How to Use Window Molding for Baseboards

Avoid using a common window molding known as colonial casing because it’s usually thin and not substantial enough for baseboards. Select a hardwood molding that resists cracking and warping, such as elm, maple or oak.

Choose a window molding for your baseboards that’s 1 to 2 inches wider than the molding that surrounds your windows. Purchase molding in the longest lengths possible to avoid joining baseboards to lengthen them upon installation.

Measure the length of the molding needed for each wall and cut the molding to fit with an electric miter saw. Use the saw to make 45-degree miter cuts at the ends of the molding to fit adjoining pieces at corners. Make straight 90-degree cuts at the ends when the molding abuts other surfaces, such as door moldings.

Sand the ends of the molding smooth with 120-grit sandpaper. Place the molding against the wall so that the thickest part of the profile is on the bottom. Ensure that the flat bottom edge meets the floor.

Locate wall studs with a stud finder, and nail the molding to the studs. Use a pneumatic finishing nail gun to shoot 1 3/4-inch nails through the center of the molding's front side. Take a putty knife and fill the nail holes with a small amount of wood putty. Sand the putty smooth with 120-grit sandpaper after it dries.

Add base shoe trim, which has a rounded top and two flat sides that meet at a point. Set the flat sides of this trim between the bottom of the window molding and the floor. Attach the trim to the molding with the nail gun by shooting 1 3/4-inch nails through the top of the trim every 12 inches. Fill and sand the nail holes the same way you did for the window molding.