Drainage below ground

Also see:

5.3.14Protection of pipework

Drainage systems shall have pipework adequately protected against damage. Issues to be taken into account include:

  1. pipes passing through substructure walls
  2. pipework under finishes
  3. movement joints.

Pipes passing through substructure walls

Where drains pass through structural elements; allowance should be made to accommodate movement.

Pipes passing through substructure walls should accommodate movement by:

  • a 50mm clearance all round
  • a sleeve, with 50mm clearance all round and suitably sealed, or
  • bedded pipes, connected on both sides of the wall with flexible joints located a maximum of 150mm from the face of the wall.

Flexible joints should be made in accordance with the pipe manufacturer’s recommendations.

Pipework under finishes

Where drains pass under roads and drives, the final compaction should be sufficient to prevent later settlement.

Movement joints

Where rigid pipes are to be encased in concrete, movement joints should be:

  • provided around the spigot next to the socket either at 5m maximum intervals or at each joint
  • 13mm thick compressible board.