Cracking in Tile Grout

[jesteh]

See if anyone can give pointers what went wrong.

Got following setup:
Anhydrite floor dried for 2 years (fully dry).
Water underfloor heating - comissioned prior to start of tiling
Area - L shape with longer dimensions 7 x 7m (does not exceed 8meters in any dimension)
BAL Prime APD used to prime screed
BAL Rapid Mat
BAL Rapidset Flexible Adhesive
Weber Joint Pro Grout
Large format porcelain tiles (600x600)

Job was done professionally with no issues and solid bed used throughout.
Underfloor heating comissioned very slowly 2 months after job completed.
At about 36deg water temperature, noticed a crack in one of the tiles and small cracks in grout throughout - cracks in grout are hardly visible but they are there. Grout otherwise seems stable.
The cracked tile is on the external corner and had to be cut to L shape so is obviously weaker.
Grout is however cracked in number of places. Shouldn't the Rapid Mat have prevented all of this?

 

[J Sid]

Flow temp seam high, I understand 28 degrees max.
Others may tell you different.
Have you spoken to BAL ?

 

[Ajax123]

36 degrees water temp is fine. That will give a surface temp about 28 and a room temp of about 22

Sounds like movement though. The floor trying to expand and contract in two different directions leads tore strains and stress within the tile face. The weakest point is the grout joint so that will crack first. A joint at that point would have helped.

 

[jesteh]

Flow temp seam high, I understand 28 degrees max.
Others may tell you different.
Have you spoken to BAL ?

Flow temperature according to manufacturer should be left around 43 degrees although it can go higher - if pump is set right, floor tempreature is then around 28 degrees. We got to around 23 degrees floor temperature before we got cracks.

Yes, I had BAL rep to have a look today. He had a quick look at the tile and said that the tile cracked due to vertical movement (only thing not covered with Rapid Mat :hurray: so obviously not their problem)

He said grout cracking is perfectly normal with underfloor heating and nothing to worry about. Then he suggested tiler should have added flexible addy to the grout to stop it cracking (which is actually incorrect).

 

[tubs]

Did the Bal Rep not mean GT1 added to the grout ?

 

[jesteh]

Obviously expansion joints would have helped. I could have split the floor into small 3m x 3m segments but that would have looked crap and was not suggested by tiler, BAL or any standard I have seen. As it is the longest length is below 7m and the whole tiled area is 30 sqm - its not a massive area!

Also, I understood the purpose of the Rapid Mat was to reduce any movement to tiles. Tiler thought its unnecessary expense to have it but I insisted to avoid exactly these sort of problems. As it is, I am left wondering if I would have had these problems had I used Ditra.

 

[jesteh]

Did the Bal Rep not mean GT1 added to the grout ?

Yes sorry, Bal rep did say tiler should have added GT1 to grout. Weber says its better not to add it as its already flexible.

 

[J Sid]

Adding to much water to the grout in mixing or washing will weaken it. I am sure the Weber rep could test for this.
Personally I use Ditra, even though I am not keen on the bal mat, which i have tried, would hope this is not the root of your problem.
All the wet underfloor heating floors I have done have used Detra with with lower flow temps and never had problems with floor or customers complaints above heat up times etc.
Was there any expansion joint round room perimeter?
Speak to Weber tec about grout cracks.

 

[White Room]

Flow temperature according to manufacturer should be left around 43 degrees although it can go higher - if pump is set right, floor tempreature is then around 28 degrees. We got to around 23 degrees floor temperature before we got cracks.

Yes, I had BAL rep to have a look today. He had a quick look at the tile and said that the tile cracked due to vertical movement (only thing not covered with Rapid Mat :hurray: so obviously not their problem)

He said grout cracking is perfectly normal with underfloor heating and nothing to worry about. Then he suggested tiler should have added flexible addy to the grout to stop it cracking (which is actually incorrect).

