QUESTION

Installations over CMU (concrete masonry unit)- Applying ceramic tile directly over CMU with latex modified mortar thin set on exterior wall, what type of waterproofing / moisture barrier do you apply on CMU ?
Or do you even recommend the method of direct application of ceramic tile on CMU with thin set mortar ?
Thanks,

ANSWER

ANSWER - Yes, you can bond directly to CMU if it is properly prepared.  Normally it is not completely plumb and flat.  It can be ground down and evened up with thin-set.  CMU is a big source of salts that lead to efflorescence, so it is advisable to apply a waterproof membrane that meets ANSI A118.10 such as a liquid applied material the manufacturers of tile setting materials manufacturer.  It should run up and over the top of the wall.  The backside of the wall should be waterproofed if it is against soil.  If the CMU is way off it would be better to shoot in 3.4 galvanized self-furred metal lath and apply scratch coat and mortar.  Then apply the waterproof membrane.

We do provide quality assurance and quality control services for tile and stone installations for architects and others.  If you want to ensure a successful installation, then you need to determine the suitability of the tile for the application and installation method.  Then you need specific installation guidelines and a quality control plan to be implemented by a third party.  For more