How to replace rotten sills

Damp or exposure to the elements can cause wood all sorts of problems. A rotten window-sill is just one of the problems that can occur. Read our guide on how to replace one here.

Level of difficulty

Level 2: Intermediate

What you need

• Screwdriver
• Hammer
• Chisel
• Pencil
• Hacksaw
• Wood preserver
• Putty
• Nails
• Screws

The steps to follow

1. Remove window.
2. You can either remove it by taking out the nails and driving out the rotten sill, or you can cut it into three pieces, drive out the e piece first, then the ends. Be extremely careful not to damage the window frame when you remove the rotten sill.
3. Use the old sill as a template to trace over the new sill by putting the old sill on top of a new piece of wood, tracing its shape and cutting it out.
4. If you've cut the old sill in three pieces, put them into the required shape and place the pieces on top of the new piece of wood so that you can trace along them.
5. Next, insert the new sill from the front.
6. Trim it to fit in place.
7. Check that it is levell with a spirit level.
8. Apply two coats of wood preserver to the sill.
9. Glue it to the posts and secure with nails or screws.
10. Use putty to fill any holes.
11. You can now fit your new window.