Building a Planter Box: A Perfect Weekend Project
A well-built planter box is functional, beautiful, and one of the most satisfying weekend projects you can tackle. Whether you’re adding raised beds to a vegetable garden, building window boxes, or creating a cedar planter for a deck, the construction principles are the same. This guide walks you through a classic cedar planter box from start to finish.
Materials for a 4′ x 2′ x 12″ Cedar Planter
- 1×6 cedar boards — 4 pieces at 48 inches (long sides), 4 pieces at 22.5 inches (short sides)
- 2×2 cedar for corner posts — 4 pieces at 11.25 inches
- 1×4 cedar for bottom slats — 3 pieces at 45 inches
- Stainless steel or coated exterior screws — #8 x 1-5/8 inch (150 count)
- Exterior wood glue (Titebond III)
- Landscape fabric (optional, to line interior)
Tools Required
- Miter saw or circular saw for crosscuts
- Drill/driver with countersink bit
- Clamps (at least 4 bar clamps)
- Speed square, tape measure, pencil
- Sandpaper — 80 and 120 grit
Step 1: Cut All Pieces to Length
Set up your miter saw and cut all boards to length before starting assembly. Cedar is straight-grained and cuts cleanly with a sharp blade. Label each piece after cutting to avoid mix-ups during assembly. Take a moment to check each piece for twist or bow — set aside any boards that are significantly warped.
Step 2: Build the Side Panels
Stack two 1×6 boards for each side panel (two long panels and two short panels). Apply glue between layers and clamp together — this creates a laminated panel that’s strong and stable. Alternatively, secure the layers by driving screws through 2×2 corner posts that will also serve as the corner connections.
Step 3: Assemble the Box
Pre-drill and countersink all fastener holes to prevent splitting. Drive stainless screws through the long side panels into the ends of the short side panels. Use corner posts for additional strength — attach them flush at each interior corner with glue and screws. Check for square diagonally before the glue sets.
Step 4: Add the Bottom Slats
Space 1×4 bottom slats with a 1/4-inch gap between each for drainage — a planter box that doesn’t drain freely kills plants from root rot. Secure each slat with two screws at each end. Do not use a solid plywood bottom — drainage is non-negotiable for plant health.
Step 5: Sand and Finish
Sand all exterior surfaces starting with 80 grit to remove tool marks, then finish with 120 grit for a smooth surface. Cedar weathers naturally to a beautiful silver-gray without finishing, but an exterior oil (Cabot Australian Timber Oil, Penofin) extends life and maintains color. Apply two coats to all surfaces before filling with soil.
Find the drills, saws, and exterior fasteners for this project at Pro Tools Hub.
