(1) For the purposes of this section "vestibule" means a small room or hall between an outer door and the main part of the resident bedroom.

(2) The adult family home must ensure each resident bedroom has a minimum usable floor space as follows, excluding the floor space for toilet rooms, closets, lockers, wardrobes and vestibules:

(a) Single occupancy bedrooms with at least eighty square feet; and

(b) Double occupancy bedrooms with at least one-hundred twenty square feet.