Cracking Floor Grout !!!!!!!!!!!!!!!!!! - TilersForums.co.uk | Tile Forums

Daywalker · 04-04-2008

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

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

Northern Bird · 04-04-2008

Was the ply sealed?

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

Daywalker · 04-04-2008

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

.

murf · 04-04-2008

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

**enduro** · 04-04-2008

Yeah sounds like grout was too wet.

TilingLogistics · 04-04-2008

What tiles were they and what size?

Kev

groutpad · 04-04-2008

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

TilingLogistics · 05-04-2008

Quote:

Originally Posted by groutpad

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 · 05-04-2008

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** · 05-04-2008

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 · 05-04-2008

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** · 05-04-2008

Quote:

Originally Posted by 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

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!!!!!