How to Build a Planter Box
This planter box is built with a top and a bottom exterior frame, with cedar panels affixed to the frame and bottom. Just add plants for a touch of spring anywhere.
The width of the windows determines the final length of the planter. The depth and height should be large enough to hold pots or an amount of dirt that will retain moisture for a few days. In our project, the box is 7 inches deep and 7 inches high to accommodate 6-inch flower pots.
Use brackets to support the weight of the box and the dirt that will fill it. The siding on the house may prevent the brackets from evenly adjoining the house exterior. To accommodate the siding, make a cardboard template that will help to cut notches into the bracket.
Certain types of wood aren't suitable for this project. Pine rots easily and oak turns black when wet, so they are not good choices. Cyprus has a high oil content which makes it weather-resistant. Cedar is both decay-resistant and affordable; it can be left natural or can be stained, and it is available in smooth or rough finishes. Teak and mahogany are beautiful, but expensive.
After determining the full width of the planter, cut front and back boards to the appropriate length. After cutting the ends, trim 1" x 8" piece of lumber to 7 inches wide.
Mark lines with square and use a belt sander to bevel corners at a 45-degree angle -- this will reduce splintering. Remove any additional sharp or rough areas. Repeat beveling for all corners. Smooth with sanding block.
Cut a slot at the end of the two boards to adjoin sides and increase strength. Measure width of side boards for slot and mark board 1/2" from end. The slot can be cut with a handsaw and chisel, a router or a radial-arm saw. If you use a radial-arm saw, set the blade to cut a 1/4" groove. Repeat cutting until groove is completed. Use chisel to clean up slot.
Cut scrap wood left over from cutting down width, and already 7" high for end pieces. These pieces are cut to 7" long. Apply glue to the slots in one of the longer pieces the front or back. Add end pieces to the slot and tap into place (Image 1). Pull remaining long pieces to the end pieces. Use bar clamps to secure all pieces during drying (Image 2).
Measure the bottom piece for snug fit. Cut to proper width and length. Apply a bead of glue inside the bottom edges of planter. Align the bottom with bottom edges of front, back and side pieces. Use mallet to tap into place. Use screws to secure bottom piece to edges of side, front and back pieces.
Drill drainage holes in bottom, spacing about 12 inches apart, beginning about 6 inches from each end.
After the box planter is assembled, cut brackets to support the weight of the planter, dirt and plants and secure to the home’s exterior. This design uses 2-inch thick wood and borrows a design already on the front porch. The brackets can be cut in any design desired, but this project uses the cardboard template to cut the notches necessary for the brackets to fit flush with the exterior surface.
Trace around cardboard template onto wood after determining the height and width for the brackets (Image 1). Use a handsaw to cut bracket curve and notches for siding profile (Image 2). Remove any marks with a sander (Image 3). Finally, countersink holes on each bracket's edge for screws to be added during installation. Repeat process to complete two additional brackets.
Once the planter is completed, a finish can be chosen to protect the wood and add color if desired. Plain wood can turn gray, dry out and rot without protection, so stain or paint is vital to this project's longevity. Although paint initially provides good protection and good coverage, it can later peel — it's an option with a short life. Clear varnish looks good on smooth wood, but on some woods — such as the rough cedar we are using
Position each bracket where needed to provide good support here there’s one at the middle and each end. Use a level to make sure the top of each bracket is correctly aligned. Drill 3-inch screws into countersunk holes to attach bracket to house exterior. Use wooden buttons to hide screws and fill holes
Add remaining brackets and place box atop the brackets. Add dirt and plants or potted plants as desired.