Every building used for nonresidential purposes which customarily receives or distributes goods by motor vehicle shall provide sufficient space on the premises for all loading and service purposes on the basis of the following minimum regulations:
(a) Every building having over 5,000 square feet of gross floor area shall be provided with at least one truck loading and unloading space not less than twelve feet in width, forty feet in length, and fourteen feet clearance. An additional truck space of these dimensions shall be provided for every additional 20,000 square feet or fraction thereof, of gross floor area in the building.
(b) Access to truck loading and unloading space shall be provided directly from a public street or alley or from any right of way that will not interfere with public convenience and that will permit the orderly and safe movement of such trucks.
(c) Loading space as required under this section shall be provided as area additional to off-street parking spaces as required under Section 1157.02 and shall not be considered as supplying off-street parking space.