How to Build an Interior Wooden Arch

Remove the drywall or molding from the inside of the doorway to expose the frame. This allows you to attach the arch directly to the door frame.

Cut two sheets of 1/2-inch plywood boards and a 2-by-3 board that match the width of the doorway. Wear safety goggles when sawing the wood.

Cut an arch into one of the plywood boards, then using that as a template, trace it onto the second board. Cut the second plywood board along the line you traced.

Measure the sides of the plywood boards, and cut two 2-by-3 boards that are 2 inches shorter than the sides.

Nail the 2-by-3 boards together to form a frame that is shaped like a U. Nail one of the plywood boards to each side of the 2-by-3 framing, with the sloped edge of the plywood boards over the open side of the framing.

Nail the arch framing to the doorway, with an assistant's help.

Measure the length between the inside edges of the two plywood boards, and cut a series of wooden blocks to fit that length from 1-by-2 boards. Cut enough blocks that you can install one block every 2 inches along the curve of the arch.

Place the 1-by-2 blocks into position along the bottom of the arch (between the plywood boards), using one every 2 inches, and screw them to the arch framing with drywall screws.

Cut a strip of 1/4-inch drywall to fit along the curve of the arch. Spray it with water to get it damp enough that you can flex the drywall without cracking it, then screw it to the 1-by-2 blocks with drywall screws. Use two screws at each block.

Staple flexible corner beads to the edges of the arch along the joint between the drywall and the plywood, adding the staples every 3 inches.

Spread joint compound over the plywood and 1/4-inch drywall with a 12-inch putty knife. Smooth the joint compound as much as possible with the putty knife, and allow it to dry overnight.

Sand the joint compound with fine-grit sandpaper to smooth any rough, uneven patches on the surface, then wipe it clean with a tacking cloth.

Place two more applications of joint compound onto the arch framing, using the same method you used when applying the first application.

Cover the arch framing with primer, and allow it to dry.

Paint the framing with a coat of paint to match the surrounding walls. Allow it to dry, then add a second coat and allow that to dry.