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Extension over drains

Discussion in 'Building Regulations and Planning Permission' started by SpecialK, 10 Sep 2019.

  1. SpecialK

    SpecialK

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    Hi,
    I'm thinking of changing my conservatory into an extension.
    To do this the rainwater drains/manhole at the back of the property would be covered. I have attached some sketches to show their location now and when covered.
    The water authority have no knowledge of these drains (conversation on phone), but they are communal as two houses upstream use them too.

    Am I going to be able to build over these drains or am I wasting my time with an extension? Will building control still insist on a build over agreement even with the drains unregistered?

    I'm thinking total removal of current manhole and join pipe together. Relocate house and extension gutter drain to the right side of the house. Build a new manhole to the right of new extension that feeds back under the foundation into the existing drain. Neighbours manholes are approx 10m each way if rodding is required....
     

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  2. Notch7

    Notch7

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    Yes building control will insist on a buikd over agreement. Anyway the risks of building over an adopted drain are not worth it......you could be forced to remove extension. Or if you sell....you will beed a build over that may not be granted.

    Yds you should get a build over agreement in your situation. Check with your water authority to find out costs. I reckon its worth getting tge buildover agreement before paying out for building regs drawings -although a good architect should be able to advise on possibilities.
     
  3. SpecialK

    SpecialK

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    Thanks, Most appreciated. I will get the drain registered and enquire about a build over agreement!

     
  4. Notch7

    Notch7

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    Im not sure you need to get it registered.

    All drains that cross over to a neighbours became public drains and were adopted in 2011.

    There must be 10s of thousands of such drains that were built over prior to that.

    You can aplly for a build over fir your new extension -you can do it yourself, although you will need to put the correct technical info on the drawing.

    Bear in mind foundation will need to 150mm deeper than invert level -so if your drain is 1500mm down, founds will be 1650mm
     
  5. SpecialK

    SpecialK

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    Great, thanks. Southern water have no knowledge of the drain at the moment - So I guess apply for a build over and inform them the drain exists?
    Thankfully the manhole is only 0.5m deep, so should be ok as I'm on clay so the foundations will be 1m+ deep anyway.

     
  6. noseall

    noseall

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    Looking at the image drawing, what exactly is that new IC location supposed to be doing? You do realise that the reason the IC is there presently is so that the connections from your house onto the sewer are roddable?
     
  7. SpecialK

    SpecialK

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    I assumed it would be needed so the connection from my house to the drain would still be roddable? There will be nothing connected to the original manhole once its covered over..

    Currently the rainwater drain from the roof comes down and over the conservatory at the middle of the house via a downpipe - I would move it so its over the right hand side, either via a downpipe or pours onto the extension roof?

     
  8. noseall

    noseall

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    Yes, but putting an IC in that position isn't going to achieve diddly. You will either need to leave the IC where it is and fit a double seal screw down lid, allow for a rodding eye further upstream but still on your property or do away with the IC altogether (re-hash the IC into a 'y' connection) and then rely upon your neighbours access for rodding (contentious).
     
  9. SpecialK

    SpecialK

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    I would make the current IC into a straight pipe as nothing needs to get into it, then have a Y connection further down with an IC outside the footings for rodding my connection to the drain and downstream?

    If I go full width on my extension there will be no room for a rodding eye unfortunately ... im sure the neighbours upstream would be OK with it being rodded from their houses as if its blocked it will effect them not me? Or does this sound totally unreasonable?
     
    Last edited: 11 Sep 2019
  10. ^woody^

    ^woody^

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    It's not up the building contol, its up to the water authority, and you need to speak with them first as each will have their own specific policies.

    You certainly wont be permitted to do what you have drawn in that proposed sketch.
     
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  11. Londoner2

    Londoner2

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    You need a build over agreement with your water supply company, i did it with Thames water and paid £299 for the priveledge of telling them thsi and supplying some drawings and talking them through it. They will supply u with a letter giving you permission providing you stick to the plans, my drainage plans have changed and TW are not aware of teh new changes, iother wise thats another £299 down teh drain.

    I do not have a surface dran, only foul, agreed with TW to put in a water butt.
     
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  12. SpecialK

    SpecialK

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    So after some research southern water do not allow a manhole to be inside the floorplan.

    I will probably need to make the extension smaller on one side to accommodate an access point and run the extension and house roof water in.

    So the question is how much room do I need to leave? Will I require a full sized manhole or just an inspection chamber/rod point?
     
  13. Londoner2

    Londoner2

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    Normal practice is for you to concrete over existing manhole and have an inspection chamber outside (that is roddable).

    I'm doing the same thing after getting a Thames Water Agreement, they too stated no manhole inside.
     
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  14. Nakajo

    Nakajo

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    'southern water do not allow a manhole to be inside the floorplan' They all say this, but somehow or other, there are lots of manholes inside properties.
     
  15. Londoner2

    Londoner2

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    The law changed in 2011, before this it was allowed.
     
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