How to Install Mitered Window Casing Part 1

What You'll Need
1x4-inch Lumber
Tape Measure
Miter Saw
Drill/Drill Bit

One of the ways that you can finish off your window installation is with a mitered window casing. This will give the window a finished off look like it is framed within the wall. Working with miter cuts is usually something that many homeowners feel is outside of their DIY skills set, but if you take your time and use some common sense, you can easily complete this project. Follow the steps below to begin installing mitered window casing.

Step 1: Measure Wood for Cutting

For a tight fitting miter for your window casing, you must make sure that the measurement is correct. For most people, this is the hardest part of the entire installation. There are two ways that you can measure your miter cut for the window casing. The first way is with a tape measure. Start at one side of the window and measure the vertical height. This will give you the measurement to transfer to the wood.

The second method bypasses the tape measure and immediately place the mark on the wood. Set a length of lumber on one side of the window, and mark the top and bottom edges. From there, you can use a carpenter's square and draw the 45-degree angle. Do that for both the top and bottom of the side piece. Repeat the process for the other side.

Step 2: Cut Side Pieces

Once you have the marks made in the boards, you will be able to cut them with a miter saw. Remember that the angles on each piece of wood will be facing in a different direction. Line up the lines with the blade and carefully cut the wood with a smooth chop of the saw. Cut both side pieces.

Step 3: Install Side Widow Casing

Place the boards back up to the window, and make sure that they are cut correctly. Remove the board, and apply a bead of construction adhesive to the back of the board. Press the board onto the wall where it is going to go on the side of the window. Repeat the process with the other board.

Step 4: Drill Pilot Holes

When working with lumber like 1x4-inch boards, there is the potential that the wood will split when you nail it into place. You can protect the wood from splitting by drilling pilot holes into the wood first. Use a drill with a bit that it the same diameter of the nail, and drill in holes every 6 to 10 inches along the outside of the casing. 

Step 5: Secure Boards with Finish Nails

After the pilot holes have been drilled into the wood for the casing, you can then begin to secure it with the finish nails. Use a small hammer and nail the casing boards to the wall with 2-inch finish nails. Be careful not to strike the wood, or you will leave hammer indents.