How to Make Concrete Flower Boxes or Planters
With little to choose from in stores, this project shows how to make a stunning concrete flower box or container for the garden, patio or deck.
30/11/2023
diy carton crafts
This concrete planter box is so easy to make you will most likely want to make a few for your home and all you need to make this concrete planter box is cement, pieces of cardboard and some offcuts of shutterply and PVC pipe. It is so easy that you can start this project on a Friday and it will be ready for use by Sunday!
The corrugated cardboard lends itself to the unique design it leaves on the outside of the concrete planter box and gives the planter box a unique and contemporary design that you won't find in any garden centres.
The nice thing about this project is that you can easily modify the measurements to make concrete planter boxes of any size for indoor and outdoor plants and because it is concrete it will last a long, long time.
YOU WILL NEED:
16mm Shutterply sheet or half sheet
Corrugated cardboard
Bucket or container for mixing
Cement
Trowel
OPTIONAL: Brackets, threaded rod and nuts **
4 x 45mm cut screws
PVC pipe 20mm + 50mm offcuts
Wire fencing staples
**A better alternative for this is to use a drill and screws to fasten the form or mould together - or use a nail gun.
TOOLS:
Jigsaw, table saw, circular saw or handsaw
Drill and bits to assemble the form
Craft or utility knife
Tape measure and pencil
Rubber mallet
Spirit level
Gloves
HERE'S HOW:
Step 1 - Make the Form or Mould
For the concrete box or planter, the first thing you need to do is to make the form or mould in which to pour the concrete. The height of the outer frame is 200mm while the inside dimensions of the outer frame are 150 x 380mm which you can modify to make a box or planter of any size you want.
Cut corrugated cardboard to fit snugly on the inside of the outer frame. This will add unique detailing to the flower box once completed. DO make sure that the edges where the cardboard meets is neat as this will show on the outside once the box is finished.
GOOD TO KNOW
The inside dimension of the outer frame for the box or planter is 150 x 380mm with a height of 200mm.
The inside frame needs to be smaller than the outer frame as this will create an open space inside the box as well as provide the base. Calculating that the thickness of the concrete box is 20mm all around the inner box dimensions are 110 x 340mm. The height of the inner box is 180mm which allows for a 20mm thick base.
GOOD TO KNOW
The dimension of the inner frame for the box or planter is 110 x 340mm with a height of 180mm.
The inner box is filled with sand and you will discover why in a later step.
GOOD TO KNOW
When I was going through this project, I could not determine any use for the steel frame, threaded rods and nuts. If the outer frame is screwed together properly, this setup is not necessary.
Step 2 - Mix and pour the cement
Combining water and cement, the consistency should be slightly runny so that it will easily flow into the form and fill corners. It also needs to be runny enough that it takes the shape of the corrugated cardboard that is on the inside of the frame
After pouring the cement into the form, use a rubber mallet to tap around the outside to loosen any trapped air bubbles. Also use your trowel to smooth off the bottom of the box, as shown below.
Step 3 - Add the final details
GOOD TO KNOW
Allow the concrete to harden for approximately 2 hours before moving on to the next step.
The concrete planter needs feet to be added to the base and this is easily done with wire fencing staples as shown above and cut sections of PVC pipe shown below. The pipe offcuts are filled with cement and levelled off. Use a spirit level to ensure that the legs are the same height.
Use the 20mm pipe to create a drainage hole in the base of the box.
Step 4 - Removing the form and finishing
GOOD TO KNOW
Leave the concrete to cure for 2 to 3 days before you remove the forms.
Flip the box over and use your trowel to remove the sand from the inner box and remove the inner box frame and then remove the screws to release the outer frame. It doesn't matter if the cardboard stays in place at this stage.
Wet the box with a mist of water to make it easier to remove the cardboard around the outside of the box. You can peel this away and use more water until it is all removed.
The concrete box or planter is now finished and ready for you to add your favourite plants.