Ou can build circular openings into brick or stone walls using a single semicircular wood form. Moon windows can be built to any dimension, although lifting and placing stones is more difficult as the project grows larger, while tapering stones to fit is a greater challenge as the circle gets smaller. To minimize the need for cutting and lifting stone, we built this window two feet in diameter atop an existing stone wall. Before doing this, you’ll need to check with your local building inspector regarding restrictions on wall height, footings, and other design considerations. You may need to modify the dimensions to conform with the local building code.
Make sure to have at least one helper on hand. Building with stone is ahvays physically demanding, and steps such as installing the brace and form (opposite page) require a helper.
A moon window is just about the most dramatic garden element you can build. We constructed the wall shown here using cut ashlar mortared around a semicircular form, but using brick is also an option. Once the bottom half of the window has set up, the form is flipped and the top stones are placed. The construction technique for the form is the same one used in building an arch (pages 156 to 159).