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TOPIC: Research/Data

Ground Metal Roofs

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We are trying to get a certificateof occupancy. An inspector related to the Health Department for buildings with short term residences claims the national electrical code requires a ground on a metal roof. Our roofer, the manufacturer, electrician et al have never heard of such a thing, and have no idea how to do it. Is there such a requirement, and, if so how is it done? Thank you. Wells Jones, CEO, Guide Dog Foundation for the Blind
Guest User

8/15/2002
In all of my years, I have never encountered a grounding requirement in any code. If you can get me more information on the code section number, I will investigate it further. However, I think that there might be a misunderstanding at hand. There are numerous studies and reports available which indicate that a metal roof does not increase the risk of a lightning strike. Metal conducts electricity but would not "attract" lightning. Lightning attacks the path of least resistance so it strikes the highest object. If a metal roof is struck by chance, it should ground out through the structure without damage. The only risk I can think of would be if a metal plumbing pipe or electrical conduit comes through the roof and is in contact with the roof -- it could carry a charge into the living area of the home potentially. However, by code, those items should be PVC and not metal. If someone does choose to have lightning protection or grounding on a metal roof, I would contact a lightning protection specialist.
Todd Miller
Isaiah Industries, Inc.

8/16/2002
I have encountered this situation but I am not sure of the NEC Section. We have a cabin with a metal roof that has heat tape on the roof for snow melt. The roof is about 8' high at the soffit where the hot tub is. The inspector rejected our hot tub install because the non-bonded roof was within 5 feet of the top of the hot tub. We used a grounding clamp and #6 copper wire to "ground" the roof to the external ground wire.
Guest User

9/27/2009
250.4(A)(4) Bonding of Electrically Conductive Materials and Other Equipment. Normally non–current-carrying electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.
Guest User

2/8/2010
250.4(A)(4) Bonding of Electrically Conductive Materials and Other Equipment. Normally non–current-carrying electrically conductive materials that are likely to become energized shall be connected together and to the electrical supply source in a manner that establishes an effective ground-fault current path.
Guest User

2/8/2010