Here’s how to to about dressing up drywall window returns by installing stock wood window casing molding around the opening.
Window Casing Materials List:
- 4 pieces window casing
- 1 piece window stool
- 6d finishing nails
- Painter’s putty or spackling
- Primer and paint
Window Casing Tools Needed:
- Measuring tape
- Miter saw
- Nail set
- Pry bar
- Utility knife
- Caulking gun
How to Add Window Casing
- Remove Window Stool: If the existing window stool doesn’t extend past the drywall on each side by the width of the new wood casing plus 1/2”, remove it and the apron molding under it by cutting through the caulking with a utility knife, then using a pry bar and hammer to take it out.
- Cut Window Stool to Length: Cut the new window stool to length, so it extends 1/2” past the width of the casing (casing width x 2 + 1” = stool length).
- Notch Window Stool: Center the stool on the window opening, and mark the edges of the drywall return on the stool. Measure from the window to the wall and transfer that distance to the inner side of the stool. Cut the notches on the stool to fit using a jigsaw.
- Attach Window Stool: Slide the new window stool on the window, and nail it in place.
- Cut Top Casing to Length: Add 1/8″ to the width of the casing and mark that distance on the wall on each side of the window opening to determine the length of the top casing. Miter the top window casing on each end at a 45° angle, so the short mitered edge is 1/4” longer than the width of the window opening to allow for the 1/8” reveals on each side of the opening.
- Attach Top Casing to Wall: Align the top casing evenly 1/8” above the opening and nail the casing in place, leaving a 1/8” reveal between the casing and drywall opening.
- Cut Side Casings to Length: Measure from the window stool to the top of the top casing to find the length of each side casing. Miter the top end of each side casing and cut the bottom square to length.
- Attach Side Casings: Align and nail each of the side casings in place with a 1/8” reveal between the inside edge of the side casings and the drywall edge.
- Cut Window Apron to Length: Cut the window apron to the same length as the top casing with a 22½° angle bevel cut on each end.
- Attach Window Apron: Center the apron below the window stool with the long edge facing up, and attach to the wall with nails.
- Putty and Caulk Molding: Use a nail set to set the nails below the surface of the molding, then fill the nail holes with painter’s putty or spackling. Caulk the molding where it meets the wall and fill any gaps in the mitered corners.
- Paint Molding and Return: Sand the filled nail holes smooth and wipe off any sanding dust. Prime and paint the molding and drywall returns to match the trim in the room.
- Tips for Cutting Molding (article)
- How to Turn Stock Molding into Custom Molding (video)
- Tips for Finishing Trim Molding (video)
- How to Cut and Install Crown Molding (video)
If you try to compare a drywall return window with a cased window, forget about it. There’s just no comparison. A wood cased window has a much richer look. The good news is that converting a window to that luxury look is very easy to do and relatively inexpensive.
Begin by choosing window casing that suits the overall décor of your home. Molding that is no more than 3½” wide is usually sufficient. It’s also likely that you’ll need to replace the window stool.
For tools, you’ll need a motorized miter saw (or a simple miter box with a hand saw), jigsaw, hammer, pry bar, 6-penny finish nails, nail set, utility knife with a sharp razor blade, caulking gun with caulk (or a squeezable tube of caulk), measuring tape, pencil, and some 100-grit sandpaper or a medium grit sanding sponge.
Using the razor knife, carefully score around the existing window stool to cut the caulk line between the stool and the window, and the stool and the wall. Beneath the stool is a separate piece of casing called the apron. Score any caulk lines around it as well.
Use your hammer and pry bar to carefully remove the window stool and the apron. If your windows were ever replaced, it may be that the window stool extends below the window. If this is the case, you’ll need to use a sharp chisel and sever the stool flush with the window bottom. This will allow you to remove the stool without disturbing the window.
With the stool and apron removed, measure the width of the opening. To that measurement, add the width of the casing times two PLUS an additional inch. This measurement will allow the new casing to sit on top of the stool and have an additional 3/8” protruding at either side, an 1/8” reveal between the inside edge of the casing and the window opening. Cut a piece of window stool to this length.
Next, you need to cut out the notches in the stool to allow it to slip into the window opening. Measure the distance from the front edge of the window to the edge of the wall. This will be the depth of your notch.
Next, take the width of the casing plus 9/16”. This will be the width of the notch. You’re adding the 9/16” instead of 1/2″ to allow some wiggle room. You don’t want the notch so tight that it scratches the wall going in. Both these measurements will be used on each end of the window stool to determine the amount to be cut in order to notch it.
Draw the notch using your measurements and a pencil and cut out the notch with a jigsaw. Set the stool in place and attach it to the window stool using 6-penny finish nails. Be sure to recess the nails into the wood using a nail set.
Measure in 3/8” from the outside edge of the window stool and make a small pencil mark on the wall. Do the same on the other side of the stool. This is the width of the top piece of casing.
With your miter saw set at a 45-degree angle, cut a piece of casing. Then reverse the angle on the saw to cut a 45-degree angle in the opposite direction. From the outside point of the first angle, measure and mark the width of the top piece of casing. This mark will be the point of the opposite 45-degree angle.
Place this piece of casing 1/8” above the top edge of the window opening, centered over the window and parallel with the window stool. Attach with 6-penny finish nails and recess the nails into the wood with your nail set.
You’re now ready to measure from the top of the window stool to the points of each 45-degree angle cut on the top piece of casing to determine the lengths of the side casing. Each of these pieces will be square cut at the bottom and a corresponding 45-degree angle at the top to mirror the angle on the top piece.
Fit these pieces in place to fit the angle on top and against the pencil mark at the bottom you made at 3/8” from the outside window stool edge. Once again, attach with 6-penny nails and recess them with your nail set.
Finally, set your miter saw to 22½-degrees and cut a fourth piece of casing the same width as the top piece with the outside angles on each side reversed as before. This is the apron that attaches below the window stool.
Now, to complete the illusion of a full wood casing, take your sandpaper and sand the inside drywall surrounding the window to smooth out any texture. Caulk the perimeter of both sides of each piece of casing and use painter’s putty to conceal all nail holes. Prime and paint the casing and inside drywall the same color. The final results will be a window that appears to be completely surrounded by a rich wood casing.