Tiling On Concrete

Discussion in 'Tilers' Talk' started by nev, Aug 20, 2004.

  1. nev

    nev New Member

    Hi All
    I am about to attempt to tile my conservatory Floor(porcelain floor tiles) Which has just been laid. Does the new concrete need to be sealed Before i can lay the tiles?


  2. squeaky

    squeaky New Member


    I recently tiled my conservatory. First thing i'd check is that is as close to level all the way across. I didn't and topped up using more adhesive than I should of to make up for the deviances in the floor.
    The concrete should be sealed. What sealer you use is dependant on the adhesieve you use. I used diluted PVA it advised this on the adheiseve I was using (although I read somewhere on one of these forums you shouldn't use PVA). This prevents the floor from sucking the moisture out of the adhesive before it sets and seals in any dust on the surface.
  3. PVA isn't good, don't use it with any form of tiling...

    You should seal the floor with a suitable primer that is compatible with the adhesive you buy. i.e. buy Ardex primer for Ardex adhesive, BAL primer for BAL adhesives...

    Effectively it stops the draw (the sponge effect of the dry concrete) and creates a better adhesive bond.

    Also with porcelain tile, check that the adhesive you choose is suitable for porcelain, ceramic tile adhesive is not good enough. A quick read of the bag should tell you that it's suitable.

    BAL produce most of their adhesives containing "Porcelbond" and additive which makes them suitable for porcelain tile.

    But Ardex don't - so you would have to use an expensive admix - Ardion 90 to overcome this.

    Do your homework and you'll be just fine.
  4. squeaky

    squeaky New Member


    You say don't use PVA on any form of tiling. All the advice I've ever been given has said use PVA to prime walls/floors. When I search websites for info on this I can find various websites that tell you to use PVA but none that tell you not to. This website is a good example


    (sorry it's not a proper "link" as I don't know how to insert them)
    If you read any of the website in detail the guy really seems to know his stuff.
    I'm not saying you don't. I'm just puzzled as to the conflicting advice. Plus I don't want my tiles to fall off of my bathroom walls or come loose from my flooring as I primed with PVA.

  5. Mr GrimNasty

    Mr GrimNasty Active Member

    There are many roads to Rome. What works for one person is a disaster for another - such is life!
    I think there are many different grades/types of PVA product on the market. Over-dilution with water causes problems too.
  6. Hi Squeaky,

    I took a look at the webstie you linked, this sadly is the misinformation I'm faced with on a daily basis.

    I should expand on who I am and why I appear to hate PVA so much!

    I'm a professional tiling contractor, I now mainly specialise in natural products but over the years I've stuck up (or down) every type of tile there is.

    I have to give guarantees for my work (many of these projects are commercial such as sports centre showers and changing rooms). For me to be able to give guarantees I need to follow strictly the specification of the adhesive manufacturers.

    Ardex, BAL and Nicobond are the three suppliers I use most. Their products are similar in many respects, sometimes one will make products the other don't, and I also find some of there products more useful in different applications. All three of them have one thing in common, they all specifiy that under no circumstances may PVA be used before using any of their adhesives. If you do all guarantees are void.

    OK why then? Well I asked this question to Ardex when I once had problem, I'd tiled a bathroom that had been constructed in 25mm Marine ply. Thinking he was doing the right thing, the builder got his guys to seal the ply with unibond PVA...I wasn't aware of this.

    I tiled it and 6 months later every single tile fell off the ply, the adhesive solidly stuck to the tile but came clean a whistle off the ply.

    We had Ardex Technical down to the site to compile a report, the basis of which was it's the PVA that causes the problem.

    When you treat a surface with PVA it partly soaks in and parlty sits on the surface of the substrate much in the same way as wallpaper paste.

    If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky.

    When you spread tile adhesive onto the wall, the water in the adhesive makes the PVA live and stops the adhesive from penetrating the substrate and providing a mechanical grip. Basically your tiles, grout and adhesive are being held to the wall by a thin layer of PVA.

    Most tile adhesive works by crystalising when it sets (some are slightly different such as epoxy based ones) but generally they all work the same way. Once the adhesive starts to set crystals from and expand into any imperfections in the substrate surface (at a microscopic level) to create a grip. PVA stops this process by creating a barrier between the substrate and the tile adhesive.

    Ok so whats the difference between this and Ardex or BAL primer, well basically the tile manufacturers primers soak right in to the substrate and stop the sponge like "draw "effect but they don't coat the surface in any way, they are an impregnator as opposed to a barrier.

    I hope this clears up any misunderstandings.
  7. dewaltdisney

    dewaltdisney New Member

    Very interesting reply Mudster. For the record do you always mix your own adhesives or use ready made stuff. I used powder mix Bal grout, following advice off this forum, and I was amazed at how much better it is than the ready mixed stuff I have used in the past. Is this true of all adhesives as well?

  8. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    So we shouldn't be putting pva on the walls before plastering, then????????????
    Handyandy - really
  9. squeaky

    squeaky New Member

    As point out Ardex, BAL and Nicobond say don't use PVA. I have only had experience with unibond products and they say on the instructions that
    "very porous surfaces should be primed using a mixture of 1 part unibond PVA and 5 parts water, which must be allowed to dry"
    This is the reason I advise to use PVA. Obviously in future if I post advice I will add this to it so there is no confusion.

