(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.
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(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.