Hi I have read loads on here about the pva issue for priming/sealing plaster before tiling and I would like to open the debate once again.
Back in 1993 i tiled my bathroom with ceramic tiles on to a plaster skim sealed with pva, there is a shower over the bath that has been used 3 or 4 times a day throughout that period and there is no sign of any loose tiles.This was at a time when there was no alternative to pva and no internet like today to discuss this sort of thing. Anyway time has come and Iam about to refit the bathroom, i will be removing the bath and fitting a 1700mm shower tray in its place and will be tiling the walls floor to ceiling using 305x305x10 travertine and a cement based adhesive and profesional stain resistant wide joint grout, both Larsen products, I will seal the tiles with Seal-Guard Impregnator,3 coats. I have used these tiles before on a plaster skim but in a dry area and the result is impressive. My main question is concerning waterproof PVA. I have some "Evo Stik waterproof adhesive,sealer & primer" The instructions on the tub state and Iam quoting here under the title Wall Tiling "Waterproof Evo-Bond PVA is ideal for priming walls before tiling in wet areas such as showers" It only states priming, does the plaster need to be sealed as well and why should water penetrate through the whole thickness of the tile anyway if it is sealed properly.
For porus surfaces mix1:5 with water non porus surfaces1:1 with water.
Is the issue with using pva to do with using cement based adhesive as opposed to straight out of the tub cheap stuff.
Iam an experienced diy'er having done lots of building projects and have been in engineering for the last 35 years so it would be nice to get to the bottom of this with facts or evidence. You are the best people to ask who are doing the job every day. Iam not a greengrocer or bank clerk type who has no idea.(no disrespect intended) Thanks in advance for your comments.
Neill

unfortunately some 'diy' companies still haven't learned of the pitfalls of using pva as a primer for tiling. just like tubbed adhesive it goes back to it's liquid form when in contact with water which in turn could de-bond the tiles. your sealed tiles may well not leak water but even water resistant grout is not 'waterproof' hence the need for tanking the walls prior to tiling. if you're not familiar with this do a forum search. a tanking kit can be obtained for around £60 and is well worth the money. most tilers won't do a bathroom without using one (unless the shower area has waterproof backer boards installed). also it would be worth you spending a few minutes registering on here then you'll get more replies

There was alternitives even in 1993!

Thanks Ball.B
But it proved that pva was more than ok over a long period and it would'nt have been waterproof

Originally Posted by Unregistered

Thanks Ball.B
But it proved that pva was more than ok over a long period and it would'nt have been waterproof

just because you got away with it it don't make it right. we're just trying to advise you to the best way

There were other materials that could have been used 30 years ago for sealing but many went with the pva as it was all they new at the time, power showers and the like are now fitted and people are having larger tiles fitted which now needs cement based adhesives to fix them.

It maybe worth looking at tile weights for your plastered walls as well Tile Weights.

Thanks for your reply Mike
Yes, i did as you say get away with it and Iam looking to do the job properly and for it to last a long time, that is why Iam here looking for sound advice but I would also appreciate the reasons behind the advice so I can understand why Iam doing what is advised, so I can make an informed decision.
Thanks

My Grandad smoked like a trooper for 70 years and didn't die of lung cancer.
I guess he got lucky!
The PVA argument isn't an argument anymore.

So what did he die of then

PVA poisoning

cut down in his primer was he.

Be sensible

????????

Originally Posted by Gall.B

????????

Not your post Brian

Sorry

Sorry!

Shame. 13 replies and only two sensible answers, what am I supposeto think of that? And no, luck does not come into it, obviously the job was done well for it to last as long as it was needed.

Originally Posted by Neill1

Shame. 13 replies and only two sensible answers, what am I supposeto think of that? And no, luck does not come into it, obviously the job was done well for it to last as long as it was needed.

If you wish to continue to use PVA then go ahead.. you have been told it is not suitable as a tiling primer and all you want is to be told other wise.. PVA does not prevent Etterignite failure and can become live again with moisture from the adhesive or water ingression, so why take the risk no matter how long it was tiled before..?

I cannot see why you persist in this matter.


This info might help you,, who knows..

PVA stands for polyvinyl acetate, and it is a rubbery synthetic polymer. It is commonly emulsified in water and used as glue. Many know it simply as "wood glue", or "carpenter's glue".

Cementious materials, such as many tile adhesives and grouts, or other materials which contain cement, such as concrete, are alkaline. Simplified, that means they have a high pH.

Alkali slowly attacks polyvinyl acetate, forming acetic acid, which has a low pH. Cement doesn't dry per se; it cures through hydration, which means it binds the water you mix it with chemically. This causes the pH of the substance to rise dramatically. Introducing an acid negates that process to some extent, preventing the cement or conrete from binding all the water it needs to harden properly.

It is hydrolysis which gives cement and concrete products strength, and holds them together. Without this process, it would merely be the powder you started with.

The acetic acid which is formed when cement and PVA comes into contact, either through mixing them, or "priming" with PVA, will continually free the water bound in the cement, and that will weaken the bond and/or integrity of the material. The effect is accelerated if the material is subjected to moisture, which is more or less always the case.

PVA isn't water resistant. It becomes slightly live when exposed to moisture, and this in combination with the exposure to alkali, accelerates the forming of acetic acid. PVA which is marketed as "water resistant" or "exterior grade", has additives which makes them water resistant, but they're not alkali-resistant.

I thought impish's pva poisoning reply was funny But on a serious note, I really like the chapter above, Dave, can I quote this to my mosaic artist friends? Did you write it or someone else? There are still too many who seal garden pots with pva, then using cement to fix the mosaics and then are surprised when stuff falls off. This would be perfect to send out....

Yes use it.. it was part of sWe's guides..

Originally Posted by Neill1

Shame. 13 replies and only two sensible answers, what am I supposeto think of that? And no, luck does not come into it, obviously the job was done well for it to last as long as it was needed.

Sorry I didnt take you seriously Neil, the impression I got was that you where some know it all spoiling for a fight, or it was somebody at the wind up.

Profesional fixers who know there stuff dont use KIDS glue as a bonding agent but you know better, why dont you show Delia how to cook next?

Originally Posted by Gall.B

Sorry I didnt take you seriously Neil, the impression I got was that you where some know it all spoiling for a fight, or it was somebody at the wind up.

Profesional fixers who know there stuff dont use KIDS glue as a bonding agent but you know better, why dont you show Delia how to cook next?

When someone tries to get a reaction then this is trolling.. please do not react or feed forum trolls.. This is a friendly forum and it stops that way..


Thread closed to prevent anymore unwarranted replies.