How to Build Your Own Window Casings

What You'll Need
Various wood boards (1x3 inches and 1x4 inches, as well as lath boards)
Decorative trim molding for the window
Table saw
Hammer and nails
Power nail gun
Wood or carpenter's glue
Sanding block and medium grit sand paper
Wood filler and caulk
Protective equipment (goggles, gloves)
Measuring tape, straight edge, and pencil

Window casings are the areas that immediately surround the window frame in a home. The frame consists of the stool and apron, and the casing is the area above and below that, as well as to the sides of the window. In order to make your windows look attractive and to set them apart from the other parts of the wall, a window casing is necessary. While many homes have pre-designed window casings set up, others will not; in these cases, you can make your own window casing to fit into the aesthetic design that you have for your home.

Step 1 -- Measure and Design the Casing

Begin by measuring the inside of the wall. Measure from the sheet rock or the area in which the wall ends to the edge of the window frame. Take note of this distance and mark it on 3 of the small wood boards. Generally, this will be no more than about 4 inches. If it's less than that, use the table saw to cut the boards down to the distance that you measured.

Next, measure the difference in height between the ceiling and the window frame at the dog ear portion of the stool, where the stool is narrow.

Step 2 -- Install the Inner Casing

You must install the inner casing first so that the window trim on the wall will cover up any edges of the interior casing. Measure the frame of the window and cut the decorative trim molding to size for the base. Use the hammer and nails or the power nailer to attach the cut molding to the bottom of the window frame. Insert nails at the top, the middle, and the bottom of the casing. Repeat the process with the top of the casing on the inside of the frame as well.

Step 3 -- Measure and Install the Outer Casing

The outer casing will cover from the window stool to halfway into the inner casing that you previously installed. Cut the trim to size, and apply it in the same method, leaving the inner portion of the inner casing exposed for a decorative purpose.

Step 4 -- Install Side Casings

With the top and bottom portions of the casing complete, you can now install the side casings. Measure the height of the frame, and cut the trim to the right height. Then use the nail gun to attach it along the length of the side.

Step 5 -- Finish the Casing

Sand down any inconsistencies in the casing using the sanding block. If there are any gaps in between casings, use the wood filler and caulk to fill them in.