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Drains, CCTV surveys, and build over agreements

Everything you need to know about your home extension and drainage issues - you might be surprised by how much you need to consider!

4 min read

Drains: they’re not the most glamorous part of a household, but when it comes to extending you might be surprised by how big their role is.

Every year we provide thousands of free consultation calls to homeowners, and one of the biggest surprises many face is the work and cost sewers add to a project. Due to legislation implemented in October 2011, any home improvement must make proper provisions to make sure the work has the approval of your local water board.

How do you go about this? Well, here’s our complete guide to your home, drains, sewers, and build over agreements…

Why sewers are important

You might not spend too much time thinking about them, but sewers provide a valuable service to homes across the UK. And as they’re often located near private property, it’s up to everyone to help make sure they stay functional.

For this reason, when extending your home you must first establish if whether or not your future development will be built over or close to (within 3 metres) of a public sewer. If so, you’ll need to get consent from the relevant sewerage company in order for your project to go ahead.

The applies to all building projects, regardless of whether or not it falls within permitted development, or if building control needs to be notified.

You’ll not only to need to show consideration for pipe damage in your plans, but ensure continued access to the sewers for future maintenance - eg. manholes. Only once approval has been given can you commence construction.

Commissioning a CCTV survey

In order to check whether or not your project will run into any sewer problems, you’ll need to carry out a CCTV survey, which stands for Closed Circuit Television Survey. It’s a fancy term for getting a professional to check both the conditions of your pipes, and where they’re placed. The word television comes into it because the surveyor will use a camera to inspect the pipes in question.

At Resi, we arrange CCTV surveys on behalf of our customers, charging £360 for the process.

Self-certification vs build over agreement

If you find your project will be close to or over a sewer system then there are two ways you can get approval from your local water board. These are…

A self-certification declaration

If the pipes in question are 150 mm or less in diameter, then you can get automatic approval by submitting a self-certification declaration. Forms are obtained from your local water board, and will incur an application fee. Answer their questions and your project will be reviewed within 10-14 days for approval.

Rejections typically only happen if their records show your affected sewer has pipes larger than 150 mm.

Questions you’ll face include:

  • What material are your pipes made of?
  • What condition are your pipes in?
  • Whether pipes will be at least 500 mm from external face of your building
  • Whether any manholes will be affected
  • Provisions for pipe safety if walls are constructed above
  • Confirmation of a CCTV survey being undertaken

Build over agreement

If you don’t qualify for a self-certification declaration, then you’ll have to apply for a Build Over Agreement. This must be sought out if any of the following applies to your proposed work:

  • Building over or close to a pressurised sewer
  • Building over or close to a pitch fibre pipe (material)
  • Building over or close to sewers 300mm diameter or greater
  • Building over or close to sewers up to 225mm
  • Manhole, inspection chambers or rodding eye within extensions or within 500mm of an extension
  • Sewers with a Legal Easement affected
  • Using raft foundation for building works
  • Using a piled foundation for building works

These are more costly in terms of fees and require your building to be assessed pre-build and post-build. This means two separate CCTV surveys will need to be undertaken.

If approval is given, your home will have to follow conditions set out by the water authority to ensure the protection of affected sewers. Not only this, if during your final assessment post-construction you don’t acquire approval, you’ll need pay for any alterations or repairs the water company demands. You might even be asked to buy new pipes for your affected sewer, or need to build a new manhole cover so they can access the area easily in the future. For this reason, it’s always worthwhile to have some budget to fall back on in the event of these unexpected costs.

If you're looking for an all-in-one experience for your home extension, you can get a quote from us in minutes!

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