Hello. A friend of mine owns a house who's foundations he says are built directly on sandstone. The house was rendered with an impervious cement render. He has damp downstairs on all the lower walls. He maintains this is due to the fact that it has sandstone foundation's. He also tells me that there is clay placed all around the house. Does anyone here know anything about this? He wants to sell it and I would like some advise as to how we could remedy this problem. Many thanks!