Tiling over a concrete floor which has already had a coat of PVA - TilersForums.com

[Ajax123]

in the

Just asking, how does one know that vinyl tiles has asbestos? what made you suspect they had asbestos in them?

many thanks

during the 1940's and right up to the early 80's some tiles were made using asbestos. they were used extensively in council housing so if you have a councli house with the old style marley tiles on the floor and it was built before about 1980 there is a good bet they contain asbestos. it is possible to proove under a microscope but the reality is that people operate under the law of averages as it is likely they do rather than deffinite. the thing is though with asbestos it is not dangerous unless you start messing about with it, e.g. drilling cutting or snapping it... or chucking it on a bonfire... if these tiles are on the floor my opinion is that it would be better to come up with a solution whereby they can be left in place but that doesnt sit well with tiling. lots and lots of asbestos has ben removed un necessarily over the years. it is not illlegal to do this yourself but disposal is difficult. some local authorities still assist by offering special bags and advice and where i used to live there was a tip that handled asbestos waste under very strict rules. nevertheless it is probably better to get a professional acresditted company to deal with it for you if you aRe not sure

 

[NZ_Tiler]

This is from an old member, sWE, I think it's a pretty good explanation.

PVA and Cementious Materials

I hadn't even heard of using PVA for anything tiling related before I came on here. Thus, I read up on it, and here follows my findings:
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 hydrtion 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.

 

[Matt Bott]

Wow that is really helpfull

 

[Dan]

We have the perfect combination of tile and flooring related geeks.

We'd give NASA a run for their money building rockets if we had the time eh