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How to level internal slab?

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  1. #1
    Apprentice (new member)
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    Default How to level internal slab?

    Hi all,

    I have a small Victorian cottage. Sometime in the dark past a previous owner has poured a concrete floor in the lounge (about 25 sqm). Unfortuantely the floor is incredibly uneven - probably about 3-4 inches between the highest and lowest parts, think mountain and valleys rather than just not level.

    To level it, I think I will need to remove a couple of the peaks and then fill the troughs but have no idea how to go about it or who I could get in to do that sort of work.

    Any help would be much appreciated.

    Cheers,
    Raz

  2. #2
    Senior Member DvdHntr's Avatar
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    You can get grinders to grind down the peaks.

  3. #3
    A Member of the Holy Trinity echnidna's Avatar
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    I'm just about finished doing some leveling on a similar house.
    I took the really high bits off with an angle grinder and built the low sections up with
    mortar mix (bags).
    Regards
    Bob Thomas

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  4. #4
    1K Club Member Pulse's Avatar
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    As the guys have said:

    grind the high spots with a angle grinder and a "diamond cup wheel" Gasweld recently advertised them for under $50 but a good one will cost more than $100

    fill the low spots with levelling compound in thin layers after priming. Lanko levellers are in bunnings and can be "stretched" with sand or gravel for deep holes.


    Cheers
    Pulse

  5. #5
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    Thanks guys, really helpful, I was thinking that it might be more difficult than that - although I think it might be messy!

    Raz

  6. #6
    Member rileyp's Avatar
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    You can buy floor leveler in bags like bags of concrete (lenko as suggest before or arnet or something is another....Grollo buys it by the pallet!
    Its a simple matter of cleaning the original concrete with a good grind would be the best.(you can hire a concrete grinder from Kennards etc)And you can use this to knock down the high spots as well.You would then vacuum the whole area and apply a etch with a house broom.(bondcrete pehaps?)
    Then when sticky the floor leveller is applied in thin layers as before was stated.
    The floor leveler itself is like a very thin runny mortar.
    and is simply poured all over the floor and you let gravity do the work.
    Its a good idea to mark the areas you want to grind the most with a setting out spray can! Full instructions come on the back of the leveler bag anyway!
    I have never done it and can only tell you what I have seen done on site.Im sure someone else could add to this.
    cheers Rileyp.

  7. #7
    1K Club Member Pulse's Avatar
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    the grinding is really messy, good breathing gear is essential. The proper way is to hire the dustless stuff but buying a cup grinding wheel is the cheapest. I used it before laying a floating floor. Grinding is good for small high spots or ridges but bad for lowering large areas... simply too slow, messy and expensive.


    Best way is with a dumpy or a laser level. Then use a self leveller in different areas. If you need to raise more than 30mm then a new slab on top would be cheaper, with its own reo.

    Cheers
    Pulse

  8. #8
    Old Chippy 6K
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    A bit hard without onsite inspection, but if the floor is that dodgy you might also have issues with underfloor or edge moisture and what is it poured onto?

    I reckon that removal and renew with either a new concrete floor or a timber floor might be a better option. Also allow you to see what is underneath too.

    Depends on how hard is the concrete and how good access to get tools in to break it up and get the rubble out.

    Be worth a few drill holes around the room to see what is in the slab and how thick it is - for example is there reinforcing at all (there might not be any).

    That said the levelling compounds are OK up to 20mm or so and grinding works OK to get rid of about the same amount, but it is very dusty and messy - it will get throughout the house not just in that room and protective gear is essential.

    If you have a decent ceiling height and don't mind a step into the room (depends on how many doors etc) you could just re-floor over the top - with clever placing of battens you could do it at about 50mm or so above the highest point, but it is not for a novice to try.

  9. #9
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    The more I look at it, your answer might be the right plan. Best to do things right rather than quick. Any thoughts on what sort of company can help me, a builder? a concrete company? I am in Melbourne if you have any specific thoughts.

    Cheers,
    Raz

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