How to Make an Arch in a House

Use an existing doorway to create your arch. The doorway will have the necessary dimensions to form the archway.

Use a utility knife to gently pry the door casing away from the drywall. Use a claw hammer to separate the doorjambs from the drywall.

Measure the width of the opening. Divide this measurement by three. Mark the measurement on a 1-by-4-foot wooden board with a one-inch thickness. For example, if your doorway is 36 inches, mark the board at 12 inches.

Cut wood to act as nailing boards to secure your arch. The nailing boards will provide your arch a base to nail the arch in place. Cut two pieces of wood 1 foot by 8 inches at a one-inch thickness. Nail them to the trimmer studs on the sides of the doorway in the top corner.

Nail the longer boards that are equal to 1/3 of your doorway’s opening to the doorway’s header. You will now have your doorway in place with two side boards that are flush in the corner and two header boards. These boards will secure your arch in place.

Make a template for your arch on cardboard. Use the width of the doorway to get you started. Mark the two ends on your cardboard and mark the point exactly in the middle of the two points. Draw a perpendicular line up to the point to where you want the incline of the arch. A short line will produce a shallow arch and a long line will give the arch a semi-circle look. Tape the cardboard at the top of the doorway to make sure there is enough clearance.

Use the piece of cardboard to trace the pattern onto a piece of 1/2-inch thick plywood. Cut the plywood in the arch shape with a saber saw. Repeat the pattern and cut out a second piece of plywood.

Nail one arch to each side of the doorway. Nail to the top and the sides of the arch so that you are nailing into the nailer boards you installed.

Cover the plywood arch with 1/4-inch thick drywall. This type of drywall is more pliable and will contour to the shape of the arch better. Press the drywall into place. Use a utility knife to make scores in the back of the drywall every inch so you can fit the drywall around the curves. Push each one-inch section into place around the arch. Nail the drywall every four inches with drywall nails.

Add flexible plastic corner bead to reinforce the arch. Run the bead from the top of the arch to the floor, stapling it in place every three inches.

Cover the corner bead with joint compound. Add two more coats of compound. Sand the compound after it has set. Paint the arch in your desired color.