What Is a Soakaway?
Written by James Walker · Last reviewed 16 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
A soakaway is an underground pit or crate structure that collects rainwater and lets it disperse gradually into the surrounding ground, rather than discharging it into a drain or the road.
Where they are needed
Driveways. A soakaway is one way of satisfying the requirement for impermeable front surfacing over 5 square metres, by keeping run-off on your own land.
Extensions. A new roof adds rainwater the existing drainage was not designed for, and building control will want to know where it goes.
Anywhere surface water cannot go to a drain, either because there is no capacity or no connection.
Whether the ground suits it
Soakaways only work where the ground drains. Clay soils drain poorly, and a soakaway in heavy clay can fill and stay full.
A percolation test establishes whether the ground is suitable and how large the soakaway needs to be. On anything substantial this should be done rather than assumed.
Position
There are minimum distances from buildings, water discharging close to foundations is exactly what you do not want, and it can cause subsidence or damp.
If a contractor proposes a soakaway tight against the house, question it.
How it works
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