Made things worse with SLC - what now?

Discussion in 'Floor Preparation' started by Jerdes, Sep 30, 2019.

  1. Jerdes

    Jerdes New Member


    Hoping for a miracle or some advice..

    Recently tried to pour SLC over our concrete slab in preparation for some loose lay vinyl planks. Didn't realise how hard the stuff was to use and have ended up with a lot of waves and high spots as a result..

    I then thought it would be a great idea to try and scrape up as much of it as possible before it fully set.. thinking I could get the whole house done.. that didn't end up happening..

    So now I have a house with rooms that have a really bad SLC job and the rest of the house that are partly scraped up.

    I've spent the day trying to contact professionals to fix it. Spoke to a couple concrete grinders today and the cheapest quoted $6.5k to grind it all back.

    Have a couple flooring contractors coming tomorrow to quote.

    What would be the best way to fix something like this? Get someone to flood the floor with SLC to relevel? Grind it all back to a flat finish? Or is there a way I can break all of the SLC to return to the original concrete slab?

    Thanks heaps in advance! Thought I would try to DIY but can see this being a very expensive and costly mistake..

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  2. Jim McClain

    Jim McClain TFP Owner/Founder Administrator

    Did you apply a sealer to the concrete before you poured the SLC? Please name the products you use so we can offer the best advice. Each product is different.

    If you forgot the sealer, that would actually make the removal job easier. Although, if your product didn't require a sealer or if you did apply a sealer, then removal might not be your best option. You also didn't tell us how thick the bed of SLC is. That makes helping you more difficult too.

    I'm not the pro with the best knowledge of SLC, but if it were my job, I'd probably try to rent a buffer type sander and buy several grit levels of abrasives. You would need a lot more disks of the coarsest grade than of the others because that will be the grit that can tear through some of those high trouble spots. Once it got as flat as possible, it will need to be skim coated with a compatible patching compound to fill in any depressions and low spots remaining.

    Soon you'll get replies from other pros with far more experience. If you want to be notified by email when someone replies to this topic, you should change the email address you registered with. We have had 13 years of off and on bad luck with your provider (and all of the other Microsoft owned email domains). Notifications sent to your current address will very likely be considered spam and you will never see them, even though I have never sent a spam message to anyone ever.
  3. Jerdes

    Jerdes New Member

    Thanks for your prompt reply and advice Jim.

    Primer: Lanko 124
    SLC: Lanko 173

    I used 17* 20kg bags throughout the house but managed to scrape back a bit while it was still wet.

    With the primer, the instructions said to use at least 15 litres to cover the floor space but I only used 5 litres across the whole house and thought that was a little odd. Looking back at it now I must of only used just enough to coat the floor but not as much as the instructions had specified.
    The thickest parts throughout the house would be around 3mm.
  4. Jim McClain

    Jim McClain TFP Owner/Founder Administrator

    That's less than 0.12" - less than 1/8". Are you sure? It looks a lot thicker just in the bad spots in your photos. If 3mm is all you actually needed, you should never have used SLC.
  5. Jerdes

    Jerdes New Member

    That's what hurts the most. The slab was in quite good condition minus a couple of small holes that needed to be patched and one high point of 4mm.

    Was swayed by all the talk about loose lay vinyl showing any slight imperfections in the slab over time.

    I feel like I have completely butchered this slab
  6. Jon Scanlan

    Jon Scanlan That Kiwi Charter Member I Support TFP Senior Member

    Jerdes if it makes you feel any better I have been in the flooring game for about 50 years and the big boss decided that he and I should have a go with this SLC We played with it too much with the SLC ending up like corrugated roofing iron
    I learnt after that let the guys who know what they are doing do it. Never touched the stuff since
  7. epoxyman

    epoxyman Pro Member

    We do a lot of self leveling
    And it can be tricky at times
    Sorry about your problem and hopefully it can be fixed and not cost a ton to do it
  8. Mark Brown

    Mark Brown On The Surface Flooring I Support TFP

    If your leveler is that thin, just rent/buy a 5 inch grinder, take a weekend and grind it down. A good dustless and a vacuum and it isn't that bad.

    The first time i poured leveler i spent the day putting it on the floor and the next day my boss made me spend the day taking it off the floor. Some of us learn the hard way. My advice comes from experience, no point sweating about the problem, your gonna sweat fixing it :p

    But if you feel like spending 6.5 k to fix it, you make sure you let me know lol
    • Like Like x 1
  9. Incognito

    Incognito No more Mr. Nice Guy! I Support TFP Senior Member

    Yes, as stated above------1/8" maximum depth is actually part of your problem, aside from the primer. The best self-leveling I know of has a MINIMUM 1/8" thickness. On a slab with nothing more than 1/8" (3MM) irregularities you NEVER would use a self leveling product.

    I agree with the advice above to SAND/GRIND off anything loose, hollow or high and PATCH with a trowel----------NOT self levelor.

    If you are not skilled with a cement finishing trowel please find and pay a pro.

    marshaltown 5" x 18" - Google Search
  10. Mike Antonetti

    Mike Antonetti I Support TFP Senior Member

    Where to start with analysis?

    First? Yeah, you used a product you probably didn’t need to start off with.

    Where country you located?

    If I were a pro to come on this jobsite I would have to run through some questions to you but not sure you evaluated slab properly to begin with. Was the slab very porous? Or did the primer absorb at a normal rate. Were there any contaminants like drywall overspray etc for bonding issues. One coat or two of primer? Do you realize the compressive strength of leveler? 5k?,6k? Psi. Grinding leveler is most viable the next day, after that it becomes extremely hard to grind.

    So I would need to see how well it bonded to slab, is there a shear point between slab and leveler? What is the bond strength and separation force needed to part the two.

    If I were to grind and remove would the leveler stay intact in order to incorporate the leveler or would it separate and need to be ground to top of slab surface plane?

    There’s a lot of evaluation involved, did you mix correctly, was ambient air proper, even though it’s a floating floor, how the leveler reacts to equipment is considered as well.
  11. Tom Potter

    Tom Potter I Support TFP

    As stated above, a buffer machine with a sanding disk. Clean it up and a good heavy skim coat & you're back in the game.

    Going to take some time & finesse but it's not as big of a nightmare as you think. Only your time & the expense of the SLC & primer are all you're out.
    • Agree Agree x 2
    • Like Like x 1

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