All hoistways shall be enclosed throughout their height by enclosures of fireproof material. Every such enclosure shall be set flush with hoistway line on all landing sides and shall have a roof of fireproof material. If the enclosure extends to the top story, it shall be continued 36 inches above the roof, or to the roof if it is fireproof, and shall have at the top a metal frame skylight at least three quarters of the area of the shaft or an exterior window with metal frame and sash. The bottom of the enclosure shall be of fireproof material unless the partitions extend to the cellar bottom. All openings in such enclosures shall be provided with fire doors set substantially flush with the hoistway line. (See § 8-1.62.)