Tiles coming up

[dhsanta65]

A tiler friend of mine has just laid 60m2 of 300x600 porcelain on a very stable chipboard floor overboarded with 12mm ply. He grouted some of the floor then went back the other day to finish grouting only to find that some of the grout craking on previous grouted areas, so he tried to pop a tile wich came away clean and had not bonded to ply.
The overboarding was do a month prior to tiling and has now found out from the customer that she had been washing the ply with soapy detergent, ply had been bonded with a SBR primer (this was after she had washed floor) but could the detergent be the cause of the adhesive not bonding to ply??

[hillhead]

Hello Ian,
I would say the detergent has added the moisture without a doubt.
Then the SBR has sealed it in.
Plywood is mainly from china now and it's not good for tiling( fact).
Backer boards would have been the safer option.
It will all have to come up IMO and replace with hardie backer or similar, the moisture destroys it when penetrated.
I'm on a job here and have marble windowboards to cut and shape and the clown joiner raised the levels for me, when he was gone I looked and he has damp ply on there, I'm going to stick and screw ditra on top for safety.

[hillhead]

Also the back and edges of the ply should only have been primed, it's so prone to moisture it's unreal. I'm after covering here with ditra, adhesive and screws. Hope that works too.

[Dave]

Contaminated ply will be a mare to stick anything too.. Over lay with a cement board would be the best option.

[Bob McLean]

A 2 part adhesive may have resolved the problem the latex causes the adhesive to stick to anything. BAL have a product which can be used to secure tiles underwater (swimming pools) and with the chemicals used in pools it works. I've also found it to be more flexible than Mapei Kerraquick & latex. Both products are expensive especially BAL.

[Dave]

If the ply is contaminated Bob, then sometimes nothing will bond.. as in soap scum etc..