Surprise surprise

 

[Ajax123]

Flow temperature according to manufacturer should be left around 43 degrees although it can go higher - if pump is set right, floor tempreature is then around 28 degrees. We got to around 23 degrees floor temperature before we got cracks.

Yes, I had BAL rep to have a look today. He had a quick look at the tile and said that the tile cracked due to vertical movement (only thing not covered with Rapid Mat :hurray: so obviously not their problem)

He said grout cracking is perfectly normal with underfloor heating and nothing to worry about. Then he suggested tiler should have added flexible addy to the grout to stop it cracking (which is actually incorrect).

How did he demonstrate vertical movement. Is there a lip or a height differential either side of the crack?

 

[Stef]

Looking through your check list, did the screed have the laitance removed prior to tiling & how many coats of primer did the tiler use?

 

[jesteh]

There is no lip or height differential. To be quite honest - I am disappointed with BAL. Yes they did send the rep round very quickly but both the tech support and rep seemed to be very much on defensive and were really looking for issue thats not their problem. The rep did check whether there is a lip on the crack - there wasn't but still concluded that its vertical movement. So not their issue. Also, I don't really get the 'grout cracks with UFH' answer. It really tells me that Rapid Mat was a waste of money - tiler could have laid the tiles straight onto screed (which is what he wanted to do) and grout would have cracked all the same - I would have just saved some money.

Weber seemed much more unbiased and interested in getting to the bottom of it (even though I just used their grout). They suggested to bring the tiler round to lift the damaged tile and have a look underneath whats going on and take a few picture and samples to analyse - so this will be the next step.

 

[jesteh]

Looking through your check list, did the screed have the laitance removed prior to tiling & how many coats of primer did the tiler use?

Yes - I removed laitance and primed and myself so I know it was done right

 

[White Room]

How did you go about removing the laitance and how many coats of primer was applied...

 

[jesteh]

Laitance - hired a floor grinder.
Primer - one coat diluted 50-50 in one direction then another coat undiluted in other direction
Used BAL Prime APD

Why would this make a difference to grout cracking though - the tiles are not moving, they are completely solid, no hollow sounds at all anywhere. Or are you suspecting they are moving with cracks forming?

 

[Ajax123]

To be fair it probably isn't their problem but a mid diagnosis is unhelpful in dealing with the issue. Is there any movement either side of the crack if you put your epweight either side of it.

 

[Stef]

Laitance - hired a floor grinder.
Primer - one coat diluted 50-50 in one direction then another coat undiluted in other direction
Used BAL Prime APD

Why would this make a difference to grout cracking though - the tiles are not moving, they are completely solid, no hollow sounds at all anywhere. Or are you suspecting they are moving with cracks forming?

I had to use Bal rapid set on top of an anhydrite screed to push a job on, I only ever use a compatible addy (AnhyFix),
I gave that 6 coats of primer.
I personally haven't used Bals rapid mat & I don't think I ever will as I can't truly understand how it works as I use Ditra & when you see the technical side of it you realise how that works & how it decouples.
I would get someone to stand on a tile & move their weight whilst you check very closely to see if there is movement in the tile.

 

[Andy Allen]

Yes sorry, Bal rep did say tiler should have added GT1 to grout. Weber says its better not to add it as its already flexible.

Don't know why bal rep would suggest that when they don't recommend adding gt1 to there own modified grout ( super flex)

 

[jesteh]

I did consider using gypsum based adhesive. Problem is no mat manufacturer will say their mat is compatible with it. If you ask Schluter whether you can use Ditra with gypsum adhesive, they'll say they do not recommend it. Same with BAL Rapid Mat. So you are going against manufacturer recommendation by using that. I did ask both before the job started.

As far as using 6 coats of primer - why only 6? Again, if I asked Bal or Schluter whether to use 6 coats of primer they will say we do not recommend this - use 2.

