Help please ! Bathroom floor

[Realstokebloke]

Hi - have covered this on "my first job" thread but...i fear the floor aspect (potentially most serious) has got lost in amongst the wall disasters...and i'm still floundering.

I had previous tiles straight onto green chipboard with a tub flexi (no ply) no nothing infact & used an ordinary tubbed grout with a flexi additive. &, against all odds (i now know) it was solid & uncracked.

They were solid & a to get off in fact - the adh. was a little "spongy" is the best way to describe it - but it worked!

this time i bought (what i thought) to be a decent cement adhesive (but now, not so sure) Unibond Rapid set ultraflex & the best Mapei flexi coloured grout - forgot the exact name - (both as mixes) thinking i'd get a better result.

This time, i 'ply-wooded' it & did a 5:1 PVA seal over as per the bag instructions on the unibond.

But...two of my tiles popped straight off. i phoned unibond who told me the ply i used was too thin (6mm vs 15mm as per BS Regs) but...that should affect it too much & to be fair got me to send back a sample for testing (still at the lab) & gave me a credit for a new bag of same.

I cleaned it all off & them down again but the still move a little & so have to come up.

I also contacted mapei about the grout (cracking accordingly) & they scoffed at the 6mm & laughed at the use of PVA.

But, as per above, i really, really, don't want to take the floor up (the tray, toilet are in & down as above - & there would be a divorce) to start putting 15mm + down + more new tiles.

Any ideas?

Obviously, i'd scrape any PVA off & add more screws into the chip / joists below for added stability.

But,how 'far' back will i have to go?

Can i re-stick them with a better adhesive?

Can i add a dollop of flexi additive to the grout to help?

Also, where it's stuck, the grout has really 'stuck' - any best ideas for grout removal where it's cracking?

And any better grout instead? Mapei even said silicone ?? : 0

I really, really don't want to have to strip out the tray & loo (sink not in yet) etc to start again on the floor if i can possibly help it...

[macten]

We did answer your floor problem mate - just not the answer you wanted to hear.
If you're going to ask the advice of professional tilers then all of them will tell you
6mm ply is no good and runs a high risk of failure and therein lies the problem if you do not start over.

[GirlRacerRed]

And I think we'll leave it at that. Your other thread is still open RealStokeBloke so if you still have any further questions or concerns, you can put them there and our members will do their best to help.