DIY: Window Sills

Gather Materials

• Before you begin cutting wood, measure the window base and determine how much of an overhang you want, as well as the length of sill that will extend past the window itself. The most common style of window sill is made of wood like oak or poplar, which may be stained or painted to match any existing décor or style of the room. Once you have taken the measurements of the window frame, add the desired length and width to the measurements to get the ideal fit.

Prepare the Sill

• Lay out the single plank of wood, and mark in pencil where cuts are to be made based on measurements. Typically, the sill notches that extend past the window frame are only about one inch on the left and right of the window, but you may custom design the sill to be as long or wide as you want. Use an electric saw to cut out notches on the window sill so it will sit in the frame. Paint or stain the window sill and apply multiple coats if necessary. Allow to dry and then add a clear protective coat to prevent sun and water damage.

Installation

• Once the paint or stain has dried, drill two holes into the wood where nails will secure the sill to the window frame. Drilling first will prevent the wood from becoming stressed and splitting. Use finishing nails to secure the sill to the window frame, and use a countersink tool to drive the nails in just below the surface of the window sill. Fill the holes with wood putty and touch up with paint or stain once the putty has dried. For an additional touch, install a decorative piece of molding, called an apron, under the window sill. Cut the molding to the length of the window sill, and drill two holes for easy installation. Nail the apron to the wall, and cover nail holes with wood putty.