§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.