(1) A building used as a storage garage with all storeys constructed as open-air storeys and having no other occupancy above it is permitted to have its floor, wall, ceiling and roof assemblies constructed without a fire-resistance rating provided it is,
(a) of noncombustible construction,
(b) not more than 22 m high, measured between grade and the ceiling level of the top storey,
(c) not more than 10 000 m2 in building area, and
(d) designed so that every portion of each floor area is within 60 m of an exterior wall opening.