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Concrete over dodgy concrete in bathroom

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  1. #1
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    Default Concrete over dodgy concrete in bathroom

    I've been working through the fun of demoing a 1970s bathroom. I was hoping to tile over the floor tiles but it would have created a 40mm step up into the bathroom which we didn't want.
    As a result, I knocked out the sand cement bed under the tiles which came up relatively easily.

    What i'm left with is a cement bed with aggregate up to 30-40mm. I can see some rebar throughout the concrete. It is pretty uneven (combination of where some of the concrete has come up and where some of the sandy cement remains).
    My question is can I just lay another layer of concrete on top? I've got plenty of floor height now to play with. How much prep work do I need to do? I feel like i've been sweeping it for days, and I think essentially by sweeping i'm just pulling out another layer of dust/rubble/rock.

    img_4250.jpgimg_4251.jpg

  2. #2
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    If it was my place I certainly would - As long as the base you are going over is nice and stable, (as stable as say compacted road base) I don't think you will have any problems

    If there's was enough height I would probably lay 100mm slab with mesh in it -

    If it saved me a heap of work I'd probably go down to 75mm thickness - I don't think it would meet code (happy to be corrected) but on a nice stable base i would bet on it being OK

  3. #3
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    Looking at the house plans, its already a 100mm reinforced concrete slab. Definitely not enough height for an additional 75mm or 100mm overlay. Id say id probably have max 20mm to play with on top of what is already there.

  4. #4
    1K Club Member Pulse's Avatar
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    Default Concrete over dodgy concrete in bathroom

    i’d dig it all out with a jackhammer, you need a 100mm reinforced concrete slab, don’t forget termite treatment under the slab. You might find 75mm is enough if the base is concrete of some sort after it has been dug out. You will get cracked tiles otherwise.

  5. #5
    1K Club Member havabeer's Avatar
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    could you vacuum all the dust up.
    self level so its flat
    attach a 20 - 25mm compressed cement sheet
    water proof and tile over that?
    Remember if you don't sin, then Jesus died for nothing

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