5.3.8 Durability
Drainage systems shall be adequately durable and protected against damage. Issues to be taken into account include:
- loads from foundations
- bedding of pipes
- loads from overlying fill and traffic
- chemicals in ground and groundwater.
5.3.8.1 Loads from foundations
Drains should be located so that foundation loads are not transmitted to pipes. Where drainage trenches are near foundations:
- foundation bottoms should be lower than adjacent trenches, or
- the drain should be re-routed to increase separation.
Where the bottom of a drainage trench is below foundation level, the trench should be filled with concrete to a suitable level.
Figure 8: Pipe protection in close proximity to foundation

Figure 9: Pipe protection within influence zone of the foundation

5.3.8.2 Bedding of pipes
Bedding should be in accordance with Clause 5.3.15.
5.3.8.3 Loads from overlying fill and traffic
Special protection may be required where pipes are near the ground surface or where they could be damaged by the weight of backfill or traffic load from above.
For flexible pipes, and where greater safety is needed, the bedding class and grading of backfill should comply with BS EN 13242, BS EN 1610 and BS EN 752.
When using proprietary systems assessed in accordance with Technical Requirement R3, pipes should be supported accordingly.
5.3.8.4 Chemicals in ground and groundwater
Where the ground or groundwater contains sulfates, concrete and masonry work may require special precautions.
Last updated: 2nd January 2025