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Discuss Grout coming out and crackling noise under some tiles in the Tile Adhesive and Grout Advice area at TilersForums.com.
Interesting that both Weber and mapei have gypsum based adhesives in mainland Europe though where there's quite a lot ,more anhydrite used. In the UK it is still increasing at a huge rate with this year acheiving something like 3million square meters plus.with increased penetration into all market sectors. A huge proportion of this is tiles without any issues whatsoever. There are many issues with sand cement screed. People dont generally choose their screed based on the fact that numpty tilers dont do the job properly. There are a good many good competent tiles who tile anhydrite screed almost daily and do not have issues. Stop blaming the screed and start looking more closely at what you are doing...They're a complete pain in the arse. I've never had a failure myself but have re-done a few where the people before didn't know what to do and so there often were failures. Its always the same things too, too much moisture/laitance not removed/removed wrong time/inadequate priming/etc/etc and they're still not always flat. What's wrong with a sand & cement screed, you know where you are with one of those and if you want it flat, lay it flat. It's interesting that the regular firms I use such as Mapei/BAL/Weber here don't sell a gypsum adhesive. Do they know more than me? Well probably but I'm not going to tile onto anhydrite again. Too many variables. If they want to tile onto anhydrite they can get some other idiot to do it, I don't need it.
Which is of course your prerogative and your choice. However that is not because anhydrite screeds are bad or tricky or "a complete pain in the wotsit". If they were that bad or that tricky they would not be so incredibly successful and widely used. There are so many really tangible advantages to using gypsum as a screed binder when compared to cement screed in many cases it is a no brainer. What made me laugh most of all was the fact you said you have never had an issue with one yourself and you have been perfectly happy to sort out other tillers **** ups on them... your comments are in conflict with themselves...I know perfectly well what I'm doing than you very much. And working on a gypsum floor isn't going to be one of them.
Maximum single bay size is indeed 300m2 but there should be movement joints at door thresholds, between independently controlled zones and where heated meets unheated. Unfortunately these joints are very often not included. The reason for using gypsum adhesive is to do with chemical compatibility. Gypsum adhesive is actually as strong as cement based in general but the level of shrinkage is much lower.The bolts and braces way would of been to put a decoupling membrane down, something like durable c++ after the floor is primed. This let's the floor flex, has a water/moisture barrier and let's a small amount of air under the tiles. Done this many times and, touch wood, never had a problem, even on floors twice this size. My understanding is with most anhydrated screeds is that you don't need any expansion joints under 300m2 unless you see cracking. It's softer than a typical concrete floor so most don't recommend using a cement adhesive but a Gypsum based as the cement based is too strong for the floor. To be honest if you do see cracking, which is quite common, you would use a decoupling membrane anyway.
Reply to Grout coming out and crackling noise under some tiles in the Tile Adhesive and Grout Advice area at TilersForums.com