(a) Proper sizing of footings depends on the load carrying capacity of both the piers and the soil. To determine the load bearing capacity of the soil, the installer may use any of the following methods:
  (1) Using a pocket penetrometer;
  (2) Soil surveys from the U.S. Department of Agriculture;
  (3) Values from tables of allowable or presumptive bearing capacities given in local building codes. Such tables are commonly available from the local authority having jurisdiction; or
  (4) Any other test data from soil analysis reports.
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(b) The footing must be placed on firm, undisturbed soil, or fill compacted to at least 90% of its maximum relative density is required and must be verified every 6" - 8" vertically on the build-up. Installation on loose, noncompacted fill may result in settlement/movement of the home and may invalidate the home's limited warranty.
(c) Footer Configurations.
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(d) Footer sizing and capacities: The Footer Capacities table in subsection (a)(4) of this section represent maximum loads and spacings based on footer size and soil bearing capacity. Other footers may be used if equal or greater in bearing area than those footer sizes tabulated.
(e) Piers and pier spacings: Spacing and location of piers shall be in accordance with the tables listed in this chapter.
  (1) Spacing shall be as even as practicable avoiding obstacles that are not in control of the installer along each main I-Beam. Pier spacing may exceed tabulated values up to 30% so long as the total pier count remains the same. End piers are to be located within 24 inches of the end of the main frame.
  (2) Piers shall extend at least 6 inches from the centerline of the I-Beam or be designed to prevent dislodgment due to horizontal movement of less than 4 inches.
  (3) Load bearing supports or devices shall be registered with the Department in accordance with §80.26 of this chapter (relating to Registration of Stabilizing Components and Systems).
  (4) Sidewall openings greater than 4 feet shall have perimeter piers located under each side of the opening, i.e. patio doors, recessed porches/entries, bay windows and porch posts. Perimeter piers for openings are not required for endwalls.
(f) Pier design: Piers shall be constructed per the details in the Pier Design.
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  (1) Shimming (if needed): Shims are commonly used as a means for leveling the home and filling any voids left between the bottom flange of the I-Beam and the top of the pier cap. Wedge shaped shims must be installed from both sides of the I-Beam to provide a level bearing surface. The allowable height must not exceed 1 inch. Shims shall be a minimum of 3"x 6" nominal. All adjustment shims (marriage and perimeter) must be installed in manner which prevents dislodgement.
  (2) Table for pier spacing without perimeter piers.
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  (3) Table for pier spacing WITH perimeter supports and the Perimeter Pier Front and Side View.
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(g) Typical Multi-Section Pier Layout.
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(h) Typical Single Section Pier Layout.
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(i) Multi-section units mating line column supports:
  (1) On multi-section units, openings larger than 4 feet must have piers installed at each end of the opening. And within 6 inches of each end.
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  (2) Column loads for each section may be combined when the columns are opposite each other. The footer must be sized for the combined loading.
  (3) Additional piers are required under marriage walls (see wall between column #3 and #4 in the Marriage Line Elevation figure in paragraph (1) of this subsection. The maximum spacing is the same as the spacing at the main I-Beams, without perimeter piers, and one half the spacing of the perimeter piers, with perimeter piers installed.
  (4) See the table for the mating line column loads.
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(j) Temporary support is required to insure the structural continuity of homes placed at the retail location. Thirty (30) days after the arrival of multi-section and sixty (60) days after the arrival of single-section manufactured dwellings to the retail location, homes must be temporarily lot set. If the manufacturer has instructions for temporary blocking, home should be blocked according to the manufacturer specifications. In absence of any manufacturer instructions, State Generic requirement, either paragraph (1) or (2) of this subsection, shall be used:
  (1) Manufacturer dwellings supported by its running gear (left on their wheels and draw bar/hitch) shall be adequately supported under the main beam (I-beam) of within 5 feet of each end of the beam, within 5 feet of a supporting wheel and 10 feet on-center of each floor section. Any required marriage line and perimeter pier locations that are clearly marked by the manufacturer are also to be installed. Sidewall openings less than 4 feet in length do not have to be supported. Multi-section homes shall be sealed at the centerline and at all other openings to prevent exposure to the elements.
  (2) Manufactured dwellings not supported on their running gear shall be adequately supported under each main frame (I-beam) within 5 feet of each end of the home and 10 feet on-center along the length of the main beam. Any required marriage line and perimeter pier locations that are clearly marked by the manufacturer are also to be installed. Sidewall openings less than 4 feet in length do not have to be supported. Multi-section homes shall be sealed at the centerline and at all other openings to prevent exposure to the elements.

Source Note: The provisions of this §80.23 adopted to be effective January 29, 2008, 32 TexReg 8790; amended to be effective January 20, 2009, 33 TexReg 9459