How To Install a Half Round Window

Lead Image for How To Install a Half Round Window
  • 3-6 hours
  • Intermediate
  • 400-900
What You'll Need
Tape measure
Scribing compass
Reciprocating saw
Circular saw
Your half round window
Utility knife
Marking utensil

Installing a half-round window in your home is a great idea. Especially if you are looking to add a bit of elegance, and some design to your home.

Below are the steps that are needed to be taken in order to make this a simple do it yourself project. With the right tools and a bit of time, you should have your half round window installed in no time.

Make a Pattern

The first thing you will want to do is to get out your cardboard, and your new half-round window. Lay your window unto the cardboard, and trace it out. Use your marking utensil to do so, and trace the complete window unto the cardboard. Then you can take your utility knife and cut out what will now be your pattern.

Mark Out On Sheathing

Take your newly made pattern, and use tape to fasten it to your sheathing. Using your marking utensil once again, mark out where the opening will be.

Cut Out The Opening

Use your reciprocating saw to cut out the opening following the outline that you have just marked. Make sure to cut outside the line, but as close to on the line as possible. This will ensure the correct size pattern.

Framing Piece

Use a two by four and your square to measure a framing piece on the header. You will want to measure along the edge, going towards the header itself.


Using your circular saw this time, cut the measured piece leaving a bevel at both ends. Then fit it in so it is outside the curved cutout. Once it is in, correctly, you can secure it down with nails.

Remove Siding

Now you will have to remove some siding in order to fit your window into place. Use flashing from the bottom, going up, and then put your window into place.

Mark the Siding

Now you can mark the new siding with your scribing compass. Mark it out making sure to keep your compass level when you do so.

Cut the Siding

Using your jigsaw, you can cut out your siding. You will want to make sure you stay on the markings you have made so a good fit is ensured. Test the fit of the siding, and make any adjustments necessary.

Then you can mark out the length of the siding for cutting once it fits correctly.


Take out your caulk, and apply it to the area the siding will be applied. Take your siding, and place it in the correct area, making sure it lines up just as it did when you test to fit it. Push the siding into place, and then secure it down with galvanized nails.

Once the siding is all in place you can apply caulking all the way around the window. That should be all you need to create a beautiful looking window.