Advice was structural steelwork a last resort for an earth electrode:why?

If this is specifically regarding a farm.. (you've mentioned it here and may have mentioned it to them?) the susceptibility of livestock to leakage currents is a major reason to say 'aww h*ll no'.


If not farm related and you just used that as an example here with no such example given to them... i am unsure. But intrigued. I know in the USA, rebar in concrete foundations (surely similar to structural metalwork in the ground?) is suggested in the NEC (their equivalent of 7671) as an earthing electrode. I imagine the attachment point would also bear on this. Attaching the bond to anywhere but actual steel underground would mean that future corrosion could, hypothetically, disconnect it from the subterranean steelwork?

Probably a lack of understanding, or at least the uncertainty of how well the steel is connected and how well it would handle fault currents. Also if the depth is unclear, the performance in dry weather may be variable.

But, if it is designed in from the outset for steels to be used as an earth, with well designed connections,  such as welded on earth studs, then steel piles or rebar in concrete can be very effective, especially if the concrete is seeded with marconite to make it more conductive - a floor slab is then one large area conductive plate.

I'd be more wary of trying to drill and lug to random bits of tinplate that you don't know if they may not be well connecting. The key is knowing something about the building construction.

I have had  single figure ohms off a marquee before, that was 'nailed' to the ground with multiple steel pins at the base of each upright.

Yeah, the resistance needs to be tested with a decent current