Off-street loading and unloading spaces. In the Office District, for every building or part thereof hereafter erected which is to be occupied for manufacturing, storage, wholesale store or warehouse or other use similarly requiring the receipt or distribution in vehicles of materials or merchandise, there shall be provided and maintained on the same premises with such use, at least one off-street loading space, which shall be at least 12 feet wide, 40 feet long and have a fourteen-foot overhead clearance. A loading space shall only be permitted in a side or rear yard, and no part of such space shall be nearer than 25 feet to any property line.