Built over drains

[peach1234]

Hiya

In the process of buying a property and after having a survey done it has come to light they have built over shared drains, does anyone have any experience of this?

They haven't got a build over agreement so are going to get one retrospectively, anyone know of this being done and how long it takes/how easy it is to get?

Secondly anyone had any issues with building an extension over a shared drain?!

Thanks!

We built our extension over the drain that serviced three houses ‘uphill’ of us. We needed a Buildover Agreement from Thames Water which meant a 4 week application period, then a CCTV survey, plans submitted to TW and a final survey upon completion. It was a long process, but no actual issues arose, other than the spec of the newly installed IC having to be ‘like for like’ rather than replacing old brick with other materials.

Thank you! But obviously there are risks right? Thames water can take it down if they need to access the drain can't they?

Is the inspection chamber under the house, or just the pipes? Thames Water told us that they must have access to the Inspection Chamber (which is why we had to relocate it 2 metres to the left) but the entire extension was built on top of the pipe, which ran the width of the house (mid-terrace) about 1m from the back door and continued down to the end of the terraced row. The layout meant the extension was always going to have to sit on top of the drains. The structural drawings demonstrated that the extension would not cause collapse, and I believe lintels (?) were installed above the drain to keep the weight off it.

The only scenario where I have heard of people needing to rip down buildings to access drains is when the inspection chamber itself has been built on top of - not the drains

Thames water have guidance on their site. Up to 3 houses in a row can build over drains, but there there needs to be access via a manhole / inspection chamber. So someone may not actually be able to do an extension in a terrace!

And yes - the water board can demolish to get access to shared drains to fix. So an accessible inspection chamber is important for unblocking. Pipes can be fixed / replaced with burrowing diggers rather than a big trench though. Hopefully with a build-over agreement they'd go for the burrower!

Our Last house had an extension built over the sewers and we had to take out an indemnity for it. You solicitor, if they have anything about them (many conveyancers don't, these days) should be able to advise you.

This is what I'm concerned about as they don't have a build over agreement I'm worried the work wasn't don't correctly! Good to know about the inspection chamber though thank you I will check this isnt obstructed.
Sorry what's the difference between having an indemnity and build over agreement? With the agreement I believe Thames water have to pay for any damage anyway?