Hi Hope someone can advise on this - we have a very uneven garden and there is a about a 3 foot gap between the existing retaining wall and our neighbours garage and this gap goes the whole width of the garage (Our neighbour's garage has it's side and back in our garden) which we could make use of. We decided to build a new retaining wall approx 25mm away from their garage so we can fill in between the 2 retaining walls and largen our grass area. We have put a polystyrene board and plastic sheeting in the 25mm gap to stop any waterproofing probs and anything falling in the small gap between the new wall and their garage wall eg. leaves soil etc. We are also going to waterproof the concrete blocks before the gap is filled in so it gives more protection and keeps the wall strong. The wall is only approx 3 foot high to their garage. They don't seem very happy about it!!! We have invited them to come round and showed them what we have started and what we are doing. Can they object to it and have us remove the wall or move it further away from their garage wall?