Several times per month I receive questions over the telephone that are generic for all manufacturers of metal panels. I rely heavily on literature printed by industry associations/organizations. The Metal Construction Association (MCA) has several technical bulletins that I find useful, and I will cover the key points of each below.

Question: Do I need lightning rods on my metal roof?

Answer: Lightning should be analyzed concerning the probability and the consequence of the strike. No measures are known that will lessen the probability of a strike, short of moving the structure to a different location. Buildings located on the top of a mountain or hill will increase the probability of a strike over those that are not. Also, the size and height of a structure will increase this probability when compared to surrounding structures, as will a building's proximity compared to smaller or shorter ones. Metal roof panels do not attract lightning more or less than any other roof covering. Two direct quotes are from MCA Technical Bulletin 1040, "the probabilities of a strike to a metal roofed structure are no more or less than any other kind of structure, as these probabilities have to do with height and size of the structure and its surroundings, rather than its construction materials."

Metal roofs do not attract lightning. The consequence of a lightning strike on a structure can be minimized if materials are electrically conductive, thus minimizing fire and explosion damage to the building and occupants. "Because metal roofing is both an electrical conductor, and a noncombustible material, the risks associated with its use and behavior during a lightning event make it the most desirable construction material available." The closing paragraph of the technical bulletin states that, "it may, in some cases, be prudent to consider lightning protection. A lightning protection system provides for a continuous conductor from earth to sky (and visa versa) so that the electrical charge is furnished an obvious path through which to flow, thereby reducing the risk to (electrically) resistive construction materials and human life."

Question: What, if anything, should I do to maintain my metal roof?

Answer: Direct quotes are from MCA Technical Bulletin 1050: "Painted metal roofs fabricated from pre-finished coils are formulated specifically to last longer than ordinary paints. Applied to coil strip in an extremely complex process, these paints are baked on over the corrosion alloy previously applied to the base steel. Warranted for adhesion to the coil substrate through the roll forming process, and chalk and fade according to ASTM test standards, the painted surface is constantly exposed to atmospheric pollution and ultraviolet rays at a high incidence to the sky."..."Apparent discoloration of the paint may occur when it has been exposed in dirt-laden atmospheres for long periods of time. Slight chalking may also cause some changes in appearance in areas of strong sun- light."

Generally, a thorough cleaning will restore the painted surface, prolonging the aesthetic appearance. This cleaning should also include the underside of the panel overhang at the eave in coastal geographic locations, to remove corrosive salts on areas not washed by rainfall. Cleaning solutions are easily mixed from readily available ingredients. One cup of common detergent, or household ammonia, in five gallons of water at room temperature are recommended. Apply with a soft rag, mop, or sponge. "Solvent containing cleaners (examples: Fantastic or Formula 409) are very effective and can be used without concern." Mildew or fungus that cannot be removed with the cleaners above can be treated with household bleach in a concentration of one gallon per five gallons of water along with one cup of detergent. Detergent or bleach cleaning should be completed by rinsing the roof surface with clear water.