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Building over a sewer

Are you considering extending, renovating, or building a new property? We’re sure you’re excited and possibly a little daunted too. To help your project be a success, we’ll explain why it's important to consider any nearby sewers at this stage.


Why is considering nearby sewers important?

Building an extension, a new property, or renovating can be an exciting time, but it can impact the public sewer network serving you and your neighbours. Some extra planning may be needed if you're going to be building over or near a sewer.

If you’re planning to build within three metres of a public sewer, you’ll need to submit a build over application. We're here to help and guide you through an application.

Here are a few reasons why it's important to get our permission:

If not considered, building near a sewer could cause them to collapse under the weight of the new structure. This could damage your property, interrupt drainage for other properties, and increase the likelihood of flooding.

Submitting a build over application allows us to check the necessary precautions are in place and that the sewer is in good structural condition.

We’ll also check that your plans allow for 24-hour access to all public sewers and manholes. We need this to be able to carry out routine inspections, maintenance, and repairs. These are essential to help us protect your home and our pipes.

A building control surveyor will expect to see our permission before giving you a completion certificate or ‘sign off’ your work.

If you sell your property in the future, the buyer’s solicitor may ask for a copy of the Build Over Agreement showing our permission. Without this, selling your property could become more complicated.

When won't you need to submit a build over application?

  • If you're constructing a new extension

    First, you should check if it is subject to the Building Regulations. 

    If it is, then you'll need to confirm that it meets the standards set out in section H4 of the Building Regulations. Either a Local Authority Building Control (LABC) department or an independent approved inspector can assess this.

    Some LABCs or inspectors may be able to progress your proposals in consultation with us, rather than you submitting a build over application.

    You can use this route if your development meets all the following points:

    • Pipe size is 225mm or less
    • Pipe depth is less than 3m
    • The total length of the public sewer built over is less than 6m
    • Access to the public sewer is unimpeded, and you’re not building boundary to boundary (within one metre of the property line)
    • It’s an extension, not a new detached structure
    • Building over/near only one public sewer
  • Building over a sewer

    If you're building or undertaking changes to a non-residential building over or near a public sewer. In this case, you may need to request a sewer diversion. If you're unsure, please contact us.

Building proposals we won't accept:

  • Over or near public infrastructure

    Building over or near public water mains, pumped or rising mains, vacuum mains and strategic or ‘trunk’ sewers.

  • Over or near existing sewers

    Building over or near existing sewers on new development sites or re-development sites. Instead, you can look to divert the sewer, or to save cost, adjust your plans so that your building is at least three metres from the sewer.

  • Over internal an manhole or change in pipe direction

    Where there would be an internal manhole or change in pipe direction (i.e. Y-connection or a junction of a public sewer) within the proposed building. These are not allowed due to potential odour and flooding issues. You’ll need to relocate these outside the property, where we have full access, to get approval.

  • If there are easements or restrictive covenants

    If there are easements or restrictive covenants on the pipework by your proposed works, we won’t allow you to build near or over the pipework.

  • Impact access to existing sewers

    The pad, raft and cantilever foundation types over the public sewer are not permitted as they can impact our future access to repair the adjacent public sewer. This can significantly increase the risk of damage to the structure during repair works. We also don't permit reinforced concrete floor slabs over public sewers for the same reason.

  • If you have a Boundary-to-Boundary infill structure

    Where there are already structures on both sides of the boundary, that will restrict future access to the public sewer.

Making an application for a Build Over Self-Declaration

It’s likely you can progress with a self-certified build over approval known as a Build Over Self-Declaration if:

  • You're building over one public sewer, where the total length of sewer built over is less than six metres
  • The sewer to be built over is a non-critical public sewer with an internal diameter of 225mm or less
  • The sewer is less than three metres deep
  • And not a boundary-to-boundary extension

As part of the application process for building over a sewer route, we ask you to complete a list of questions to determine if you meet the criteria. The below guide shows the application process step by step. Before applying, you should make sure that you've got:

  • An existing and proposed site plan (.pdf) (1:100 or larger clearly showing the location of sewers and manholes)
  • A site location plan (.pdf) (1:1250 or larger)
  • A cross-section foundation design (.pdf) (1:100 or larger)

Copies of all drawings submitted for building regulations approval.

The step-by-step process


Apply online

Fill in our online form, submit your required documents and pay a fee for the self-declaration using our GetConnected portal. We’ll review your application within five days and let you know if we have everything we need to progress.

Login to GetConnected

We'll send you a conditional approval

We'll review your application and send you a conditional approval letter within the next two weeks. You'll need to share this confirmation with your builder. If you're relocating a manhole chamber or undertaking minor pipe repairs, you'll need to pay an inspection fee of £84. Your letter will state if this is needed.

Request a callback

We understand that all projects are different, and it might be hard to understand what the right and most cost-effective option is.

If you have more questions, please fill out this form to arrange a callback.

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