill this gap?
I should say in explanation that the sill was put in when our sash-windows were restored. We didn't actually ask for the sill to be put in; I presume the builder did it because he thought the existing setup did not do justice to his window.
Also the space is probably there to level the sill.