If the crack goes all the way through the sill and water is leaking into the wall cavity below, or if the sill is warped and pulling away from the brickwork, a repair will likely be temporary. In these cases, replacing the sill is the safer option to prevent structural damp damage.
Use . Wet the paper and gently sand the scratch in a circular motion. Use light pressure to avoid creating a divot. Check your progress frequently. how to repair upvc window sill
By following these steps and using the right materials, you should be able to successfully repair your UPVC window sill. If the crack goes all the way through