Travatine tiles cracking on underfloor heating system - HELP!

[Rex]

Help!
Can anyone please advice me on how to solve the following problem...
Have travatine marble tiles laid on top of an underfloor heating system, and they have started to crack in a row along the door threshold.
Laid ontop of screed floor, and I think without any membrane.
If anyone can offer a simple solution for this, I'll be very grateful.

Will patching in with Ditra at the problem area solve it?

Thanks

 

[DHTiling]

High tight were they cut to the edges and threshold..?...have you got any pics..?

 

[Rex]

Hi,
The cracked tiles run along the threshold of a sliding door and also along wall at either side.
There is a foundation for the wall which is solid, that I believe is meeting the under floor heating area, and this is where the cracks have appeared.
Sorry haven't got photos.
Any suggestions gratefully received!

 

[DHTiling]

Ahh i see......you need to put an expansion joint at this point....leave about a 5mm joint over that point and fill with a matching Silicon...

You have 2 individual substrates that are expanding against each other and to use an isolation membrane would only work if across the whole floor area but if you put in a cold expansion joint ( Silicon ) then that will relieve some of the stress causing the tiles to crack..

 

[Rex]

Apologies for my further questions but I'm not a tiler.
How do you put in an expansion joint?
Take up tiles, excavate in the wall foundation an expansion joint?
Or replace new tiles to a lesser width allowing an expansion joint filled with Silicon?
Thank you for your speedy response.

Also, as no ditra membrane was laid under the entire floor is it likely to crack elsewhere?

 

[DHTiling]

You just replace the cracked tiles and leave a joint directly above the break in the floors..and fill with a matching colour Silicon to your grout...as for the rest of the floor...hard to say really...