During the installation of any roofing project, it is extremely important to thoroughly clean the roof of all debris on a daily basis. This includes nails, fasteners, metal cuttings, and anything that can absorb moisture (dirt, wood, rags, etc.). Permitting these materials to remain on the cladding material is inviting rust to develop. All the above should also be done on completion of the cladding process.

Prefinished material can also have its original appearance and service life extended by occasional thorough cleaning. This may be done by the use of plain water and a pressure spray.

In areas where heavy dirt deposits dull the surface, a solution of water and detergent may be used: 100 ml (1/3 cup) of a typical laundry powder detergent per 4 litres (1 gallon) of water. A soft bristle brush should be used for scrubbing, followed by a thorough rinse with clean water.

Mildew may occur in areas subject to high humidity. To remove mildew along with dirt, the following is suggested:
            (1) 100 ml (1/3 cup) laundry detergent
            (2) 200 ml (2/3 cup) trisodium phosphate (TSP)
            (3) 1 litre (1 quart) 5% sodium hypochlorite solution (laundry bleach)
            (4) 3 litres (3 quarts) water
            Use in a well ventilated area and follow with  a clear water rinse

Solvent and abrasive cleaners should be avoided. Caulking compounds, oils, tars grease, wax, and similar substances can be removed with mineral spirits applied only to the affected areas. Detergent cleaning and thorough rinsing should follow the use of any solvents.

CSSBI Fact Sheet