How to Make a Cornice for a Bay Window

If you have a bay window in your kitchen nook or living room, you may have wondered just how you would find window treatments to fit into the awkward space.

Make a Cornice for a Bay WindowMake a Cornice for a Bay Window
Custom made window treatments are quite expensive and usually not changeable once they are installed. You can make a cornice for a bay window that can easily be changed with each season.

Measure the width of each window to 1 1/2 in. outside of the window frame. Use the electric kitchen knife to cut the length of foam to those measurements. Do not use a sawing motion; this will cause the foam to shred. Cut a 1 1/2-in. slit into the middle of the back of each foam piece about 3 in. from each end. Cut a slit the same depth on each end about 3 in. wide, forming a T-shape at each end of the long slit.

Lay the fabric face down on a flat surface and place the foam face down on top. Use scissors to cut the fabric around the foam, adding about 4 in. on all sides for tucking.

Beginning on one side, pull the fabric up in the center and tuck it into the slit and pin it into place with a sewing pin. Pull the fabric up on the opposite side of the foam and repeat. Next, pull the fabric up and tuck it into the slit all the way down to each end on each side, and pin it into place with the sewing pins. Fold each end of fabric, forming a point on each end like you would when wrapping a gift. Pull the point up and tuck it into place on each end and secure it with a sewing pin.

Hold the cornice up to the window and mark the wall with a pencil just above the window where the T-shape in the foam hits the wall. Attach the mounting brackets into the wall with the plastic anchors on each side above the window where the marks are. The mounting brackets require no tools and simply screw into the drywall. Slide the cornice onto the brackets, pressing the foam up against the wall.

Things You Will Need

  • Measuring tape
  • Dense foam 3 in. thick cut into 4-in. wide long strips
  • Fabric
  • Electric kitchen knife
  • Sewing pins
  • Scissors
  • Two mounting brackets for each window
  • Two plastic anchor caps per window


  • Change the fabric with each season to give your window a festive, updated look.


About the Author

As a freelance writer and online marketing consultant, living and working in South Florida, Tiffany Holley provides copy writing services and online marketing strategies for businesses and website owners of all types. Holley specializes in SEO content writing, product reviews, search engine marketing, and social media marketing for businesses.