Cracking Floor Grout !!!!!!!!!!!!!!!!!!

[Daywalker]

Hi all, grouted a bathroom floor this morning using Granfix Ultimateflex floor grout no problems, tiles spaced using 5 mm spacers, timber floor with 9 mm ply over lay, no under floor heating.
2 hours later found hair line cracks down the centre of every grout line :huh2:

Any one else had this happen and whats caused it ????????????.

 

[Northern Bird]

Was the ply sealed?

What kind of ply was it?
----
Was the adhesive premixed?

 

[Daywalker]

Hi Northen Bird,
The ply was sealed as all jobs are.
The ply was WBP expensive 9 mm board used.
The adhesive was powder mix fully flexible.

Been back to the supplier and told them the news etc, they say the local rep will come along for a look etc.
Still scratching me head why its happened :huh2: .

 

[murf]

this can sometimes happen if the grout is mixed too wet. when it starts to dry it shrinks and cracks

 

[enduro]

Yeah sounds like grout was too wet.

 

[TilingLogistics]

What tiles were they and what size?

Kev

 

[groutpad]

Did you put PVA in the grout mix. You don't need a lot but it does help.

 

[TilingLogistics]

Did you put PVA in the grout mix. You don't need a lot but it does help.

How does PVA help if I may ask? I thought the polymers in it were entirely different to grout admix?

Kev

 

[shamrock72]

hi daywalker ive only seen this happen for 2 reasons..not using flexable floor grout. too much bounce on the floor causing cracks ,ply not screwed down securly.. or just as simple as the grout was gone off .when fully dry it would power like and easy to get out...would suggest new grout if if movement on the floor is not the prob. add pva to your new grout to give it more flexability small areas at a time it will dry very fast..hope this helps

 

[grumpygrouter]

Using pva as an admix is a new one on me. I would have been inclined to use a proprietory admix from the grout manufacturer. Would mixing pva with the grout invalidate any manufactureres warranty?

Grumpy

 

[Kenny C]

The adhesive was powder mix fully flexible. Quote from Daywalker

Hi Guys

I am just about to start my floor ( DIY ) with a natural stone the inter locking sort with a mesh back pretty expensive so I dont want to mess up,after reading about 6mm & 12mm ply and cracking grout got me worried. I have used 6mm ply screwed down every 6inch square on to new floor boards which are on top of new joists. does anyone have any sugestions regards to adhesive and what do you think regarding my ply 6mm, does fully flexible adhesive mean fully flexible even when dry? Sorry if any of this sounds silly but tiling is a new string to my DIY bow.
Cheers Kenny

 

[MICK the Tiler]

Hi all, grouted a bathroom floor this morning using Granfix Ultimateflex floor grout no problems, tiles spaced using 5 mm spacers, timber floor with 9 mm ply over lay, no under floor heating.
2 hours later found hair line cracks down the centre of every grout line :huh2:

Any one else had this happen and whats caused it ????????????.

How long did you leave the floor tiles to dry before grouting?


Please guys don't use pva for admix use a proper admix for grouts and glues pva is not designed for use with cement based products and you will gain no advantage in doing so.

Using pva in your adhesives and grouts will cause the pva to be slowly attacked by alkali, forming acetic acid as a hydrolysis product. not something you want in a grout or adhesive as they will slowly break down as a result.

Please refrain from using pva as an admix PLEASE!!!!!

 

[shamrock72]

the pva i use is ardion 90.. expensive but very good never had any problems...

 

[MICK the Tiler]

Remember though ardion 90 is only an admix for cement based adhesives only not an admix for grouts.

And it must not be used as a primer.

 

[grumpygrouter]

the pva i use is ardion 90.. expensive but very good never had any problems...

is it definatley PVA? Would have thought it might have been an acrylic admix. I use the E101 with ardex grouts and I am pretty sure that it is acrylic and not PVA.

Grumpy