Slate over Anhydrite screed - commissioning a

Really helpful advice - thanks so much Ajax & Dave. One reason I'm tying to really understand this is because this sits between 3 trades: i) screed manufacturer/installer, ii) UFH designer/installer and iii) tiling/tile installer - and I'm getting conflicting views. So I'm back to basics - keep asking why!
I wonder if any prof tilers have actually experienced a screed cracking due to being heated up and then needing repair before tiling?
It sits between 3 trades but you are the main contractor/client so you carry ultimate responsibility. You are also the one who is paying so if it goes wrong you will be the one who ultimately picks up the bill. I'm not sure what you are trying but failing to understand. Conflicting views on what... conflicting views on the requirements of the standards...that comes down to the level of expertise that individuals have. I personally gave a fair degree of experience with these screeds. I'm asked the same question a lot... the answer... see my previous post.

That your boiler is not available would not constitute a defence in any civil action you might take if the floor fails. You can just hire a temporary boiler... job done.

As I said you can do whatever you like. You may get lucky you may not... it's a lottery regardless but if you follow the rules it mitigates risk. We dont make recommendations for the sake of it.
 
Dave, thanks. For your example, had the floor properly dried out before commencing heating? - or were they force-drying?

A bit more context for my situation ...

I can't heat the floor because I don't yet have the UFH boiler installed - that is months away and we need a functional floor ASAP. If I had the ability to heat the floor - there is no question about doing that - I would take the floor through several thermal cycles. I also do not question stone fed, TTA etc guidance and best practice.
The cost of hiring in a temp set up to heat the floor is significant (£ hundreds + time - hassle). So I am trying to do a cost-benefit assessment.
Another factor to consider is that the slate tiles will be randomly placed - so there are no straight-line grout lines. Also slate is one of the strongest natural stones and is resistant to cracks, etc.
You seem to be fishing for answers that dont exist. You clearly have it in mind to ignore the advice so I'd suggest you just get on with it. You'll not get anyone to say " yes...good idea bat man, you clearly know your stuff better than the experts" unless in a sarcastic manner.

It's not a cost vs benefit exercise, it's a lottery. Up to you. Pay your money make your choice.
 
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Dave, thanks. For your example, had the floor properly dried out before commencing heating? - or were they force-drying?

A bit more context for my situation ...

I can't heat the floor because I don't yet have the UFH boiler installed - that is months away and we need a functional floor ASAP. If I had the ability to heat the floor - there is no question about doing that - I would take the floor through several thermal cycles. I also do not question stone fed, TTA etc guidance and best practice.
The cost of hiring in a temp set up to heat the floor is significant (£ hundreds + time - hassle). So I am trying to do a cost-benefit assessment.
Another factor to consider is that the slate tiles will be randomly placed - so there are no straight-line grout lines. Also slate is one of the strongest natural stones and is resistant to cracks, etc.
Its not the cracks etc. It’s the de-bonding , listen your talking yourself into an installation without the correct procedures. We can only advise. Good luck and report back when it fails.
 
So some feedback from the bat cave: the decision is to go for a thermal shock using a hired-in boiler. Screed supplier is suggesting 7 day shock cycle given that no additioinal time is required for drying (usually the boiler would be hired out for a 3 week period). Thanks again for all the advice - much appreciated.
 
So some feedback from the bat cave: the decision is to go for a thermal shock using a hired-in boiler. Screed supplier is suggesting 7 day shock cycle given that no additioinal time is required for drying (usually the boiler would be hired out for a 3 week period). Thanks again for all the advice - much appreciated.
7 day cycle is insufficient and likely to crack your screed. You should follow the procedure here. See post installation section.
 

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