Section R4-34-803. Soil and Materials

A.      A licensee that contracts with a consumer for an installation shall perform or contract for any site preparation necessary to make the site compatible with the manufactured home, mobile home, or residential single-family factory-built building to be installed. The licensee may contract with a licensed installer or other qualified professional to assess site and soil compatibil- ity or perform any necessary preparation work. The party actu- ally performing the site compatibility assessment or work is primarily responsible for work related to site compatibility or preparation. The licensee that contracts with the consumer, if a different entity, is secondarily responsible.

B.       Soil Preparation

1.        Unless contrary to law, an installer or contractor shall:

a.        Divert any surface water away from the dwelling, any accessory structures, and their support compo- nents;

b.        Provide sufficient drainage to prevent standing water and soil saturation detrimental to structures;

c.        Establish soil grades that slope away from the dwell- ing, any accessory structures, and their support com- ponents; and

d.        Compact all fill and backfill within 6 feet of the perimeter of the unit to prevent displacement.

2.        When determining soil compaction an installer or con- tractor shall:

a.        Assume a minimum bearing capacity of 1,000 psf; or

b.        Test and prove a minimum bearing capacity of 1,000 psf to the onsite inspector; or

c.        Adhere to the specifications of a registered engineer, provided onsite, to an inspector.

C.      Materials: An installer or contractor shall use materials that comply with applicable standards incorporated in R4-34-102.

D.      Footings: An installer or contractor shall:

1.        Place each footing on a surface capable of distributing equalized transfer of applied loads;

2.        Calculate and use the minimum size of each footing, nec- essary to minimize settling of the unit accounting for local soil conditions;

3.        Use piers with a maximum square base of 11 1/2 inch installed on 12 inch by 12 inch footings to support mobile and manufactured homes manufactured before January 1, 1984;

4.        Use main frame blocking installed on footings with 144 square inches of surface placed 3 feet, 6 inches from cen- ter, or footings with 256 square inches of surface placed at 6 foot intervals to support manufactured homes manu- factured on or after January 1, 1984;

5.        Use footing material with one of the following attributes:

a.        Minimum 3/4-inch thick plywood or two layers of 5/ 8-inch thick plywood no less than 12 inches wide. The plywood shall be Grade CDX APA Rated Sheeting Exposure 1, PSI-treated for ground contact, conforming to International Building Code or Inter- national Residential Code, as applicable under R4- 34-102(2)(a) or (b);

b.        Minimum 2-inch nominal thickness wood no less than 12 inches wide, and treated for ground contact, conforming to the International Building Code or the International Residential Code, as applicable under R4-34-102(2)(a) or (b);

c.        Minimum 3-inch thick precast concrete pad with either 256 or 144 square inches of ground surface. The concrete shall have a minimum of 28 days com- pressive strength of not less than 4000 pounds per square inch; or

d.        Hard plastic pad with either 256 or 144 square inches of ground surface. The plastic pad shall with- stand a minimum vertical concentrated load failure rating of 15,000 pounds when tested on very dense and coarse gravel soils. “Failure” means that a crack at least 4 inches in length has appeared anywhere on the pad or the pad’s surface has curled or bowed.

6.        Stack plywood with face grain perpendicular and fasten the plywood with corrosion-resistant nails or 7/16-inch wide-crown staples or screws;

7.        Fasten wood products that are stacked with corrosion- resistant nails or 7/16-inch wide-crown staples or screws;

8.        Not use any 2-inch thick piece of wood with split penetra- tion greater than 4 inches into the end of the piece and parallel to the edges of the piece;

9.        When precast concrete pads are stacked, use pads with equal sized surface sides;

10.     When concrete masonry unit (CMU) building blocks are used for supports, use only 256 square inch ground and 8 inch by 16 inch caps;

11.     Stack plastic pads only when the pad is provided with an interlocking system; and

12.     Stack no more than two equal sized concrete pads per support.

E.       Supports (piers): An installer or contractor shall:

1.        Place supports or piers on footings that do not exceed the size of the footing;

2.        Ensure that supports or piers bear no greater load than 8,000 pounds;

3.        Ensure that supports or piers have a minimum vertical concentrated load failure rating of 15,000 pounds;

4.        Not use supports with a height in excess of 36 inches or less than 12 inches for more than 25% of the supports along the main beams of the chassis, including footing;

5.        For a below ground installation, ensure that the height of the bottom of the perimeter rim joist is a minimum of 6 inches above finished grade;

6.        Ensure that the height of the bottom of the floor joist is a minimum of 18 inches above soil base unless otherwise specified by the manufacturer in instructions consistent with this Chapter;

7.        Locate supports or piers under the main beams of the chassis at intervals no greater than 6 feet and no more than 2 feet from either end of each main beam. When intervals no greater than 6 feet are not feasible because of running gear, supports shall be located as close as possi- ble to the running gear with the remainder of the supports spaced according to the 6 and 2 foot requirements;

8.        Stagger the flanges on top of supports or piers so that every other flange is on the opposite side of the beam; and

9.        Construct permanent support heights to the International Building Code or the International Residential Code as applicable under R4-34-102(2)(a) or (b).

F.         Wedges: An installer or contractor shall:

1.        Use two wedges in alignment per support;

2.        Use wood wedges that are a minimum of 1 1/2 inches by 3 1/2 inches by 6 inches; and

3.        Drive wedges in tightly so that the height developed does not exceed 2 inches at the support; and

4.        Provide each I-Beam of the building with full bearing on the wedge; or

5.        Use listed or approved shimming material according to the manufacturer’s wedge instructions; or

6.        Use material and methods designed by an Arizona profes- sional engineer or architect and approved by the authority having jurisdiction.

G.      Anchoring: An installer or contractor shall use an anchoring system that is certified by a registered, professional engineer.

H.      Snow/Wind Loads

1.        Under 24 CFR 3282.11 and 3280.305, the authority hav- ing jurisdiction may not require manufactured homes to be built or installed to a snow load greater than 20 pounds per square foot unless the jurisdiction has received approval from HUD.

2.        Manufactured homes may be manufactured and installed, at the owner’s option, to withstand greater than a 20 pound snow load. An installer or contractor shall install these units according to the manufacturer’s instructions for the foundation support system if the instructions are consistent with this Chapter.

I.        Permanent Foundation Systems

1.        An installer or contractor shall install factory-built build- ings in compliance with R4-34-102(2).

2.        An installer or contractor shall install manufactured and mobile homes according to the manufacturer’s permanent foundation requirements or sealed engineered plans if the requirements or plans are consistent with this Chapter.

Historical Note

New Section adopted by final rulemaking at 6 A.A.R. 145, effective December 8, 1999 (Supp. 99-4). Amended by final rulemaking at 11 A.A.R. 464, effective March 5, 2005 (Supp. 05-1). Amended by final rulemaking at 14

A.A.R. 286, effective March 8, 2008 (Supp. 08-1). Amended by final rulemaking at 18 A.A.R. 944, effective

June 4, 2012 (Supp. 12-2).