Permeable paving

Permeable paving is a surface system that allows rainwater to infiltrate through the joints or matrix of the paving into a storage and infiltration sub-base below. It is a key sustainable drainage system (SuDS) technique widely specified for new residential and light commercial developments across Greater London under Building Regulations Part H3 and local planning requirements. The system normally comprises concrete or clay block paviors with widened joints filled with clean angular grit, laid over a 200mm to 350mm crushed stone sub-base. Where ground conditions permit, water infiltrates directly into the subsoil; where they do not, the sub-base discharges through a controlled outlet to sewer or watercourse. Permeable paving reduces run-off, supports flood risk management and is generally permitted for front driveways without planning permission, provided design guidance is followed.