On 1/4/2017 9:58 AM, James Wilkinson Sword wrote:
Somebody in one of these two groups recently said that a concrete based
house means you're earthed. Concrete is a bloody good insulator!

Sorry, can't find the post it was mentioned in.

Can't help with a link, but I recently replaced my water main with PEX.
That broke the ground to the house and wouldn't pass inspection.
Long story short, research indicated that using rebar in concrete
was a trend in establishing a safety ground. Apparently, there's
enough conductive salt and water in concrete to make it work,
as long as the concrete sits on the ground and you're not in
the desert. Contact resistance is high, but there's a lot of area.

I followed the code and installed two ground rods.
I did some impedance measurements between the rods and the
electrical system ground (before connecting) and determined that the
"grounding" was insufficient to do anything more than
dissipate static electricity, but the
inspector liked it.
I'd guess that hooking to the rebar is at least as good.