How to Build a Spanish Arch

Measure the width of the entrance way or passage where you want to install the arch.

Draw a line of the measured width onto the flat edge of a sheet of plywood, and mark the center point.

Divide the measured width by 2, then cut a length of string and tie a loop in either end to this calculated length.

Hold one loop at the center mark along your line from Step 2, and hold a pencil through the other. Draw on an arc starting at one end of the line and ending at the other, creating a perfect half circle for your arch. Cut this plywood half circle out of the sheet with a jig saw and then make a second, copying the first exactly.

Determine the thickness you wish the arch to be, then cut enough 2 x 4 planks down to this length. Make sure you cut enough planks to completely cover the circumference of your half circle template.

Beginning at one edge of your half circle template, nail through the plywood and into the ends of your 2 x 4 supports all along the circumference of the half circle. Attach one plywood half circle first, then turn it over and secure the other half circle template in the same fashion.

Determine the height you wish the arch to begin. This is generally determined by using the height of the tallest person that will regularly use the doorway. Cut four 2 x 4 pieces to this length to be used to support the arch frame.

Place your wooden arch frame into the doorway, supported on each of its four corners with a 2 x 4 that was cut in Step 7.

Place the keystone brick at the very top of your arch, on top of the template. Begin mixing your mortar, then start laying bricks from the top of the wall toward the keystone following the template frame.

Apply a layer of mortar to each brick you add until you reach the keystone which will be mated to the bricks on either side of it. Allow for the mortar to dry and cure according to the manufacturers recommendations before removing the arch frame.