The Russian practice of lightning protection has been successfully using reinforced concrete foundations of buildings as grounding devices for a long time. Even their gas-tar waterproofing does not prevent this. With the soil moisture above 3% and the area of an underground part of the foundation being more than 900 sq. m, it can drain the lightning current to the ground. Particular requirements to the grounding resistance in the Russian standards for lightning protection do not imply any requirements to foundations. However, this issue may become important when the building foundation is used as a grounding device for any other purpose than, e.g. to provide electrical safety. In this case, its grounding resistance should not exceed the rated value which may be not available in the soil where the foundation is installed. In such conditions, we often recommend to arrange the grounding circuit along the external perimeter of the building. This circuit is coupled with the embedded features and the reinforcement of the foundation by means of a metal. It is also recommended to attach current collectors thereto to transport the lightning current to the ground. It is clear that in such conditions, the circuit should nearly abut the foundation, usually under a pavement or a perimeter walk.
It is feasible to evaluate the efficiency of the external grounding circuit to reduce the grounding resistance.
Read more details in the article by Prof. E. M. Bazelyan Is There a Need in the Grounding Circuit Around the Building If a Reinforced Concrete Foundation Is Used as a Grounding Device for the Lightning Protection System?.