How to Build a Cedar Planter Box

Lucy Fitzgerald
·5 min read

Planter boxes are a great alternative to conventional gardening, especially if you live in an urban area or want to showcase your plants on your porch or along a walkway. They also help you conserve water by retaining it close to the plants’ root systems. Root health is also improved by the simple fact that weeds will have a hard time flourishing in a raised, contained environment.

You can use special soils or fertilizers for your container plants that might not be suitable for other plants in your in-ground garden. Neighboring plants won’t soak up all of those good nutrients for themselves, either. Container gardening is a smart method of growing foods like tomatoes, beans, lettuce, and peppers as well. Not only does the height of the planter protect the plants from hungry animals, but you can set it close to your kitchen door for quick and easy access. And don’t forget about herbs, either: Basil, rosemary, thyme, and oregano flourish in containers.

To grow your container garden, build this DIY planter box. It requires few tools and can be accomplished in a day. Make sure to use wood rated for outdoor use, like cedar. Follow our step-by-step tutorial to make your own cedar planter box.

How to Make a Cedar Planter Box

Tools Needed

  • Tape measure

  • Pencil

  • Table saw

  • Carpenter’s square

  • Power drill

  • Countersink or 3/16-inch bit

  • Clamps

  • 3/8-inch spade bit, optional

Materials Needed

  • 1-inch x 6-inch x 8-foot cedar boards (x3)

  • 1-inch x 2-inch x 6-foot cedar boards (x2)

  • 1-1/4-inch deck screws

  • 2-inch deck screws

Cut List

Walls:

  • 1-inch x 6-inch x 18-1/4-inch (x6)

  • 1-inch x 6-inch x 16-5/8-inch (x9)

Braces:

  • 1-inch x 2-inch x 14-inch (x4)

Base:

  • 1-inch x 2-inch x 16-1/2-inch (x2)

  • 1-inch x 2-inch x 14-3/4-inch (x3)

Step-by-Step Directions

Follow these simple how-to instructions to assemble your cedar planter box. You should be able to complete the project in a day.

Step 1: Form the Base

On your work surface, lay two 1-inch x 2-inch x 16-1/2-inch boards parallel to each other, then lay two 1-inch x 2-inch x 14-3/4-inch boards perpendicular between the longer boards to form a square. Lay three 1-inch x 6-inch x 16-5/8-inch boards flat across the top of the square to form the base of the planter.

Step 2: Shape the Walls

Set two 1-inch x 6-inch x 18-1/4-inch boards on end flat against two parallel sides of the base frame. Set two 1-inch x 6-inch x 16-5/8-inch boards on edge in between them against the other two parallel sides to form the first course of boards making the walls of the planter. Use a carpenter's square to make sure the corners are at 90-degree angles. Once in position, use clamps to hold the boards in place.

Step 3: Drill Pilot Holes in the Braces

Measure and mark pilot holes on all four of the 1-inch x 2-inch x 14-inch braces. Starting from the base of one brace, mark two pilot holes where the brace will meet each of the 6-inch wide boards on each side of the wall. (Our first two holes were placed about two inches apart due to the height of the base of the planter, then about three inches apart for the remaining two sets of holes.) Repeat on the other side of the brace, then on the remaining braces. Using a 3/16-inch bit or countersink tool, drill pilot holes into the braces.

Step 4: Attach the Walls

Starting with the first course, square one brace in one corner of your planter. Use 1-1/4-inch deck screws to attach the brace to the side board through the wider side of the brace. Use 2-inch deck screws to attach the brace through the narrower side of the brace. Repeat with remaining braces, making sure that the longer sides of the braces are all parallel to each other.

Rotate the courses as you build up the walls, so that each side of the planter has alternating 18-1/4-inch and 16-5/8-inch lengths.

Step 5: Screw in the Base Pieces

Carefully flip the planter over. (The center baseboard may fall off since it has not yet been attached.) Rearrange the bottom frame pieces as necessary. Screw the bottom frame into the planter sides with 1-1/4-inch screws. Flip the planter right-side up again, and use 1-1/4-inch screws to screw the bottom boards into place along the edges and into the bottom frame pieces.

Step 6: Attach the Bottom Brace

Flip the planter back over. Lay the last 14-3/4-inch base piece across the middle of the bottom, perpendicular to the baseboards. Attach with 1-1/4-inch screws.

Step 7: Drill Drainage Holes

We highly recommend taking the extra step to drill drainage holes into the bottom of your planter box, as proper drainage is integral to the health of your plants. If you do not want to drill drainage holes, you can fill the bottom of the planter with rocks or stones. This helps to keep some space open for water to drain out of the soil below the roots, allowing for airflow and preventing rot.

If desired, drill drainage holes through the bottom of the baseboards using a 3/8-inch bit.