The roof of a facility containing off-street parking spaces, not otherwise covered by a building, which is larger than 400 square feet, shall be landscaped. No parking spaces shall be provided on the roof of such facility. Up to five percent of such roof area may be used for mechanical equipment, provided that such mechanical equipment is screened from view by a fence which is at least 75 percent opaque or by at least three feet of dense planting. No less than 75 percent of such roof area shall be accessible for the recreational use of the occupants of the building in which it is located; and no more than 25 percent may be accessible solely from an adjacent dwelling unit. Hard surfaced areas shall not cover more than 60 percent of such roof area.