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Make and Install Window Boxes

Build these window boxes and fill them with flowers for instant curb appeal.

three custom built green window boxes

Project Overview

Skill Level


Estimated Time

1 weekend

Estimated Cost


Tools & Materials


  • Circular saw
  • Jigsaw
  • Straightedge
  • Half-round file (optional)
  • Cordless drill with driver bits
  • 1/8-in drill bit
  • Random-orbit sander and 150-grit sandpaper
  • Wood clamps
  • Hacksaw
  • Caulking gun
  • Painter’s tape
  • Carpenter’s square
  • Electronic stud finder


  • 1 x 8 x 8 pine board (1 per window box)
  • 5/4 x 6 x 8 treated deck board per window box
  • 3 - 3/8 x 2 x 3 pine boards per window box
  • 3/4 x 36 square poplar dowel (1 per window box)
  • 2 x 12 x 12 pine board (enough for 3 window boxes)
  • 2-in deck screws
  • 2-1/2-in deck screws
  • 9.8 oz. silicone caulk
  • 1/4-in fender washers
  • 1/4-in hex nuts
  • 1/4-in x 4-in eye bolts
  • 1/2-in x 4-in zinc screw hooks
  • Valspar exterior latex primer, quart, #165218
  • Valspar Ultra exterior semigloss paint, quart, Pantone Universe Palm (#PN11030)

Items may be Special Order in some stores. Product costs, availability, and item numbers may vary online or by market. Paint colors may vary slightly from those shown. Availability varies by market for lumber species and sizes.

Missing anything? Shop Online

Project Resources


These boxes hold potted plants and provide drainage so they can hang around for a long time. The box is easily adapted to your window. Add or subtract to the length in 3-inch increments up to 39 inches. The window boxes are centered on the window and can be slightly wider for a single window or slightly narrower for multiple windows.

Cut the Sides

Step 1

Cut the ends to shape using a jigsaw

Cut 22-inch-long 2 x 12s to make a blank for each planter end (A). Mark out the circles using a compass on one. Then draw the connecting lines and make the cuts with a jigsaw (Project Diagram, Drawing 1).

Good to Know

Use the appropriate jigsaw blade for the material to be cut. Very small teeth like a hacksaw blade cut metal, and larger teeth cut wood. In general, the thicker the material, the wider the blade you will need so it won’t flex around curves. Next, count the teeth. More teeth make a cleaner cut, but they can burn the wood. Fewer teeth remove wood faster, but leave a rougher cut.

Step 2

Sand the cut edges of the ends. If the shape is very rough, a half-round file can be used to help shape the curves and make them flow smoothly. Use the flat side for the outside curves and the round face for the inside curves. Then sand the finished shape. Set the finished end on top of the remaining end blanks and align the edges. Trace the shape and cut the remaining ends along the traced lines.

Good to Know

Each side will be a little different because they are traced and shaped individually. Using the original as a template will help keep all of the sides close to the same shape.

Step 3

From a 1 x 8, cut the front and back (B). Cut the bottom slats (C) from a 5/4-inch  deck board (Project Diagram, Cutting List). Sand all of the parts with 150-grit sandpaper.

Step 4

Secure the front and back to the bottom boards

Attach the front and back to the ends of the slats (Project Diagram, Drawing 2) so that the end slats are even with the ends of the front and back and the remaining slats are evenly spaced. Drill a pilot hole and drive two screws through the front and two through the back for each slat.

Step 5

Secure the ends to the front, back, and bottom using screws

Flip the box on to its top and raise it off the work surface with 1/4-inch-thick spacers. Now rest the ends against the box, mark out the screw locations, and drive screws through the ends into the front, back, and slats (Project Diagram, Drawing 3).

Good to Know

Note the locations of screws securing the ends to the front, back, and slats. Wood will expand and contract as the humidity changes. The screw positioning allows the sides to change width through the season without splitting the ends.

Step 6

Cut the front trim parts (D) and sand them smooth. Mark the locations of the trim boards spaced evenly across the length of the front.

Step 7

Add the front time using glue and painter’s tape

The front also needs to expand and contract. Apply glue to the top half of each trim board and tape it in place. (If you glue the trim solid across the front, it cannot expand with the seasons.) When the glue dries, remove the tape.

Step 8

Cut a 3/4-inch square dowel to the same length as the back for the back support (E). Glue and clamp it even with the top edge. This piece reinforces the back of the planter for hanging.

Finish and Install

Step 1

Apply an exterior primer and two coats of exterior paint to the planter box. The planter boxes can be attached to wall studs, the structural sheathing that makes up the outside of your home, or to brick. Your installation may be slightly different from those shown in the illustrations (Project Diagram, Drawings 4 and 5).

Good to Know

When drilling holes in the outside face of your home, locate the studs underneath. To find studs beneath material like vinyl siding or wood shingles, use a stud finder and transfer the locations to the siding surface.

Step 2

Mark two 3/8-inch holes under your window. Apply silicone caulk in and around the hole, and thread the screw hooks into the wall. The silicone will help prevent water infiltration into your home.

Step 3

When the paint dries on the planter box, drill two 1/4-inch-diameter holes 2 inches from the top edge of the back -- spaced the same distance apart as the screw hooks. Install two eye bolts in the back of the box using a washer and a nut on each face. Trim the remaining thread that extends into the box using a hacksaw.

Step 4

Hang the planters under the window and add potted flowers or herbs of your choice.