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Building extension over the sewer - advice

Discussion in 'Building Regulations and Planning Permission' started by SilvanA2, 1 Jul 2021.

  1. SilvanA2

    SilvanA2

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    Hello
    I was hoping someone could help us / provide some advice.

    We are in the process of buying a house with the purpose of extending it to the side and rear.


    The searches just came back and there is a "Public Foul Sewer" running through the side and the back of the house (brown line), giving us no chance to extend without building over it.

    We like the house, the location, and the area, but we really need to be able to extend it.

    We understand we can ask for permission to build over and potentially move the manhole access at our cost, but our question is: is it common to get permission to do this? Or is this too complicated or costly to obtain?

    Has anyone gone through a similar process?

    Thanks
     
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  3. ^woody^

    ^woody^

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    If it's 150mm or less, then it's straightforward to get a build over agreement.
     
  4. Notch7

    Notch7

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    There's no guarantee the map is correct or accurate - you are best to have a look and check.

    Lift a MH cover and see what size pipe and how deep.

    In 2011 the water authority adopted all public drains (a private drain becomes public as soon as it crosses into another persons land).

    Whichever the water authority that owns it will want it protected so it won't block, or can accessed if it does.
    That means either moving it and or building over in a way that doesn't compromise it in any way.

    Most foul drains with just a few house connections will be 110mm and are usually ok to be built over.

    Anything over 250mm and over 3 metres deep, you can't, It'll be refused.


    When you appoint an architect / architectural technician they can do do the drawings for the drainage and build over agreement.
     
  5. thomp1983

    thomp1983

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    Just been through this recently, whoever your local water authority is will have their build over requirements listed online, for my authority severn trent the pipes had to be less than 300mm diameter and no more than 2m deep and there had to be no practical way to move the pipe outside of the build area, we met these criteria so paid the fee and all that we now have to do is provide them with a cctv survey once building work is complete. The sewer pipes will also need lintels over them wherw they pass through the foundations, your builder should know how to do this it's fairly common practice.

    We chose to dig down and replace the original clay pipe with new plastic so we could be confident there would be no future issues with the sewer as that would mean digging up my extension again.
     
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  7. td2304

    td2304

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    I got a BOE from thames water recently for a pipe under 160mm, no cctv needed

    I'm quite incompetent but managed to do the drawings myself and they were fine with issuing the agreement.

    It is not that difficult just follow the guidance on your water companies website.
     
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  8. Apacheuk

    Apacheuk

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    Got a sewer running across the back of our house, so would need a build over as well. Is this worth doing? replacing plastic pipe from my one side of my garden boundary to the other?
     
  9. But is it straightforward that hed get PP for a side extension on a semi-detached?
     
  10. thomp1983

    thomp1983

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    Are you extending all the way across your garden? Your issue will be where you join onto the existing pipes and what access you've got to do so, our clay pipe was absolutely fine but given it ran diagnolly across 20m of our extension I decided it was worth the cost of replacing it as if it needed repairing in the future I'd have to dig up 3 finished rooms to repair and I wasn't happy with that against the £1500 it cost to sort out now.
     
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