    Thanks for all you advice.
    icidentally do think Ardex, BAL and Nicobond products are better than unibond?

  10. screwfox

    screwfox New Member

    And what about Dunlop?
    I'm about to tile my bathroom floor, and the tile supplier suggested Dunlop adhesive with an additive to make it flexible.
  11. I've always used mixed my own adhesives and grouts, mostly because they are far higher specs than any ready mixed product.

    I can also mix the adhesive to a consisency that suits what I'm doing, and as a general rule cement based adhesives that require mixing can be bedded substantially thicker than ready mixed adhesives.

    However because I dont use ready mixed products I'm not really in a position to say of they are good or not, I tend to stick with what I know works.

    As for the BAL Grout, real easy to use, but always mix these things mechanically if you can (a whisk in a drill is perfect).

    Ardex F4 wall grout is not as nice to use as BAL - Nicobond tilers grout is just the same as Bal grout but can be ordered with a brilliant white finish (sometimes the bal finish can appear a little creamy against a bright white tile).

    Alwaqys remember to read spec sheets in conjunction with what it says on the side of adhesive tubs. Many adhesives that say they are suitable for showers are designed to cope with a hand held shower off bath taps, once a pumped shower or shower cubicle enters the equation, this type of adhesive is often no longer within the required specification.
  12. Squeaky,

    Unibond know what they are doing with their own products, and I have to say I've never used a unibond product. Not because I'm prejudiced, but because I've had no need.

    If were honest, Ardex, Nicobond and BAL primers probably contain PVA, but they also contain other chemicals that make them suitable for the purpose for which they are designed.

    If unibond say it's okay to do this with their adhesive, then you can get no better than the manufactureres recomendation.
  13. Screwfox,

    Every manufacturer provides a spec sheet or has information about what substrates it's adhesive is desgined to be used on. They also offer technical help lines and are genuinely pleased to offer advice on these lines.

    I'd be surprised if you tile supplier would advise you to use something unsuitable.

    If you want to double check, pick up the phone and call the number on the back of the Dunlop bag..:)
  14. Handyandy,

    I can't comment on this, I'm a tiler not a plasterer and the answer to this question probably is "It depends on the what the substrate is and how much mechanical grip is available to the plaster".
  15. dj.

    dj. New Member

    i have pasted most of your answer from mudster with a few adjustments for treating before plastering.....

    When you treat a surface with PVA it partly soaks in and partly sits on the surface of the substrate much in the same way as wallpaper paste.

    If PVA gets wet it becomes slightly live again, it doesn't completely return to it's liquid state but it becomes sticky. this is where it is ideal to skim

    When you spread plaster onto the wall, the water in the plaster makes the PVA live but stops the plaster from penetrating the substrate and providing a mechanical grip, thus giving a barrier from the existing wall plus an adhesive for your new skim.
    there is no need to skim whilst pva is still tacky as, with your new skim, it 'comes back' with moisture conterary to popular belief.
    hope this clears a few things up &
    thanx to mudster.
  16. carl8176

    carl8176 New Member

    Hi Mudster i have a question i have just formed a concrete shower base and intend to tile it, can you advise best adhesive and grout to use in a tiled shower and what to seal the concrete with? would really appreciate your advice.
  17. devil's advocate

    devil's advocate New Member

    Hi Mudster (I'm really going to have to resurect my 'choice of username' thread...)

    Excellent info - very useful, thanks.

    DWD, I've given up on ready-mixed adhesive/grout because it relies on the solvent (water?) evaporating, which causes the stuff to shrink - this is very evident with grout especially, which often needs to be re-applied to fill in the collapsed middle. So, mix-to-use type is so much better in every respect.
  18. Hello Carl,

    A shower base is about as hard going as it gets for tiling (apart from being outside). So go for a good quality powder based adhesive.

    If setting time is not an issue (you don't need to walk on it same day) then there is no reason to go for rapid set materials.

    I'd recommend Ardex X7 and buy the colour adhesive that suits your grout - white for light grout - grey for dark grout. Your Ardex supplier will have a suitable primer for use with the adhesive.

    If your supplier doesn't stock Ardex, then ak for an X7 equivalent as they are considered industry standard.

    BAL floor tile adhesive with BAL APD primer would do the same thing. The main thing is find a tile distributor if you can and buy from them - you'll be sold the correct product.

    Always tell them what you are sticking to - and what you are sticking down...stone, ceramic or porcelain.

    Good luck.
  19. carl8176

    carl8176 New Member

    Hi Mudster,
    really appreciate your help, cheers.
  20. Scousemouse

    Scousemouse New Member

    As I've now found "THE" PVA thread I'll stick my 2 penneth here.
    Plasterer was going to resurface my bathroom - all different thicknesses and surfaces. A weak PVA seal was advised so I did it. I used Wickes Waterproof PVA, thinking that I didn't want it soluble.

    Result was than the plaster skim didn't stick particularly well to some of the surfaces (I chased it and noticed it coming away quite easily). Also the skim plaster, which had the guy's usual amount of PVA in, but this waterproof one again, took much longer than usual to go off.

    Luckily I haven't sealed all over the plaster with it. It might be perfect for that, but I'm not prepared to experiment!

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