I am in a dark, may i get some advice here? This is regarding 2 semi-d single storey house. Let say A and B both share a party wall of a semi-d house. A decided to build a new 2 storey house on the same piece of land. After some survey, A "find out" that the party wall that both side share "encroached" into his side.
A then demanded B to demolished the nearly whole part of "encroached party wall" since A claimed that he already demolished his house. and the party wall is no longer an issue for him. A also demanded B to build a new wall themselves that aligned to the boundary line. Since this is semi-d party wall build by both party long long time ago, is it that B must follow what A said and demolished the shared party wall, rebuild a new one on his own boundry even though it is not B intention to build a new house?
I understands that it is ok for fencing, but is it normal for party wall? Can any lawyers or experts here give some hints? Tq.

Has B done any renovation previously in his life that the party wall moved? usually the semi-d's were built together by the developer and the party wall should sit on the boundary line of both wall.

Sorry, don't know where to put this post.
Thanks for the reply. As a further info, this semi-d kampung baru style house was constructed by small type contractor and not developer. Later on, the said party wall was built by both party in the course to change the wall from plywood to brick type in 70'. In 99', because of prolong termite problems, B change their ceiling and their part of roof to industrial iron sheet by adding some cement sand bricks on top of certain part of the party wall. Is this considered as "moved wall"?