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Building a Window-Box Planter
This weekend project combines building skills, love of flowering plants, and adding beautiful decorative features your home’s windowsills.
Window boxes add to your home’s appearance in two ways: They provide color over landscape shrubs, even as they frame your outdoor view with flowers.
Window box planters are easy to build, and even easier to install beneath windows.
Rather than being filled with soil, this planter box features a rack that holds plants in containers. It’s convenient for planting progressions of different flowers throughout the season, replacing those that have finished their bloom.
You’ll quickly learn how to grow plants in containers to the stage at which they flower and set them into the window box.
To build your window-box planter, assemble the materials listed and carefully follow the easy building steps shown.
Materials and Fasteners
Required Materials:
Cut from 2 x 2 (38 x 38-mm) dimensioned lumber:
2 – 59-1/16-in. (150-cm) back rails
2 – 59-1/16-in. (150-cm) front rails (see step #1)
2 – 9-1/2-in. (24.1-cm) top crossbars
13 – 7-1/4-in. (18.4-cm) bottom crossbars
Cut from 15/32-in. (12-mm) ACX plywood:
1 – 10 x 60-in. (25.4 x 152.4-cm) front panel
1 – 9-5/8 x 59-1/16 (24.4 x 150-cm) back panel
2 – 10-15/32 x 9-5/8-in. x 12-15/16 x 10-in.
(26.6 x 24.4 x 32.9 x 25.4-cm) trapezoidal end panels (see step #2)
Other Materials and Hardware:
1 – 48-in. (122-cm) 1 x 4-in. (19 x 89-mm) ledger rail
2 – 6-in. (15-cm) 1 x 4-in. (19 x 89-mm) spacer blocks
30 – No. 8 x 3-in. (No. 8 x 75-mm) deck screws
50 – 4d x 1-3/4–in. (4d x 45-mm) galvanized finish nails
4 – No. 8 x 1-3/4-in. (No. 8 x 20-mm) lag screws
1 – Qt. (1 l) exterior latex primer and paint
Step-By-Step Instructions
Planted with successions of flowers from spring until autumn, a window-box planter is a beautiful addition to a home’s window, and provides the bonus of viewing its flowers from within the house.
Gather the materials listed, and follow these steps:
How to Build a Window-Box Planter
Cut wood components for the frame and ledger pieces.
Rip or plane a diagonal bevel on one face of each of the two front rails, 3/8-in. (10-mm) deep.
Cut the front and back panels using a circular saw mounted with a plywood blade. Score each cut with a utility knife to avoid marking the face or splinters during cuts.
Cut the trapezoidal end panels.
Score and cut plywood to 9-5/8 x 23-15/32-in. (24.4 x 59.6-cm).
Mark points on the cut panel’s top and bottom edges, 10-15/32-in. (25.4-cm) from the two opposite diagonal corners. Join the two points with a marked line for cutting.
Score and cut along the line to make two end panels.
Build bottom frame.
On a layout table, set the front and back rails parallel, with the front rail bevel facing to the outside.
Mark points at 4 in. (10 cm) on center from the centerpoints of each rail. Clamp, and drill 1/16-in. (1.5-mm) holes at each mark.
Fasten each bottom-frame crossbar in place using a deck screw.
Build the top frame.
On a layout table, set the front and back rails parallel, with the front rail bevel facing outside. Flush a top crossbar with each rail end and clamp.
Mark and drill 1/16-in. (1.5-mm) holes, then fasten the crossbar to the rails with deck screws.
Attach back panel to the frame.
Stand the top and bottom frames upright on their front rails.
Square and clamp the back panel flush with each rail end. Fasten the panel with finish nails spaced 4 in. (10 cm) on center.
Attach side panels.
Square and clamp each side panel so it is flush with the beveled rail ends and with the back panel.
Fasten with finish nails spaced 4 in. (10 cm) on center.
Attach the front panel.
Square and clamp front panel so it is flush with the beveled rail ends. Fasten with finish nails spaced 4 in. (10 cm) on center.
Attach the ledger to the house wall under the windowsill.
Use an electronic stud finder to mark the position of each casing stud on the home’s exterior wall, under the window frame.
Prime and paint the ledger. Position the ledger under the window sill, drill, and fasten it to the wall studs with four deck screws.
Install the window box to the ledger rail.
Mark four points along the box’s top back rail, 1 ft. (30 cm) on center. Drill 1/16-in. (1.5-mm) holes through the panel and rail at each marked spot.
Fasten the two spacer blocks to the back bottom corners of the box. Level the box vertically. The box should hang with an air gap between it and the house’s siding or exterior wall.
Re-level the box horizontally. Fasten deck screws through the top frame of the box to the ledger rail.
Optional: Add decorative trim moldings, priming and painting them before fastening them to the box.