Make this window box in a few hours and watch your flowers or herbs grow for years.
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Measure the width of the window to get the final length for the front, back, and bottom of this easy-to-make window box, and adjust the dimensions as needed. Add an additional brace for every 24 inches added to the box.
Cut the bottom (A) and sides (B) to length (Project Diagram, Cutting List and Drawing 1). The combined length of the bottom and thickness of the two ends should match the width of the window where the box will be installed.
For the best results, double-check part lengths by first assembling parts with tape or clamps but no glue. Then cut parts to fit, even if the sizes vary slightly from what’s shown in the Cutting List. The wood may have subtle variations in width, which will affect the length of the front and back.
Drill 1/2-inch drainage holes in the bottom of the box about 2 inches from each end and then evenly spaced every 9 to 10 inches.
Apply glue to one end of the bottom and position a side there. Drill 1/8-inch pilot holes through the side into the bottom, and drive 1-1/2-inch deck screws through the holes. Repeat for the other side.
Cut the front and back (C) to match the length of the bottom/sides assembly.
Apply glue to the edges of the sides and bottom, place the front onto the box, drill pilot holes for the screws and screw the front in place. Flip the box over and attach the back in the same manner.
Lightly sand the wood to remove any sharp edges and apply the paint or exterior finish of your choice following the manufacturer’s instructions.
Secure 6-inch angle braces beneath your window. The top surface of the brace arms should be 9 inches below the bottom of the windowsill. Drill 1/8-inch pilot holes into the siding and drive stainless-steel screws through the siding into the wall sheathing.
Rest the completed window box on the arms of the angle braces and drive screws through the braces into the bottom of the box.
For planting in the box, it is best to use small plastic or clay pots for easy removal and replanting throughout the year.
If you choose to fill the box with dirt instead, first cut a piece of screen cloth to line the bottom and use a staple gun to apply a plastic sheathing liner to the inside surfaces of the window box. Poke holes through the liner over the drain holes in the bottom so water can escape.