We are going to replace the flat roof on our garage with a pitched roof. The garage sticks out at the front of the house and, facing from the front, the left side of the garage wall is the boundary between us and our neighbour's front open garden. We are opting for boxed guttering as he didn't want us overhanging his air space. Despite knowing about this job for some months and with it due to start in next week or so, he now wants a party wall agreement. Can someone help - we have looked for example letter online re party wall act, but no one section appears to cover this. Our architect was of opinion it wasn't necessary, but neighbour is adamant.