Does a Metal Roof Need to be Grounded?
The short answer is no, a metal roof does not need to be grounded. In most cases, you will not incur additional risk if you don’t ground it. Metal does conduct electricity. But when dealing with a full roof, a lightning strike would ground out through the structure, causing no more harm than non-metal roofs would. Lightning will strike whatever gives the least resistance, as a path to the ground. Therefore, a metal roof won’t pose any greater risk of a lightning strike than a standard roof on the same structure. As an electrical conductor and a noncombustible material, metal roofing has a lower risk of damage from a lightning strike. Occasionally, some municipalities or local building codes may require metal roof grounding. But major building code organizations do not recognize grounding of metal roofs as necessary.
Keep in mind, the lack of a national code requiring a ground assumes that we’re following all applicable building codes. This includes using only PVC piping to extend from the interior of the house up through the roof. Not following this code could pose a serious risk to the occupants inside the structure. In this case, the lightning would not be grounded through the rest of the structure. It could instead travel down the pipe inside the building causing damage.
Although lightning protection and roof grounding are not national code requirements, it is becoming routinely specified. These requirements vary based on local codes.
While not required by national code, there are instances when you might consider lightning protection or grounding your metal roof, for peace of mind. An engineer can use a risk assessment calculation based on the NFPA 780 guidelines to help decide if lightning protection would be a recommendation for your home. Any official requirement for a lightning protection system would come from the authority having jurisdiction (AHJ) in your area. If you wish to have lightning protection or grounding on a metal roof, please consult a lightning protection specialist.
For additional information on the use of lightning protection, see NFPA 780 Standard for the Installation of Lightning Protection Systems, 2017 Edition, National Fire Protection Association.
Disclaimer: This article intends to offer general knowledge on this topic. While every caution has been taken to provide accurate information, it does not intend as professional advice. Please consult with an industry professional in your area to obtain proper advice based on your unique circumstances. Rare Mfg. Inc. will not be held liable in any way should you suffer any loss/damage because of the information in this blog.