More in Windows Walls and Doors
Pre-fabricated arches come in a set width, typically 48". A piece a plywood or a 2 x 4 may need to be added to adjust the size of your rough door opening to accomodate the arch. Measure the rise (height) of the arch and transfer that measurement to the side walls of the doorway.
Set one end of the arch at the wall mark and slide the other end into place, then nail the arch into the door frame.
Lay enough drywall over the arch to make up for the space where the old wall surface was taken out. In this demonstration, 3/4" had to be made up because of the old plaster, so we started with a 1/4" layer and then an additional 1/2" layer over that.
Using the edge of the arch as a guide, trim the drywall along the underside of the arch with a rotary cutting tool.
Cover the underside of the arch with drywall. To prevent the drywall from breaking, spray the drywall piece with water and let it set for 10 minutes to make it more flexible. Using two separate pieces will also help. To attach the drywall, use self-tapping screws to go through the metal form. Use a rasp to finish the edges of the arch (Image 1).