Bow Window Installation Step-By-Step

  • 4-8 hours
  • Intermediate
  • 200-500
What You'll Need
2x4 lumber
2x8 lumber
Support cables
Circular saw
Tape measure
Fiberglass insulation
10 penny nails

A bow window is a great alternative to a traditional bay window. Instead of having sharp angles jutting from your home, this type of window curves outward, forming a shape like a bubble.

Since the windows are very heavy, the hardest part of installation will be placing them. You will need another person with you to help you. You can generally install a bow window in a few hours.

Step 1

Build a frame or brace with the 2x4 boards. This will be placed against the ceiling several feet back from where you want to actually install the window. A header can be made using the 2x8 lumber.

Step 2

Create a rough frame for the opening of the window. The size of this will depend on the size of the window. Use double studs on each side of the header for support.

Step 3

Have a friend help you lift the window into the frame. Use shims to level the window under the footboard. Nail through the extension jambs into the framing studs with the 10 penny nails.

Step 4

Measure the height of the window. Install a sill by nailing studs to the double studs you created earlier. This doesn’t have to be perfect, it’s just a rough version for right now.

Step 5

Use cables to secure this through the screw eyes and set it into the rafter tails. Tighten the cables for security. You may need to install an exterior knee brace underneath the window for added support. This will depend on the size of the window and what the manufacturer recommends.

Step 6

Run the support cables from under the footboard up through the headboard. Some windows will have the support cables built in to the window, and other times they are provided for you with the window when you purchase it. If not, you need to purchase these separately.

Step 7

Install flashing to the sides and bottom of the window on the exterior. Take your time with this since poorly-installed flashing will increase the likelihood of leaks and other damage. Once the flashing has been installed you can add the interior jambs. After that go ahead and insulate around the window using your fiberglass insulation.

Step 8

Your window is done except the finishing touches. Add interior trim or molding, and you are ready for window treatments.

This isn’t the easiest project to complete, but the result is well worth the effort. Bow windows look great and can provide more light in your room.