A storage building for one-family, two-family or multiple-family use with permitted accessory buildings or one portable building may be located upon a lot or unplatted tract; however, a storage building may never be used as a main building for residential use. Every dwelling shall face or front upon a public street or approved place, other than an alley, which means of access shall have a minimum width of 30 feet. Where a lot is used for multifamily, retail, commercial, or industrial purposes, or a combination of same, or for a combination of retail and dwelling purposes, more than one main building may be located upon the lot. Such buildings shall conform to all open space, parking and density requirements applicable to the uses and district and when all such main buildings face upon a public street or other approved means of access, other than an alley. No parking area, storage area or required open space for one building shall be computed as being the open space, yard or area requirements for any other dwelling or other use. An approved site plan shall be filed with the chief building official to ensure compliance with this article. Any deviation of more than one foot from the said site plan as filed with the chief building official is prohibited.