Clay

Landscaping on clay ground requires special considerations. If you’re thinking of contracting landscaping services, or doing it yourself. This is important reading…

Whilst it is more stable than sandy soil, the problem is that Clay expands and contracts with moisture, or a lack of it. This results in ground movement, which can destabilise the work you’ve had done - normally in the first year or two. Commonly seen in patios cracking with the heave and haul of the ground.

An unstable patio is the last thing you want, so it better to prevent rather than eventually replace.

The basics of non-woven membrane and well compacted Type 1 MOT (50mm layers) are even more critical with clay soils as the mineral composition of clay can basically weaken the cement over time or inhibit its curing. A concrete / mortar slab of any form should never ever be in direct contact with clay!

Beyond this absolute basic of patio installation, we always go further to safeguard the installation on clay ground. For one, we install a ‘capping layer’ beneath the membrane. This membrane is then deeper… built up in layers to at least 150mm. Furthermore, concrete fibres into mortar strengthens the mix.

In addition (where a hard clay pan has been particularly close to the sub base layer) whilst excavating as much as possible, biaxial membrane is an additional safeguard or sometimes steel mesh.

Another safeguard is to prevent the natural presence of the hydrating water being capped off from the clay, resulting in shrinking. So, an additional measures to safeguard the installation may include flexible land drains under the subbase… or designing in water-absorbing shrubs if the landscaping will lead to the clay becoming too wet thus expanding.

Basically, different measures can be used to maintain the natural hydrology of the ground and add structural strength.

These are the aims when landscaping on clay soils for a long lasting, strong and durable installation.