How to Install Round Window Casing

  • 2-6 hours
  • Beginner
  • 150-500
What You'll Need
8d nails
Round window casing
2x4 wood
Tape measure

For a little character, a round window casing can be installed along stairways, in dormers, or garages. These round window casings resemble portholes on a battleship and are common in a lot of homes along the coastal regions of the country. In renovating homes, many people will choose to install a round window casing instead of a regular rectangular window. Installation is much the same, with a few differences.

Step 1 - Take Measurements

Before you install the window casing, you need to take some measurements to ensure your casing will fit. You will also need to make the area the right size for the round casing.

Step 2 - Build Supports for Window Casing

Like any type of window casing you will need to build the support for holding the window in place. With the measurements taken from the window casing, cut 2 by 4 lumber to these measurements. Typically, you will need a top header and a bottom sill for the window casing. These should be positioned at the height of the window casing. Secure with 8d nails.

Step 3 - Build Corner Supports

In order to install the round window casing you will need to place some corner supports to make a semi-circular shape. You will not be able to get a round shape with straight wood, but you only need to close in the rectangular area around the casing. Set the casing in the hole and measure from the corner to the casing. In each corner nail in a 2 by 4 piece. This should be secured with the edge at the measurement you just took and with angles cut into each end.

Step 4 - Lay Down Silicone Caulking

Before you insert the window casing into the area, you will need to make sure it is going to be weatherproof. With some silicone caulking you will be able to seal the window casing so rain and water do not enter the home. This is also important to keep the home energy efficient and not allowing heat to escape. Lay a bead of caulking on both the inside and the outside of the area where the window casing will go.

Step 5 - Install Round Window Casing

Hold up the window casing into the hole prepared for it. Make sure that it is centered in the hole before you secure it permanently. Use some shims to make sure that the window casing sits level in the hole. Pound the shims into the casing and do not touch until installed permanently.

Step 6 - Nail Window Casing

Use a hammer and some 8d nails. Drive the nails in the top and bottom as well as on each side. The window should not move and must feel solid. Once you have nailed the casing in permanently you can then cut the shims. Use a small saw and cut off the ends of the shims until they are even with the casing.

Step 7 - Apply Caulking

For a little added weatherproofing, then apply another bead of caulking around the outside of the casing perimeter. Fill in the crack between the casing and the support lumber.