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Clay and plaster as hard core in a room?

Discussion in 'Building' started by what goes on here, 13 Sep 2021.

  1. what goes on here

    what goes on here

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    Hiya.

    We've decided to replace our timber floors due to a lack of ventilation (and 120 year old VERY rotten joists) with concrete, but our contractor has - shall we say - lost some trust.

    We're at the 'hard core' stage, but the floor base which is about a foot deep is a mixture of brick, a large amount of clay (huge lumps of it dug out from extension foundations), and a fairly large amount too of plaster/soot/bits of wallpaper.

    A: is this a problem; I suspect so, but I'm struggling to find a definitive answer in order to demand a: money back or b: remedial work or both

    B: WHat is the likely outcome to be? We're planning to put down parquet on top.

    Many thanks !
     
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  3. JP_

    JP_

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    I would think it should be built like a modern floor - concrete oversite, damp membrane, insulation, screed, top floor finish. Unless it is deep and this layer is effectively the same level as the ground would have been if timber floors were not installed.

    If there is no damp membrane and they are filling in with whatever they can find, then the clay will soak up water and cause damp issues.

    Can you post photos?
     
  4. what goes on here

    what goes on here

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    Thank you for the reply. It's supposed to be hardcore, concrete, damp membrane, insulate etc as you say. So far its the hardcore before the concrete is where we're at. The lines across these rooms are retaining walls which are three and four bricks deep depending on the area of the room so there's a lot of material to bring the level up for pouring concrete.

    We were concerned about the potential for problems or cracking from using clay and plaster etc as hardcore. NHBC has the following guidelines for hardcore which is where some of our concern surfaced. I can't find much more information on it though.

    The middle photo is a close up of the clay chunks.

    The one room is 6.2 x 4.5 and the other is a 4.2 m square ish. There is no lining underneath.
    Many thanks.
     

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    Last edited: 13 Sep 2021
  5. sxturbo

    sxturbo

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    Tell them to remove it and use proper hardcore compacted with a Wacker plate.

    I'm not convinced the huge lumps of clay are a good idea, they are not a "stable" material and could cause issues with sinkage. But as its internal I doubt sinkage would be an issue
     
  6. Dereekoo

    Dereekoo

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    What has BCO got to say, what does your spec say, what does your common sense say
     
  7. Dereekoo

    Dereekoo

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