§912.23. Foundations and piers
The following guidelines shall be used when the installation of foundations and piers is not specified in the manufacturer's instructions or when the manufacturer's installation instructions are not available:
(1) Piers:
(a) Piers shall be centered under the I-beam and installed as provided by rules promulgated by the commission. The first pier shall be within two feet of either end of the home. The pier foundation shall be a minimum of three and one-half inches by sixteen inches by sixteen inches solid concrete pad precast or poured in place, or other pad meeting the 2,500 PSI rating, or other approved material.
(b) Piers may be constructed of regular eight inches by eight inches by sixteen inches concrete blocks, open cells, solid (minimum eight inches by ten inches top), centered on the footing or foundation. A one inch or two inch by eight inch by sixteen inch treated or hardwood plate, or other approved material shall completely cover the top of the pier with shims, one-fourth inch minimum and one and one-half inch maximum, centered and driven tight from both sides of the I-beam between the wood plate or cap and the main frame. Single-tiered block piers shall be installed perpendicular to the main I-beam. However, when a pier has been capped with at least a four inch (three and one-half inch) solid concrete block or other approved material, one- fourth inch of wood stock or wood shims shall be installed between the pier and steel I-beam.
(c) Center line piers shall be located at each end of center line and shall be located on each end of the opening within six inches of jamb studs or ridge beam posts where openings four feet wide or greater occur. Any openings four feet or larger in the exterior sidewall or marriage wall shall require blocking at each end of the opening with four inch by sixteen inch by sixteen inch pads. Piers shall also be installed on each side of any perimeter door or fireplace. Bay windows or any opening forty-eight inches or more shall require blocking at each end. Fourteen feet or wider units with an I-beam spread of less than eighty-two inches and twelve feet wide units with an I-beam spread of less than seventy-five and one-half inches shall have perimeter blocking installed at a minimum of eight foot on center. Piers shall not be required under the clear, open, spans between ridge beam posts.
(d) All piers over thirty-six inches and corners over twenty-four inches in height shall be double tiered with blocks interlocked and capped with two four inch by eight inch by sixteen inch solid concrete blocks side by side and perpendicular to the I-beam, or other approved material and cushioned with wood shims or treated plate. Pier height is measured from the top of the footer or foundation to the top of the cement block stack, including four inch cap blocks.
(e) All piers over fifty-two inches shall be designed by an architect or engineer.
(f) Metal or precast support piers shall be installed on a base or footer of a minimum size of four inch by eight inch by sixteen inch solid concrete or other approved material. (g) Metal or precast support piers shall be restricted to a maximum two inch locking mechanical height adjustment and shall be restricted to a maximum height of not more than twenty-four inches measured from the ground base or footer. This twenty-four inch maximum shall not include the two inch mechanical extension or adjustment. However, center line or perimeter supports are permitted to exceed the twenty-four inch maximum.
(h) The minimum distance between the finished grade under the manufactured home and the bottom of the I-beam shall be twelve inches.
(2) Foundations:
(a) Concrete, precast, sand and gravel pads or foundations shall be a minimum of two thousand five hundred pounds per square inch (PSI).
(b) Plastic pads or foundations shall be tested in the lower fifty percent of each soil class. (1,000-1,500 PSF soil type).
Acts 1997, No. 970, §1; Acts 2001, No. 718, §2; Acts 2008, No. 217, §1; Acts 2023, No. 349, §1.