Nothing contained in this article shall be construed to apply to mobile homes, house trailers or recreation vehicles parked on premises within the City for the purpose of use as a construction office during construction, remodeling or demolition of improvements on the premises, or parked on the business premises of the user thereof, or to trailers used for the transportation of goods, wares and merchandise in commerce, while being loaded or unloaded or while parked on the business premises of the owner thereof, or upon the business premises kept by persons doing business with the owner thereof, or while being parked within legal loading and unloading zones within the City. (1978 Code Sec. 27-3.)