Why clay is tricky
Clay swells when wet and shrinks as it dries. In a wet winter the ground can be soft and waterlogged. In a dry summer it can crack. A patio on a thin base moves with it.
A deeper base
We remove topsoil and soft clay down to firm ground, then build a sub-base of compacted crushed stone. The depth depends on what we find. A geotextile membrane under the stone can stop clay pushing up into it.
Getting rid of water
Clay drains slowly, so water that runs off a patio has to go somewhere. We fall the patio away from the house towards a border, a channel drain or a soakaway. A soakaway on clay often drains poorly, so a pipe to an existing drain can be a better option, where allowed.
Trees and hedges
Large trees and hedges dry clay out as they drink, especially in summer. A patio close to a big tree is more likely to move. We'll suggest keeping a sensible distance or adjusting the base.
New-build gardens
On new estates, the ground under the lawn is often compacted clay mixed with builders' rubble. We dig it out and start again with a proper base.
Front gardens and planning
Paving over more than five square metres of a front garden with an impermeable surface that drains to the road normally needs planning permission. Back garden patios at ground level usually don't. If you're unsure, ask North Yorkshire Council.