Tiling on a sandy wall

[nahcartsnai]

Hi, my wall tiles in the kitchen were starting to come off and large chunks of them sounded hollow.

We decided to retile the kitchen and they just fell off the wall with the plaster attached. The cement on the walls was so sandy that the plaster was not sticking to it.

All tiles have now been removed and if I rub my finger along the wall a few times I can create a groove in the sandy cement. That lets you see how sandy it is.

I am now ready to start tiling, but should I use some sort of stabilising solution or PVA to prevent them from falling off with a layer of sand , or should the tile adhesive be sufficient?

many thanks
nahcartsnai

 

[novicetiler]

It sounds as if that cement needs to come out. I am not an expert but if you tile on top of it you are gluing the tiles to sand, which is why they came off in the first place. if you put pva on it (don't by the way) then you are sticking your tiles on to a thin sheet of unsitable primer attached to unsuitable cement.

assuming there is no rising damp in the wall, then sadly i think you should chisel out the cement with a boulster, then replace it with a sand and cement mix and a trowel. Ideally then you should skim it with plaster, run a clear strip silicone bead along the the worksurface and plaster (i.e back seal it). then tile straight on to the plaster (no pva) and then seal as usual.

what does anyone else think?

 

[nahcartsnai]

Novicetiler, thanks for the reply.

Chipping out all the sandy cement seems a bit much, but if thats the only way to do the job I suppose I will need to do it.

BTW: The sandy cement screed on the walls is about 2cm thick, and I have to tile approx 9sq metres - so chipping it all off is not a task I would take on lightly.

I have read the post on why not to use PVA, but I just need final confirmation that I cannot use a stabilising soloution (Blackfriars or Leyland etc), or that the use of a primer such as BAL APD or Ardion 51 would not sufice.

 

[novicetiler]

If you hired a kango you could get the whole lot off extreemly quickly.

As for the stabilising solutions, to be honest i don't know, it might be a case of following manufacturers instructions and hoping for the best!

 

[Loony Paul]

I would plum for you not taking the cement off unless as last resort as its one hell of an extra job to have to do. It should be possible to bind it using a suitable primer - look at the bal adhesives website and phone their technical helpline to ask for the best product.

 

[joe-90]

Wickes do a waterproof PVA that IS reccommended for tiling (even in showers). It's on special at the moment.

However, if it sounds hollow it's not fastened to the wall and must come off. You can patch it if it has only blown in places.


joe (who has never had PVA problems in 30 years)

 

[Mudster]

Wickes PVA is recommended for use in showers by the manufacturer of Wickes PVA, there is no one who will sell you an adhesive that will not have a voided guarantee if you use this. (Ironically including Wickes who sell a rebranded adhesive).

Wickes also sell low quality marble, on the box of marble it states quite clearly that the back of each piece of marble should be coated with PVA before it's fitted.

I'm a marble importer, I specialise in marble and the associated products. What Wickes advise, is quite possibly the worst thing you could do to marble before fitting it.

I have written to Wickes to actually point this out and am yet to recieve a reply.

A great deal of the advice provided by Wickes, in writing is factually wrong.

 

[joe-90]

No company will put a label on a product that isn't true and tested.

I've tested it. It is completely waterproof. I've left it submerged all day on card, wood, and brick. It does what it says on the pack - stays waterproof. It doesn't reconstitute at all. The other companies are simply trying the oldest trick in the book to make you buy their own product. This stuff is good.




joe

 

[Softus]

No company will put a label on a product that isn't true and tested.

I've tested it. It is completely waterproof. I've left it submerged all day on card, wood, and brick. It does what it says on the pack - stays waterproof. It doesn't reconstitute at all. The other companies are simply trying the oldest trick in the book to make you buy their own product. This stuff is good.

What does your label read joe? I suspect that whatever it says it represents a repudiatory contravention of the Misrepresentation Act.

 

[joe-90]

It says: Waterproof PVA Add Mix adhesive. sealer and primer.
Specially forumulated for exterior and wet conditions.
Waterproofs cement and render.
Toughens floors and screeds.

Tiling: This PVA is ideal for priming porous surfaces prior to wall tiling in wet areas such as showers.




I've left some on card in water overnight and there is no sign of it reconstituting. Once it has dried it stays dried.

It's just like the sealents that other companies make that has a modified polymer base that doesn't reconstitute. All the other sealents are PVA based just the same.


joe

 

[Softus]

I didn't mean the product label, I meant your label - the one with "joe-90" somewere written on it. Do you do what it says on the tin joe?

 

[Mudster]

No company will put a label on a product that isn't true and tested.

I've tested it. It is completely waterproof. I've left it submerged all day on card, wood, and brick. It does what it says on the pack - stays waterproof. It doesn't reconstitute at all. The other companies are simply trying the oldest trick in the book to make you buy their own product. This stuff is good.

joe

Actually that's not true, company's will put labels on products until they are proved wrong.

Is this Poly Vinly acetate or Poly Vinyl alchohol?

It does make a difference.

And you state it's waterproof, yet is must be water soluble to be able to mix in the situations you descirbe or it wouldn't combine.

So which is it?

Water soluble or water proof...because chemically it can't be both.

 

[joe-90]

And you state it's waterproof, yet is must be water soluble to be able to mix in the situations you descirbe or it wouldn't combine.

So which is it?

Water soluble or water proof...because chemically it can't be both.

Then why doesn't exterior varnish wash away? Or bathroom paint? Or masonary paint?


joe

 

[Mudster]

It could be a polymer modified primer in whch case they are doing themselves no favours describing it as PVA as technically it's no longer PVA once the acrylic polymers are added to it.

It becomes an SBR.

But whatever has been added to it, it's used before any of the main manufacturers primers negates any guarantee that they offer.

And seeing as the correct primer costs the the same a tub of Wickes All singing all dancing you can build a swimming pool with it PVA, then why would I choose to use this and negate any guarantee offered by the adhesive manufacturer.

Also it's advised use on the back of natural stone before any form of fitting is plain wrong no matter what polymer modification is included in it, it will provide a barrier to the adhesive holding the stone in place.

 

[Mudster]

And you state it's waterproof, yet is must be water soluble to be able to mix in the situations you descirbe or it wouldn't combine.

So which is it?

Water soluble or water proof...because chemically it can't be both.

Then why doesn't exterior varnish wash away? Or bathroom paint? Or masonary paint?


joe

Lets deal in facts:-

PVA is water soluble, it is also not waterproof even when set.

If PVA is modified with polymers or Acrylics,( which can make the end product waterproof) then it is no longer PVA it should be described by another name which is relevant to what it's modifications are.

So if Wickes are selling a genuine waterproof pimer they are doing themselves no favours calling it PVA.

So best case scenario, they have misnamed their product, worst case they are misdescribing it's properties.