Build Over Application

When is a Build Over Application Required?

 

If you are building a new dwelling or extending an existing building, any work involving new foundations, underpinning, piling or basements within 3m of a public sewer will require a Build Over Agreement approval prior to works commencing on site.

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What is a Build Over Agreement?

If the above is the case, a build over agreement is entered with your public sewer supplier for the building work that is planned over or near the public sewer. This way the supplier can approve the new foundations and that the correct clearance has been allowed for. It also ensures that sufficient access to the sewer is maintained so they can clean or repair it if necessary. It also gives certainty of these facts to anyone looking to buy the site, should it be sold following the works.

How Do I Know How Close a Public Sewer is?

There are a number of ways of finding where the drains are located near to the site. One option is to consult the local council to search for the drainage plans of the area. You can also request this information from your public sewer supplier. You can use the following map to find out who is the local public sewer supplier:

https://www.ofwat.gov.uk/households/your-water-company/contact-companies/

 

How Can I Get an Accurate Image of the Drains?

An on-site CCTV drain survey can also map and record a more accurate idea of the drainage system on your property if you are unable to find information from the above resources, or if the above resources are not detailed enough.

 

An OS map will usually have locations of public inspection chambers/manholes. This along with CCTV, and conducting an on-site architectural survey of the property can give you the best picture of the location of drains and inspection chambers and help prepare the drawings for a build over application.

What is a CCTV Drainage Survey?

For residential projects a CCTV camera and dyes will be used to see the condition and direction of existing drains. This, along with site measurements of inspection chamber location and depth, combined with public drain information, can help to build a better picture of drain location, direction, condition and depth. This information is also necessary if an existing inspection chamber needs moving and extending or if new drains are being added to an existing system.
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What Drawings Are Needed for a Build Over Application?

Whilst every sewer supplier will have different requirements for a build over application, most are covered in the following two sections.

Building Near a Public Sewer

Building Near a Public Sewer
  1. Site location plan
  2. Existing building and drainage layout – This must show the sewer, manholes and flow direction in relation to the existing structure.
  3. Proposed extension and drainage layout – This must show the sewer, any manholes and flow direction in relation to the proposed structure.
  4. Building section – A drawing to show foundation design in relation to the pipe may only be required if the building is within 1.5 metres of the sewer.

Building Over a Public Sewer

Building Over a Public Sewer
  1. Site location plan
  2. Existing building and drainage layout – This must show the sewer, manholes and flow direction in relation to the existing structure.
  3. Proposed extension and drainage layout – This must show the sewer, any manholes and flow direction in relation to the proposed structure. Suitable external access to the sewer must be maintained.
  4. Building section – A drawing showing foundation design in relation to the pipe is
  5. Required if building within 1.5 metres of the sewer.

For further information on requirements, contact the local sewer supplier.

Author

Written by Aida Rodriguez-Vega, architect and researcher. At the Detail Library, Aida keeps busy by carrying out technical research and drawing new details for the ever-growing library.