Every building, structure or part thereof of more than 5,000 square feet of gross building area erected and/or occupied for commerce, hospital, laundry, dry-cleaning, places of public and quasi-public assembly, industry and other similar uses involved in the receipt and distribution by vehicles of supplies, materials or merchandise shall be provided with at least one permanently maintained adequate space for truck standing, loading and unloading services on the premises. One additional truck space shall be provided for every additional 20,000 square feet or fraction thereof of gross area in the building.