Is lightning attracted to rebar grid?

[dunnahill]

I posted this to Cecil but am awaiting response… anyone here care to take a shot at it too?

Question: The National Weather Service warns that leaning on a concrete wall or standing on steel reinforced concrete during a thunderstorm could be hazardous. Therefore, does a rebar reinforced concrete foundation INCREASE the risk of a lightning strike to a home? Case in point, house in question has rebar arrayed in a 1 foot square grid pattern within 12 inch thick concrete foundation walls. House was hit by lightning within 4 months of concrete foundation walls being poured under this 55 y/o house. Is there a correlation… or just ‘luck of the draw’?

Dunny

[Ice_Wolf]

Possibly.

Controversy surrounds the premise that reinforcing bar in the foundation of site buildings should be grounded. Some argue that rebar is insulated inside the concrete, and does not need to be grounded. The debate centers on the conductivity of concrete.

Under normal circumstances, concrete is not conductive.

However, when the ground is wet and lightning strikes, rebar that is close to the surface could collect energy. There is a risk that the energy passing through concrete could turn the water portion of the concrete into steam, cracking the concrete.

Ufer grounding, named after the engineer who originated the concept, can protect against this risk. With Ufer grounding, the rebar is grounded inside the concrete block, and a ground strap is run along the underside of the foundation to a ground rod. Charges in the concrete are dissipated down into the earth.

[Padeye]

Consider that foundations are underground or close to it. Keep in mind I come from Arizona where basements are rare and house floor leves are typically only a few inches above grade. It adds no more risk of lightning strike than the well grounded water pipes coming into the house, probably marginally less.

A concrete wall is well above ground and may provide a shorter and more direct path to ground for a lightning strike, just a bit less obvious than shaking your golf club at G*d in a thunderstorm.