CFR > Title 24 - Housing and Urban Development > SUBTITLE B—Regulations Relating to Housing and Urban Development > CHAPTER XX—OFFICE OF ASSISTANT SECRETARY FOR HOUSING—FEDERAL HOUSING COMMISSIONER, DEPARTMENT OF HOUSING AND URBAN DEVELOPMENT (parts 3280 to 3800) > PART 3285—MODEL MANUFACTURED HOME INSTALLATION STANDARDS > SUBPART E—Anchorage Against Wind (§3285.401 to §3285.406) > 3285.402—Ground anchor installations.

3285.402—Ground anchor installations.

(a) Ground anchor certification and testing. Each ground anchor must be manufactured and provided with installation instructions, in accordance with its listing or certification. A nationally recognized testing agency must list, or a registered professional engineer or registered architect must certify, the ground anchor for use in a classified soil (refer to § 3285.202 ), based on a nationally recognized testing protocol, or a professional engineer or registered architect must certify that the ground anchor is capable of resisting all loads in paragraph (b) of this section for the soil type or classification.
(b) Specifications for tie-down straps and ground anchors— (1) Ground anchors. Ground anchors must be installed in accordance with their listing or certification, be installed to their full depth, be provided with protection against weather deterioration and corrosion at least equivalent to that provided by a coating of zinc on steel of not less than 0.30 oz./ft. 2 of surface coated, and be capable of resisting a minimum ultimate load of 4,725 lbs. and a working load of 3,150 lbs., as installed, unless reduced capacities are noted in accordance with note 11 of Table 1 to this section or note 12 of Tables 2 and 3 to this section. The ultimate load and working load of ground anchors and anchoring equipment must be determined by a registered professional engineer, registered architect, or tested by a nationally recognized third-party testing agency in accordance with a nationally recognized testing protocol.
(2) Tie-down straps. A 1 1/4 inch x 0.035 inch or larger steel strapping conforming to ASTM D 3953—97, Standard Specification for Strapping, Flat Steel and Seals (incorporated by reference, see § 3285.4 ), Type 1, Grade 1, Finish B, with a minimum total capacity of 4,725 pounds (lbs.) and a working capacity of 3,150 pounds (lbs.) must be used. The tie-down straps must be provided with protection against weather deterioration and corrosion at least equivalent to that provided by a coating of zinc on steel of not less than 0.30 oz./ft. 2 of surface coated. Slit or cut edges of coated strapping need not be zinc coated.
(c) Number and location of ground anchors. (1) Ground anchor and anchor strap spacing must be:
(i) No greater than the spacing shown in Tables 1 through 3 to this section and Figures A and B to this section; or
(ii) Designed by a registered engineer or architect, in accordance with acceptable engineering practice and the requirements of the MHCSS for any conditions that are outside the parameters and applicability of the Tables 1 through 3 to this section.
(2) The requirements in paragraph (c) of this section must be used to determine the maximum spacing of ground anchors and their accompanying anchor straps, based on the soil classification determined in accordance with § 3285.202 :
(i) The installed ground anchor type and size (length) must be listed for use in the soil class at the site and for the minimum and maximum angle permitted between the diagonal strap and the ground; and
(ii) All ground anchors must be installed in accordance with their listing or certification and the ground anchor manufacturer installation instructions; and
(iii) If required by the ground anchor listing or certification, the correct size and type of stabilizer plate is installed. If metal stabilizer plates are used, they must be provided with protection against weather deterioration and corrosion at least equivalent to that provided by a coating of zinc on steel of not less than 0.30 oz./ft.2 of surface coated. Alternatively, ABS stabilizer plates may be used when listed and certified for such use.
(3) Longitudinal anchoring. Manufactured homes must also be stabilized against wind in the longitudinal direction in all Wind Zones. Manufactured homes located in Wind Zones II and III must have longitudinal ground anchors installed on the ends of the manufactured home transportable section(s) or be provided with alternative systems that are capable of resisting wind forces in the longitudinal direction. See Figure C to § 3285.402 for an example of one method that may be used to provide longitudinal anchoring. A professional engineer or registered architect must certify the longitudinal anchoring method or any alternative system used as adequate to provide the required stabilization, in accordance with acceptable engineering practice.

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Notes: 1. Refer to Tables 1, 2, and 3 to this section for maximum ground anchor spacing. 2. Longitudinal anchors not shown for clarity; refer to 3285.402(b)(2) for longitudinal anchoring requirements.

