Drainage problems close to foundations can be very costly to rectify.

The proximity to the property can complicate any excavation works and even affect the structural integrity of the foundations.

This is a worst case scenario but it could still happen, learn how to avoid this costly issue.

It may sound simple but the easiest way to avoid issues with drainage pipes running adjacent to foundations is to reroute their trenches further away from the foundations.

Obviously this is not always practicable.

The key thing to remember is that where drainage trenches are close to foundations it is vital that any loads are not transferred into the drainage trench excavation from the foundations. The best way to achieve this is by increasing the foundation depth.

Where the bottom of the drainage trench is to be below foundation level it should only be done in stages (like underpinning stages) and be filled with concrete to the appropriate level as shown in the diagram below.

Where the drainage passes through the wall of the property measures need to be put in place to allow for movement such as:

  • Providing 50mm clearance around the pipe
  • Installing a sleeve with 50mm clearance

For more information on drainage and building services check out Chapter 9 of our Technical Manual.

Check out our blog How to Deal with drainage issues to find out how to get your drainage right to avoid common claim issues.

By Craig Ross

Please Note: Every care was taken to ensure the information in this article was correct at the time of publication. Any written guidance provided does not replace the reader’s professional judgement and any construction project should comply with the relevant Building Regulations or applicable technical standards. However, for the most up to date LABC Warranty technical guidance please refer to your Risk Management Surveyor and the latest version of the LABC Warranty technical manual.

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