Newly installed floor tile grout cracking, breaking up

clairehi

Dear All

have got a problem with my recently laid ceramic tile floor as the grouting is now cracking and in some places bits have come out. before I see the builder about it can anyone advise what the possible causes may be?

the floor was laid 2 weeks ago and the tiler did the whole job ie laying the tiles and grouting all in one day. The (black) grout he was using looked virtually liquid when he put it on. he told me to mop the floor the next day to remove "dust" from the surface of the grout which I did. however when it dried after mopping it still looked "dusty" and the colour was an uneven mid-dark grey, but I didnt notice any cracking at first. its only in the last few days that I have noticed the cracking and bits missing/crumbling.

the tiles have been laid on top of screwed down plywood, as advised elsewhere. Also, I have the same tiles in another room which have been down about a month, laid on top of the same subfloor but by another contractor and they are fine.

Isleman

I feel sorry for you but I can see two problems:
1. Tiles should be left at least 24 hours before aplying the grout .
2. Grout consistency should be like a thick paste and when gaps are very large , 6 mm + like clay.

Obviously the grout is too weak . If it comes out easily there is no other option but to grout again.

clairehi

thanks for this, which confirms my suspicions.

tightrs

did he use flexi grout ?

Rosebery_2

Isleman wrote: »

1. Tiles should be left at least 24 hours before aplying the grout .

Actually thats not necessarily so. It would be if he'd used tubbed adhesive which is airdrying but I hope he didn't use such stuff for a floor. It should have been a cementatious flexible bagged adhesive. Some of these can be grouted within 3 hours.

2. Grout consistency should be like a thick paste and when gaps are very large , 6 mm + like clay.

Mmm don't know what you mean by clay but the thick paste example is correct for 5m or so which is iro what it should be for floor tiles.

Obviously the grout is too weak.

Yes that seems to be so but I'd also be interested to know what grout he used. It should have been flexible for a floor. If it ain't then no wonder its cracking whatever the strength of it.

If it comes out easily there is no other option but to grout again.

Whilst thats true I'm more concerned about the addy he used. If he didn't use the correct adhesive its not just a "grout again" scenario. Its a "take it all up and tile again" scenario.

Cheers

missile

It is quite difficult to successfully replace bad grout.

It is important that the plywood is the correct thickness and the distance between the screws is not excessive. I hope the floor is not moving or you really are screwed, if you will pardon the pun?

clairehi

He commented that the adhesive was a quick drying kind which would go off in an hour or two but I dont know what type it was or what the grout was.

He used 3mm spacers as I did not want really thick grout lines. The grout was not like a thick paste, it was a pourable consistency. I can understand it would need to be thinner for narrower spacings, however, he did not warn that this could cause any problems with the grouting.

the ply was (I think) 6mm thick and screwed at 30 mm centres, we have used the same subfloor and tiles in another room (which was tiled by a different guy using 5mm spacers) with no problems.

I am worried that it will be hard to replace especially as there is 20 m2 of it, although not all of it has cracked (yet). it wont be me replacing it though!

Rosebery_2

clairehi wrote: »

the floor was laid 2 weeks ago and the tiler did the whole job ie laying the tiles and grouting all in one day.

There is NOTHING wrong with that IF the correct adhesive and grout were used. What adhesive did he use? What grout did he use?

The (black) grout he was using looked virtually liquid when he put it on.

That seems a bit thin.

he told me to mop the floor the next day to remove "dust" from the surface of the grout which I did. however when it dried after mopping it still looked "dusty"

Now the alarm bells start to ring. If he really did say "mop" and with a wet mop at that then thats not correct. Grout haze should be removed with a DRY cloth. If you wet the haze you never get rid of it.

and the colour was an uneven mid-dark grey,

Yes it would be. Too much water and its dried unevenly.

the tiles have been laid on top of screwed down plywood, as advised elsewhere.

How thick is the plywood, is it OSB or is it WBP ply and what is it screwed into - joists through floorboards or straight into joists or what?

Also, I have the same tiles in another room which have been down about a month, laid on top of the same subfloor but by another contractor and they are fine.

Its almost certainly not a tile issue - its a prep and materials issue. Are the first lot of tiles on an upper floor or the ground floor? Are the second lot of tiles on an upper floor or the ground floor? Did the first contractor do any other prep work such as laying a decoupling membrane that the second one didn't? Is there a major difference in floor area between the first lot of tiles and the second?

As a matter of interest why not use the first contractor for the second project?

Cheers

clairehi

Rosebery wrote: »

There is NOTHING wrong with that IF the correct adhesive and grout were used. What adhesive did he use? What grout did he use?

