RULE 661-322.11 - Support and anchorage of manufactured homes

RULE 661-322.11. Support and anchorage of manufactured homes

(1) First time installation. Manufactured homes shall be installed according to one of the following requirements, as applicable:

a. Homes manufactured prior to October 20,2008, which are being installed for the first time shall be installed with support and anchorage as recommended by the manufacturer and as required by federal manufactured home construction and safety standards, 24 CFR Section 3280.306(b), as published April 1, 2004; or

b. Homes manufactured on or after October 20, 2008, which are being installed for the first time shall be installed with support and anchorage as recommended by the manufacturer and as required in accordance with 24 CFR Part 3285, Model Manufactured Home Installation Standards, as published April 1, 2008; or

c. With a support and anchorage system which is designed by an Iowa-licensed professional engineer and which meets or exceeds the requirements of 24 CFR Part 3285 as published April 1, 2008; or

d. Homes installed in areas subject to a disaster emergency proclamation issued by the governor pursuant to Iowa Code section 29C.6 may be installed in compliance with subrule 322.11(5).

(2) Reinstallation of homes.

a. The provisions of this subrule apply only to homes that have been previously installed in the United States and are being reinstalled at either the same location or a different location.

b. The following definitions apply to this subrule.

"Ground anchor " means a specific anchoring assembly device designed to transfer home anchoring loads to the ground.

"Pier" means that portion of the support system between the footing and the manufactured home, exclusive of shims. Types of piers include, but are not limited to: manufactured steel stands; pressure-treated wood; manufactured concrete stands; concrete blocks; and portions of foundation walls.

"Pier footing " means that portion of a support system which supports the piers or blocking, is sized to adequately support the weight of the home at that load point, and is capable of transferring all design loads to the ground.

"Support system" means pilings, columns, footings, piers, foundation walls, shims, and any combination thereof that, when properly installed, support the manufactured home.

c. Homes reinstalled pursuant to subrule 322.11(2) must meet the following requirements. Requirements in this paragraph regarding the reinstallation of homes are mandatory minimum requirements.

(1) Aboveground support systems must meet the manufacturer's specifications or must meet the requirements of subrule 322.11(3).

(2) Ground anchors must meet the manufacturer's specifications or subrule 322.11 (4). Engineered ground anchoring systems that do not extend to the frost line may be used only if they are approved by the commissioner.

Note 1: Pier footings may be, but are not required to be, placed below the frost line.

Note 2: If the home is still under a manufacturer's warranty, the manufacturer's installation instructions should be followed or the warranty may be void

d. Pursuant to 661-subrule 16.623(2), prior to the reinstallation of a manufactured home, the installer reinstalling the home or the installer hired to inspect the home that is being reinstalled by the owner shall complete the portion of the installation certificate relating to the installation of frost-protected footings. This portion of the certificate must state that the home is not being installed with frost-protected footings and must be signed and witnessed by the installer and the owner. Upon completion of the reinstallation, the installer shall complete and submit the certificate to the commissioner as prescribed by 661-subrule 16.623(2).

Note: Iowa Code sections 335.30 and 414.28 have requirements that may affect the reinstallation of homes.

(3) Requirements for support system installations.

a. Piers placed on foundations shall be installed and centered directly under the main frame longitudinal beams. The piers should not be farther apart than 10 feet on centers for manufactured homes 12 feet wide or less and not more than 8 feet on centers for manufactured homes over 12 feet wide to less than 16 feet wide and no more than 6 feet on centers for manufactured homes 16 feet wide or more. The main frame, front or back, should not extend farther than 2 feet beyond the centerline of the end piers.

