Actually, it's not exactly a garden wall. I live in a terraced house. On the front of each house is a parking space (on the property, behind the pavement) The wall I want to build is between my parking space and the next-door neighbour's parking space. I want to make the wall as high as legally possible, because he has an excessively noisy car whose noise I want to deflect as much as possible. Ok, yes, the wall will be a form of 'subtle hint' but it should prove quite effective too - and it'll stop him taking shortcuts over my parking space to reach his own.. he he...
Mike F