grounding metal roof

This question was asked on a farm forum and I think it was a lightning concern. "I'll be putting a metal on a garage, over an asphalt roof, think I should ground it. Anyone with experience here"? I know antennas are suposed to be grounded to the grounding electrode of electric system,, how about this?

 

I would be inclined to look at that from a lightning protection perspective, anyway. If there is enough concern to warrant lightning rods, then grounding the roof might be a good idea. Otherwise, I doubt that it is of great concern. Lightning tends to strike where there is ground potential. That accounts for it striking utility poles, which are grounded; antennas which are at least indirectly grounded because they connect to an appliance in the household electric circuit; trees are obviously grounded.

One thing to consider with a metal roof and grounding is that the individual pieces of the roof are not bonded to each other. Grounding only one piece can create potential with the other pieces. To ground the roof, bonding all the pieces together would be necessary. Otherwise, the rest will be above ground as a television chassis is. Before going to all the trouble to bond all the roofing pieces together, it seems that it would be much simpler and probably more effective to install a lightning rod system.

Hope this helps.