DIY: How to Repair a Half Moon Window

A half moon window is most often found on entry doors.
Replacing window glass can easily be accomplished.Replacing window glass can easily be accomplished.
It looks exactly like it sounds and is shaped like a half moon. These windows are also known as fan lite windows. They can become cracked or damaged over time and need to be replaced. Replacing the half moon window on your front door can be completed without going through the manufacturer and replacing the glass. All you need is a few tools to do it yourself and fix that cracked window.

Step 1

Cut out the cracked piece of glass from inside the window with a utility knife. Score the glass along the edges with the knife and carefully hammer out the glass. Scrape off the glass along the frame of the window with a putty knife. Dig the knife into the frame and remove any excess glass from the frame.

Step 2

Set a piece of plexiglass over the window frame and outline the glass with a black marker so the proper size cut can be made. Set the plexiglass on a flat surface and score it along the cut marks with a utility knife.

Step 3

Follow carefully along the marks with the utility knife multiple times until the knife goes through the plexiglass. Break the plexiglass into the desired shape and place it into the opening of the window to verify it fits properly.

Step 4

Slide a tube of window and door silicone sealant into a caulk gun and cut off the tip with a utility knife. Position the caulk gun at the edge of the window along the inside of the frame and run a thin bead of caulk around the entire perimeter of the window.

Step 5

Set the window into the opening and press it up firmly against the sealant. Run your hands over the entire surface so the adhesive can adhere to the plexiglass. Wipe away any excess adhesive from the surface of the plexiglass with a clean rag.

Things You Will Need

  • Utility knife
  • Hammer
  • Putty knife
  • Plexiglass
  • Silicone sealant
  • Caulk gun
  • Clean rag

About the Author

Alexander Callos began writing in 2005 for "The Lantern" at The Ohio State University and has written for various websites, including Bleacher Report, Top Ten Real Estate Deals and Columbus Sports. He has published articles for CBS Sports, SI.com and other websites. He graduated in 2007 from The Ohio State University with a bachelor's degree in public affairs journalism.