Exterior Windows

How To: Make a Window Box

Amp up your home’s curb appeal with a flower-filled window box that you can make yourself.

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A window box can add enormous curb appeal to a house and provide a garden opportunity for even city dwellers. And, they are easy to make.  Just follow this simple summer DIY tutorial to deck your sills with beautiful summer blooms this weekend.

– Tape measure
– Pencil
– Carpenter’s square
– Handsaw or power saw
– Sandpaper
– Tack cloth
– Power drill with 11/64-inch, 1/2-inch, and carbide-tipped bits
– Screwdriver
– Hammer
– Safety goggles
– 1×8 or 1×10 redwood or cedar stock
– 1×2 decorative molding (optional)
– Wood glue
– 1-1/4-inch brass or stainless steel flathead wood screws
– Miter box and saw (optional)
– 6-penny brass or stainless steel finishing nails
– Exterior grade primer and paint
– Paintbrushes
– Heavy-duty brackets (optional)
– 2-inch brass or stainless steel flathead screws, or 2-inch lag screws with lead masonry anchors

Measure the inside width of the window frame. Using a carpenters’ square, measure and mark one board to this measurement, and two boards to this measurement plus 1½ inches, then cut them with a handsaw or a power saw. For the side pieces, measure and cut two pieces of board equal to the width of the stock. Use sandpaper to smooth the cut edges, wiping off dust with a tack cloth.

Adjoin the pieces together with simple butt joints. Align the edge bottom of the front of the box along one edge of the bottom, edges flush. Mark and drill 1/16-inch holes through the face of the front board at each end and about every 4 inches all along the joint line about 3/8-inch from the edge of the board. Set the board into place, mark the screw holes on the bottom board, and drill starter holes into the board edge at the marked points. Repeat for the back and side pieces.

Apply glue to the front edge of the bottom board and set the front board into place, edges flush. Secure the joint with 1 1/4-inch brass or stainless steel flathead wood screws through the predrilled holes. Repeat for back and sides.

If desired, add strips of molding across the front and around the sides, cutting to allow for mitered corners at the ends of the front and two side strips. Glue the strips to the front and sides and hammer in penny brass or stainless steel finishing nails about 4 inches apart all around.

Drill a series of ½-inch-diameter weep holes every 4 inches along the center of the bottom board to prevent water logging.

Prime and paint the inside and outside of the box with two coats of primer and two coats of exterior grade paint, letting dry between coats.


  • You can attach the window box using several different methods. One option is to drill holes into the siding or brick and use heavy-duty deck screws to attach the box directly to the area directly under the windowsill. Or you can use window box brackets or try a cleatless system, which eases water damage issues. To fasten the box to a brick or concrete-block wall, use 2-inch lag screws with lead masonry anchors. Wearing safety goggles, drill holes for the anchors with a power drill and a carbide-tipped masonry bit; insert the anchors and then drive the screws in flush with the wall surface.
  • To extend the life of the window box, add soil and plants to a window box liner rather than placing them directly into the box.