1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Tiling a floor-Do I need decoupling? Primer? Self levelling?

Discussion in 'Floors, Stairs and Lofts' started by RRRRRR, 26 Apr 2011.

  1. RRRRRR

    RRRRRR

    Joined:
    4 Feb 2010
    Messages:
    122
    Thanks Received:
    2
    Location:
    Surrey
    Country:
    United Kingdom
    Hi- I have a kitchen floor to tile- 25sq. m.
    Two areas are newly screeded on jabfloor insulation where rotten old wooden floor was, and two areas original cement where quarry tiles were. Now for the questions....
    1/. The new screed is solid, but powdery on top with some loose sharp sand stones as we've been walking on it on boards for almost a year. I guess I must vacuum then seal it. It has a DPM and is dry, so can I use PVA or should I use a specialist product?
    2/. Is self levelling essential? In the past I've build up adhesive and a spirit level on each tile.
    3/. If self levelling is essential, can I do a 3 soft sand/ 1 cement/ 4 water/ 1PVA to save money, or any recommendations of make/ type?
    4/. I believe I need to encourage the SLC to go to low spots etc. as it won't do ALL the work for me. How do I mark where the low/high spots are when I push the SLC around?
    5/. I guess I need a decoupling membrane as the old floor joins with the new in several places, but could a flexible adhesive with flexible grout take the place of decoupling matting?
    6/. If I need the matting, is there a quicker way than doing primer, then SLC, then adhesive for matting, then adhesive for tiles, as I only have about 50 years of life left?
    Any help very gratefully received. Thanks.
     
  2. Richard C

    Richard C

    Joined:
    26 Apr 2005
    Messages:
    10,619
    Thanks Received:
    998
    Country:
    United Kingdom
    Is the screed over the jabfloor insulation a floating floor?

    For unglazed quarry tiles, you need an SBR bonding primer; glazed tiles can be more difficult & really need an SBR slurry bonding coat.

    DO NOT use standard PVA on any tile base, it remains water soluble & will reactivate if it gets wet; use an acrylic/SBR tile primer/bonding coat.

    It’s best to have the tile base as flat as possible. Building up with adhesive can be done but has its limits; normally a solid bed would be 2-6mm but can be up to 12mm in small localised areas. With large format tiles a flat base is even more important or, if you’re inexperienced, it’ll be all over the place even with careful use of a spirit level. As you have several different requirements an appropriate SLC may be the answer to them all.

    No, you can’t lay a conventional sand/cement screed less than around 40mm thick, it won’t last 5 minutes & will take 1 day/mm to cure & dry out before you can tile it. You need a specialist SLC/screed something like this;
    http://www.ardex.co.uk/smoothing_levelling.asp

    It’s called an SLC & when mixed correctly, will find its own level with little effort or perhaps some encouragement using a sponge float.

    Can you answer as above; is this a new floating floor? If it is or the new floor has different expansion characteristics/rates then you could have more of a problem. If it’s old/new flooring of the same type you may need a decoupling membrane but, unfortunately, a flexible addy & grout will not take the place of one; you may, however, get away with using a latex based SLC & tiling over that but consult the manufacturer. You will definitely need to use a flexy addy/grout when tiling over an SLC

    Unfortunately there are no shortcuts if you want it to last ;)
     
    • Thanks Thanks x 1
  3. RRRRRR

    RRRRRR

    Joined:
    4 Feb 2010
    Messages:
    122
    Thanks Received:
    2
    Location:
    Surrey
    Country:
    United Kingdom
    Hi Richard C-
    I can't thank you enough for such a fantastically helpful reply. It gives me faith in human-kind again! I shall read and re-read until its all sunk into my rapidly slowing brain. As for your question, 'Is it a floating floor?' I'm not a specialist, but the new floor was dug down to solid chalk with no hardcore as Mr. Building Control said it was solid, DPM sheet, then concreted, 100mm Jabfloor then 75mm-plus screed. The DPM comes up behind the skirting. Whether that's a floating floor I'm not sure. Oh, and the tiles I'm planning on are porcelain I think (colour all the way through).

    Thanks again, another Richard
     
  4. Richard C

    Richard C

    Joined:
    26 Apr 2005
    Messages:
    10,619
    Thanks Received:
    998
    Country:
    United Kingdom
    No you’re OK; you haven’t got a floating floor. Due to their construction the top part can move independently from the slab & for obvious reasons can be difficult to tile. How long has the base been down? You need to allow 1 day per mm thickness for the screed to dry before over tiling!

    As it’s not an extension it shouldn’t move so no expansion joint should be necessary but I would use go with a decoupling membrane or check out if a latex SLC would be sufficient. I’ve also noticed that BAL have some new SLC’s in their range one of which may be suitable;
    http://www.bal-adhesives.co.uk/products
    I haven’t checked them out yet but if you contact BAL they will advise.

    Some porcelain tiles can be susceptible to staining & need sealing before laying & even re-sealed before grouting, some come ready sealed; use any addy colour appropriate for your tile colour. Others are fine & can be laid as they are so check which you have with your stockiest or do a water test. You will need a wet diamond wheel cutter, porcs can be difficult when using a manual cutter.

    Floor tiles must be laid on a solid adhesive bed, use either a thick bed solid bed trowel or a large format trowel.
     
    • Thanks Thanks x 1
  5. DIYnot Local

    DIYnot Local

    Joined:
    3 Sep 2019
    Country:
    United Kingdom

    If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

    Select the supplier or trade you require, enter your location to begin your search.


    Are you a trade or supplier? You can create your listing free at DIYnot Local

     
Loading...

Share This Page