Section 20 of the Party Wall Act defines Building Owner as:
“building owner” means an owner of land who is desirous of exercising rights under this Act;
Section 20 of the Party Wall Act further defines Adjoining Owner as:
“adjoining owner” and “adjoining occupier” respectively mean any owner and any occupier of land, buildings, storeys or rooms adjoining those of the building owner and for the purposes only of section 6 within the distances specified in that section.
If an adjoining owner sells their property after an award has been published, the award is valid. If an adjoining owner sells their property after notices have been served but no award is in place, their is an adjoining owner who has not been served notices as per the award. Surveyors who do not understand the law often argue that because the act makes no provisions for events (ie change of ownership) and their is no case law that there is a consequential lack of authority. However the act in these circumstances should be read pedantically which prevents aggrieved adjoining owners from thwarting a building owner rights.
Interestingly, for example under section 8 which seems not to mention the adjoining owner or indeed to only refer to the Building Owner, if an adjoining owner wishes to exercise rights under the act they then become the Building Owner because a “building owner” means an owner of land who is desirous of exercising rights under this Act