Cracked conglomerate.

[alexander]

Hi Tilers forum,
These pics are of a conglomerate granite bathroom floor 5m2 about 4 months old.
Customer recently noticed fault lines appearing across the tiles in three places.

The fault lines(beginning of cracks) run across 3 or more tiles but seem to unaffect the grout and tiles still seem well bonded.

At the same time the bathroom was done the adjacent kitchen floor was tiled in 600x600 porc 20m2, the kitchen floor remains ok at this time.

The prep and materials for each floor was the same. 9mm no more ply was glued and fixed to the timber floor boards and tiled using single part flex addy and grout.


Thanks for looking, regards craig new member.

 

[Mike]

were the floor boards normal t & g ? how solid were they before you overboarded? is the floor floating? we would need to know them before giving opinions

 

[Rich]

Bit more detail please.

Is 9mm recommended for floors?

What did you glue the boards down with?
How many screws did you screw into them?
Did you get 100% contact between tile and adhesive?
Was there any movement the floor?
What adhesive did you use?

 

[Colour Republic]

do you remember if these cracks are inline with a joint between 2 sheets of no more ply?

 

[alexander]

Just timber planks onto timber joists, all loose boards were fixed down well before i started, and once the no more ply went down the floor felt sound.

 

[Colour Republic]

Is 9mm recommended for floors?

What did you glue the boards down with?
How many screws did you screw into them?

both the 6mm and 9mm are recommended but I always opt for the 9mm on floors.

I assume he used the 'No More Ply' adhesive and screws which in fact the instructions say you don't need that many screws per board (i think 8 from memory) but again I personnally put a lot more in.

But OP will have to confirm what he did

 

[Gazzer]

You say the floor felt sound after the NMP went down ?? What about before as NMP does not add strength to a floor.

 

[alexander]

plenty of screws used, megastength on back of boards and edges, floor and boards dusted with a damp sponge, no more ply primed with diluted primer G, tiles mostly fixed on a serrated bed with each tile back butered in kera quick grey, grouting in ultra colour and sealed with mp90.

 

[Gazzer]

A bathroom floor ? Is that a washing machine ? and who chewed the bottoms of the wood units ?

 

[alexander]

the units were old and re -used. yes there is a washing machine in there bathroom, at least one fault is on the join of the nmp, and i used full sheets with staggered joins ( one way!)

 

[alexander]

some more pics to help, the 600x600 is the adjecent kitchen with the same prep.

 

[DHTiling]

So you didn't use jointing tape on the joints..?.. and they do look like a tight joint..

 

[Gazzer]

So you didn't use jointing tape on the joints..?.. and they do look like a tight joint..

NMP say to fill joints with the mega strength adhesive, No mention of tape. Should be 2mm joint gap .

 

[DHTiling]

OH!!.. Hardi say to tape the joints.. thought the nmp might have been the same.. but looks like that is a stress cracking though to me.

 

[Sean fsy]

i use keraquick often and im sure it says on the bag that its suitable for tiling onto timber etc only if a latex based additive is added to it.

 

[Gazzer]

i use keraquick often and im sure it says on the bag that its suitable for tiling onto timber etc only if a latex based additive is added to it.

I think it has been upgraded now to allow to use without additives.

 

[Gazzer]

i use keraquick often and im sure it says on the bag that its suitable for tiling onto timber etc only if a latex based additive is added to it.

he hasnt tiled onto timber, He has used 9mm No More Ply tile backer boards.

 

[DHTiling]

kera-quick has always been ok for timber overlays, it is if you want to tile direct to floorboards etc then you upgrade it to an S2 with latex plus.

 

[Gazzer]

Yeah, couldnt remember but you are right Dave.....as usual 😛rrr:

 

[tfs]

A bathroom floor ? Is that a washing machine ? and who chewed the bottoms of the wood units ?

Not much gets past you hawk eye:lol:

 

[simon1]

I'm sure using the mega adhesive the way its directed would leave voids between NMP and floor boards.

i always stick with flexy tile addy and screw

 

[Stewart]

I'm sure using the mega adhesive the way its directed would leave voids between NMP and floor boards.

i always stick with flexy tile addy and screw

Same way for me.....

 

[Sean fsy]

Things like this are getting more common every week, Doesnt seem that any prep work we do is ever enough. especially with granite, conglomerate tiles. i seen a gulfstone tiled floor destroyed the other week £7k worth of damage, the floor had shrank that much.

 

[Colour Republic]

I'm sure using the mega adhesive the way its directed would leave voids between NMP and floor boards.

i always stick with flexy tile addy and screw

it's an expanding adhesive and the boards are really quite strong, there are less voids than screwing ply down, once down there is no way they are coming back up without a lot of damage to either the floor boards of the 'No More Ply' itself

 

[Gazzer]

it's an expanding adhesive and the boards are really quite strong, there are less voids than screwing ply down, once down there is no way they are coming back up without a lot of damage to either the floor boards of the 'No More Ply' itself

I have never had to take one up but I know someone who has and as you say it was a lot of damage to the floor boards. If the floorboards were cupped badly then I would use the SPF adhesive method.

 

[DHTiling]

If voids are underneath then it will flex.. hence why i only use adhesive as the bed for this type of board..

 

[sblunde]

unbalanced washing machine on spin cycle causing excessive vibration in the suspended floor?

 

[alexander]

bedding the backer board in a thin set to act as a packer then screwing down and taping joints. This seems a good idea, as floor boards often not that flat. I was told this method some years ago at the hardy backer board stand at a tile show, but with ring shank nails.

 

[Rich]

plenty of screws used, megastength on back of boards and edges, floor and boards dusted with a damp sponge, no more ply primed with diluted primer G,tiles mostly fixed on a serrated bed with each tile back butered in kera quick grey, grouting in ultra colour and sealed with mp90.

What do you mean by 'tiles mostly fixed on a srrated bed'?

Im pretty sure that NMP dont recommend priming before tiling, a wipe with damp sponge should be enough.

 

[alexander]

What do you mean by 'tiles mostly fixed on a srrated bed'?

Im pretty sure that NMP dont recommend priming before tiling, a wipe with damp sponge should be enough.

"Mosty on a serrated bed" , I mean the floor was quite flat (for a change) and i was able to fix onto just a serrated bed that i trowelled out , with not too much packing out.

No more ply do recommend priming it helps to makes the board water proof!!

 

[Rich]

As far as Im aware you only need to prime the boards when installing ufh, I was told by the nmp rep that priming is more likely to reduce the bond of the adhesive. cement boards are impervious to water as the are.

Im only asking to try to work out what has gone wrong with your floor.

Is it possible that there were voids left under the tiles? If not then it may have been a void under the cement boards?