Concrete Tile

[Bennyhonda]

Here's one I haven't run up against before. One of my clients has asked what to do about the concrete tiles they have throughout their building. The tiles have been laid atop of sand, which is on top of a rubber roof. There may be another layer but I cannot remember. Nonetheless, it was a professional job.

The overhead areas of the tile are covered, except for the top floor where there is an open terrace, however, rain can and will blow in from the open sides.

I dont think cleaning the algae would be a problem on this tile if it were not for the efflo they've begun the experience. It's not terrible but is noticeable.

I'm afraid that chemicals could damage the rubber roof. That leaves me with pressure but doesnt pressure tend to cause more efflorescence?