Pva Versus Primers | Always Use A Primer When Tiling, And Not Pva

[paul dignam]

Re: P.v.a. Versus Primers......

bal apd the best

 

[afright]

SBR All the way used bal bond for over forty years use it on walls and floors never had a problem

 

[digbysdad]

THIS SOUNDS LIKE SOME OF MY PROBLEM. i KNOW THEY USED PVA ON THE CALCIUM SULPHATE FLOOR. SO WHAT TO DO. DO YOU THINK WIRE BRUSHING ALL 50 SQ MTR AND PRIMING IT WOULD BE THE WAY TO GO?

 

[afright]

In the early 70s Bal primer came in a one gallon tin and it had a reddish tint so you could see where you primed ,it had a few drawbacks it was highly flammable

(as one of the tiler,s I work with found out while using the primer the boiler came on and the whole kitchen had a flash over) and the other was any dropped on a plastic bath stained it I was so glad when they took it of the market.

 

[Concrete guy]

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.​

I wrote this article quite a few years ago in a previous business life. It's funny seeing it still in use today.

At the time I took a lot of flak for it, I even had PHD Chemist take me to task and tell me it was a load of hogwash despite the adhesive manufacturers spending hundreds of thousands of pounds on research and developing suitable primers and adhesives.

I'm glad it stood the test of time though and is still relevant today.

 

[DHTiling]

There used to be a link to your site as well but over the years i cannot remember where it went lol lol.. but deffo served a lot of peeps well by reading this and not using pva.

 

[Concrete guy]

There used to be a link to your site as well but over the years i cannot remember where it went lol lol.. but deffo served a lot of peeps well by reading this and not using pva.

I'm no longer tiling, my knees and back couldn't cope with it any longer!

My business now would conflict with one of your forum sponsors so it's not really appropriate to link any longer.

It is good to know people made (and are still making) use of it.

 

[bramleyman]

Re: P.v.a. Versus Primers......

enjoyed this thread and feel newly educated. can someone please tell me what SBR stands for so i can die a happy man?
regards Alf

 

[White Room]

Styrene Butadiene Rubber....

 

[robbieraven]

Re: P.v.a. Versus Primers......

Victor, many years ago before I knew what I was doing I did exactly what you did. My tiles are still on in a shower cubical in my own house, 6 years on. But like you when I first found out I went numb, have never done it again, listen to the advice of the guys and do it properly, you'll sleep better at night

 

[High Peak Tiling]

Another brilliant post Dave,

 

[Sean SML Tiling]

What about sbr bond is this classed as pva or more of a primer?

 

[DHTiling]

SBR is not PVA and yes ok as a primer.

 

[Sean SML Tiling]

So is it ok to use sbr as an additive or would u recommend using webber primer if using webber addy?

 

[DHTiling]

Additive..? .. Weber supply additives for the adhesives and one for the grouts.. what are you trying to achieve..?