Cracking grout

[tileman]

Hi, I have been reading daywalkers post on cracking grout and thought I would start a new thread, because I have the same problem.

I have just completed a 30m2 floor with 600 x 600 black polished porcelain tiles, Granfix recommended 9mm ply on top of the chipboard floor, ultimateflex adhesive and grout. the ply was screwed down at 150mm centres, the floor was primed with acrylic primer and tiled onto when dry, the grout was mixed correctly and pushed into the joints.

Next day the grout was a grey colour and most of the joints have cracks.
If I wet the grout is black.

The problem I had was the ultimateflex adhesive was drying very quickly on the face of the tiles, so I had to keep cleaning it off with a damp sponge, It was a nightmare of a job, I assume all the cleaning got the grout too wet.

I don't know what else I could have done.

Is it necessary to clean out all of the grout, cut into cracks or reake the top off.

john

[Dave]

Originally Posted by tileman

Hi, I have been reading daywalkers post on cracking grout and thought I would start a new thread, because I have the same problem.

I have just completed a 30m2 floor with 600 x 600 black polished porcelain tiles, Granfix recommended 9mm ply on top of the chipboard floor, ultimateflex adhesive and grout. the ply was screwed down at 150mm centres, the floor was primed with acrylic primer and tiled onto when dry, the grout was mixed correctly and pushed into the joints.

Next day the grout was a grey colour and most of the joints have cracks.
If I wet the grout is black.

The problem I had was the ultimateflex adhesive was drying very quickly on the face of the tiles, so I had to keep cleaning it off with a damp sponge, It was a nightmare of a job, I assume all the cleaning got the grout too wet.

I don't know what else I could have done.

Is it necessary to clean out all of the grout, cut into cracks or reake the top off.

john

When you say adhesive and grout..was this an all in one product......?..

[tileman]

Hi Dave, no it was granfix ultimatflex powder adhesive and ultimateflex powder grout.

[Dave]

I have used the grout before but not the sticky......the grout sticks like SH**...
Could be to much water or maybe there is too much deflection for it to handle.....

How long was it before you allowed anyone to walk on the floor after grouting..?..

Should really be overnight at least then if there is slight movement then it won't break the key between the tiles and the grout.....

[tileman]

I grouted on monday, I finished at 3 pm I don't know if the owners went in and walked on it, they don't live there, what would cause it to have a grey coating.

[Dave]

If the grout was wet too much it is more than likely Efflorescence.....Use something like lithofin cement away...........

[tileman]

Is it necessary to cut out all the grout or just rake it out and refill the joints.

[Sir Ramic]

Can i ask a few questions?
What size joint have you left ?
Did you use a washboy?
Have you used a washboy long?
The reasons for the washboy question is that most people when first using one have the sponge far too wet. This can be put down to the sponge being new too and not just technique.

[Dave]

Efflorescence will be on the surface..it is salt residue and can be removed with the lithofin cement away..

have a read of this thread as well... http://www.tilersforums.co.uk/tile-a...=Efflorescence

[tileman]

Hi Dave,
Joint 4mm.
I haven't used the washboy a lot for the reason below.
Yes I used a wash boy on this job, it is a Karl Damm, I run the sponge over the rollers many times (as per the instructions)and also try to force the water out with my hands but cannot get the sponge as dry as I think it should be, always water going into joints.
I was doing a floor today and changed to a new sponge and that was better, but still not good.
john

[Sir Ramic]

I think that would be the cause of the Efflorescence then. The washboy takes getting use to, i made the same mistakes when i first used one. Sponges seem better if left in water for a few hours to pre soak IMO. It makes the sponges easier to wring out when running over the rollers.

[Dave]

Most of all john you will need to address the cracking as well......

Was there much movement in the floor before you sheeted it..?..

Don't want you raking the grout out if it will happen again.....You could try a stronger latex grout mix but you need to determine how much deflection there was .....thats why you should have maybe used a thicker sub-floor........