Window Dressing: How to Build a Window Planter

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A lush window box spilling blooms can boost curb appeal in ways that a new paint job or reseeded lawn don't quite equal. I'm building six for my 15-year-old Cape—and after cranking up my power tools and making a big mound of sawdust, I was able to finish the first one in just one weekend.

Each box is essentially a 6- to 8-inch-deep trough with a slanted front, supported by two thick brackets, and centered just shy of the window's width. Two brackets will support boxes less than 48 inches long, but longer boxes need a third, center bracket. I installed the boxes an inch beneath the sill of sliding and double-hung windows. On out-swinging casement and awning windows, I'd mount the box 6- to 8-inches below the sill, to leave clearance for the plants.

I'll repaint, one day. For now, I'm happy with the new splash of color.

Some Tools You Might Need

12-Inch Miter Saw

DeWalt $299.00

$219.00 (27% off)

Random Orbital Sander

Bosch

Classic French Curve

Alvin

Plans Cutting

I crosscut the 1x8s to length using a miter saw. I cut the bottom, back, and front of the window box to 36 inches long, and the two ends to 5¼ inches. The cleats, which mount to the house and support the box and braces, are 13 inches long. I used a table saw to rip the back to 6 inches wide, the bottom to 6¼ inches, and the two cleats to 2 1/8 inches [1].

To create the box's slanted front, I adjusted the bevel angle of the table-saw blade to 15 degrees and bevel-ripped both edges of the front panel [2]. I adjusted the blade back to vertical, set the table saw's miter gauge to 15 degrees and made the angled cut to both window-box ends. I smoothed the cut edges with 80-grit sandpaper.

Next, I used a drafting implement called a French curve to draw the profile of the braces onto paper. I cut the paper along the curve, then traced the shape onto 5/4-inch pine, and cut along my line with a saber saw [3]. I sanded the curved edges smooth using a drum sander in a drill press. You can also use the "nose" of a belt sander, or do it by hand.

Assembly

To add a decorative touch to the curved profiles, I routed a shallow cove into the edges of the braces. First, I clamped the router upside down, creating a makeshift router table. Then I carefully moved the curved edges of each brace and cleat along the bit [4].

Using an orbital finishing sander fitted with 120-grit sandpaper, I sanded each piece smooth. Using 1 5/8-inch stainless-steel trim-head screws, I fastened the back to the bottom, and then attached the two ends, which were inset ½ inch [5].

💡When driving a screw close to the end of a board, stay within 3 inches or so, and be sure to drill 1/8-inch-diameter screw-pilot holes to prevent the wood from splitting.

Using 1 5/8-inch trim screws, I fastened the front panel to the bottom and to the angled ends [6]. I used exterior-grade wood putty to fill the screw holes in the front panel. Once the putty dried, I hand-sanded it flush with 120-grit paper. Using a 3/8-inch-diameter spade bit, I drilled six drainage holes through the bottom of the window box.

💡I used two coats of exterior-grade primer and three coats of acrylic latex to paint my clear pine boxes, but I would have stained them if I had used red cedar or redwood.

There are generally three tinted types of stains: semitransparent (1), semisolid (2) and solid (3). As you move to more solid stains, hue can change as pigment concentrations increase. More pigment offers more protection, but it obscures the woodgrain. Clear and semitransparent stains allow the wood's grain to show. They're less protective, though, and require more frequent reapplication.

Installation

I attached the braces to the cleats with 5/8-inch stainless-steel trim-head screws driven through the back of the cleats [7]. The braces were centered on the 2 1/8-inch-wide cleats, and placed 1 5/16 inches from the bottom edges of the cleats. I then primed and painted.

To install, I drilled two counterbored screw-pilot holes through each cleat at 2½ inches and 5½ inches from the top edges. Holding a plumb level vertically against the first bracket, I used 3-inch decking screws to mount it 1 inch down from the windowsill and 5 inches in from the window-frame edge. With a 4-foot level across both brackets, I installed the second one just as I had the first [8].

I set the box in position, then centered it against the window and brackets. I drilled counterbored pilot holes through the upper back of the window box at each cleat. I then fastened the box to the cleats with 1¼-inch decking screws, driving near the top so I could remove the box without emptying it [9].

Then, I filled the boxes with a potting-soil mix made specifically for containers.

How to Build a Window Box