If you see water on the slab it could also be a dewpoint problem. Don't any of those people there have thermohygrometers and an infared thermometer to check the slabs temp and ambiet rh and temp?
Here is a good tutorial about dewpoint issues on slabs. You should also have the slab tested using the relative humidity with interior temp test, in U.S called ASTM F-2170-11.
http://www.pbawichita.com/blog/4/dew-po ... tallationsHere is another example with a dewpoint chart on the scecond page.
http://www.buildwithbps.com/assets/down ... 0Chart.pdf