Hiya Mark.
I think you'll find there are an a great deal of tilers put off by these screeds.
You've arrived on this Forum a bit late to witness a load of us guys trying to make sense of this system that has been forced upon us.
I took it upon myself to try and have a good go and get to the bottom of these screeds, and to be honest i've given up on them as they are NOT worth the risk for us end trades, or at least ones who really care about their finished product. I'll explain as well as possible:
I've been tiling over 20 years and i kinda know when to tile a floor on concrete that it will stay put,. I know the recommended drying times, the ideas behind adhesives and their performance, blah blah. I do a floor, I get paid and the customer and myself are happy, for years, as the floor does what it's supposed to, it's stayed put.
So along come these screeds, ''ooh this is flat, i dunno what it is but its nice to tile too."
"The builder poured it really fast and it can be tiled in a few days", great stuff, we think, he says it fine to tile to.
Then (having not tiled too many i may add),we actually find out it's not cement based but gypsum, ooh thats odd, why use gypsum for a floor as it's not waterproof??
So then further research shows the drying are nothing like the ones we've been told, and can and ARE even slower than cement screeds.
Then we hear of failures," you should have sanded", "no one told us", "oh you should use epoxy primers", "that's not what BAL say, they spec the same as cement based adhesives".
So back on the phone:
Moisture testing, conflicting conversations from EVERYONE. Lafarge are vague as too whom is responcible, and what method.
One method recommended by one guy is poo poo'ed by another. Testing manufacturers say they don't agree with recommended practise.
Preparation: Who is responcible for sanding, if it even needs it, some say it does, some not.
Adhesives: People like Bal say prime and cement based, other like Kerakoll etc say gypsum friendly, others gypsum based adhesives.
Weren't we taught NOT to use Gypsum based adhesives as they don't stick porcelain, hence the move to modify adhesives when porcelain came out ten years ago?
I've tested all these adhesives with very mixed and mainly unsatisfactory results. Most gypsum adhesives i found didn't stick well at all to porcelain, and then have to be put through the rigours of lateral expansion with underfloor heating.
The best i found was creative impressions GBTA, and it cost £750 to tile a 63m2 slate floor to anhydrite, twice as much as cement based.
How the hell do you quote well for that and then programme it into your schedule to allow the vaugeries of it's drying times???
I've found two ways to approach these screeds:
Sand, prime, GBTA, Ditra Mat and then cement based adhesives. And even then Schluter aren't too happy with Gysum adhesive and Ditra, and the customer is certainly not happy with the price.
The second way is too say, "sorry, i'm not tiling this".
So i have been FORCED by your cack screeds to stop doing a job that i like, and make money at, to change the way i work, simply because NO ONE is helping out us tilers, the dunces taking the flack at the end of the job.
I know Ajax will read this, and he is a legend, and he has tried. But i'm a tiler and i have no confidence in this system at the present time, i am not alone, and the nimber will grow as these failures happen more and more.
This site is having more and more posts from failures from this screed and it needs to be dealt with by the people selling the screeds.
Yes you've sold loads for years in Europe, then bring the
standards over here NOW.
Rant over.