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repairing cracked concrete floor ?

Discussion in 'Plastering and Rendering' started by george07, 4 Oct 2011.

  1. george07

    george07

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    after having a 2 metre approx square section of flooring laid with a sand/cement mix by a guy i know..it has now cracked and sounds hollow to walk over which i know is going to want ripping up and re-laying as i want to tile the floor...it is approx 20mm in depth, firstly do i need to apply a primer before the concrete mix and then what is the best way of carrying out this task..sand/cement mix but lay in 2 intervals ? or would a wickes deep fill self level mix suffice as it can do up to 50mm i hear ? advice on best way to do this guys plz cheers again :)
     
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  3. Micilin

    Micilin

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    Right.

    It lifted from a dry /dusty/unprepared floor.

    For that depth, you should have a grout onto a clean sub floor, then screed onto the tacky grout.

    A normal grout would just be cement and water mixed together and brushed in , but in your case, SBR and Cement slurry 1:1, with a screed of sharp sand:eek:pc (3:1) laid in one go. I would also have SBR in the screed, 1:1 with your water . For such a small area, no need to skimp
     
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  4. george07

    george07

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    micilin would i get sbr from likes of b & q wickes etc + how much would i need..cheers :) also can you tell me what tools i need to do the job + can you explain what i need to do in stages a little clearer if you dont mind plz :LOL: 1st time ive tried this tbh.. thanks again
     
  5. george07

    george07

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    is there anything wrong with using pva as a bonding agent then either 2 layers of self levell or a sand cement mix ? just been told that is an option to do it this way
     
  6. roy c

    roy c

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    I would go with what Micilin says, he knows what he's talkin about ;)
     
  7. george07

    george07

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    ok roy i agree but unsure exactly how to do it properly tbh.. i would like to do it myself if i knew how to go about the right way + where can i buy sbr ? or would wickes/b & q have something similar is it classed as an admixture bond or something... im desperate to get this done now tbh as need to get floor tiled then kitchen fitted skirtings doors etc before christmas & move in ..cheers for info/advice more of the same to get this job done :confused:
     
  8. Micilin

    Micilin

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    Builders merchant for SBR.

    Clean the area and wet it down so it is damp, but no standing water.Right.

    SBR and Cement slurry 1:1, brushed on.



    with a screed of sharp sand:eek:pc (3:1) laid in one go. I would also have SBR in the screed, 1:1 with your water .

    Fill the hole with the screed, pack it in well then level off with a bit of straight timber, which will reach from one side to the other, * scrping off the high spots and filling the low spots.

    * or one that will reach halfway across, but putting a strip of screed along the middle ,levelled off , and using this as a guide.

    When it is ruled off, you can use a float to smooth it in, then a trowel to give it a smoother finish
     
  9. george07

    george07

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    ok mcmilin cheers for that :D
    i will give this ago now as i have no choice really its really holding me up,i will follow your instructions and mix as you say(although will have to mix by hand no access to a mixer :( ) + i will make sure it is flush using a peice of wood etc...i do have to do some self levelling close by where the floor dips etc as i am getting the floor tiled using 500x500mm porcelain floor tiles & obviously the floor has to be very flat... 5 litre tub of sbr from builders merchants for the grout/screed ? cheers again :D
     
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  11. Micilin

    Micilin

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    That's load. The secret is in the grout make sure it is well brushed in and tacky when you lay the screed. Don't mix up too much, but if you do just put it in with teh screed.

    You don't want a mixer for screed anyway, as if you are not very quick and very used to it, you will ruin screed. It's semi dry , so goes into 'balls'

    Just do a good warm up and cool down afterwards!!

    Let us know how it goes
     
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  12. george07

    george07

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    screfix do 5 litre tub of sbr 19.99 decent brand although they do cheaper brands...i presume i need a 5 litre tub as there is a diy centre nearby that possibly may stock a 1 litre tub if that is sufficient..im also prepping/cleaning floor for the self levelling this w.e mcmilin...although it pretty much levells itself as you spread it can you tell me what type i should lay as wickes do 4 different types i noticed recently..also any do,s & donts for carrying out self levelling..ive already got 1 litre tub of wickes primer although prob need more etc :) cheers again mcmilin :D
     
  13. stevethespreader

    stevethespreader

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    how come your prepping the floor for the self leveling compound? i thought you was screeding the floor? your not planning on self leveling and then screeding are you? thats the wrong way if you do a level screed like mich said then that will take your hollows out , if you dont get the screed level then you can use some self leveling compound
     
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  14. george07

    george07

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    steve im filling in a 2 metre section of flooring... the self levelling to be done is nearby where the floor has a dip init etc i did intend to do a screed like mcmilin said but js found out it will take as long as 28 days to fully dry ? as i cant wait that long to be able to tile the floor im now advised and going to use some wickes deep fill (2-50mm) slc to fill in the 2 metre 20mm section of concrete flooring..i will upload photos to have a look at..ive restored the dpm with some bitumen paint..and bought some wickes floor primer to apply b4 the deep fill slc...
     
  15. roy c

    roy c

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    I think that the the whole of the floor screed is not deep enough, floor screed depth should be 50-75mm. The min depth being 35mm. at a push. But there is not a lot you can do about it now except what you are doing... I personally would have bought a few bags of rapid set floor tile adhesive and filled the small area you have prepped with it and bought it up to level with some old tlies sunk into the adhesive and when it had gone off you could tile over it,,,I am not too clued up on self levelling compounds as I cant say I have used them that often but if you have been told to prime the bitumin then put down a deep fill self leveller I suppose that should be ok....Keep us informed with the pics ;)
     
  16. stevethespreader

    stevethespreader

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    george im not sure all slc are compatable with bitumin paint i would check that the wicks slc is if i were you
     
  17. george07

    george07

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    yeah cheers i will check with wickes... another point is will bitumen paint suffice to restore the damp proof or ive seen at screwfix you can get dpm sheets in different widths etc...am i better off laying some of this instead before i do the slc + do i need to get a spiked roller to use on the poured slc to get out airbubbles ? :confused: :)
     
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