CC-15 – Drains Through or Near Foundations Detail

Drains through foundations detail: This drawing illustrates three common situations where below-ground drainage pipework passes through, beneath or close to building foundations.

The first arrangement shows a drain beneath a structural lintel or bridge, with clearance around the pipe, a short rocker pipe and flexible joints close to each wall face. The second shows a foundation bridging a drain trench without bearing on the pipe, joints or loose backfill.

The third arrangement identifies the foundation bearing zone to avoid when a drain runs parallel to a wall. Supporting notes cover granular bedding, pipe flexibility, sealed DPM penetrations and protection of foundation stability. Structural advice may be required where drainage enters the bearing zone. For statutory guidance, see Approved Document H on GOV.UK, or review the foundation principles in our strip foundation guide.