Cut 3/4″-thick cypress or cedar boards to following dimensions:
(3) 8″ wide x window length
(2) 1-1/4″ wide x window length
(3) 1-1/4″ wide x 5-3/4″ long
(2) 8″ wide x 11″ long
Cut 2″ x 4″ pressure-treated lumber into three (3) 8″-long pieces.
To create cleats, cut three 8″ pieces of pressure-treated 2×4. Hold the 2×4 tightly against the exterior wall and drill two pilot holes where you’d like screws (Image 2). Drive two 3/4″ concrete screws through pilot holes to secure the cleat to the wall (Image 3). Repeat process on other cleats.
Place the bottom of the window box flat on the work surface. Stand in front of the box on end and press tightly against the side of the box bottom. Clamp or hold in place, then drill pilot holes every eight inches using 1/8″ drill bit (Image 1). Insert 1-1/4″ screws into pilot holes (Image 2). Remove clamps (if used) and repeat them on the backside of the box.
When measuring dimensions of side panels, allow an extra 1-1/2″ overhang on the back side to cover up exposed cleat on house. Attach sides to planter using 1-1/4″ wood screws.
Cut two 1-1/4″-wide trim pieces to exact length of the front panel of window box. Make sure that each trim piece is flush with top and bottom of the front panel, then tap into place with nails. Position three 1-1/4″-wide x 5-2/4″-long pieces on left and right side of the box and one centered. Tack into place with nails.
Holding window box in place against cleats, drive four screws through back panel into each 2″ x 4″ block.
Using a 3/8″ drill bit, drill holes straight through the bottom panel to allow for drainage. Drill one hole roughly every six square inches.
Add a 1″ to 2″ layer of gravel in the bottom of the window box, to allow excess water to drain. Cover the gravel with potting soil, filling a box to about an inch from the top. Add plants and thoroughly water.