I am not saying you are wrong. But you are going against manufacturer recommendation. Probably because you know better.

I on the other hand don't have a clue. I am not a tiler, I don't years of experience or time or inclination to start testing different mats with different amount of primer and different adhesives and see what works best. My tiler also has no interest in material science - he buys tile adhesive in bulk whatever works out at good price. Which is fair enough.

So what I did was to select a supplier and follow their instructions to the letter, trusting that they know what they are talking about. Where I am getting ****ed off is that now I have a problem, they are very quick to say its nothing to do with them and walk off. The entire investigation from BAL consisted of knocking on the tile (it was solid) and poking a nail at the grout. Then blame vertical movement for crack an say that grout is not flexible enough.

I am not saying its a problem with BAL mat or adhesive, I have no idea and neither do they right now. What I am saying is that BAL have shown no interest in finding the root cause which right now puts a very low value on their 25 year material guarantee.

 

[Rich Midge]

The arrogance of these big manufacturers is a joke. We've had similar problems with Norcros. They actually came out and inspected floors in a new build, produced a detailed plan of how we should tile including location of expansion joints, primer, adhesive and even what size spacers. Needless to say the floors failed, not just cracking but lifting in all areas. They came out to it and diagnosed vertical movement so not in any way their fault! The main contractor sent some adhesive samples off for independent testing which found a low polymer content so said manufacturer did their own test. Surprise surprise that test showed the adhesive to be perfect in every way. Vertical movement, a licence to get away with all sorts.

 

[Ajax123]

Can you put a picture on ... That'll make it much easier to diagnose.

 

[Stef]

I did consider using gypsum based adhesive. Problem is no mat manufacturer will say their mat is compatible with it. If you ask Schluter whether you can use Ditra with gypsum adhesive, they'll say they do not recommend it. Same with BAL Rapid Mat. So you are going against manufacturer recommendation by using that. I did ask both before the job started.

As far as using 6 coats of primer - why only 6? Again, if I asked Bal or Schluter whether to use 6 coats of primer they will say we do not recommend this - use 2.

I am not saying you are wrong. But you are going against manufacturer recommendation. Probably because you know better.

I on the other hand don't have a clue. I am not a tiler, I don't years of experience or time or inclination to start testing different mats with different amount of primer and different adhesives and see what works best. My tiler also has no interest in material science - he buys tile adhesive in bulk whatever works out at good price. Which is fair enough.

So what I did was to select a supplier and follow their instructions to the letter, trusting that they know what they are talking about. Where I am getting ****ed off is that now I have a problem, they are very quick to say its nothing to do with them and walk off. The entire investigation from BAL consisted of knocking on the tile (it was solid) and poking a nail at the grout. Then blame vertical movement for crack an say that grout is not flexible enough.

I am not saying its a problem with BAL mat or adhesive, I have no idea and neither do they right now. What I am saying is that BAL have shown no interest in finding the root cause which right now puts a very low value on their 25 year material guarantee.

You are doing everything by the book & that should be enough to cover you for a guarantee but they will find anyway out of it as you have found out.
I don't phone technical now as some of the things they recommend I don't agree with.
This forum is the best place to come for advice but it's normally when someone has a problem like your own case.
It's all well & good us surmising what has led to failure but unless you physically look at the job then it's a guessing game.
I hope you get to the bottom of it.

 

[J Sid]

Like Stef says, they wouldn't admit to anything that would mean there product has failed.
I had this with another adhesive manufacturer who's adhesive failed on some jobs the company I was working for had done. The adhesive company claimed all the normal things, mixed with to much water, not enough water, all the standard excuses.
End of the day, some samples were sent to be tested at an independent chemist. Result, the product was not suitable for what they claimed. The product was withdrawn from sale.
If you believe that any product that was used on your project has not performed as you understood it would or should, sadly it will be down to you to prove that a product has not performed as claimed.
You will get possible reasons for your failure from knowledgeable people on here and hopefully it will point you in the right direction to sort your problems.