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Notes: 1. Vertical Straps are not required in Wind Zone I. 2. The frame must be designed to prevent rotation of the main chassis beam, when the diagonal ties are not attached to the top flange of the beam. See § 3285.401(d)(3) .
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Table 1 to § 3285.402 —Maximum Diagonal Tie-Down Strap Spacing, Wind Zone I
Nominal floor width, single section/multi-section Max. heightfrom ground to diagonal strap attachment I-beam spacing82.5 in. I-beamspacing99.5 in.
12/24 ft. 144 in. nominal section(s) 25 in 14 ft. 2 in N/A.
33 in 11 ft. 9in N/A.
46 in 9 ft. 1in N/A.
67 in N/A N/A.
14/28 ft. 168 in. nominal section(s) 25 in 18 ft. 2in 15 ft. 11 in.
33 in 16 ft. 1 in 13 ft. 6 in.
46 in 13 ft. 3 in 10 ft. 8in.
67 in 10 ft. 0 in N/A.
16/32 ft. 180 in. to 192 in. nominal section(s) 25 in N/A 19 ft. 5in.
33 in 19 ft. 0 in 17 ft. 5 in.
46 in 16 ft. 5 in 14 ft. 7 in.
67 in 13 ft. 1 in 11 ft. 3 in.

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Notes: 1. Table is based on maximum 90 in. sidewall height. 2. Table is based on maximum 4 in. inset for ground anchor head from edge of floor or wall. 3. Table is based on main rail (I-beam) spacing per given column. 4. Table is based on maximum 4 in. eave width for single-section homes and maximum 12 in. for multi-section homes. 5. Table is based on maximum 20-degree roof pitch (4.3/12). 6. Table is based upon the minimum height between the ground and the bottom of the floor joist being 18 inches. Interpolation may be required for other heights from ground to strap attachment. 7. Additional tie-downs may be required per the home manufacturer instructions. 8. Ground anchors must be certified for these conditions by a professional engineer, architect, or listed by a nationally recognized testing laboratory. 9. Ground anchors must be installed to their full depth, and stabilizer plates, if required by the ground anchor listing or certification, must also be installed in accordance with the listing or certification and in accordance with the ground anchor and home manufacturer instructions. 10. Strapping and anchoring equipment must be certified by a registered professional engineer or registered architect, or listed by a nationally recognized testing agency to resist these specified forces, in accordance with testing procedures in ASTM D 3953-97, Standard Specification for Strapping, Flat Steel and Seals (incorporated by reference, see § 3285.4 ). 11. A reduced ground anchor or strap working load capacity will require reduced tie-down strap and anchor spacing. 12. Ground anchors must not be spaced closer than the minimum spacing permitted by the listing or certification. 13. Table is based on a 3,150 lbs. working load capacity, and straps must be placed within 2 ft. of the ends of the home. 14. Table is based on a minimum angle of 30 degrees and a maximum angle of 60 degrees between the diagonal strap and the ground. 15. Table does not consider flood or seismic loads and is not intended for use in flood or seismic hazard areas. In those areas, the anchorage system is to be designed by a professional engineer or architect.
Table 2 to § 3285.402 —Maximum Diagonal Tie-Down Strap Spacing, Wind Zone II.
Nominal floor width, single section/multi-section Max. height from ground to diagonal strap attachment Near beam method I-beam spacing Second beam method I-beam spacing
82.5 in. 99.5 in. 82.5 in. 99.5 in.
12 ft/24 ft. 144 in. nominal section(s) 25 in 6 ft. 2 in 4 ft. 3 in N/A N/A
33 in 5 ft. 2 in N/A N/A N/A
46 in 4 ft. 0 in N/A N/A N/A
67 in N/A N/A 6 ft 1 in 6 ft 3 in
14 ft/28 ft. 168 in. nominal section(s) 25 in 7 ft. 7 in 6 ft. 9 in N/A N/A
33 in 6 ft. 10 in 5 ft. 9 in N/A N/A
46 in 5 ft. 7 in 4 ft. 6 in N/A N/A
67 in 4 ft. 3 in N/A N/A N/A
16 ft/32 ft. 180 in. to 192 in. nominal section(s) 25 in N/A 7 ft. 10 in N/A N/A
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33 in 7 ft. 6 in 7 ft. 2 in N/A N/A
46 in 6 ft. 9 in 6 ft. 0 in N/A N/A
67 in 5 ft. 4 in 4 ft. 7 in N/A N/A

