A building cleaning system for cleaning a side of a building can include an elongate brush structure that is rotated by an electric motor, a frame for supporting the brush structure that can be oriented to face toward the side of the building, and a plurality of air moving devices mounted to the frame for generating counterforce to force the frame toward the building. The air moving devices can including fans or blowers. The air moving devices can be being spaced apart from one another in an orientation that extends along the length of the frame. A lift arrangement can be provided for moving the frame along the side of the building.