Build your own planter box


A simple planter adds a nice touch inside or outside at your front entrance or in pairs on a deck.

Dwarf conifers, citrus or standard roses all look good in this type of planter. It is a small project and therefore inexpensive to build, but some care is required in cutting the grooves and trenches in the timbers.

STEPS 1 & 2

Materials Required

Any planter will be in contact with soil and moisture, and therefore it is important to use the right timbers which will not rot. These are called “durable timbers” and will last for a long time when exposed to moisture. Typical timbers which are suitable for a planter are – treated pine, cypress pine, jarrah and cedar. The side panels are constructed from readily available ship-lap profile cladding, in either a sawn or dressed finish, as shown in diagram 1.

Tools Required

To build this planter you will need the following tools: power saw, drill & 4mm bit, hammer, tape measure, screw driver, router & straight cut bit and a square. Specialist tools such as the router are not essential but do make woodworking easier and provide a much neater finish to the job. Remember these may be hired from your local Home Store.



Cut each leg to 540 mm length. Each leg is to have two trenches cut along adjacent sides, as shown in diagram 2. This can easily be done with a router, or by running a power saw along the legs several times to achieve the desired dimensions. The trench is to be 20 mm wide and 13 mm deep. If cutting by power saw, clamp the leg in a vice and use a “side fence” on the saw to keep the cut parallel with the leg. The round ends of the trench can be squared up with a chisel. To create the decorative grooves at the top & bottom of the legs, mark them 25 mm from the ends, 6 mm wide and 5 mm deep and cut with a hand or power saw. The top of the legs can now be chamfered with a hand plane or wood rasp.


Side rails

Cut the top and bottom side rails to 432 mm long. The rails need to be grooved as shown in diagram 3. This can be done in the same manner as the trench in the legs - with either a router or a power saw. The grooves run for the full length of the rails.

planter box post

Diagram 2.

Planter box rails

Diagram 3. 


Side panels

Four pieces of panelling are used in each side. Cut all pieces to 368 mm long. The end pieces in each side need to be trimmed so that they fit neatly between the legs, as shown in diagram. 4. These dimensions are only suitable for 140 mm panelling (with 126 mm cover). Other size panelling can be adjusted to suit, with the aim being to end up with a side panel width of 456 mm.


Assemble side panels

Assemble the panel boards into the side panels, using a board without a tongue, two normal boards and a board without a groove. Test fit the rails top and bottom. The side panels should not protrude past the ends of the rails by more than 12 mm. (If they do, trim the end boards again. The grooves in the legs were made 13 mm deep to allow for slight expansion of the side panels when in use.) Round the outer corners of the end boards of each panel and check that they fit easily into the leg grooves.

planter box panels

Diagram 4

planter box diagram

Assemble the side panels


Final assembly

To aid assembly, pre-drill the legs for the nails. Mark lines 70 mm in from the ends and using a 4 mm drill bit, drill through to the grooved faces from the outside, drilling either side of the line on adjacent faces to ensure the nails do not intersect. To assist in locating the rails, mark the legs 50 mm in from both ends on the grooved faces. Assemble the planter box with 50 mm galvanised nails, punching them well into the wood. It is easier to assemble two opposite sides complete and then fit the remaining components in between. The tops and bottoms of the rails should be level with the assembly lines drawn and the panel sides fully home in the grooves. After nailing, clamp the planter box with sash or bar clamps, check to ensure they are square and screw the galvanised brackets to the inside corners, top and bottom, to prevent the nails from pulling out of the end grain during use.


Insert bottom slats

Cut the bottom slats to length and nail in place inside the planter box with 30 mm galvanised nails, leaving a small gap between each for drainage and notching around the corner posts if necessary. Before filling with earth or compost place the box in its intended position, as it will be too heavy to carry. Place a layer of gravel screenings on the bottom to keep the earth from washing through the drainage slits. Note that offcuts of treated pine must not be burned.

Tips from the trade

  • Measure carefully and accurately. It makes all the difference to the end result and it will save miss-cutting expensive timber. Measure twice, cut once.
  • Always plane with the grain. Don’t take off too much with each sweep.
    An easy and accurate way to cut several pieces of timber to the same length is to clamp them and measure and cut them as one.
  • A tungsten carbide tipped blade is recommended for cutting Permapine, as the metal salts used in the preservative treatment tend to dull blades quickly.
  • Stopped trenches are required in the legs. If this project is chosen to be made without a router, an extension on the rip fence will be needed to attach a stop block. Also needed is a chisel to square the ends of the trenches, which will be less than full depth at the ends for some distance due to the curvature of the sawblade.