In this part:
"party wall"—
(a) means a wall or structure designed for the common use of 2 or more buildings and erected, or to be erected, on a common boundary, or part of such a boundary, between 2 parcels of land, and extending laterally into each of those parcels of land; and
(b) includes any wall that is completely or partly used to support 2 or more buildings, if the wall was erected in connection with a building for which there is a certificate of occupancy under the Building Act 2004
.