Waterlogged garden? Fixing drainage on London clay

Much of South West London sits on London Clay. It holds water, cracks in dry summers and turns lawns and patios into puddles after heavy rain. If your garden stays wet for days, drainage needs to be part of any new design.

Signs of a drainage problem

• Puddles that sit on the lawn or patio for hours or days after rain.

• Moss, soft spongy turf and plants that rot rather than grow.

• Water running towards the house or pooling by airbricks and doors.

• Green algae on paving that never seems to dry out.

Solutions that work on clay

• Falls on paving: every patio should slope gently away from the house so water runs off rather than sitting on the surface.

• Channel or slot drains: a linear drain at the edge of a patio or at a door threshold collects surface water and carries it away.

• French drains: a gravel-filled trench with a perforated pipe collects water from a lawn or border and moves it to a suitable outlet.

• Soakaways: these let water disperse into the ground, but on heavy clay they need to be sized carefully, and in some gardens they simply cannot drain fast enough.

• Permeable paving and gravel: these let water pass through rather than run off, and are often the simplest option for paths and front gardens.

Plan drainage before you build

Drainage is far easier to install while a garden is being rebuilt than to retrofit under a finished patio. On every garden we build, we plan where the water will go before the sub-base goes down.

Need help with a wet garden?

Koniu Construction designs and builds gardens, patios and paths across South West London and Surrey, with drainage planned in from the start. Tell us about your garden.