Hello all, Just finished my small ensuite 1.5m2 area and I have just noticed that the grout has cracked. Under closer inspection all the tiles have not bonded to the ply. The tongue and groove floor was solid so i used 6mm wbp ply screwed every 150mm centers. I know 6mm ply has no structural benefit but provided a nice smooth surface. Adhesive was bal rapidset flexible which has never given me any problems in the past. I have thought of one possibe reason this could have happened.......as it was a small area I applied the adhesive to the tile then pressed them down onto the ply. The ply was not primed as recommended by Bal. Have I made a schoolboy error? Tiles from good old B+Q!
Any thoughts??

The problem may well be the 6mm ply. It is just too thin and you may well have created voids beneath it. Also with that thickness of ply you should have used (according to BAL) Fastflex.

I fear you will need to start again.

^mm Ply just not good enough was it exterior grade if not the water in the adhesive would just be sucked out to quickly and not alow the adhesive to harden properly

hi m8 i done 2 bathroom floors and a kitchen floor in my brothers house with 6mm ply even though i told him it was no good his girlfriends dad got it free from his work so they insited i tiled on it, so i did but told him if anythin goes wrong not to blame me, so i tiled it and the tiles have now cracked even the small bathroom floors, will never tile on 6mm ply again just causes problems.

John

The floor is solidly built, the joists are 250mm thick, 400 mm centers and the floor lies right on the bearing plate for the joists. The ply was wbp. The addy was mixed using water from an outside tap so it was pretty cold....but it would have heated up pretty quickly....

9mm minimum ply m8...and imo ..you should have followed the manufacturers advice....rip up the bad ones and scrape all adhesive and grout off and then do what it says on the bag and see how that goes.

Some tiles were loose but the others could easily be pinged off with a screwdriver!!!...even the ones behind the wc and pedistal sink. Not one blob of addy has stuck to the floor!! This is the concerning bit as I have never had a problem like it and always use the bal stuff.

If you tell BAL what has happened they will come to site to and tell you whats gone wrong.

Like the others have said, 6mm Ply is too thin. The fact that you didn't prime it, as per recommendations, would be my main worry though. I'm thinking that the Ply has sucked the water out of the addy, which is why it hasn't stuck. I'd expect cracking from the deflection, but the fact that you have loose tiles, suggests to me that the addy has failed.

That would be my best guess, but you should be aware that i'm pretty new to tiling, so wait for more experienced tilers for confirmation.

Originally Posted by beanz

Like the others have said, 6mm Ply is too thin. The fact that you didn't prime it, as per recommendations, would be my main worry though. I'm thinking that the Ply has sucked the water out of the addy, which is why it hasn't stuck. I'd expect cracking from the deflection, but the fact that you have loose tiles, suggests to me that the addy has failed.

That would be my best guess, but you should be aware that i'm pretty new to tiling, so wait for more experienced tilers for confirmation.

BAL say not to prime ply with their addys Beanz.

Grumpy,they say to prime the underside of ply.

Dont think they would send anyone out(BAL) BECAUSE THE PLY WAS NOT WHAT THEY SPECIFY...TOO THIN.....this is my opinion.

No point in trying to blame the adhesive here, you used the wrong over lay simple as.

6mm ply will swell with the moisture from the adhesive and deflect against any defects in the floor boards.....

wrong product used on wrong overlay.....

totally agree..

Originally Posted by Superally

Some tiles were loose but the others could easily be pinged off with a screwdriver!!!...even the ones behind the wc and pedistal sink. Not one blob of addy has stuck to the floor!! This is the concerning bit as I have never had a problem like it and always use the bal stuff.

6mm exterior ply is big hear over 18mm spanboard i have never seen any trouble with it not what i would recommend but thats the way its done using flexible rapid set

Is the addy stuck well to the tiles, could it be grime or dust on the ply

Originally Posted by brian c

Grumpy,they say to prime the underside of ply.

