How to Build an Arched Doorway at Home

Cut through the paint adhering the door casing to the wall, using a utility knife. Slide a 4-inch putty knife between the wall and the casing. Insert a pry bar between the putty knife and the casing and use it to pry the casing away from the wall. Remove the baseboards next to the doorway in the same way. Remove only the baseboards if your door does not have casing around it and your archway kit comes with side columns.

Insert a reciprocating saw blade between the rough opening and the doorway's jamb. Run the blade down both sides and across the top to cut through the nails holding it in place. If your doorway does not have a jamb, use a utility knife to cut through the paint covering the doorway's corners. Hit the doorway's edges with a hammer to break the drywall, then pull it away from the rough opening to expose the wood. If your archway kit does not come with columns, only remove the drywall about 1/3 of the way down from the doorway's top.

Cut four 10-inch long wood cleats from 1-inch by 4-inch boards. Butt 2 boards perpendicularly into each corner and secure them in place with 2-inch wood screws.

Measure the doorway's width and transfer this measurement to a piece of drywall. Hold a straightedge against the drywall at the measurement and use a utility knife to score the drywall, then bend the drywall on the score line and cut the paper backing. Measure 10 inches up, along the drywall's length, and cut the drywall along this measurement in the same way. For example, if your doorway is 4 feet wide, you would end up with a piece of drywall measuring 4 feet by 10 inches. Cut a second piece, the same size, for the doorway's other side.

Lift one piece of drywall up to the doorway. Rest the drywall against the wood cleats you installed earlier. Use drywall screws to secure the drywall to the wood cleats' edges. Repeat on the doorway's other side with the second piece of drywall.

Create an arch template out of a piece of cardboard. Some archway kits come with a template. Hold the template on the drywall you just hung and trace along its edge to transfer the arch to the drywall. Move the template to the drywall on the opposite side.

Cut the drywall along the arch line, using a drywall saw. Tape and finish the new drywall to blend it into the old drywall. Use a 4-inch putty knife to apply the first coat of drywall mud. Allow this coat to dry, then apply a second coat using an 8-inch putty knife. Once the second coat dries, sand the surface smooth with a sanding sponge.

Paint primer onto the new drywall, with a paintbrush, and allow it to dry. Paint one to two coats of paint over the primer, with a paint brush or paint roller. Allow the paint to dry.

Lift the arched portion of the doorway kit up on the doorway's top edge. If your kit comes with side columns, slide them onto the doorway's sides. Hold a level against the columns to check for plumb. Slide the arched portion down until it rests on the columns. Secure the arched portion and columns to the wall using a pneumatic nailer and finishing nails.