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Building over or near a sewer

If there’s pipework near where you’re planning to build, it could affect the design of the building. As well as checking with the local authority's Building Regulations, it's important you work with us to make sure the pipework is protected and our access to it isn't restricted.

It's best to know where the pipework is when you're designing the building, to help avoid delays and additional cost. Don't worry if you're not sure how to do this – we’re here to help.

Why we need to know about your work

When planning your building works, you’ll need to check whether there's pipework nearby. If so, you might need our approval before work begins. You’ll then need to apply to us in line with the Building Regulations 2010. These are enforced by local authorities, but they have a duty to consult us if they’re aware that a sewer might be built over.

We need to know about building work that's over, or close to, a public sewer in order to:

  • Prevent the sewer collapsing, due to the extra weight of a new building. This could cause structural damage to the building, interrupt drainage to other properties and lead to flooding.
  • Make sure we have access to carry out maintenance and repairs.

We have a legal obligation under Section 94 of the Water Industry Act 1991 to provide, improve or extend sewerage systems for our customers, and powers to maintain, repair and renew public sewers in order to achieve this.

Without our permission, your local authority might not provide a Building Regulations Completion Certificate. This could cause problems when you try to sell your property, as a buyer’s solicitor could advise them that the building was extended over or near a sewer without our permission.

What we need to know

You’ll need to apply to us for a build over agreement if:

  • You’re building within three metres of a pipe serving just one other property – a lateral drain.
  • You’re building within three metres of a pipe serving more than one property – a public sewer.

You don’t need our approval if you’re building outside these distances. We’re happy to check your plans and provide written confirmation if you’re not sure. Read more details.

Planning and carrying out your work

We’ll assess your plans when you apply, and won’t permit work to start before we’ve given our consent. Agreeing to amendments to your design when work has begun is extremely difficult and can cause delays on site.

We’ll need to carry out CCTV surveys before and after your work and a local authority building control officer will also need to inspect the work.

If you need one of our field engineers to make a site visit, we can usually get someone out to you within a week.

Locating the sewer

There are several ways to do this:

  • Lift the nearest manhole to see which way the pipework runs. Please take care – covers are heavy and you may need help and/or specialist equipment.
  • Use dye to work out the flow of effluent.
  • Speak to a drainage specialist.
  • Use our Property Searches page to get a copy of the sewer records

You can also view the public sewer record for free at our offices shown below, or by visiting your local authority offices.

Rose Kiln Court
Rose Kiln Lane

When are build overs not permitted?

New detached properties can’t be built over a public sewer and will require a sewer diversion instead.

Manholes can’t be built over either due to the increased risk of flooding and odour issues from internal manholes. Wherever possible, manholes should be removed and piped through. If it’s not possible to construct a manhole outside a building, we can discuss alternatives when we receive your application.

We also won’t allow pumping or rising mains, or trunk sewers, to be built over.

Download our booklet to learn more about building over a sewer.

Apply to build over a sewer

You can apply online in just a few minutes.

Apply now