Build a Planter Box - Canadian Woodworking Magazine

Outdoor Project: These solid-looking planter boxes can be custom sized to fit that perfect spot in your yard. The build process is fun and easy, and the finished look is great.

Build a Planter Box

Build a Planter Box

Photos by Heather Craig


We have this somewhat awkward open area in our backyard. When we bought the house it was pavement, and we soon learned it created an unbearable heat sink. Seven years later, we finally did something about it. We needed some colour in the space, and decided on cedar planter boxes.
As you can imagine, cost was a significant factor. When I explained my project to a sales associate at the local home improvement store and expressed my concern about the cost, they told me about ‘cull’ lumber. These stores like to keep their lifts of lumber looking pristine and remove the cull lumber, selling it at a significant discount, up to 70 percent off. This helped out with bringing the cost down quite a bit.
Once I had collected enough lumber, I finalized the plans for the planter boxes. I decided on two small boxes measuring 25"W × 25"L × 21"H and a large planter box 25"W × 25"L × 33-1/4"H. I also decided to put the shelf near the top of the box so that the additional weight of soil would be minimal or a saucer and pot could be used.

Trim the 4×4s

First I cut the side rails to length. I then dry fit them, placing them with their ends alternating. I wanted to make sure the imperfections were on the inside or underside of the box and that the color was relatively even. I mixed the light and dark sections of wood.
Once I was satisfied with the way it looked, I labelled each piece. Start by labeling the end of one of the bottom pieces; this will be the starting point. Then label each piece sequentially from left to right and bottom to top. At this point you should also decide the level to insert the shelf and mark it. This way you will remember to install the shelf pieces before you have all the side rails screwed together. I chose to put mine three 4×4s down from the top, leaving me with 11-1/2" from the shelf to the top of the finished trim.

Cut and Stacked – With all the side rails cut to length, Craig dry fit them and marked where each one would go. This helped with final assembly.

Caster holes

Next I disassembled the mock-up and drilled the recesses for the casters. Start by marking the center. The holes should be the middle of the width of the 4×4, and 1" from the end. Secure the board to the drill press and cut the hole with a 3" Forstner bit to 1-1/8" deep. This will allow the casters to protrude about 3/4" past the bottom of the box, appearing hidden. You may end up with different casters, so drill a test hole in some scrap and check for depth, if that’s the case. If placing the planter boxes on a firm surface, you may want to recess the casters another 3/8" so they don’t show.
Large Recess – A recess to hide most of the caster is drilled into the underside of the lower side rails. Be sure to clamp the workpiece in place for this operation or the bit could catch and cause the workpiece to quickly move.

Final assembly of the planter box

Once all four bottom pieces have been bored for the casters, begin assembling the side rails. Start with the piece with the marked end and lay out the first layer according to your labeling. Lay the second layer on top. Secure them in position with clamps and drill 1/2" holes to a depth of 1-1/2". Then, using 4" deck screws, attach the side rails through the counter-sink holes. Continue securing the layers until you reach the level where the shelf will be installed. Offset the screws each level so they don’t contact each other.
Good Side Out – The interior of one of the taller planter boxes is shown here. Any knot-free, or otherwise visually appealing, faces are aimed outward for people to see.
Layer by Layer – Stacking layers of side rails on top of each other, then screwing them in place with 4"-long screws, secures everything together. Clamps help bring the joints tight before adding the screws.

The shelf

I used cedar fence boards for the shelf. With a rabbet bit secured in your router, rout a rabbet that will allow the top surface of the fence boards to sit flush with the upper surface of the layer of side rails. This might have to be done with a few passes. You could also machine stop dados with your table saw. Cut the fence boards to size, and place in the groove. They should be flush or ever-so-slightly below the top of the 4×4. You don’t need to fasten the fence boards in place, as the next layer will take care of that, but if you feel the need to, a single nail near both ends of each board will do the trick.
Continue adding the side rails as previously described, until they’re all installed in place.
Routed Rabbet – A rabbet to house the shelf boards is routed to the inside corner of one of the side rail layers.


Once you have attached the top layer of side rails, flip the box over and install the casters.
I used 1-1/2" casters, two swivel and two stationary. This allows the box to be easily moved without lifting them. I find the swivel casters allow it to be turned easily, and the stationary ones help prevent it from rolling away. Center the casters and screw in place. Make sure the stationary casters face the same direction. Before screwing down the swivel casters, rotate them to make sure they move freely and don’t contact the edge of the cedar.
Flip the box right side up, and fit the trim on the top. I used 1x6 cedar decking. Mitre the corners and dry fit. Once fitting to your satisfaction, glue the corners with exterior glue and clamp them together, essentially make a rough picture frame. Attach the top frame assembly to the box with 2-1/2" deck screws. Countersink the screws so they can be hidden with plugs. I cut the plugs from leftover cedar so that it blends in better with the trim.
Remember to drill a drain hole in the shelf. I put the planters in place. Then I poured water in the box to see where it pooled, removed the water and then drilled the hole. Once dry, I proceeded with the finish.
Add Casters – With the planter upside down, Craig attaches the casters in their cavities, and ensures they spin freely.
Top Frame Assembly – After mitering and assembling the top frame, Craig sets it on top of the planter to dry.

Apply a finish to the planter box

I always struggle choosing a finish, especially when it’s for a project that will live outdoors. I love the look and ease of application of penetrating oils such as teak oil. They don’t crack, peel or chip since the finish is in the wood. But depending on the exposure to sun and rain it may need recoating one to two times a year, and I’m just not likely to do that. The alternative is to use spar varnish, which builds up a layer on top of the wood. They may be able to withstand the impacts of sun and rain a little longer, two to four years, before breaking down. However, there always seems to be a section that breaks down sooner than the rest. When I try to repair just the section that has deteriorated, it never looks right. I’m not keen on sanding them all down and recoat them every two years or less.
So, after some research, I decided to mix teak oil and spar varnish 50/50 and apply it to the boxes. I applied three coats, sanding lightly between coats and wiping off the residue before allowing it to dry. The rich color of the cedar is prominent and there is still some protection with this finish.
These planter boxes can be made to suit just about any area of your yard. Even a few, all at varying heights, widths and lengths, can make for a dynamic look if done tastefully. Flowers add a lot to a home, and with our summers so short, we shouldn’t take the nice weather for granted.
Top it Off – With the frame dry, Craig fixes it to the top of the planter and plugs the holes.


Wall Planter (June/July 2008)
Garden Trellis (Aug/Sept 2012)
Materials for the Great Outdoors (Oct/Nov 2012)

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