The use of soil concrete is not widely known, although it has been around since Victorian times. The soil should be fairly sandy or friable enough to be able to mix with ordinary Portland cement much as a sand and cement mix would be made, although it is easier to handle when mixed using a sheet of plywood, rather than in a machine due to its sticky nature.
The customer already had a rock feature in their garden, mainly Purbeck, which had been constructed in a fairly amateurish manner, with the reasonable sized boulders being used on one side, with smaller and less attractive stones to the other………..
The brief was to create a seating area, capable of holding a table and chairs without sinking into the ground, yet visually soft enough to match in with the rockery feature, and allow some form of planting to be made. I decided to recommend crazy paving, using soil concrete, and they clients agreed with the principle, although they had never seen it used.
I imported some Purbeck walling stone, as I needed greater depth that would normally be found in the crazy paving material that is widely available, in order to construct a surface that would be solid, without using ordinary mortar. The walling stone was split or riven into plates between 75mm and 150mm, with the new face upwards for a uniform colour and allow weathering to be consistent.
The area was excavated to a depth of 200mm and each stone plate was laid singly, with a suitable amount of semi-dry soil concrete firmly rammed into position as the job progressed. No planting gaps were left empty, with the soil concrete finishing to within 15mm or so from the surface level of each stone.
Once the paving was finished, it was lightly moistened with a hose to ensure a solid contact between the soil concrete and stone, then a layer of screened sandy topsoil was spread over the surface and the project allowed to cure for ten days.
Following a brush down with a stiff broom, the client planted small alpines into any suitable sized gaps, including helexine and thyme, which quickly colonised the seating area.
