Abstract: A system for treating an external surface of a building, has (a) at least one treatment unit configured to treat the external surface of the building with a pressurized fluid; (b) at least one suspension system for suspending the treatment unit adjacent to the external surface; (c) at least one suction unit associated with the treatment unit, being activated by the pressurized fluid to generate suction at a suction port; and (d) at least one suction head in fluid connection with a suction port to clamp against the external surface.