Constructing bespoke raised planters without the requirement for foundations is usually achieved by using timber or perhaps metal – both types often purchased as products, and not as bespoke units. Obviously, if you are a talented carpenter, and have the facilities, tools and workspace to create planters, then you have an advantage.
The raised planters in the photographs were constructed using 100 x 50mm treated softwood for the main frame, clad with shuttering ply – 18mm, waterproof and inexpensive, with a false floor, raised 50mm off the ground to allow for drainage, with 25mm holes drilled at 20cm centres.
Taking care to construct a timber planter with overall dimensions to suit the outer cladding – in this case, Travertine slabs – without the need to make any cuts in the slabs, staple expanded metal sheeting to the whole of the outer skin of the ‘box’ and ‘glue’ the paving slabs into position with a wet strong mortar mix (3 parts soft builders sand to one part OP cement) with a full bed, combed over the whole surface area of the slab and gently tapped into position, ensuring a full bond between the slab and the plywood/expanded metal.
I have shown the planters, now three years old, having been through two very cold winters, awaiting replanting and new compost, rather than fully planted and looking very pretty with annuals and alpines. These planters are situated near to swimming pool, and look clean and tidy during the summer months.
The only reason I used Travertine was because I had spare slabs! However, I suggest that a natural stone slab would always be preferable to a man- made unit in this situation. Each planter took around four hours to complete from scratch, using only a battery operated drill, hand saw and tin snips for the expanded metal (plus a hammer and trowel!)