How to Make a Doorway Into an Archway

Cut along the door casing with a utility knife. Insert a four-inch putty knife underneath the door casing near the upper edge. Slide a pry bar between the casing and the putty knife and use it to pry the casing away from the wall. Move the putty knife down about six inches and use the pry bar to pull the casing away from the wall. Continue to work your way down the casing until it is free from the wall. Repeat with the upper casing and the casing on the opposite side of the door opening.

Pry the door jambs away from the door opening with a pry bar. Measure the opening's width and divide by three. Cut two 1-by-4 inch boards to that length with a circular saw. Cut two more 1-by-4 inch boards eight inches long.

Place one of the first two boards on the door opening's header. Push one of the board's ends into the corner. Secure it in place with nails. Repeat with the other board in the door opening's opposite corner. Place one of the eight-inch boards against one of the door opening's sides. Press its upper edge tight against the 1-by-4 board nailed to the header. Nail the eight-inch board in place. Repeat with the second eight-inch board on the other side.

Cut a 15-inch wide strip from a piece of drywall using a utility knife. Transfer the measurement for the door opening's width onto the strip. Cut the strip to this length with a utility knife. Repeat this step a second time so you are left with two drywall rectangles.

Lift one of the rectangles over the doorway and press it against the 1-by-4 boards mounted on the top and sides. Drive drywall screws through the drywall and into the 1-by-4 boards. Repeat with the second piece of drywall on the doorway's other side.

Slide the columns supplied with the arch kit onto the door opening's sides. Place the cardboard template, that comes in the drywall arch kit, over one of the pieces of drywall you just installed with the bottom edge resting on the columns. Trace along the cardboard with a pencil. Repeat on the drywall on the door opening's other side.

Set the columns aside. Cut the drywall, following the pencil line, with a drywall saw. Apply a strip of adhesive drywall tape over the seams where the new drywall meets the old drywall. Use a four-inch putty knife to apply a thin layer of drywall compound. Allow the drywall compound to dry.

Apply a second layer of drywall compound with an eight-inch putty knife. Allow this layer to dry. Apply a third layer of drywall compound with a 12-inch putty knife. Feather out the edges to blend the new drywall into the old drywall. Allow the third layer to dry. Sand the drywall compound smooth with a sanding sponge.

Pour interior latex primer into a paint tray. Roll a paint roller through the primer. Apply the primer over the drywall compound and new drywall. Wait one to two hours for the primer to dry.

Lift the arch over the door opening. Fit the two columns over the door opening's sides. Pull the arch down so it rests on the columns. Hold a level against each of the columns to check that they are plumb in the door opening.

Drill 9/64-inch pilot holes through the columns and arch and into the door opening's frame. Space the pilot holes approximately 12 to 18 inches apart. Drive 2½-inch finishing nails through the pilot holes with a pneumatic nail gun.