Self Levelling over old adhesive

Discussion in 'Builders' Talk' started by cybervic, Aug 9, 2019.

  1. cybervic

    cybervic Member

    I am fitting LVF in my kitchen and need to level the floor, I've removed old vinyl with hot air gun but there are still some brown/yellow glue residue that seem impossible to clean off. Can I use latex self levelling compound over the old glue directly without grinding it down?
  2. DIYDave.

    DIYDave. Well-Known Member

    A lot of questions lately regarding floor levelling compound ...... must be the season !

    Sweep/hoover floor to remove dust and loose material

    Diluted SBR painted over the floor/glue/etc, likely mix to be 1-4 water but check container for ‘recipe’ and instructions

    Wickes sell a 1lt SBR, many other places only a 5lt

    Can buy a specific tile primer like Ardex ...... ???? but it’s expensive and SBR does a great job in this instance

    Will aid adhesion between SL, floor and any bits of remaining crud brilliantly
  3. cybervic

    cybervic Member

    Thanks. Good job I asked here I was thinking of using PVC.

    What’s the difference between SBR and brand specific primer? Some google search seems to say it’s best to use same brand of SLC and primer to avoid problem?

    I only want to SLC part of subfloor, the centre area in kitchen already has SLC (previous vinyl sheet).
    Is there any tip on spreading new SLC to meet old SLC? Is it the same as plastering or repairing plastering?

    Ps.Kitchen is around 7m2, Total area to be filled is around 4m2.
  4. DIYDave.

    DIYDave. Well-Known Member

    Definitely no to PVA - 100% NO

    SBR is perfect for this job, just some folks may prefer a branded primer or as you say, tied in with same brand as SL

    I just don’t think it’s a critical consideration here, you would ‘probably’ get away with laying the SL without even priming the floor, it’s not going to go anywhere but, good to bond the old to the new, especially as some crud intact

    So go SBR -really can’t see an issue myself, but I am diy only but, have used SL several times along with SBR, never a problem (various brands but like Mapei SL)

    The SL does flow nicely but needs a little work with a trowel or some people suggest a spiked roller to remove air bubbles. Not done this myself, just don’t overmix and keep
    speed on drill low to minimise air entrapment

    Much much easier than plastering as the mix is so much looser and gravity plays its part, along with just a little encouragement

    Again SBR the edges of existing SL to bond old and new

    I’m not gonna calculate quantities for you but if you have a pair of hands to help, so much easier as one can mix whilst the other pours and levels

    Just follow instructions on SL for quantities / mixing / etc and all will be fine ...... Go for it ...... Enjoy :)
    KIAB likes this.
  5. CGN

    CGN Well-Known Member

    SBR, about 1:4 ratio to prime floor.

    Mix up standard set (not rapid) SLC following manufacturers instructions, then add a tad more water.

    Work quickly mixing a bag up at a time and carefully pour, spreading it around in a couple of square metres at a time. Don’t pour too near the edges though as it will work it’s way across the floor.

    Carefully spread it out using a spiked roller.

    Repeat till floor covered.

    I’d level the whole floor if you’ve never done it before and definitely invest in a spiked roller. About £12 off eBay etc.

    Make sure there are no cracks where it can drain away. Fill with foam etc beforehand and create a dam at door thresholds etc.

    It’s not the hardest job, but as with anything, there is a learning curve, but the spiked roller just may save the day ;)
    KIAB likes this.
  6. cybervic

    cybervic Member

    Thanks for the encouragement. Dave & CGN.

    I am going to use Mapei Ultimate 1210 sold by our host.

    A question slightly off topic, How smooth should the subfloor be for LVT? Several slightly coarse spots (size bigger than 50P) throughout old SLC because sponge/rubber glue hasn't been removed completely before old SLC was poured. They are very levelled otherwise and if I can get away with it I rather not touch it.
  7. CGN

    CGN Well-Known Member

    No problem. Any high spots, just scrape off.
    cybervic likes this.
  8. DIYDave.

    DIYDave. Well-Known Member

    What’s actual floor construction - solid / concrete slab kinda thing or suspended timber ?

    Just the SL Ultimate is more for solid floors and isn’t flexible and has limitations in single pour thickness

    Ultraplan is dbl the price but is flexible and can single pour up to 40mm ? (From memory) so more suitable for suspended timber floors
  9. cybervic

    cybervic Member

    I am in a flat. The original floor is cast concrete in situ. The middle section is grey SLC.

