An arched alcove or doorway might be the perfect touch to set off that redecorated room, and it’s not as tough as it looks.
The first step is to make four curved plywood sections to install in upper corners of the rectangular door frame.
To cut the plywood, decide where you want the arch to begin on the side of the doorframe (point A), and where it will meet the top (point B). Mark your plywood at these two dimensions. To draw your curve, tie one end of a string around a pencil and the other end around a nail (shorten the string by wrapping it around the nail.) Now, position the nail (your pivot) until you can draw the correct curve from point A to point B. Once you’ve cut one section, use this as a template for the rest, and cut four pieces of drywall to match.
Using plywood blocks, install the plywood corners so their surfaces are flush with the wall framing. Then surface the plywood with the drywall pieces you cut earlier.
Now, cut a strip of drywall the length of the entire arch. Score across the back of the strip every inch or so, and lightly spray it with water. Starting at the top and working down both sides of the arch, screw the strip to the edges of the plywood corners. Add flat drywall strips to the door jambs from the arch to the floor. Finally, attach bendable corner bead to the edges, and finish with drywall mud.
An ornamental “keystone” adds effect. To create a pedestal look, trim the opening from the floor to the bottom of the arch, and cap with small cove molding.