Knowing how to build a window box is useful whether you live in a small space with no yard, have no garden space or simply want to beautify your windows naturally. A window box only takes a little planning and can be built with materials from any local hardware store. In a few easy steps you can add an accent to your living space that will provide years of beauty and productivity.
You will need to custom design your window box, which is easier than it sounds. Just measure the entire width of your window frame: that equals the length of your box. Choose weather-resistant timber like redwood, teak, mahogany or cedar, about 1 inch thick. Cedar is probably the best choice since it is plentiful, reasonably priced and decay-resistant.
Cut your wood or get it pre-cut to the dimensions you desire. When cutting the sides, back and front, consider a window box depth of at least 7 inches. This assures retention of moisture in the soil for several days. Cut the end pieces as wide as the stock plus 1 ½ inches to assure coverage of the front and back edges.
To put your window box together, you will need standard wood glue and either flathead brass wood screws or treated nails. Make sure the back panel is butted against the bottom panel, and then apply a bead of glue along the edge of the bottom panel. Drill small pilot holes every four inches along the joint line. For 1-inch-thick wood you’ll be using 1 ¼-inch screws, which means your pilot holes should be 11/64 inches wide. (If you have some carpentry experience, you can avoid drilling pilot holes and follow the same steps using nails, which will take less time. But wood screws assure a more solid structure which is better for inclement weather and movement, should you need to relocate your window box.)
Fasten the back to the bottom with the wood screws. Then secure one side to the back and bottom with glue. Drill pilot holes in the face of the side piece, one hole at each end and one between top and bottom, and secure with wood screws. Then simply repeat these steps for the front and the next side. Don’t forget to drill holes for drainage, ½ inch wide every four inches along the bottom, if you’re planting items that need regular watering.