New Self Levelling Floor

Discussion in 'Subfloor Preparation' started by James Herbert, Jan 23, 2023 at 11:51 AM.

  1. James Herbert

    James Herbert Member

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    Hi all,



    I'm after some advice. I am an experienced DIY'er and have a keen eye for a good finish but I'm clearly not that experienced as I seem to have royally missed a trick with this.



    I have recently installed 50m2 Karndean (2 months ago) in one area of my house that was solid concrete about 25 years old. I applied Larsen SLC 1550 3mm self levelling compound, let it cure and then laid karndean on top. It looks fantastic.



    I am also now doing another room and I laid 15mm of the SLC again at the weekend on top of old concrete.



    My problem is that I have potentially been an absolute idiot as I failed to read the preparation part of the product and went straight to the installation section. I only read it after I mentioned to a friend what I had done and he asked if I primed the concrete first.



    So what I'm after knowing, is it absolutely necessary to prime old concrete first before self levelling or is that just belt braces? The old concrete was rough and I cleaned off any contaminants before I started.



    Am I likely to run into problems with this later down the line and if so how long can it take to shows issues? If I have to I will take up the latest 15mm section I did. It's not ideal but I will do it if that's how it should be done but the area I have laid karndean on is finished so I guess I just have to hope that will be ok?



    I guess what I'm hoping for is for someone to tell me I have been an idiot but it should still be ok! How long would it take to find out if the SLC worked and was keyed to the original concrete. any signs to look out for?



    Really appreciate any advice if possible.
     
  2. tarkett85

    tarkett85 Well-Known Member

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    Always prime, you will start to get a debonding between the concrete and screed it might happen immediately or in a year no way to know, also a Rh% of the concrete should have been done prior to any screeding a high moisture content will cause failure too.


    Sent from my iPhone using Tapatalk
     
  3. James Herbert

    James Herbert Member

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    Thanks for the reply. I'd be surprised if there was any moisture as it's a suspended block and beam floor with a room underneath and is 25 years old. So that should be ok shouldn't it? Suppose it's just one of those wait and see games. I'm assuming it doesn't always fail?
     
  4. Rugmunching

    Rugmunching Well-Known Member

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    It doesn't always fail but majority do from what I've came across whilst I've been in the game. I've only used larson once before and never again as I found it too chalky when dry.

    Just keep and eye on it, give it a tap every now and again and you'll soon know if it's blown or not.
     
  5. James Herbert

    James Herbert Member

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    Thanks so much. Yeah it has dried chalky! So if I tried the hammer test in a couple of weeks and it was ok, I might have gotten away with it?
     
  6. Rugmunching

    Rugmunching Well-Known Member

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    I wouldnt use a hammer incase you smash it to pieces :D

    Tap it with your knuckle and you'll know but couple weeks, couple months...could be several months like tarkett has said...who knows.

    I've replaced one that had blown 4yrs down the line before o_O the fitter didn't even sweep the floor from what I found!
     
  7. James Herbert

    James Herbert Member

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    Thanks I'll try my knuckles instead!

    I did remove all contaminants and vacuumes the area before hand.

    All the mixes were exactly 4l of water too. I'm wondering if the ones that blow is down to poor surface prep or mixing? I know I should have done my research and used a primer.
     
  8. Rugmunching

    Rugmunching Well-Known Member

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    Primer provides the adhesion, without it it could chip from the floor that easily...

    Did you use a spikey roller?
    Did you notice pinholes when it was down?

    It's just a case whether you get away with it or not, it's done now. Did you prime the 50m2 section you did already?
    I've taken up loads before the overlay screed ready for lvt
     
  9. Rugmunching

    Rugmunching Well-Known Member

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    So answer to your question is it wouldn't matter if it was vac'd to the max and you used bang on 4ltr water for example, needs the primer for the bonding.

    You'll be forever checking it now lol
     
  10. James Herbert

    James Herbert Member

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    No I didn't apply primer to the 50m2 area either and is totally solid still after a couple of months so I'm hoping it will be ok.

    I used a spiked roller on the first one but not on the new section as it was 15mm thick and the roller just kept pushing the compound.

    I'll forgot about it eventually and just pray it's all ok in the meantime!
     
  11. James Herbert

    James Herbert Member

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    I was trowelling on the last lot. It was a bit thicker than normal due to the height required
     
  12. AngryAndy

    AngryAndy Well-Known Member

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    That's the best plan. Forget about it and enjoy your new floor because there's no point fretting about something that probably won't happen and if it does then deal with it
     
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  13. AngryAndy

    AngryAndy Well-Known Member

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    Oh, and if you do any more flooring don't forget to read the instructions;)
     
  14. James Herbert

    James Herbert Member

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    Haha I will!
     
  15. James Herbert

    James Herbert Member

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    Thanks for all replies so far guys. Really appreciate the advice.

    Just checking does this sound right for next stage to self level over the existing porcelain tiles and the bit I've just self levelled so I have one area all nicely levelled.

    Clean the tiles and grout lines.
    Apply fball p141 to the porcelain tiles and p131 over the current newly self levelled area diluted 4:1 (I will wait a few weeks to ensure it seems sound).
    Apply stop gap 1200 pro to the whole area in one hit.

    Just making sure I haven't missed anything this time!
     
  16. James Herbert

    James Herbert Member

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    Also is fball the best product to use for this job or are there cheaper alternatives that will do just as well. I'm happy to pay the money for the right product but just wanted to check there is nothing cheaper that will do the job just as well. Funds running thin hence trying to save costs where I can buy doing this myself!
     
  17. Rugmunching

    Rugmunching Well-Known Member

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    141 will be OK for the porcelain, I use ardex p4 personally but they're bother very similar...

    Either way, give the tiles a good clean, couple mops and get it primed. You can use the 1200, I use mapei renovation and its alot cheaper but each to their own n all that!
     
  18. James Herbert

    James Herbert Member

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    Thanks. I'm here for advice so will definitely be taking comments from seasoned pros on board.
     
  19. James Herbert

    James Herbert Member

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    What's the main difference between using a water based like the one you've suggested and the one with latex? I've only used water based before but wondered what the extra cost benefits are?
     
  20. askarisiddiqui

    askarisiddiqui New Member

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    It sounds like you are considering removing a section of recently-installed 15mm thick Karndean flooring because it may not have been installed correctly. If that is the case, it may be necessary to remove the section and redo the installation to ensure that it is done correctly. However, it is not ideal as it will cause extra work and may result in damage to the surrounding area.

    It's also worth noting that Karndean flooring is known for its durability and resistance to water and scratches, so it may be possible that your flooring will be ok even if the installation is not perfect. It's hard to say for sure without seeing the specific installation in question. If you are unsure about the quality of your installation, it may be best to consult with a professional flooring installer or the manufacturer of the Karndean flooring for guidance.
     

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