crackin stone floor

[philthetiler]

hi all am after a little help. i have been tiling (stone) 4 some yrs now and i have come across a few problems in my time as most people do. am now stuck and unsure on this 1so am hopin u may help if not no worried thanx 4 readin
i have a screed floor over under floor heating its 70mm thick screed i waitied 70days 4 it 2 dry and then the stone didnt turn up so we waited a further 2 months more
while this was goin on the underfloor heating was tested fully. when i came 2 tile the floor there were no cracks in the screed and the heated was off (had been 4 over a week) i used a fan heater 4 the heat
all went well floor looked great 30m2
i told the customer 2 leave the heating off 4 3weeks and they did. 2 days after turning the heating on slowly the floor has 4 long cracks in it. flex adheasive0 was used and flex grout was used the heatin was turned up slow
tile is trav at 13mm (600x400) laid in brick patten
stone was covered in stain stop
i have also left an expansion gap round the room of 15mm (covered by skirtin board)

here is wot i have done so far
i have found a tile with a crack in it and removed part of the tile (where the crack was bout 40mm either side of crack) removed the adhesive and there is no crack on the screed so i fig its the adhesive or the tile ?it looks just like the screed has moved
adhesive used it webber white flex
grout the webber iroy flex
stone 12-13mm thick travertine
sorry 4 waffle on hope u can help
oh i have asked the adhesive company 2 come out and have a look
my first thought was the floor (screed ) is at fault but havin not seen any cracks i cant how this can b
any help u can give will b greatfull
i have been tilin 4 bout 8 yrs now stone 4 bout 4 of them

[grumpygrouter]

Hi Phil welcome to the forums. I have virtually no experience laying stone, just done my first one (granite) over a heated screed. My only thought is maybe the customer turned up the heating too quickly after the tiling. I understand that it should be turned on low and the heat increased by 5c per day until normal temprature requirements are met.

Good luck.

Grumpy

[philthetiler]

i hope goes well m8 and stone is a lot harder work but im sure u will no this. thanx 4 the advice m8.but the didnt turn the heating on until 3weeks after the tiling was completed her husband made sure of it. thanx anym8 and if u need any help feel free 2 ask

[TheWrightTiler]

that could be the prob mate if they waited 3 weeks to turn on as they prob whacked it right up to the max test it after the 3 weeks rather than turn it up bit by bit until it was at max operating temp

prob the best man to check with is dave

cheers

andy

[MICK the Tiler]

Could it be possible that the trav tile had a hairline fracture before it was fixed, i know this sounds odd but its not always easy to pick this up while fixing only ever shows up after floor is cleaned and sealed. marble can be a bugger for this along a vein.

[JOHNNYCLARKE]

Mick

Sounds very strange to me .
Youve done everthing right.
I lay nearly more than 150 sq mts a week limestone 90% of which is on heated floors and do see cracking, but there is always a logic to it.
when there is a continuous crack from one tile to another there has always been
a corresponding crack in screed.
I know this because I get called back to dig tiles up at least ten times a year. but am always covered because they have not had expansion joint through floor on big screeds or ditra or similar.
This crack is caused by any of the problems you have already stated or few other options.
Apart from lack of expansion joints a very common denominator is beam and block floor below screed. These move and so does screed but screed has always cracked.
So your problem is baffling.
sEND

[JOHNNYCLARKE]

send me private message with your tel no and we can discuss.

Johnny

[TilingLogistics]

Dave PM'd me this one but I might as well answer you on here!!! What sort of screed was it? Was it anhydrite? Did it have a sort of milky finish? Was the floor primed? Any chance of some pics please?

Kev

[Dave]

sometimes when using stone over UFH the stone will crack.. The substrate moves at a different rate to the tiles and with travertine being one of the softer stones then it can be prone to cracking,,this is where an isolation membrane comes in, something like ditra..........I think it is may be down to stress from the substrate transferring to the tiles.....
Also what is the longest run of tiles.....?......should only be about 4 to 5 mtrs with UFH..........

[MICK the Tiler]

Originally Posted by JOHNNYCLARKE

Mick

Sounds very strange to me .
Youve done everthing right.
I lay nearly more than 150 sq mts a week limestone 90% of which is on heated floors and do see cracking, but there is always a logic to it.
when there is a continuous crack from one tile to another there has always been
a corresponding crack in screed.
I know this because I get called back to dig tiles up at least ten times a year. but am always covered because they have not had expansion joint through floor on big screeds or ditra or similar.
This crack is caused by any of the problems you have already stated or few other options.
Apart from lack of expansion joints a very common denominator is beam and block floor below screed. These move and so does screed but screed has always cracked.
So your problem is baffling.
sEND

Your absolutly right Johnny, Sorry!!! I completly misunderstood the post from Phil and read the question as the problem being with only the one tile that had cracked, easy to overlook whilst laying. It seems though (Now i'm reading this sober) the cracking is more extensive which would require further investigation.

Again my sincere apologies for misunderstanding the question being asked.

Cheers Mick.