Tutorial: Window Sills and Casings

Tutorial: Window Sills and Casings

Kristen and I have been wanting to install window sills and casings on our family room and kitchen windows for a long time. We have been putting it off for a long time as other projects have come up first. When Kristen received some money for her Birthday, she asked to buy wood for the window sills and casings.

We started by determining the materials we wanted to put around the window. We decided to match the casings to the casing around our doors. We wanted to match the crown molding under the window sills to the crown molding we used at the stair cap.

Estimated Project Cost: $200.00 (This cost will depend completely on the amount you are covering.)

Difficulty: Medium

We forgot to take a before picture of the three windows in the family room, but we dug through our photo archives and we found one from when we moved into our house in 2008. 

We did remember to snap a before picture of the bay window. It looks extra bare because we had already take down our curtains.

The depth of our existing window sills were about 3 1/8" deep. We decided to buy 3/4-inch MDF at 5 1/2 inches deep for the window sills and the header piece at the top. We made sure the sill would extend past the casing by about 1/2-inch. The casings were 3 inches wide, so we measure the window opening and added 7 inches to the length of the sill (3 1/2 inches on each side. Then we drew the notches in the 3/4-inch MDF and cut them out with a jig saw. We routed the edges with a 3/8-inch roundover bit. We raised the bit high enough to get beading at the top. This also matches the cap on the stair wall.

The existing window sills sloped away from the window, so we had to level the window sill. We used wood shims to level it out. We used a torpedo level to check the level and glue it down with dabs of liquid nails adhesive. I then used my nail gun to nail it in place while the adhesive dried.