Cracking Floor Grout !!!!!!!!!!!!!!!!!!

[Branty]

Most adhesive manufacturers will tell you your ply was to thin.
As the grout has cracked down the middle I'd say that could be your problem.
If it was coming away from the tile, then it could that you haven't allowed enough time for the grout to fully cure.
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[quote=groutpad;71298]Did you put PVA in the grout mix. You don't need a lot but it does help.[/quote]
And you're going to train people to tile this way?

[MICK the Tiler]

Originally Posted by maudegonne

Gosh..... it sounds like I really have to stop listening to advice given in my local tileshop. Because they told me to use PVA (so it spreads easier) and they also told me to seal travertine before grouting.....
How long before this breakdown of the grout will occur? I did use it on my own floors. They have been down for a year and a half almost and it still looks fine.....
Just wondering.... suppose there is nothing I can do about it now....

Hi Maudegonne,

I want to clear up a few things about the term PVA as to what I understand it to be, of course the same term might be used to describe other products in use today.

The term "PVA" or polyvinyl acetate is a woodworkers glue used to bond celuloid based materials together. (Wood paper and types of cloth) to create a ridgid strong joint. It is white or yellow in colour and dries clear.

Using this wood glue as a primer or admix in glues and grouts will lead to it being attacked by alkaline salts causing it to convert some of it's chemical components to acetic acid.

All glues and grouts used today are highly engineered cements that companies have spent millions of dollars researching and developing so to give us the freedom of just ripping open the bag and mixing, making life for the tile fixer much easier indeed. These engineered cements don't need any more help from us to do there job, as long as the correct materials are selected correctly in the first place.

By adding something foreign to the cements with the assumption that it will make them proform better than they were initally designed is just plain naieve at best neglegent at worst. This practice needs to be controlled on the part of the tile fixer by only using products that complement or are authorized to be added to engineered cements. Tech spec sheets from your glue and grout manufacturer are the only way of assuring the products to be used are correct and in accordance with the terms and conditions set out by that particular manufacturer.

It is the professionals responsibility to obtain, read and understand these terms and conditions and to build his/her own reference library regarding the different materials and there uses, so at a quick glance the correct products can be choosen to proform the required tasks with absolute confidence.

Unfortunately there has been no study or concrete eviedence that using PVA as a primer or admix will adversly affect a particular installation, But basic chemisry of acid and alkaline should lead one to the conclusion that using the "True PVA" (Woodglue) would not be the wisest of decisions to make on your next installation.

Hope this clears up a few things.

Cheers Mick

[Dave]

This is an article that has been on the forums for a while now...so i thought i would add this to micks reply as well..........

PVA - Why you shouldn't use it as a tiling primer
This article has been written by Alan at AT Stone who is a Professional Tiling contractor, He now mainly specialise in natural products but over the years He stuck up (or down) every type of tile there is.

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.

[MICK the Tiler]

Nice one Dave .................................Got all bases covered wet and dry areas.

Written far better than I ever could.

[Branty]

To top posts there. Was aware of the effect water had on PVA, had no idea about the acid stuff. Very informative.

[Daywalker]

Hi all i've found out why the fully flex floor grout has cracked, its because there was'nt enough floor addy between our tiles meaning there's a bit of a deep void between the tiles, so when the grouts dried within 2hr a hair line crack appared. it happened to a tiler friend of ours so make sure you've got some addy inbetween them tiles and dont make my mistake.

[Fekin]

As others have pointed out there can be a lot of reasons why this has happened.

Most likely to blame in my view would be the thin ply allowing too much movement, but that would have only caused the cracking if it had been walked on just afterwards.
If no one had walked on it then I would be thinking the grout mix was too wet, or the room was very hot and caused the grout to dry far too quickly.

Or the grouts faulty.

lol, might as well ignore what I just said as you posted your reply as I was typing mine

When tiling floors you should always aim to get 100% adhesive coverage to avoid tiles cracking anyway.

Edit again

Just re-read your last post, you don't have to get adhesive inbetween the tiles "in the grout joint, just work the grout right into the grout line to fill it in the first place so you don't get shrinkage.

[Daywalker]

hi Fekin you could be right about the 9mm ply but i think its because i did'nt push the grout in firmly enough! and also the customer had switched her kitchendown lights on below us after us asking them to remain off etc!
Any way i'm going to use 12mm ply from now on just so this cant happen again.