This Instructable will show you how to make a modular concrete planter using cardboard and tape. These planters can be arranged in multiple different ways giving you the freedom to expand your plant collection.

Supplies

Cardboard
Parcel tape
Hot glue gun
Craft knife
Pencil Ruler
Concrete [Casting material]
Gloves

Step 1: MOULD TEMPLATES

Small square - Approximately - 450ml of concrete
Large square - Approximately - 650ml of concrete
Rectangle - Approximately - 650ml of concrete

For this mould demonstration I will be making the small square however, the same manufacturing principles apply to the other shapes.

Step 2: MAKING THE MOULD - INSIDE SECTION

The inner section is made out of 2 components. Mark and cut out two 60mm x 150mm cardboard sections making sure that the crease is in the centre.

Step 3:

Line the two components up next to each other and tape them together.

Step 4:

Once the two componets are connected, tape them together from the inside shown in the first image.

Step 5: SEALING THE CONTACT SURFACES

Once you have made the square, cover the full outside surface in parcel tape.

Step 6: OUTSIDE SECTION

The outside section is made out of two components. Mark and cut out two 60mm x 280mm cardboard sections making sure that the crease is in the centre.

Step 7: SEALING THE CONTACT SURFACES

This time you want to parcel tape the inside of the square making sure that the full surface is covered.

Step 8:

You will now have a large square with tape on the inside surface and a small square with tape on the outside. This tape prevents the mould from soaking and allows for the cast to have a smooth and even surface.

Step 9: SEALING

Place the larger square on a plastic sheet and hot glue around the base and corners of the mould. It is important to seal all of the edges otherwise the mould will leak.

Step 10: SEALING

Once dry, place the smaller square in the centre of the large square and hot glue in place. Making sure that all edges are sealed.

Step 11: MOULD SUPPORTS

Depending on the thickness of your cardboard, you may need to create a support which will help prevent the mould from bending under the concretes weight. Line a thick piece of cardboard against the top of the mould and mirror the cardboard walls. Cut out the wall spaces and place the support over the mould like shown in the photos above.

Step 12: CONCRETE MIXING AND POURING

For this mould you need approximately 450 ml of concrete.

When mixing your concrete you want to make sure that it is not too thick so you are able to pour it easily into the mould. You are able to add coloured pigments to the concrete if desired.

NOTE - Always wear gloves when using concrete.