Jobs that have gone wrong, massively..

[Phil]

There's pages and pages of threads on the tilers forum (of which I'm a member) that explains how PVA becomes 'reactivated' when in contact with wet adhesive and leads to tiles debonding.

Its seems though a lot of builders and plumbers are still using PVA, when a tiler here's of someone using it, they react the same as plumbers would if we saw a diyer fitting a Speedfit gas pipe or something like that.

There's a hell of a lot more to tiling than you may think, the main no no's are don't use tubbed adhesive, don't tile on plywood, don't tile on chipboard, dont use PVA and dont dot and dab adhesive (5 blobs).

Also when using 6mm Hardiebacker on floors, the boards must be fixed onto flexible powered adhesive, screwed and the joins taped before tiling. The adhesive is to fill any voids. Its an expensive way to do it as rapid set is not cheap but its piece of mind, you cant use driwall adhesive either as its not flexible and will void the gaurantee on the cement boards

I joined the tilers forum when I had a tiled floor fail and I was stressed big time as the customer was a nasty piece of work, the floor tiles were cracking over the joins in the 12mm plywood which I had laid over the floorboards. The guys on the tiler forum told me never to tile on 12mm ply and that the British Standard is 15mm, But who sells 15mm ply? No one so go up to 18mm.
I was advised to use 12mm back when I started and would have carried on using it had I not had any problems.

When I tile a floor now I rip up the floorboards and add noggins to make a grid layout on the floor, then glue and screw 18mm WBP ply onto joists after priming the edges, underside and face (to stop it absorbing moisture underneath), then 6mm Hardiebacker and then tiles.

Only then can I sleep easy knowing I won't get that dreaded call.

 

[H2ODAN]

Some usefull info here lads. Out of interest, going back to the bathroom wall, would i nail the plasterboard onto the ply? Then tile onto the ply correct?

 

[Phil]

Did you rip everything out today Varail?

I'd be interested to know what it was like behind the tiles, was the adhesive combed on or did you dot & dab?

What was the reason for the ply in the first place if you don't mind me asking?

:coffee:

 

[Guest123]

Excellent and very informative post you made Phil. I've always used 12mm ply, but now you've made me think!

 

[varial]

I took the tiles off the plywood today and the adhesive had failed to set properly behind the tiles where the grout had cracked for obvious reasons. only about 2 tiles actually had this problem but i took the whole lot of and then screwed hardibacker board onto the plywood and proceeded to re-tile. Hopefully this should solve all my problems and i can move on having learnt a lesson!

 

[Phil]

To be fair though system when I went back to that bathroom (3 days to sort out unpaid) I lifted the eight cracked tiles which was a job in itself and discovered that the board edges were not screwed down enough as the screws were too wide apart. I could put a screwdriver in the gap (always leave 3mm expansion gap) and I could lift the board a little.

I was kicking myself as I normally screw them down at least say 60mm centers on the edges to make sure they don't move. Why didn't I do that here? As said customer was unfriendly and rushing me so in my stessed state I got careless, also the floor for me is the last job really in this case the last of a very hard long job.

I've seen floors tiled on 6mm ply and after 10 years there's not a single crack or loose tile. At home years ago (before I knew better) I tiled on chipboard in the bathroom, kitchen and conservatory and they are still solid as a rock.

On the other hand I was in a 14k wetroom last night, 3 years old and floor tiles were loose and felt 'gritty' under foot, grout cracked on floor etc, who knows why that failed.

All I know is, doing it my new method of 18mm ply on joists with 6mm cement boards on top is absolute belt and braces and will last years and years with no comeback. It also helps with the door threshold height as its only 6mm higher + adhesive + tile rather than 12mm.

 

[Phil]

Did you use tubbed adhesive varial? if you did that is your problem (and the PVA), don't forget ready mixed adhesive is water based and dries only by evaporating through the grout lines, powered adhesive is cement based and will set under water and is all I use.

Thats why tubbed gear cant be used on large format tiles as two years down the line the adhesive in the middle is still wet.

 

[double d]

Ive had the same problem, and know of another who has had this problem, i put it down to pva, ive been using a decnt tile primer now for a couple of years and touch wood no problem what so ever, but like every one has said dont panic we all make mistakes in life, even the best workman will have a balls up one day, so chin up :icon12:

 

[Destroyer2813]

What primers is everybody using now used to use webber two part but cant get it anymore

 

[paul78]

I basically tiled onto some plywood after sealing it with PVA, Some cracks have appeared in the grout which let water leak behind.

thats exactly why its failed!
ply floors:yes walls:no
pva BIG NO NO, you could get shot for using that if a tiler is present.

lessons learnt from mistakes being made, by you, me, and everyone else.

if in any doubt before any tiling job in future do plenty of research on the tilersforum.
laying tiles is easy if you got an eye for detail but its all about the prep, ie. primers, adhesives, grouts, weight ratios per m2 for certain types of wall if tiles are large format. imagine trying to lay natural stone on a lovely skimmed wall and not understanding the potential pitfalls.......

 

[Phil]

Any decent tile shop should sell primer, my local one sells Ultra and I also use adhesive of the same brand. Its an acrylic primer and flexible additive in one and is dulited the same as PVA. Its a tenner for a 2 litre bottle and it lasts ages.

To anyone reading this thread, PVA is for plasterers only!

 

[paul78]

Any decent tile shop should sell primer, my local one sells Ultra and I also use adhesive of the same brand. Its an acrylic primer and flexible additive in one and is dulited the same as PVA. Its a tenner for a 2 litre bottle and it lasts ages.

To anyone reading this thread, PVA is for plasterers only!

I echo that!

and if any tile shop says pva is fine then run a mile.