Has the floor temperature been taken around the cracked tile for hot or cold spots, which could put undue stress on an already stressed cut tile?
Did the angle of the internal cut have a radius, to reduce the point Load? or is it a sharp point on the internal angle?
Has the max actual floor temperature be measured in the areas of the cracked grout? I know the Weber grout mixed with to much water is very weak, and can be easily done and should be an easy test. If so a re grout of the floor is not a major job.

 

[jesteh]

Thanks very much for all the responses.
I am actually not that bothered about the cracked tile - while a bit annoying its also straightforward to fix. Its only one tile thats been cut and is in a funny place. If it cracks again, it can also be replaced by two smaller pieces - its really not that visible either way. When tiler is back to look at it, we'll lift the tile and see whats happening underneath which will hopefully provide a few ideas.

Its the grout that I am more concerned about. The cracks are very small, really more a hairline fractures and they appear lengthwise either on the edge of the tiles or down the middle of the grout line (rather than across the grout). Grout is also not cracked in every single grout line but it is cracked throughout the whole tiled area. Its not limited to big sections where there is lots of movement. Even in the small separate utility room which is 3m x 1m there are cracks appearing. Cracks are also small enough that you have to get down and look closely to notice them - just walking around the room they are not visible. I only noticed when I started looking for problems after noticing cracked tile. I'll get some pictures done later today.

Is this a major issue?
Is it normal for flexible grout to develop these hairline fractures with UFH?
Should the decoupling mat have prevented this bearing in mind that its advertised as being able to take horizontal movement in milimeters.
Should I leave it for now (grout seems solid and stable enough otherwise) or do I have to regrout?
Does the grout cracking indicate potentially that tiles may start moving too?

As far as quality of grout job - I didn't do it myself so I can't say whether it was done right but the guys who did it were experienced. I actually watched them mixing the grout, they did it by feel - i.e. mixed grout in small amount of water then kept splashing in bit more water while mixing with a paddle mixer at slow speed until it felt right. I wouldn't trust myself to do it that way but its down to experience - they've been doing this for 30 years so I wasn't about to make them measure it out on kitchen scales .

 

[jesteh]

Thanks very much for all the responses.
I am actually not that bothered about the cracked tile - while a bit annoying its also straightforward to fix. Its only one tile thats been cut and is in a funny place. If it cracks again, it can also be replaced by two smaller pieces - its really not that visible either way. When tiler is back to look at it, we'll lift the tile and see whats happening underneath which will hopefully provide a few ideas.

Its the grout that I am more concerned about. The cracks are very small, really more a hairline fractures and they appear lengthwise either on the edge of the tiles or down the middle of the grout line (rather than across the grout). Grout is also not cracked in every single grout line but it is cracked throughout the whole tiled area. Its not limited to big sections where there is lots of movement. Even in the small separate utility room which is 3m x 1m there are cracks appearing. Cracks are also small enough that you have to get down and look closely to notice them - just walking around the room they are not visible. I only noticed when I started looking for problems after noticing cracked tile. I'll get some pictures done later today.

Is this a major issue?
Is it normal for flexible grout to develop these hairline fractures with UFH?
Should the decoupling mat have prevented this bearing in mind that its advertised as being able to take horizontal movement in milimeters.
Should I leave it for now (grout seems solid and stable enough otherwise) or do I have to regrout?
Does the grout cracking indicate potentially that tiles may start moving too?

As far as quality of grout job - I didn't do it myself so I can't say whether it was done right but the guys who did it were experienced. I actually watched them mixing the grout, they did it by feel - i.e. mixed grout in small amount of water then kept splashing in bit more water while mixing with a paddle mixer at slow speed until it felt right. I wouldn't trust myself to do it that way but its down to experience - they've been doing this for 30 years so I wasn't about to make them measure it out on kitchen scales .