We currently live in an old terrace cottage and our neighbour is considering building an extension . The neighbouring property was built after the terrace was completed and you can still clearly identify the old cornerstones to our property and where theirs continues, I presume that this identifies the wall as a ‘Type B’ Party wall (covering the entire gable end of the terrace) .
However our neighbour owns roughly 2 foot of land overlapping the cornerstones (on plan there is a clear step between our building and garden). We would like to know if possible whether our neighbour is able to build right up to the boundary and attach to our wall?
If I’m picturing what you describe correctly then the answer is no – you neighbour would not have the right to enclose anymore of your wall than is enclosed by the existing building – only the area that is currently enclosed is a ‘Type B’ party wall. You could allow it but you would be within your rights to request compensation for allowing the use of your wall.