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.