Strip and trench fill foundations

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4.3.6Services and drainage

All strip and trench fill foundations shall be installed to:

  1. adequately protect existing services and ground water drainage
  2. make allowance for drainage and other services.

Adequately protect existing services and ground water drainage

Any existing services, such as cables, water pipes or gas mains, may need to be supported and protected. Services should not be rigidly encased in the foundations, and drains which are redundant should be cut open and filled or removed. Precautions should be taken to accommodate the effects of settlement where drains run under, or near to, a building.

Provision should be made to divert or protect any existing ground water drains affected by excavation work.

Make allowance for drainage and other services

Where services are to pass through or above foundations, provision should be made for suitable ducts or lintels to enable later installation.
Strip foundations
Services should not pass through strip foundations but through the masonry above. Adequate lintels should be provided in the masonry.

Trench fill
The load-bearing capability of foundations should not be affected where services pass through. Services should be either sleeved or pass through a suitably strengthened opening in the foundation. This is to ensure that differential movement will not damage services.

For drainage, it is important to leave sufficient space for movement to ensure that the drain is capable of maintaining line and gradient.