Tiling on a sandy wall

[confidentincompetent]

Looked at empips link. the john94 site includes pva to be used as a primer for emulsion on bare plaster/ drylining Im not a tiler or plasterer but do dabble, Decorating is my main trip and having done it for 30+ years I have never, or cannot see why they advocate using pva. It just lays on surface and prevents emulsion soaking into plaster, You may as well paint on top off varnish Good test : if a wall has been pva'd try making an X with a knife blade, stick masking tape over the x and pull off, the emulsion will stick to tape = unsound coating. If you do same with wall that was mist coated with emulsion you wont get paint on tape,= sound coating. well only a little bit Not joining in this spat as i'm no plasterer but thought I would let you know I dont trust that site if it dont know basic decorating.
have fun

 

[joe-90]

This is a typical post of someone not understanding how to use PVA. You mix it with water so that it DOES permeate the surface. It isn't recommended for use under emulsion BTW.


joe

 

[Softus]

This is a typical post of someone not understanding how to use PVA. You mix it with water so that it DOES permeate the surface. It isn't recommended for use under emulsion BTW.

IMO, joe is absolutely correct here cc - if you read the instructions, and use the right ratio of PVA and water, then PVA will not only bond some materials to the outer surface but will also bind quite crumbly surfaces onto a firmer base.

Using an example from first hand experience, a decorator (not a good one like you, but a poor one), gaily papered a wall with what I shall call standard paste. Two days later the paper was stuck fast to the plaster, but the skim coat came away from the underlying layer.

Cause? The plasterer was not competent having skimmed over a badly prepared surface. However, having already had reason to suspect the plasterwork, I had specifically asked the decorator, before he started, if he thought the walls should be plastered again first. He said no; fair enough - we all make mistakes. But his unforgivable failing was not to run a test before doing the entire room.

So, before he went on to the next room, which was in the same state, I used PVA, letting it soak right in to bond/bind the plaster. Result? The paper stayed up until stripped off when it had outlived the appeal of its pattern.

 

[confidentincompetent]

This is a typical post of someone not understanding how to use PVA. You mix it with water so that it DOES permeate the surface. It isn't recommended for use under emulsion BTW.


joe

[b]Thats my point! The john49 website says it is suitable for priming bare plaster prior to painting[/b]. Erm I understand the principle of diluting pva btw surely you dont think I ever put this stuff on neat

 

[confidentincompetent]

This is a typical post of someone not understanding how to use PVA. You mix it with water so that it DOES permeate the surface. It isn't recommended for use under emulsion BTW.

IMO, joe is absolutely correct here cc - if you read the instructions, and use the right ratio of PVA and water, then PVA will not only bond some materials to the outer surface but will also bind quite crumbly surfaces onto a firmer base.

Using an example from first hand experience, a decorator (not a good one like you, but a poor one), gaily papered a wall with what I shall call standard paste. Two days later the paper was stuck fast to the plaster, but the skim coat came away from the underlying layer.

Cause? The plasterer was not competent having skimmed over a badly prepared surface. However, having already had reason to suspect the plasterwork, I had specifically asked the decorator, before he started, if he thought the walls should be plastered again first. He said no; fair enough - we all make mistakes. But his unforgivable failing was not to run a test before doing the entire room.

So, before he went on to the next room, which was in the same state, I used PVA, letting it soak right in to bond/bind the plaster. Result? The paper stayed up until stripped off when it had outlived the appeal of its pattern.

Well I agree this is a case for pva for hanging paper onto bare plaster. Erm what did the decorator use for size on bare plaster? did he even prime it with anything? I've always got some pva to hand it's got it's uses but not on bare plaster prior to painting.(like john49 site says) I think it's praising pva up a bit though when you reckon it will stick skimming back onto bonding no matter how thin you knock it up! more like your decorator didnt prime/size and had to put so much paste on to combat suction he destabilised the bad skimming. Any way main point is when you strip wallpaper off wall that has been pva'd then emulsiond you will get most of of emulsion stuck on paper as pva has gooed up no matter how thin it was applied resulting in a messed up flaky wall.Though have t say I have used pva to stabilise exterior dash where chippings were loose But hey that was 10 years ago and its still perfect sooo

 

[Softus]

Please don't shout - it really isn't necessary.

 

[Mudster]

I recieved a reply today from John Schmitt, a reasonable amount of which went over my head I have to admit, I've asked for a reply in more laymans terms and some answers to specific questions as most of it was very general and non specific.

I've also asked him if I can repost our conversation and will do so once I have his reply.

 

[joe-90]

I don't know John Schmitt.

I know Jack Schitt, if that helps.



joe

 

[masona]

I recieved a reply today from John Schmitt, a reasonable amount of which went over my head I have to admit, I've asked for a reply in more laymans terms and some answers to specific questions as most of it was very general and non specific.

I've also asked him if I can repost our conversation and will do so once I have his reply.

Yes, same here, John doesn't want to join the diynot forum either.

 

[Mudster]

Actually I exchanged three emails with him in total, His advice amounts to (and is stated on his website) that you take the advice of the manufacturers as they have spent alot of time and money investing in the said products etc etc....

I then pointed out that the manufacturers advice clearly disagreed with his, to which He explained that He knows better than the technical departments of either BAL or Ardex. err OK.

I asked him to comment on the waterproof PVA that wickes sell, and some other parts of the specification contents of his site and He's no longer replying.

I emailed and phoned BAL, BAL said they will only provide technical information for thier own products and only recommend or provide guarantees for thier own Primers. They were unwilling to comment on the technical suitablility of PVA only that it voids any guarantee they offer.

I emailed and phoned Ardex, Ardex said basically the same as BAL, except they did go on to give an explanation of why not to use PVA which is basically as I explained on my post "Why PVA shouldn't be used as a primer for tiling".

John Schmitt did expalin He was a specialst in this subject and had tested various primers over the years, but He would not answer specific use questions or any direct questions regarding the waterproof PVA other than stating "I'm sure Unibond would have something to say about Ardex's comments".

 

[masona]

No wonder John saying out of it

 

[Mudster]

Actually I got the feeling, particularly from the tone of his first reply, that He felt He was far to important to be discussing anything with someone as ignorant as me.

After All I've only been tiling professionally for 15 years, so what would I know.....

 

[masona]

After All I've only been tiling professionally for 15 years, so what would I know.....

Agreed, nobody can take that away from you, I've rather take advice from you than some of these manufacter's who will sell anything.

 

[jbonding]

if it was that obvious to them they would of elaborated, or if it was detrimental they would keep their mouths shut . So what did they do?

 

[Mudster]

Well actually Ardex were and are very happy to elaborate, give them a call they'll give you all the technical reasons why you shouldn't use it. Which I've covered in my post "Why you shouldn't use PVA as a tiling primer".

Ardex Technical 01440 714939.

BAL just didn't want to be drawn into it other than saying it voids all their guarantees. That says as much as any technical explanantion.