Windowsill Replacement

Tools:

workbench
putty knife
hand plane
hammer
nail set
caulking gun
drill
reversible bit
combination square
spring clamps
clear tape
5-in-1 painter's tool
kneepads
sandpaper
level
utility knife
pry bar
pull saw
paper
pencil
towel
safety glasses
plastic wood putty
wooden shims
finish nails
caulk
lumber for replacement sill
scrap 2x4 blocks (if needed)

1. Remove old caulking around the edge of the sill using a 5-in-1 painter’s tool and putty knife (figure A).

2. Since this sill was not square, it was easier to make a template using paper than to try to duplicate it by measuring. Place sheets of paper along the sill and tape them together to form a template (figure B).

3. Cut the paint seam between the trim and the old sill using a utility knife.

4. Put on safety glasses and cut the sill into two pieces using a pull saw (figure C),

5. Loosen the sill by working the painter's tool beneath the sill and tapping it with a hammer. Work one piece of the sill up enough to insert a pry bar between the pieces and pry up one piece (figure D).

6. Tape pattern to new board and clamp it to workbench. Trace around the pattern then cut board to fit using the pull saw.

7. Test fit the new sill. If necessary, insert 2x4 blocks between the drywall and wall studs to serve as mounting blocks (figure E). Secure the blocks using a power drill and screws.

8. Fit the sill into place again and check for level. If necessary add wooden shims to get things on the level (figure F).

9. Check again for level.

10. Pre-drill holes through new sill and attach using finishing nails. Be careful not to drive the nails all the way in with the hammer or you'll damage the sill. Drive them below the surface using a nail set.

11. Smooth edges using a hand plane (figure G) and finish using sandpaper.

12. Run a bead of caulk along all the seams, then smooth with your finger (figure H).

13. Fill nail holes with wood putty. Wipe away excess putty with a towel.

14. Give the caulk and putty a couple of days to set up, then prime and paint the windowsill to match.