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

 

[DHTiling]

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.

 

[DHTiling]

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.

 

[DHTiling]

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.

 

[Gazzer]

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.

 

[DHTiling]

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.com/tile-ad...ng-efflorescence.html?highlight=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

 

[Gazzer]

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.

 

[DHTiling]

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........

 

[tileman]

There was some movement, but I don't feel that is the problem, I think it's to do with the washboy and me, do I need to rake out the joints or just go over them again.
I will stay clear of the Granfix Ultimateflex in future, it stick like hell to everything.

 

[sWe]

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

It's either a really bad sponge, or it's your technique.

I've got a link to a grouting guide I wrote in my signature. I couldn't be arsed to go out and fetch my washboy, so I drew a picture on how you're supposed to get rid of the last bit of water in the sponge.

Look at the pic. Place the sponge float the same postition, and then squeese it down on the rollers while tilting the float up to a 45 degree angle. Repeat on the other side of the sponge. With new sponges you generally only need to do this once. With older, worn sponges, you might have to repeat a few times.

If this doesn't work, it's a really bad sponge.

If done properly, this technique will result in the sponge being only damp. There will be not be any excess water, at all.

 

[tileman]

Hi sWe, if you look at the Karl Dahm demo on Trade Tilers web site, thats the way I do it, I am not clear about your method, if I run the sponge over the rollers at a 45 deg angle the sponge will only run on one roller, the other side of the sponge is stuck to the handle.
john

 

[Gazzer]

Hi sWe, if you look at the Karl Dahm demo on Trade Tilers web site, thats the way I do it, I am not clear about your method, if I run the sponge over the rollers at a 45 deg angle the sponge will only run on one roller, the other side of the sponge is stuck to the handle.
john

:lol::lol::lol:


That made me laugh

I think you will find sWe means rotating the float (sponge side down) and then pushing it over the rollers.
As long as the rollers or roller squeezes the water out of the sponge then its fine. sWe is spot on with technique, most people struggle with a washboy because they dont try to adapt to this technique. Its a wonderful tool when you get it right.

 

[Turkish]

I`ve got a Karl Dahm and as Sir Ramic stated above move the sponge along both rollers flat to squeeze out the water but as you come to the end of the sponge tilt the sponge up by 45` so the very end of the sponge goes across the rollers.

Turkish

 

[grumpygrouter]

I also have a Karl Dahm washboy. I recently bought a couple of new spongeboards - Rubi. The sponges are very good but there is a problem with the board itself. The strengthening ribs of the plastic do not allow surface water to run off easily, you have to have a separate action to pour the water back into the bucket otherwise it spills onto your nice new grout! Very irritating!

 

[sevman]

Dont suppose these tiles were from B&Q? I have the same problem, however I believe the cracking is due to the tiles lifting from the edhesive therefore allowing the tile to move when walked on thus causing the crack in the grout. I am about to lift the whole lot up and start again with a different adhesive.

 

[MICK the Tiler]

Just a few questions on your grouting techniqe.

did you use sanded or non sanded grout (ultra smooth)?

how much of the floor did you grout before washing down?

Did you seal the tiles before or after grouting?

Black grout has a high content of white sand in it (Believe it or not) and using too much water while washing down will wash all of the black oxide pigment out of the grout leaving the white sand at the top of the joint. Also washing the floor down too early before the grout has had time to harden off a bit will also cause this to happen.

If your new to using a washboy only use it when you grout a floor with grey sanded grout to start with this type of grout is far more forgiving to mistakes than black grouts will ever be. The colour will also make a complete mess of your expensive equipment. When doing black I always do it by hand to save my expensive gear.

The cracking may not be all the way through the entire depth of the joint just on the surface the fine white sand will pull back from the edge of the joint once the excess water has had time to evapourate from the surface. Sealing the tiles before grouting will also cause this as there is no bonding capacity left in the grout after all the fines have been washed away through over watering. The sealer will actually repell the water along with some of the fines in the grout hence the surface cracking.

These are just some senarios that could cause the problems outlined. A solution may be a simple matter of re-skimming with black grout and washing off with a damp not wet sponge by hand. Always try a test area first to determine appropriate course of action.

 

[dock]

Sorry to hear of your dilema with the cracking grout.

Unfortunately it may well be down to the substrate prep. as it should be braced sufficiently to provide a stiff, rigid and stable floor FYI;

1 Overlay should be minimum of 18mm screw fixed at max. 300 centres.
2 Fix tiles in at least an S1 adhesive such as Keraquick
3 Grout with a CG2 grout such as Ultracolor Plus (26 colours)
4 Perimeter Moovement Joint and at 6M centres fill with Mapesil AC same colour as grout.

best of luck with remedial works................................hope it goes well

dock