That seems a bit thin.

Now the alarm bells start to ring. If he really did say "mop" and with a wet mop at that then thats not correct. Grout haze should be removed with a DRY cloth. If you wet the haze you never get rid of it.

Yes it would be. Too much water and its dried unevenly.

How thick is the plywood, is it OSB or is it WBP ply and what is it screwed into - joists through floorboards or straight into joists or what?

Its almost certainly not a tile issue - its a prep and materials issue. Are the first lot of tiles on an upper floor or the ground floor? Are the second lot of tiles on an upper floor or the ground floor? Did the first contractor do any other prep work such as laying a decoupling membrane that the second one didn't? Is there a major difference in floor area between the first lot of tiles and the second?

As a matter of interest why not use the first contractor for the second project?

Cheers

1. as before dont know what adhesive or grout.
2. he said to go over it with a damp mop, which I did.
3. 6mm ply, dont know what kind. it is on top of chipboard, on top of a framework of battens, on top of concrete block floor.
4. both rooms on ground floor, same floor construction.
5. the good floor is a small area (utility room). "good" tiles were laid by builder who was on holiday when second larger area needed doing, so main contractor brought in "specialist" tiler.

I really hope they dont need to take the tiles up as the kitchen units have been fitted in the meantime, it will make a helluva mess.

Rosebery_2

clairehi wrote: »

He commented that the adhesive was a quick drying kind which would go off in an hour or two but I dont know what type it was or what the grout was.

OK that answeres one question - it was probably rapidset or SPF but that info tells me it was the bagged varietywhich he had to mix.

He used 3mm spacers as I did not want really thick grout lines.

Oh dear. They should be 5mm for floor tiles using a flexi grout. If you had given me that instruction I would have been wanting to discuss it. I would have done it if you had insisted but only against a signed disclaimer against possible grout and tile cracking.

The grout was not like a thick paste, it was a pourable consistency. I can understand it would need to be thinner for narrower spacings.........

A moot point which i wouldn't necessarily subscribe to - it would certainly have been harder work.

........., however, he did not warn that this could cause any problems with the grouting.

That would have been a mistake on his part IMHO.

the ply was (I think) 6mm thick

Much too thin for my mind. Should be at least 12mm over floorboards and 25mm if direct onto joists. 6mm ply is just not stable enough to minimise movement. I would definately have been saying it needed a decoupling membrane as well if you didn't want a thicker ply. Who laid it? You or the tiler?

.....and screwed at 30 mm centres,

Do you mean 30mm or 300 mm? If the latter it's too much - should be min 100 - 150 mm

...............we have used the same subfloor and tiles in another room (which was tiled by a different guy using 5mm spacers) with no problems.

That 2mm can make all the difference as can using a flexi grout. Elements of fault on both sides here possibly.

I am worried that it will be hard to replace especially as there is 20 m2 of it, although not all of it has cracked (yet).

and the bigger the area the more susceptible it is to sub-floor movement and subsequent cracking. Didi you insist that the first lot was OK with 6mm ply so couldn't see why this lot wouldn't be either? What was the area of the first lot of tiles you had laid by the different guy?

it wont be me replacing it though!

I see your point which is why, if I were your contractor, I would have been making the points I stress above. If you want to tackle him though he'll robably be saying he was obeying your instructions. I don't think this one is all one sided. Sorry to be blunt.

Cheers

Rosebery_2

clairehi wrote: »

1. as before dont know what adhesive or grout.

Yes - understand.

2. he said to go over it with a damp mop, which I did.

he is to be faulted for that IMHO.

3. 6mm ply, dont know what kind. it is on top of chipboard, on top of a framework of battens, on top of concrete block floor.

Oh no!! Even worse. For 20m2 the chipboard should have been taken up completeley. Its totally unstable for tiling - particularly a large area like 20m2.

4. both rooms on ground floor, same floor construction.

Thanks - that makes it a bit easier.

5. the good floor is a small area (utility room). "good" tiles were laid by builder who was on holiday when second larger area needed doing, so main contractor brought in "specialist" tiler.

Thats part of the problem. A much larger area.

I really hope they dont need to take the tiles up as the kitchen units have been fitted in the meantime, it will make a helluva mess.

Oh was the floor tiled before or after the units were fitted? Its normally done last. I'm afraid I don't give a vast amount of hope for the survivability of 20m2 of tiles with inadequate grout spacing over 6mm ply over chipboard and no decoupling membrane I'm afraid. Sorry.

Cheers