How to Build a Residential Hallway Arch

Stretch a tape measure between the hallway's opposite walls. Basic arches are half-circles; this dimension is the circle's diameter. Divide the diameter by 2. Half a circle's diameter is the circle's radius. The radius equals the distance between the top of the arch's curve and the imaginary line that represents the flat bottom of the arch.

Mark the diameter of the arch along one edge piece of interior plywood. Move to the opposite side of the plywood sheet and create a similar mark. Stretch a chalk snap line between the corresponding marks, pull the line taut and snap the line to lay out the diameter's breadth across the plywood's face.

Stretch the tape measure across the diameter line and mark the center of the diameter on the line. This dimension is equal to the arch's radius. Move the tape to the edge of the plywood opposite the diameter line and create a similar radius mark. Stretch a chalk snap line between the radius marks, pull the line taut and snap a line to mark the arch's radius.

Attach a driver bit to the power drill and drive a screw through the point of intersection between the radius line and diameter line. Latch the tape measure's tang onto the screw's head and stretch the tape to the dimension that represents the arch's radius. Hold a pencil against the tape at the radius' dimension. Run the tape and pencil from one side of the diameter line to the opposite side of the diameter line to lay out an arc across the plywood's face.

Mount a wood jig saw blade to the jig saw. Cut along the layout lines on the plywood's face with the jig saw to create a plywood arch frame. Use the cut arch to lay out an identical plywood frame on a separate piece of plywood or the opposite side of the original piece of plywood. Cut the identical frame from the plywood with the jig saw.

Run a stud finder along the hallway to locate the wall's studs. Mark the locations of the studs where you intend to install the arch. Run the stud finder across the hallway's ceiling and mark the location of the joists where you intend to install the arch.

Mark two pieces of framing lumber to the radius of the arch minus 1 1/2 inches. Cut the lumber to size with a circular saw. Mark a piece of lumber to the width of the hallway and cut the lumber to size with a circular saw. Align the lumber that equals the hallway's width with the hallway's ceiling joists and fasten the lumber to the hallway's ceiling with a hammer and framing nails.

Align the lumber equal to the arch's radius with corresponding hallway wall studs and fasten the studs to the hallway's walls with a hammer and framing nails. Align one of the plywood arch frames with the lumber attached to the wall and ceiling. Fasten the plywood arch frame to the lumber with a staple gun or finish nail gun. Align the remaining plywood frame with the opposite side of the lumber and fasten the plywood to the lumber with a staple gun or finish nail gun.

Measure the distance between the inside faces of the plywood arch frames. Mark and cut several pieces of framing lumber to this dimension and cut the lumber to size with a circular saw. Affix the pieces of lumber between the inside faces of the plywood arch frames with a hammer and framing nails. Space the lumber blocks roughly 12 inches apart.