Dont think they would send anyone out(BAL) BECAUSE THE PLY WAS NOT WHAT THEY SPECIFY...TOO THIN.....this is my opinion.

part of the priming/sealing debate here Bri. I assumed the guy didn't prime the ply and that would be correct, but you are supposed to seal the underside and edges (withr SBR and not APD) not prime them. Ardex specify Polyurethane varnish for their stuff. This confusion arises many times in the forums and I think it is becauses peeps don't read the literature properly

I put my hands up to using 6mm ply...bad move. Tiles have only been laid 1 week and not seen much traffic as the project aint finished yet. Sides and back of ply was SBR'd. My understanding of this is to stop any water getting into the ply from either moisture vapour or bath splashes going down the wall. Already spoke to Bal rep and he will entertain a meeting with him. Thanks for input!!

Originally Posted by Superally

I put my hands up to using 6mm ply...bad move. Tiles have only been laid 1 week and not seen much traffic as the project aint finished yet. Sides and back of ply was SBR'd. My understanding of this is to stop any water getting into the ply from either moisture vapour or bath splashes going down the wall. Already spoke to Bal rep and he will entertain a meeting with him. Thanks for input!!

Glad to see they are listening. Please keep us informed of their decision, it will be interesting for the forums.

Don't like ply on the walls, had the grout turn brown from resins bleeding through once and that was enough

it's only a 1.5m2 floor even with using a 6mm ply your tiles should have lasted longer than they did,with small en-suites or b'rooms like this i use only 9mm(nearly no price diff than 6mm from b&q)and have never had any comebacks,but i prime then use toppfix flexi mostly?

I have tiled many floors with no problems and most people here have jumped up and down blaming the 6mm ply. Ply was screwed down at 150mm centers and I simply cannot believe in the short space of time that none of the tiles stuck. Its almost as if the 6mm ply was dipped in teflon!!! Will let you all know how I get on with the bal man. Any thoughts on very cold water used for the mix?.....I mixed it outside then brought it into the nice warm house....also like the idea of the ply sucking out the moisture from the addy.

if you had used fastflex they would have stayed down if your cutting corners which i have done many times with the customers insistence,you must at least use a good 2 pt addy.

might have mixed addy to thick and dry

Originally Posted by grumpygrouter

BAL say not to prime ply with their addys Beanz.

Ah! Sorry read it wrong. Although, in all honesty i'd prime it regardless.

Well, met with Bal man today and he had one look at the ply and said that there must have been oil/preservative coated on the ply (not by me). As in my first post all tiles pinged up with no spintering of the wood. But you all know that 6mm wbp ply is duff for tiling onto so lets hope that the thicker stuff has not got this coating on it also. Was going to go back to B+Q and ask them about it but hey I'm sure they could not care less!! Think backer board would have been better as you dont know where the ply has come from.

With the prices of backerboard and ply at the moment, i'm trying to think of a good reason for using ply. Interesting about the coating on the ply, cheers for the heads-up.

Having spoken to a timber supplier he tells me that even exterior ply is not waterproof just the adhesive holding the sheets together so this can mean the tiled surface can swell from the water in the adhesive and this will not help keeping tiles on to the board

I think the main problem was you put the adhesive on the tile not the floor

Originally Posted by bitter&twisted

I think the main problem was you put the adhesive on the tile not the floor

I would go with that and if there was any dust on the floor and the addy to thick

Great insight from everyone. My thoughts to look at,
1: Will the board absorb any water? Or does it bead up?
2: Sounds like the addy/thinset dried to fast. Mixture of addy was to dry, or board was to dry. (sucks the moisture from your addy/thinset) in which I reccomend slightly wetting down the board (I usually do this with a wet sponge removing dust anyways).
I really do not see the board thickness affecting the bond this early in the game. Hope this helps

Brett

I would go with that and if there was any dust on the floor and the addy to thick

I'm jumping on this thread a bit as I am about to lay 10,, rough-faced porcelain floor tiles onto 12m ply over floorboards (I have sealed the underside with SBR). In applying wall tiles first the ply has got dusty + a few splashes of wall addy etc. Is it ok to give it a good clean with hot water and let it dry fully??