NOTE: When making excavations for footings and piers on private property, installers shall take precautions to ensure that no telephone, electrical, plumbing or water lines are contacted. Utility line locations shall be verified with the property owner or property owner's representative.

b. Pier foundations shall be placed on level, undisturbed soil or on controlled fill that is free of grass and organic materials. (A small amount of sand may be of use to provide a level surface.) All pier foundations shall be set level, and piers must be installed plumb. The pier foundation shall be at least a 16" x 16" x 4" solid concrete pad, precast or poured in place, or other approved material. Two nominal 4" x 8" x 16" solid concrete blocks may be used provided that the joint between the blocks is parallel to the main frame longitudinal beam. Concrete used in foundations shall have a 28-day compressive strength of not less than 3,000 pounds per square inch (3,000 psi).

c. Unless otherwise directed by the owner of the site, the soil-bearing capacity of the site may be assumed to be 2,000 pounds per square foot. The acceptable construction under this subrule is based upon a soil-bearing capacity of 2,000 pounds per square foot. Sites with less soil-bearing capacity will require increased-size footings.

Explanation: The permissible footing sizes and pier spacing are based upon a combined live and dead load of 65 pounds per square foot of unit. This assumes that the full snow and internal live load will not be present at the same time.

d. Piers may be constructed of concrete or undamaged nominal 8" x 8" x 16" concrete blocks, open-celled or solid, placed on the pier foundation. All open-celled concrete block shall be installed with the cells of the block in a vertical position. Nominal 2" x 8" x 16" or nominal 4" x 8" x 16" solid concrete blocks may be utilized as needed to achieve the necessary heights of the piers for a particular installation. A nominal 2" x 8" x 16" wood plate, or equivalent, shall be placed on top of each pier, unless there is at least 4 inches of solid block, with shims fitted and driven between the wood plate or solid block and the main frame longitudinal beam. The wood blocking shall not occupy more than a nominal 2 inches of vertical space, and shims shall not occupy more than 1 inch of vertical space. Shims which have a thickness of more than 3/8" shall be hardwood.

(1) Piers up to 40 inches in height, except corner piers over three blocks high (a nominal 24"), may be of single-block construction and shall be installed transverse (right angle) to the main frame longitudinal beam.

(2) Piers over 40 inches in height but not exceeding 80 inches in height and corner piers over three blocks high shall be of double-block construction with every other course either parallel or transverse (right angle) to the main frame longitudinal beam. These piers shall be capped with a nominal 16" x 16" x 4" solid concrete block or equivalent. Wood blocking and hardwood shims shall be installed accordingly.

(3) Piers over 80 inches in height shall be of reinforced concrete or of double-block construction and installed exactly according to the procedure given in subparagraph (2) above. Only celled concrete blocks shall be used (with open cells vertical) with 3/8" diameter or larger steel reinforcing rods placed in the pier corners and all cells filled with 3,000 psi concrete. Wood blocking and shims shall be installed accordingly.

(4) Requirements for anchorage systems. When instructions are not provided by the manufacturer, ties shall be attached vertically and diagonally to a system of ground anchors in a manner as illustrated in Figures 4 and 5. The minimum number of ties required are listed in Table 6-A. There shall be a diagonal tie between the ground anchors and the unit at each vertical tie. Additional diagonal ties may be required between vertical ties. The ties shall be as evenly spaced as practicable along the length of the unit with not over 8 feet open on each end.

a. Ties may be either steel cable, steel strapping, or other materials that meet the requirements of 322.11(4)"f. " Ties are to be fastened to ground anchors and drawn tight with galvanized turnbuckles or yoke-type fasteners and tensioning devices. Turnbuckles shall be ended with jaws of forged or welded eyes (hook ends are not approved).

b. When continuous straps (over-the-top tie-downs) are provided as vertical ties, they should be positioned at rafters and studs to prevent structural damage. Where a vertical tie and diagonal tie are located at the same place, both ties may be connected to a single double-head ground anchor provided that the anchor used is capable of carrying the combined loads and is included on a list of approved products maintained by the commissioner.

c. Cable used for ties shall be either galvanized steel or stainless steel and shall have a breaking strength of at least 4,725 pounds. Cable should be either 7/32" diameter or greater (7 x 7) steel cable or ¼ "diameter or greater (7 x 19) aircraft cable. All cable ends should be secured with at least two I-bolt-type cable clamps or other nationally approved fastening devices.

d. When flat steel straps are used as ties, they shall be type 1, class B, grade 1, 1¼" wide and 0.035" thick, conforming with federal standard QQ-S-781-F, with a breaking strength of at least 4,725 pounds. Zinc coating (weather protection) shall be a minimum of 0.30 ounces per square foot of surface. Steel strap ties shall terminate with D-rings, bolts, or other nationally approved fastening devices that will not cause distortion or reduce the breaking strength of the ties.

