You may need a Build Over Agreement if your extension is being constructed over or close to a public sewer or public lateral drain. In the Thames Water area, an application is generally required for building work to an existing property within 3 metres of a public sewer or within 1 metre of a public lateral drain. The requirements depend on the location and type of sewer and the proposed construction, so the drainage position should be checked before building work begins.

The first step is to establish the location, size and status of the sewer or drain in relation to your proposed building work. Public sewers and lateral drains are maintained by the relevant sewerage company, whereas private drains are generally the responsibility of the property owner. Your proposed foundations, the sewer depth and its position relative to the development also need to be considered. Planning World can review your project and available drainage information to help identify whether a Build Over application is likely to be required.

For a Thames Water Build Over application, the core documents normally include a location plan, an existing and proposed building and drainage layout, and a sectional drawing showing the proposed foundations in relation to the sewer. Depending on the foundation design and project, additional information such as bridging details, piling method statements or structural calculations may also be required. Planning World can prepare the drawings and supporting technical information required for your application.

A Thames Water Build Over application is submitted with details of the property, proposed development and sewer, together with the required drawings and application fee. Thames Water then carries out a technical review and may request further information or changes before the works can proceed. More complex applications can also require surveys or additional legal arrangements. Planning World can prepare the application package and manage the submission and correspondence on your behalf..

Timescales depend on the size of the sewer and complexity of the application. Thames Water currently states that its technical team reviews applications within 21 days once the application and payment have been received. Straightforward Class 1 agreements are usually issued within 21 days where all required information has been provided, while more complex applications involving surveys, remedial works or legal agreements can take considerably longer.

Yes. Planning World provides a Build Over Agreement application service, including reviewing the proposed development and drainage information, preparing the required drawings and supporting technical documentation, completing the application and liaising with the relevant water authority on your behalf. We can also identify where additional information may be required because of the sewer position, foundation design or complexity of the proposed works.