I used Mapei Renovation screed a while back for ceramics, I was told primimg not necessary, but looking at the spec sheet I amy have been mis informed :cry:
Even on a sound concrete floor mate. To be fair, there is not a product on the market that you should not prime before use. Some manufactures will state that it is not necessary if the subfloor is - "clean, sound, dry," but its up to you the installer to decide the definition of "clean / sound" to the same aspect of what the manufacturer decides is "clean / sound" The manufactures point of view will be - "free from dust and sound" as in the surface will not allow dust to come of it when sticking cello-tape to it. So like a ceramic tile for instance. But the manufacturer will like a keyed based also or a base that will absorb. You cant have both ! THE ONLY WAY TO GET THE ABOVE IS BY PRIMING ! Nice get out clause for manufactures when a subfloor fails due to you not priming. You may ask "why dont manufactures just say you have to prime then ? " ANSWER- "most installers would not of brought their product as they would simply of brought the product that says you dont need to prime" HENCE so many people do buy the product that says you dont need to prime 'providing' .......... Its worded for pure lazy installers. End of teh day its not like it takes long to prime. Maybe 5 seconds per sq'm at a cost of xxxx (not going state cost on open forum ) but you all know what it costs.
