Thames Water Build Over Application

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.

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.

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 – known as a lateral drain
• If you’re building within three metres of a pipe serving more than one property – known as a public sewer
• You don’t need our approval if you’re building outside these distances. If you’re in doubt, we can check your plans and, if we’re happy, provide written confirmation of this.