How to Erect An Arch

Measure the width of the doorway or opening where the arch will be constructed.

Take half of the measurement to get the radius of your arch, assuming you want your arch to be round and even. Otherwise, decide on the type of arch you wish to erect and measure appropriately.

Measure out a half-circle based on the radius you measured from the doorway. Do this by drawing a line on a sheet of plywood the same length as the width of the doorway. Mark the center of the line then, using a string the same length as the radius of the doorway attached to a pencil with the other end held on the center line mark, draw an arch.

Cut two of these arches from a sheet of plywood. Cut several 2 x 4 pieces of lumber to the width of the wall and arch you wish to erect. Nail the two half circles to either end of the lumber sections to give your arch template strength to hold the weight of the bricks and mortar you will be placing on them.

Determine the height you wish to start the arch in the doorway. It is best to begin arches above the height of the tallest person that will be using the doorway. Cut four 2 x 4s to act as king studs, with one end resting on the ground by the doorway on each corner, rest the half circle template on top of them snug in the doorway.

Place a keystone brick at the very top and center of the arch to allow you to determine the amount of bricks and mortar you will need to fill the arch, taking into account at least 1/8-inch of mortar between the bricks.

Lay a string flush to either side of the wall across the arch to ensure the bricks of the arch are flush with the wall.

Begin laying bricks and mortar in the fashion you wish, beginning with the sides and working upwards, along the half circle template. Mortar and replace the keystone brick last.

Allow for at least 48 hours for the mortar to cure before removing the arch template. The cured mortar will hold the bricks in place, with their combined weight now evenly distributed along the sides of the arch.