Soil Concrete
If you are looking for a paving feature or different style of laying paving – one which greatly
reducesthe amount of cement required to construct a firm base, with all paving stonessecurely
fixed into place, the use of ‘soil concrete’is a traditional method, frequently used to lay crazy
paving (see Crazy Paving).
Excavate to suitable depths to enable the thickness of the stone being laid – soil concrete may
be used to support new or reclaimed setts, up to 20cm deep or more, as well as crazy paving
style plates of irregular shaped stones – and compact the ground as firmly as possible. Using
a wheelbarrow or mixing boards (in preference to a cement mixer, which will quickly become
clogged) to mix friable soil, free from tree roots and detritus, including stones larger than 10mm,
with ordinary Portland cement mixed with water to create a form of ‘concrete’, using soil instead
of sandy ballast. The usual ratio is one part cement to eight parts soil, although on some soils,
you may need slightly more cement, ascertained by the stickiness of the mixture.
This mix should be gluey, hence the need to use boards or a barrow, and not a cement mixer.
Once you are happy that the cement has been blended in with the soil, lay the mixture into the
prepared area, ensuring a minimum depth of 75mm under each slab or piece of stone, in the
same way as you would lay a paving slab, ensuring full contact between the stone and laying
bed, by gently hammering the stone into the mix by use of a rubber maul. Some soil mixes
may become too dry, especially if you are working with sandy soil. In this event, dip the stone
being laid into a bucket of water, or brush enough water onto the back of the slab to create a
stickier mixture which will grip the stone more securely.
Once dry and firm, brush in either grit or dry soil to act as a ‘pointing’ material. Planting
pockets may be left in the laying bed material as required to receive alpines, creeping herbs
and other small plants. Due to the nature of the soil concrete, mosses, lichens and other low
growing plants should soon colonise the gaps between the slabs or pieces of stone, creating a
firm yet visually soft garden feature, either as a seating area or pathway
