Help!: Grout cracking within minutes of applying

[StevieG]

Help! I have recently laid tiles onto a wooden bathroom floor with no real problems. Came to the grouting and problems began. Basically, my grout cracks soon after application and I do not know why! For reference, I am using Unibond Tile on Floors Waterproof Grout. The tub says it is ok for wide joints and is flexible.
Can anyone help - am I using the right stuff, or what am I doing wrong????

[marc1106]

StevieG
if its cracking when you move then it means the subfloor must be moving(big trouble)
or it could just be shrinkage cracks,
are you loading enough grout into the joints?
personally i avoid any unibond tiling products as i beleive theyre substandard
how did you prep the floorboards and what type of boards are they chipboard, t&g?

[StevieG]

Thanks for the prompt response.

The floor is stable! It's chipboard flooring - would that make a difference to the grout?

I am pretty sure that I put enough into the cracks. Just called Unibond helpline and they said it was because I was over wetting the grout when wiping clean! If it's shrinkage cracks - how do I overcome them?? What grout do you recommend?

[GirlRacerRed]

StevieG

Put a small glass of water on the bathroom floor, and then stand on the floor and bounce up and down. If the water moves, then the floor is moving.

How thick is the chipboard you have tiled on to? And are you sure all the tiles are stuck completely? When did you you tile?

[marc1106]

Thanks for the prompt response.

The floor is stable! It's chipboard flooring - would that make a difference to the grout?

I am pretty sure that I put enough into the cracks. Just called Unibond helpline and they said it was because I was over wetting the grout when wiping clean! If it's shrinkage cracks - how do I overcome them?? What grout do you recommend?

ok not teaching you to suck eggs( take no offence) , but is it a new floor, is it screwed down @200mm centers max? did it have any bounce or deflection when walked on before tilig?

[StevieG]

After jumping like a looney , the water doesn't move. Think that means that the floor is stable - phew!

Not sure regarding thickness of chipboard as it was already laid (we only moved in 5 weeks ago). All tiles are firmly fixed - laid the last one on Sunday p.m.

I grouted first time on Monday. Took it all out again yesterday as thought it may be due to me walking (only to move around to grout) causing cracking. Did small gap last night and left room straight away. No one entered room to can't be due to walking. Checked this morning and cracks had appeared!

[GirlRacerRed]

if it were me (and believe me, i've been seduced by the unibond ready mixed grouts and adhesives in the past), i'd chuck the unibond stuff and get down to your local Tile Giant and ask for a bag of powdered grout that you have to mix yourself. if you don't have a Tile Giant, try B&Q and look for a range called Buildfix.

unfortunately I'm not a pro tiler so I can't explain why the grout cracks once it's dried out.

GRR

[grumpygrouter]

What adhesive did you use to stick the tiles?

[beanz]

I've only ever seen grout crack that quickly due to movement. On another note, is the Grout Flexible? If it's not, that's your problem imho.

*edit* Not that i have a wealth of experience under my belt (been tiling less than a year).

[marc1106]

used the ready mixe grout and addy once on mosiacs and had to grout it 3 times before i was happy, for some reason it always shrinks back, ust get a decent powdered flexi gout, out of interest what sizes are your joints?
Ps glad to hear the floor is stable!

[ad tiling]

Remove the cracked grout then go to a tile shop and buy wide joint
flexible grout, mix per info on the bag if it still cracks then the floor
has movement or addy not suitible for chipboard. hope that helps

[tfs]

try Mapei Ultracolor plus. If it still happens then I am 90% sure that it is your subfloor that has not been adequatly prepared. If it wasnt your subfloor then I could only assume that you have your heating on full blast and this is effecting the grout as it sets.

Ultracolour is a Flexable grout. Make sure you mix it to the correct measurements as described on the bag.

[tfs]

perhaps you can try a test for us mate?

go to a corner of the room and with a pencil mark the point where the tile height is on the skirting board, stand on this part of the tile and see if the tile goes below the mark you made on the skirting.

If the tile apears to sink further below where you marked then you most probably have a floating floor. Some floating floors consist of sound and heat insulation boards layed directly over onto and then sheeted over with chipboard this is not suitable for tiling onto.

[Heritage John]

I would take the grout out and re grout it with bal superflex you can buy it from any topps wont be cheap if your not in the trade but i think its best flex grout out there

[Dave]

Hi Stevie...just remove and use a more suitable grout as mentioned...mapei/bal etc...not a pre-mixed one..

[Alan.P]

I can't add much to the advice already given about buying a good brand grout, the only things I would ask is with what, and how did you prepare the chipboard prior to tiling ?

[whitebeam]

You don't mention what tiles you laid

[obobsmith]

I can't add much to the advice already given about buying a good brand grout, the only things I would ask is with what, and how did you prepare the chipboard prior to tiling ?

Same here just hope chipboard has been prep'd properly ( hardibacker or ply and lots of screws).

[heavytrevy]

Grout cracks for many reasons, Overmixing causes shrinkage, drying to fast,
Too much water in the mix , im betting the chipboard is sucking the water out of the mix causing the cracks.
try a wide joint grout as somebody else has suggested


Trev

[jay]

hi as above and just how wide are your joints

[guppy]

Hello its a bit of a baffler ,without seeing the job i would suggest a good quality powder grout mixed with an apropriate grout en hancer.If your joints are 3mm the use a grout that is rated for this purpose.Some grout is suitable for 1-3mm some 1-8mm etc but put an enhancer in ,if your tiles are moving in relation to one another,regardless of the overall movement of the floor as a whole,well consider starting again

[tfs]

ultracolor is suitable for up to 20mm