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Notes: 1. Table is based on maximum 90 in. sidewall height. 2. Table is based on maximum 4 in. inset for ground anchor head from edge of floor or wall. 3. Tables are based on main rail (I-beam) spacing per given column. 4. Table is based on maximum 4 in. eave width for single-section homes and maximum 12 in. for multi-section homes. 5. Table is based on maximum 20-degree roof pitch (4.3/12). 6. All manufactured homes designed to be located in Wind Zone II must have a vertical tie installed at each diagonal tie location. 7. Table is based upon the minimum height between the ground and the bottom of the floor joist being 18 inches. Interpolation may be required for other heights from ground to strap attachment. 8. Additional tie downs may be required per the home manufacturer instructions. 9. Ground anchors must be certified by a professional engineer, or registered architect, or listed by a nationally recognized testing laboratory. 10. Ground anchors must be installed to their full depth, and stabilizer plates, if required by the ground anchor listing or certification, must also be installed in accordance with the listing or certification and in accordance with the ground anchor and home manufacturer instructions. 11. Strapping and anchoring equipment must be certified by a registered professional engineer or registered architect or must be listed by a nationally recognized testing agency to resist these specified forces, in accordance with testing procedures in ASTM D 3953—97, Standard Specification for Strapping, Flat Steel and Seals (incorporated by reference, see § 3285.4 ). 12. A reduced ground anchor or strap working load capacity will require reduced tie-down strap and anchor spacing. 13. Ground anchors must not be spaced closer than the minimum spacing permitted by the listing or certification. 14. Table is based on a 3,150 lbs. working load capacity, and straps must be placed within 2 ft. of the ends of the home. 15. Table is based on a minimum angle of 30 degrees and a maximum of 60 degrees between the diagonal strap and the ground. 16. Table does not consider flood or seismic loads and is not intended for use in flood or seismic hazard areas. In those areas, the anchorage system is to be designed by a professional engineer or architect.
Table 3 to § 3285.402 —Maximum Diagonal Tie-down Strap Spacing, Wind Zone III.
Nominal floor width, single section/multi-section Max. height from ground to diagonal strap attachment Near beam method I-beam spacing Second beam method I-beam spacing
82.5 in. 99.5 in. 82.5 in. 99.5 in.
12 ft./24 ft. 144 in. nominal section(s) 25 in 5 ft. 1 in N/A N/A N/A
33 in 4 ft. 3 in N/A N/A N/A
46 in N/A N/A N/A N/A
67 in N/A N/A N/A N/A
14 ft./28 ft. 168 in. nominal section(s) 25 in 6 ft. 2 in. 5 ft. 7 in N/A N/A
33 in 5 ft. 8 in 4 ft. 9 in N/A N/A
46 in 4 ft. 8 in N/A N/A N/A
67 in N/A N/A N/A N/A
16 ft./32 ft. 180 in. to 192 in. nominal sections 25 in N/A 6 ft. 3 in N/A N/A
33 in 6 ft. 1 in 5 ft. 11 in N/A N/A
46 in 5 ft. 7 in 5 ft. 0 in N/A N/A
67 in 4 ft. 5 in N/A N/A N/A

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Notes: 1. Table is based on maximum 90 in. sidewall height. 2. Table is based on maximum 4 in. inset for ground anchor head from edge of floor or wall. 3. Table is based on main rail (I-beam) spacing per given column. 4. Table is based on maximum 4 in. eave width for single-section homes and maximum 12 in. for multi-section homes. 5. Table is based on maximum 20-degree roof pitch (4.3/12). 6. All manufactured homes designed to be located in Wind Zone III must have a vertical tie installed at each diagonal tie location. 7. Table is based upon the minimum height between the ground and the bottom of the floor joist being 18 inches. Interpolation may be required for other heights from ground to strap attachment. 8. Additional tie downs may be required per the home manufacturer instructions. 9. Ground anchors must be certified by a professional engineer, or registered architect, or listed by a nationally recognized testing laboratory. 10. Ground anchors must be installed to their full depth, and stabilizer plates, if required by the ground anchor listing or certification, must also be installed in accordance with the listing or certification and per the ground anchor and home manufacturer instructions. 11. Strapping and anchoring equipment must be certified by a registered professional engineer or registered architect or must be listed by a nationally recognized testing agency to resist these specified forces, in accordance with testing procedures in ASTM D 3953-97, Standard Specification for Strapping, Flat Steel and Seals (incorporated by reference, see § 3285.4 ). 12. A reduced ground anchor or strap working load capacity will require reduced tie-down strap and anchor spacing. 13. Ground anchors must not be spaced closer than the minimum spacing permitted by the listing or certification. 14. Table is based on a 3,150 lbs. working load capacity, and straps must be placed within 2 ft. of the ends of the home. 15. Table is based on a minimum angle of 30 degrees and a maximum angle of 60 degrees between the diagonal strap and the ground. 16. Table does not consider flood or seismic loads and is not intended for use in flood or seismic hazard areas. In those areas, the anchorage system is to be designed by a professional engineer or architect.