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Single storey extension advice - foundations

Discussion in 'Building' started by chrismullin1, 23 Feb 2019.

  1. chrismullin1

    chrismullin1

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    Hi there
    I live in an end terrace and looking to build a small single storey side extension. My house and garden are all built on concrete - the soil in the garden is only about 3 inches thick and sits on concrete (my street sits on what used to be a big factory site). Is it still necessary to dig deep foundations or can a slab be poured on top of the existing concrete and then build a wall on top? How does having existing concrete rather than soil complicate things?
    Thanks
     
  2. noseall

    noseall

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    What if a drain company wished to dig along side your wall, thus removing your concrete? You would be mad to rely upon 'supposed' existing concrete foundations without verification. Yours will need to be independent of any other structure.
     
  3. ^woody^

    ^woody^

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    Surely 3" of soil on concrete will be 3" of mush for six months and 3" of crust for the other? And no plants.

    Is this 'built on concrete' theory correct?
     
  4. chrismullin1

    chrismullin1

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    Yes we can't plant anything. Same for my whole street.
     
  5. ^woody^

    ^woody^

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    Have a look for any any extensions in the street, note the addresses of one's that look recent. Phone the council building control team and ask to speak to the officer for your area. Ask him if he knows what the foundation situation will likely be, and if not give him a few addresses and ask if he could have a quick look at any plans.
     
  6. chrismullin1

    chrismullin1

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    Thanks, I'll do that. There are some council owned garages a few metres away and you can see that a slab has been laid on top of the existing concrete and then the brick wall built on top of that. My extension wouldnt be much taller in height than these.
     
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