    The only reason for using ultimate is because it starts at 1mm, whereas ultraplan starts at 3mm. I think the edge where new SLC blend/bond with old SLC will have less than 3mm of new SLC so safer to use ultimate ?

    I did wonder why ultimate is much cheaper, is it a less superior or weaker product?
  10. DIYDave.

    DIYDave. Well-Known Member

    As you’ve got a solid floor, the SL Ultimate will be great here, and half the price !

    I’ve only used the Ultraplan over timber floors and as far as I’m aware, this stuff is flexible and contains fibres to give it flex without cracking

    Also has a greater single pour depth than the Ultimate but, that may not be important here, can always do a 2nd pour if levels need topping up

    So Ultimate it is then, fairly sure all Mapei products are good quality so can’t see any issues
  11. cybervic

    cybervic Member


    Can SBR be any use in a bathroom renovation? If so then I might be better of buying 5L one?
  12. DIYDave.

    DIYDave. Well-Known Member

    I’m only diy me so product knowledge may be a little limited

    If I’m ever on ‘Mastermind’ then SBR wouldn’t be my specialist subject ;)

    But ....... as far as I know..........

    Use to prime plaster prior to tiling

    Increases bond strength between old and new concrete layers (or SLC)

    Add to mortar mixes for improved strength and bonding

    Can be mixed with cement powder to form a slurry, used for tanking and again bonding between layers

    DON’T use PVA for any of the above, never !

    Sealing dusty walls prior to plastering (although PVA ok here)

    That’s it mate...... the limit of my expansive knowledge on the World of SBR

    And for that...... I apologise :cool:
  13. cybervic

    cybervic Member

    The knowledge is more than enough for me to think about. Huge THANKS!
  14. cybervic

    cybervic Member

    Couple of more questions as I'm working out the logistics.

    I only have 2x 45L flexi tubs and 2x 14L buckets.
    - Do I need to clean each bucket/tub before mixing a new batch of SLC, or I can mix, pour, quickly use the same bucket mix and pour again?

    - Can I use the mixer that had been used for mixing plaster but still has some plaster residue?

    - Must I add SLC into water like mixing plaster or can I add water into SLC?

    - How long to leave SBR? Leave it completely dry? or dry once and applied again wait until tacky?
  15. CGN

    CGN Well-Known Member

    If the floor is very dry, then a 1:4 1Sbr:4water is about right, as otherwise it has a tendency to just skin and not soak in.
    Just tacky is fine but it may still be a bit wet where old adhesive was, but don’t worry about random small patches.

    Always add the powder to the water and no need to wash out between mixes. Your mixer will be fine for the job if just doing a bag at a time. Measure out the recommended amount of water per bag into a bucket and make a mark. You can then quickly gauge the water for each mix.
    KIAB likes this.
  16. cybervic

    cybervic Member

    Coated the whole kitchen floor yesterday, not happy with the result. I did everything as suggested, Scrubbed clean the floor, Vacuum, diluted SBR & brushed over, measured water in advance, mixed at slow speed, poured slowly, worked into edge and spike rolling up to 20minutes working time.

    There is an area with grain size spots, looks like trapped air bubble. The deep filled area (5-6mm) looks fine but the shallow filled area (1-2mm) dried with spike roller mark, and also has few paperthin drag marks on it slightly rough to touch.

    One good thing is that kitchen is very levelled now at least, I am wondering if I should coat it again just 1mm all over, or sand down the unsatisfactory areas.

    Any suggestion please. Thanks.
  17. KIAB

    KIAB Well-Known Member

    Can usually rub down any light drag marks, as to grain size marks,I wouldn't have used spike roller on such a thin layer as you found it leaves marks,the thin layer dries quicker than the spike marks can disappear.

    What's final flooring finish going to be, if there a underlay be used,it might be thick enough to loose the marks.
  18. cybervic

    cybervic Member

    Thanks Kiab, I did time myself to stop rolling within 20 minutes of the mixture in contact of water. learnt a lesson now.

    The flooring is supposed to be glue down LVT.
  19. KIAB

    KIAB Well-Known Member

    Needs to be smooth as a baby's bum then, as any marks in SLC will show through, got it here on kitchen floor, a few swirl marks showing through LVT,if you look at floor at certian angles,so annoying, NOT my work.:)
  20. CGN

    CGN Well-Known Member

    You may have mixed it a bit thick. I usually put a spot more water in than suggested by the instructions.
    KIAB likes this.

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