Exterior stone is a general term denoting stone installed in a place where temperature, moisture, and airborne contaminants are caused primarily or solely by the forces of nature. It can be used in a honed, textured, or polished finish in any mode in an exterior environment. Uses include building cladding, walkways, steps or stairs, retaining walls, paving, fountains, benches, planters, and decorative items such as sculptures.
Normal Maintenance. In accessible areas, routinely follow maintenance procedures as specified in article: Maintenance of Interior Stone, on this website, as applicable.
The large expanses of stone generally found on exterior applications may make it impractical to perform normal maintenance on a frequent basis. Large installations, however, should be given periodic overall cleaning as necessary to remove accumulated pollutants. Easily accessible stone surfaces such as steps, walkways, fountains, etc., should be kept free of debris and soiling by periodically sweeping and washing with water.
Normal maintenance should include periodic inspection of stone surfaces for structural defects, movement, deterioration, or staining.
Source: Marble Institute of America – Cleaning and Maintenance