the hereditaments are on consecutive storeys of a building and some or all of the floor of one hereditament lies directly above all or part of the ceiling of the other hereditament
os yw’r hereditamentau ar loriau nesaf at ei gilydd mewn adeilad, ac mae rhan neu’r cyfan o lawr un hereditament yn union uwchben rhan neu’r cyfan o nenfwd yr hereditament arall