Ignorance of the 1996 party wall act is no excuse so please don't tell me I'm stupid I now know it! My neighbour is sole owner of a garden freestanding wall dividing our properties. I have gone 6 inches from the base and erected a fence of trellis fixed to posts. The owner of the wall says I have broken the PW Act and is demanding I underpin as I have damaged his walls foundations. I scraped from his wall to a distance of 200mm and down 145mm but no foundations were found. So posts concreted in . Each post hole was checked for the same. He now says he has foundations 200mm over my side for his wall....they're not there. Any advice my neighbour is to say the least..unpleasant as a person and put to get anything he can.