Stress fracture concrete 2 joining rooms ditra? - Tile Advice

[area tiling]

Yes Peter their starting to pop up more frequently down our way, plumbers are actually pricing them into their costs when quoting with the ufh!

 

[Ajax123]

How do these poured anhydrite and hemi hydrate screeds perform under stress, do small fractures also end up being major cracks ?

The short answer is no...

the slightly longer and more complete andpswer is that Generally anhydrite is much more dimensionally stable that cement as it does not undergo the chemical reactions that cause long term shrinkage in sand cement screeds. All of the shrinkage that does occur (which is very low level) tends to occur in the first couple of days of setting and once set no further shrinkage occurs.

That said there is still movement due to thermal cycling and whilst joints are often omitted they should be placed at door thresholds and between independent heating zones where underfloor heating is present. The big difference is that rather than helping control the positioning of shrinkage cracks as would be the case with sand cement the joints take account of thermal expansion.

cracking in anhydrate can and does occur sometimes but this is usually related to design or installation/preparation issues

 

[Chalker]

When fitting underfloor, i Used to always fit expansion joints in doorways between different zones, and cut a few notches out for the screed to flow, but for the last couple of years the lads that do the screed have pulled them out. Told me they weren't needed anymore with modern screeds.
Since then I've not bothered fitting them and not heard of any problems, even on large floors.
Best practice as far as I can see before tiling, is to allow any cracking to happen in the drying process.

 

[Ajax123]

To be fair the vast majority of domestic anhydrite screeds go in without joints and there are no real issues. However best practice is still guided by the British standard which us supported by the binder manufacturers and the advice on joints remains unaltered. These "modern screeds have been around fir thirty years and have not changed significantly in that time so the same advice given then is given now.

 

[High Peak Tiling]

A question with a very relevant but slightly different case,
I have a floor coming up which has small non straight cracks in the concrete which was all pour screeded. Lafarge agilia screed.

Will these cracks cause any problems over time or shall I ditra/schuter the whole floor?
Thanks in advance?

(Floor has underfloor heating, been laid in situ for 3 years)

 

[Ajax123]

A question with a very relevant but slightly different case,
I have a floor coming up which has small non straight cracks in the concrete which was all pour screeded. Lafarge agilia screed.

Will these cracks cause any problems over time or shall I ditra/schuter the whole floor?
Thanks in advance?

(Floor has underfloor heating, been laid in situ for 3 years)

you need to find out if it's anhydrite or cement. Either way cracks should be repaired following heating being comissioned if you tile direct. However based on the description it sounds like a classic case for ditra

 

[High Peak Tiling]

you need to find out if it's anhydrite or cement. Either way cracks should be repaired following heating being comissioned if you tile direct. However based on the description it sounds like a classic case for ditra

Lafarge agilia screed is cementitious.

Can you guys give me a average price for 50m2 of ditra?

I'll ask my supplier tomorrow.
I have always used Backer board for wooden floors.

 

[Ajax123]

Lafarge agilia screed is cementitious.

Can you guys give me a average price for 50m2 of ditra?

I'll ask my supplier tomorrow.
I have always used Backer board for wooden floors.

lafarge agilia screed c is cementitious as is lafarge agilia screed 10. However lafarge agilia screed a is anhydrite. You need to check....

 

[High Peak Tiling]

lafarge agilia screed c is cementitious as is lafarge agilia screed 10. However lafarge agilia screed a is anhydrite. You need to check....

Have already checked as customer has invoice

 

[High Peak Tiling]

Have already checked as customer has invoice

I shall be pricing for ditra matting and if customer doesn't want it then I'll do without and write a disclaimer

 

[Mr Tiler]

This started out as a hairline crack,
View attachment 56386
This was after two years, it cracked the limestone much earlier than this.
The company were advised at the time to go with Ditra but wouldn't listen.

I think I shall have to save this picv stef as an example to future customers

 

[High Peak Tiling]

I think I shall have to save this picv stef as an example to future customers

I already have Ash !