Stress fracture concrete 2 joining rooms ditra?

[Stef]

[/B]
To replace 38 tiles ???

Take me a year to stick them down Mark!!

There's another few that were cracked but weren't replaced, will catch them in a few months time when I'm sent down to carry out more repairs.

 

[White Room]

Okay Rob:smilewinkgrin:

 

[area tiling]

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

 

[Stef]

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

I'm not sure, that's a question for Ajax,
On the calcium screeds I have tiled I have noticed very small cracks but only time will tell if they develop into a problem.

 

[Peter]

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

Are you getting many of these screeds round your way? Few and far between in Belfast thankfully.

 

[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)