An example of a PVA disaster... just now, in a mosaic artist group I belong to, this poor mosaic artist, commissioned to do a 24ft! community mosaic had this happen to her mosaics 2 days after it was installed - she used exterior ply (wrong), primed it with pva, (so so wrong) and then used a cement adhesive and grout - this is the result. Yes, I have given the lecture... have given it several times before but it's horses to water, isn't it... and it doesn't help that most mosaic books on the market still say, "prime with pva solution".. bladibla..

mosaic pva fail 1.jpgmosaic pva fail2.jpg

Brilliant post G, pictures really are better than a thousand words

If I are allowed,Olympic swimming pools have isolated using both variants,I think the most dependent on experience,are authorized by Mapei and Schlüter Systems.However, trying to stop water, but it is impossible in the long term.

Originally Posted by Eduardo

If I are allowed,Olympic swimming pools have isolated using both variants,I think the most dependent on experience,are authorized by Mapei and Schlüter Systems.However, trying to stop water, but it is impossible in the long term.

not sure what you mean

Hi guys

This has probably already been covered but could you recommend a primer? to go directly onto a painted wall prior to tiling? can i use a basic builders one? and what mix would i need?

the room is a en suite with a shower cubicle in it. The walls have several layers of paint on them. I was oblivious to the need for primer - but my mate mentioned that i 'would need to PVA the walls first' so any help would be most welcome! Many thanks Dan

i would strip the paint off,prime with a suitable acrylic primer not pva

Cheers dave, i've always said pva is for for making rockets outa toilet roll centre's in a classroom. lol

Hi All,
I am feeling ever so slightly gutted at the moment.
Just joined your forum and just read this thread. (God do I wish I had fund this 3 weeks ago).
Guess what?
Just spent the last 3 weekends filling and preping my bathroom walls (4) ready for tiling.
Finishing it off with 2x coats of 5:1.... PVA!
The prospect of tiles falling from walls in the not to distant future is not a vision I wish to contemplate.

Anyone got any suggestions on the best way to resolve this problem?

And please don't ask why I did this. It was on advice from a friend of a friend of a work friend (who I have subsequently just found out..... is a plasterer!).

Many thanks
Victor
(head in hands)

I would remove the PVA mate, I presume you haven't started tiling yet. You will need to soak the PVA to soften it then scrape it off, make sure you allow the wall to dry completely before applying SBR primer. Good luck.

as above you can use an abrasive pad to losen.

Originally Posted by victic

Hi All,
I am feeling ever so slightly gutted at the moment.
Just joined your forum and just read this thread. (God do I wish I had fund this 3 weeks ago).
Guess what?
Just spent the last 3 weekends filling and preping my bathroom walls (4) ready for tiling.
Finishing it off with 2x coats of 5:1.... PVA!
The prospect of tiles falling from walls in the not to distant future is not a vision I wish to contemplate.

Anyone got any suggestions on the best way to resolve this problem?

And please don't ask why I did this. It was on advice from a friend of a friend of a work friend (who I have subsequently just found out..... is a plasterer!).

Many thanks
Victor
(head in hands)

Yes Plasterers use PVA, but Tilers do it properly.. .. we use Acrylic or SBR primers.. never PVA..

Thanks for the advice.
To be honest the prospect of trying to get this PVA off is not one I particularly relish.
Could I get away with covering with a thin skim of plaster and then use a primer?

Dont beat yourself up too much victic - I found this "Expert" on the internet telling prospective floor tilers it was essential to put PVA on ply before tiling.......... Yes its a Tommy's Trade Secret (lol)

Tommy's Trade Secrets - How To Tile A Floor - YouTube

That looks like chipboard...

I just put a comment on there, don't think they will allow it though.

Originally Posted by Dave

TilersForums.co.uk recommends Mapei Adhesive, Grouts, Primers and Silicone for use with all wall and floor tilers.

See www.Mapei.co.uk for more information.

MANY PEOPLE THINK THAT P.V.A. IS OK AS A PRIMER ON WALLS AND FLOORS SO I THOUGHT THAT I WOULD LET YOU SEE THIS " LINK " AND HOPEFULLY IT WILL ENLIGHTEN SOME NEWCOMERS OR EVEN EXPERIANCED TILERS AS WHY NOT TO PRIME SUBSTRATES WITH P.V.A. INSTEAD OF PRIMERS.........DAVE.....


P.S. I always prime with primers and this will show you why!!!!!!!

PVA - Why you shouldn't use it as a tiling primer

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 specify 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 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.

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 crystallising 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 what's 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. They also stop a chemical reaction occurring between the cement based adhesive and a plaster substrate, a known problem know as "Ettringite failure"

I hope this clears up any misunderstandings.

So only use PVA before tiling if the adhesive manufacturer specifies it in the instructions.

Good point Dave

I have told old and new tiles for months and months to not use PVA and still they do. They try and make you look silly when you explain why not.

And you know what the answer i get? " I HAVENT HAD A PROBLEM YET, been using it for years" and i shake my head and say YET.

Oh well i will keep trying to spread the word and upsetting tillers when i tell them not to use PVA. Getting fed up of it now!, telling tilers to join TF to see for their selves.

Oh do you mind if i print this off Dave and put it in front of the primers in my shops?

Originally Posted by Discount Tile Supplies

Oh do you mind if i print this off Dave and put it in front of the primers in my shops?

Go for it , anything to stop idiots using pva

bal apd the best