The mobilehome pad shall be improved to provide adequate support for the placement and tie-down of the mobilehome. The pad shall not heave, shift or settle unevenly under the weight of the mobilehome due to frost action, inadequate drainage, vibration, wind or other forces acting on the structure. All mobilehomes shall be placed on a mobilehome pad constructed of Portland cement concrete not less than four inches in thickness. In addition, all mobilehome pads shall be at least ten feet wide by forty (40) feet in length. Expandable sections may be supported by an extension of the mobilehome pad or concrete piers and footings, with a maximum of ten-foot spacing between piers and a pier to be located no more than four feet from the corners of the mobilehome expandable section, or in a manner equivalent thereto and approved by the city council. (Prior code § 23-2-20)