e. The direction of pull of the diagonal ties should be at a right angle to the main frame longitudinal beam. Connection of the diagonal tie to the main frame longitudinal beam should be in accordance with anchor system instructions for those fastening devices. When steel strap ties are used, care should be exercised that the minimum bending radius is adhered to so the breaking strength is not reduced.

f. Anchors and anchorage materials shall meet the following requirements:

(1) The anchorage materials shall be capable of resisting an allowable minimum working load of 3,150 pounds (pullout in a vertical direction) with no more than 2 percent elongation and shall withstand a 50 percent overload. All anchorage materials shall be resistant to weathering deterioration at least equivalent to that provided by a coating of zinc on steel strapping of not less than 0.30 ounces per square foot surface coated. Anchors to reinforced concrete slab or to rock shall be of comparable strength as provided within this paragraph.

(2) Each ground anchor, when installed, shall be capable of resisting an allowable working load at least equal to 3,150 pounds in the direction of the ties plus a 50 percent overload (4,750 pounds total) without failure. Failure shall be considered to have occurred when the point of connection between the tie and anchor moves more than 2 inches at 4,750 pounds in the direction of the vertical tie when anchoring equipment is installed in accordance with the anchorage manufacturer's instructions. Those ground anchors which are designed to be installed so that the loads on the anchor are other than direct withdrawal shall be designed and installed to resist an applied design load of 3,150 pounds at 45° from horizontal without displacing the anchor more than 4 inches horizontally at the point where the tie attaches to the anchor.

(3) Anchors designed for connection of multiple ties shall be capable of resisting the combined working load and overload consistent with the intent expressed in this paragraph.

(4) Ground anchors shall be installed so that the load-carrying portion of the anchor in its final working position is below the frost depth (42 inches), and the anchor head shall be at ground level. Total anchor length shall be more than 42 inches as necessary.

NOTE: When installing ground anchors on private property, installers shall take precautions to ensure that no telephone, electrical, plumbing or water lines are contacted. Utility line locations shall be verified with the property owner or property owner's representative.

TABLE 6-A

MINIMUM NUMBER OF TIEDOWNS

REQUIRED FOR SINGLEWIDE MOBILE HOMES

   mobile home box length minimum number of tiedowns per side   
   not exceeding diagonal ties vertical ties*   
   40'-0" 3       2   
   54'-0" 3       2   
   73'-0" 4       2   
   84'-0" 5       2   

*If more than the minimum number of vertical or diagonal ties have been supplied, they shall all be used.

1. Doublewide mobile homes shall comply with Table 6-A except that no vertical ties are required.

2. Wherever a vertical tie and a diagonal tie lie in a plane that is vertical and transverse to the main longitudinal beam, both ties may be connected to the same ground anchor, providing that the particular anchor withstands both loadings.

3. This table shall be used only if there are no manufacturer's approved installation requirements.

(5) Installations in disaster emergency areas. In an area subject to a disaster emergency proclamation issued by the governor pursuant to Iowa Code section 29C.6, a manufactured home may be installed without a permanent support system provided that all of the following apply:

a. The installation complies with anchorage requirements and aboveground support requirements specified by the manufacturer or specified in subrule 322.11(4) as applicable;

b. A government agency or a third-party contractor is contractually obligated to regularly inspect the home while it is occupied and to loosen the ties or straps used in the anchoring system as needed between November 15 of each year and April 15 of the following year, in order to prevent frost heave from affecting the home, and to retighten the ties or straps on or after April 15 and prior to May 15 of the following year; and

c. The home shall be vacated within 18 months after installation without a support system which is fully compliant with subrules 322.11(1), 322.11(2), 322.11(3) and 322.11(4). A home installed in compliance with this subrule may continue to be occupied if it has been reinstalled in compliance with the provisions of this rule that would apply in the absence of a proclaimed disaster emergency.

(ARC 7775B, IAB 5/20/09, effective 5/1/09)

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