To build a planter box on concrete, first you will need to find some wood to use for the frame to construct it. Once you have the wood cut, set it up on top of your pouring slab. The frame can be built in any size that you want and should measure out from corner to corner how wide and long you would like your planter box to be. Use a compound miter saw or table saw to cut a four-foot, 4×4 treated post. Cut the post in half and create four 3×4-inch posts. Now cut two 3×4-inch boards long enough to span from one end of the outside wall to the other, with a few inches of overhang at each end. Screw these onto your plywood platform and place it on the post tops.
The vast majority of backyard gardens are planted in the ground, but that’s not the only option. Planter boxes can be constructed out of nearly any material and placed anywhere you want. They can hold soil and support vegetation, so whether you have a small backyard or an apartment with a balcony, planter boxes are a great way to grow your own food or flowers.
Step 1. Select the location of your planter box.
The location of your planter box should be in a sunny spot, near a water source, power source and hose. The planter box will be heavy so it is best to have it close to the back door of your home.
You may have to do some digging before you can put in your new raised garden bed or container garden. Soil composition varies depending on where you live but most soil is made up of three parts: sand, silt, clay. A few inches below the surface there are layers of roots from trees and other plants that grow there over time. Digging down too far may expose these roots which could damage them if they’re still alive.
Step 2. Determine the dimensions of your planter box.
For this project, your planter box dimensions should be at least 2″ wider than the width of your lumber and at least 1″ taller than the height of your lumber. For example, if you’re using 4x4s for all sides (and we recommend that), your planter box should be at least 8″ wide by 10″ tall.
Use a tape measure or ruler to determine these measurements:
- Measure the length each piece of lumber will be cut down to (the three pieces for each side) and mark where you’d like them cut with a pencil and straight edge.
- Use a measuring tape to measure around each side of the lumber; this is how wide it needs to be in order for everything else to fit properly into place (as well as how much pressure will be put on those corners).
Step 3. Choose your lumber and fasteners.
Once you have your lumber, you need to choose the fasteners for your planter box.
Wood glue is a great choice for these projects because it helps hold the wood together and gives it extra strength. A hammer can be used to bang in nails with more force than would otherwise be possible by hand.
For a speedier approach that doesn’t require as much labor, consider using a nail gun or screw gun instead of hammers and nails alone.
Step 4. Cut your lumber to size.
The next step is to cut the lumber to size. Use a miter saw, circular saw or jig saw to do this. You can also use a hand saw if you want; it will take more time and effort but it’s possible.
Cut your boards by measuring and marking each board as needed before using the appropriate tool to make sure they’re all even lengths and widths.
Step 5. Assemble the sides with glue, nails and/or screws.
- Use glue to attach the sides together.
- Use nails to attach the sides together.
- Use screws to attach the sides together.
In addition, you can use a combination of any of these methods in order to ensure that your planter box is as sturdy as possible.
Step 6. Attach the bottom panel with glue, nails and/or screws.
Once you’ve laid out your planter box, it’s time to attach the bottom panel. The way you do this will depend on the type of wood you’ve chosen for your planter box. If you’re using plywood or another thin material that can be nailed through without much trouble, use a hammer and nails to secure it in place. If you’re using thicker hardwood boards and don’t have access to power tools (or just don’t want to go through all that effort), screwing is also an option. You could even use both methods if needed—just make sure everything is tight and secure.
The bottom panel should meet flush with the top edge of your raised bed frame so that water doesn’t pool up inside.
Step 7. Drill drainage holes (optional).
- Drill holes in the bottom panel of your planter box. These can be any size you like, as long as they are big enough to allow water to drain out of the planter box. The exact measurement will depend on how much rain or snow falls where you live, so measure it out and use a drill bit that will work for this purpose.
- Drill holes in the sides of your planter box near its top edge (the part that isn’t going to be underground). Again, measure out what size hole works best for you — if there’s enough rain/snow coming down from above ground level that it would cause problems without drainage holes, then by all means make them big enough to do their job.
- Drill two more sets of drainage holes at opposite corners on both sides: one set should be just below where soil can accumulate within soil bags; another should be about 6 inches below those first two sets.* Put soil into each bag until it’s full but not packed too tightly (more air = better drainage).
Step 8 . Insert the plant liner or plastic bag containing gravel and compost (optional).
This step is optional. If you’re using a plant liner, make sure it fits the planter box and hangs over a couple of inches on all sides. If you are using plastic bags to contain your compost and gravel layer, use a bigger one than necessary so that it can be filled with dirt during this step.
Remember to put plants in your planter box.
Once your planter box is complete, you can add plants to the display. There are many options for planting your planter boxes. Some of them may already be in your yard and just require some creative arrangement or placement. You could also choose to buy plants at the store or grow your own from seeds or cuttings.
When it comes time to plant your planter box, there are three main seasons: spring, summer, and fall/winter. Spring would be best because this is when most roots begin growing so they will have time to establish themselves before needing water (which can be hard in a drought).
Final words
Now that you have your planter box built on concrete, you can sit back and enjoy the fruits of your labour. Don’t forget to check out our other articles on planter boxes if you need more inspiration or ideas for your next project.
