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Build Over Agreements


All drainage pipes that serve more than one property which existed before July 2011 are now public sewers (from Oct 2011) if they are on private land or not. If your house has a single drain this will be privately owned up to the property boundary* and when it crosses this, it becomes the responsibility of the water company. *Some water companies will take ownership of the private drain when it reaches 1 metre from the boundary and require a build over agreement from this point.

The water company have a statutory right of access to public sewers and nothing can be built over them unless their consent is obtained first, and this is called a build over agreement. When you are planning to build over the public sewer or build within 3 metres of it permission will need to be granted before the building work can start. If no agreement is in place the water company has powers to remove any structures that prevent their access, and they are not liable for any damage caused. Though they have the power to remove structures this can often be avoided with modern machinery which allows access from another point, however, the risk of structure removal still remains. If the build over agreement is in place the water company can not remove the structure which is the subject of the agreement.

At the design stage options can be explored to remove the need for a build over agreement including diverting the existing sewer and modification of the extension footprint to avoid it.

Identifying public sewers can be problematic, plans are available from water companies that show the location, size and depth of the sewer pipes and manholes, however, these can be inaccurate. When there is uncertainty a drain survey is a sensible precaution and will enable a plan to be produced that plots the sewer information along with revealing if there are any defects already present. They are relatively inexpensive in comparison to the costs of building over or near a public sewer without consent  and a survey can be a requirement of the water companies build over application. Proceeding without the agreement is asking for trouble, the building inspector is obliged to report any violations and at a minimum work on the extension will have to stop or you could be forced to take down the building.

When the build over agreement is required Architecture First will design the extension to be compliant with the water companies requirements. We’ll complete the application on your behalf submitting the completed application form and drawings. The water company’s fee will then be paid directly by you.

Most water companies will provide their decision within three weeks and their fee is approx. £200 for sewers up to 225mm. There is the option to replace the pipes beneath the new extension or to have a CCTV drain survey to include in the application and a further survey following the completion of the work. Internal manholes in the public sewer are not allowed and any new manholes must be least 500mm away from the new foundations.

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