How to Trim Out Basement Casement Windows

Measure 1/8 inch along the casement window's edge on all four sides, using a tape measure. Line up a carpenter's square with these marks, and draw a line all around the window's perimeter. This line indicates where to place the trim's edge to leave a slight reveal around the entire window.

Set a miter saw to a 45-degree angle. Cut about 1 inch off a piece of the trim's left end with the miter saw. Measure the top reveal line's length with a tape measure and transfer this to the same piece of trim, measuring along the trim's bottom edge, starting from the cut end. Cut the trim to the appropriate length, using the miter saw.

Place a tube of construction adhesive in a caulk gun and cut off the tip with a utility knife. Apply a bead of construction adhesive along the back of the trim piece you just cut. Line up the trim's bottom edge with the reveal line you drew in Step 1 and press the trim against the basement wall.

Drill three to four pilot holes through the trim and into the wall, using a hammer drill and 5/32-inch masonry bit. Squeeze air into each hole with an empty turkey baster to clean out the dust. Switch the 5/32-inch masonry bit for a Phillips driving bit. Drive a 3/16-inch cement screw through each pilot hole.

Measure a second piece of trim for the window's left side with a tape measure and cut it to length with the miter saw. Make sure you miter the trim's top end so it meets the upper trim's left edge to form a 90-degree corner. Secure this trim piece next to the window with construction adhesive and cement screws.

Repeat Step 5 for the trim on the window's right side and bottom edge. Once all trim pieces are secured to the wall, use a putty knife to cover each screw head with a layer of wood putty.

Allow the wood putty to dry, according to the manufacturer's directions. Sand the putty smooth with a piece of 220-grit sandpaper. Apply a second layer of putty if necessary. Stain or paint the putty to match the rest of the wood trim.