Floor tiles coming loose with clean backs

[danielz000]

Hi all,

Thought I'd sign up and see if someone can offer me some advice...

I (stupidly) laid some porcelain floor tiles using a non flexible ceramic powered adhesive. A few of these tiles have come lose and when they have the backs of the tiles are clean of adhesive but I can see that they had full contact with the adhesive from the pattern in the floor.

After re-laying one of the tiles with the correct flexible porcelain adhesive the tile once again came loose with a clean back. I've used this same adhesive on wall tiles without a problem so I'm pretty sure the adhesive is good.

I'm trying to work out what the likely causes of this is...

As I only re-laid the one tile I don't believe the adhesive skinned.

The subfloor is original 18mm x 13cm planks which I've laid 6mm hardie backer board on top of using adhesive and screws. Should this be enough to stop movement in the floor?

I can't see any localised movement/deflection in the floor but I asked a friend to jump up and down around the area in question and did feel like there was movement in the bathroom as a whole... Could this be part of the problem?

If the problem was caused by movement would you expect the back of the tile to be clean after it lifted off?

I thought about adding some primer to the back of the tile, is this something you can do and would it help with adhesion?

Any other thoughts or advice?

Cheers,

Dan

 

[Spare Tool]

Skim the back of the tile with adhesive with the flat edge of your trowel, most fixers do this to aid adhesion as a matter of course

 

[danielz000]

Thanks for the advice. I'll be certain to do that in the future.

I believe for the tile I re-laid I actually applied the adhesive directly to the tile not the floor but not entirely sure though.

Thanks again!

 

[danielz000]

Oh... Just remembered... I used a 6mm notched trowel as the felt the floor was extremely level. Is this adequate....?

Cheers all!

 

[Spare Tool]

I wouldn't use less than 10mm on a floor, 6mm won't give enough coverage, you could put 6mm on the floor and 6 on the tile with ribs in the same direction.

 

[danielz000]

Thank you very much!!!