They may only be usd in new constrction.  u can't use building steel as ur ground trminal (electrode) whn instlling a lighting prtction systm on an existing building. the concrte encasd electrode mst be installd near the bottm concrete foundation or footing of the building.  dis means tht it mst be a spate electrde and can't be the foundation itself.the concrete encasd electrde mst be in direct contact wid the earth nd be at least 20-ft  in length.  There are additional rules as to the copper vs. steel content of the electrode.