J01d Elko Mobile Units Foundation System.pdf

PH21EK01C7, Elko Mobile Units Page 1 of 3

Attachment J01d – Elko Mobile Units Foundation System PH21EK01C7 – Elko Mobile Units

March 25, 2024 This foundation system is based upon the U.S. Department of Housing and Urban Development, Model Manufactured Home Installation Standards, 2003 Edition. The original document can be found at website: https://www.hud.gov/sites/documents/225HUD.PDF and was last accessed on May 29, 2023. This foundation system is to be used in the absence of a similar standard from the Tribal, local, county, or state governments.

1. Subbase

a. All exterior finished grades shall slope to drain away from building walls to eliminate water pockets adjacent to building foundations.

b. Scarify existing soil to 12” deep, recompact to 95% min. density for the entire site, build up trailer pad to match adjacent asphalt road slope.

2. Concrete Foundation

a. Provide concrete reinforced strip footings and grade beam “waffle” type foundation system to support the Units; footings are placed on 16” deep subbase fill compacted to 90 percent of maximum relative density, concrete footings are 16 inches wide x 8 inches deep minimum poured-in-place concrete ribbons with a 28-day compressive strength of 3,000 psi, including cast-in-place concrete reinforcing steel, (2) #4 continuous at bottom of footings.

b. All concrete shall conform with ASTM C-94, with a water/cementitious material ratio of 0.58, Type V cement, and attain the following minimum strengths at 28 days (1) Footings;

3,000 PSI, (2) Sidewalks; 2,500 PSI.

c. Top of footing shall match adjacent asphalt road finish elevation.

3. Provide 4” diameter Steel Guard Post, Sch. 40, Galvanized, Height 36” minimum, fill with grout and crown top, concrete embedment 36” below grade, Type 1 Permanent concrete bollards, in accordance with Detail No. 140 Bollard, Revised 01-01-2009.

4. Frame Blocking

a. Design requirements for concrete block piers.

b. Provide frame piers less than 36 inches high as follows:

c. Frame piers less than 36 inches high are permitted to be constructed of single, open, or closed-cell concrete blocks, 8 inches, 8 inches, 16 inches, when the design capacity of the block is not exceeded.

(1) The frame piers shall be installed so that the long sides are at right angles to the supported I-beams, mortar is not required.

(2) The concrete blocks shall be stacked with their hollow cells aligned vertically and shall be positioned at right angles to the footings; mortar is not required.

(3) Horizontal offsets from the top to the bottom of the pier shall not exceed one-half inch.

d. Provide frame piers 36 inches to 67 inches high and corner piers.

(1) All frame piers between 36 inches and 67 inches high and all corner piers over three blocks high shall be constructed out of double, interlocked concrete blocks, as shown in Figure B to this section, when the design capacity of the block is not exceeded. Mortar is not required for concrete block piers https://www.hud.gov/sites/documents/225HUD.PDF

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(2) Horizontal offsets from the top to the bottom of the pier shall not exceed one inch.

5. Perimeter support Piers

a. Provide piers required at supports, perimeter piers, and piers at exterior wall openings are permitted to be constructed of single open-cell or closed-cell concrete blocks, with nominal dimensions of 8 inches × 8 inches × 16 inches, to a maximum height of 54 inches, when the design capacity of the block is not exceeded.

b. Provide piers used for perimeter support shall be installed with the long dimension parallel to the perimeter rail.

6. Pier Location and Spacing

a. The location and spacing of piers depends upon the dimensions of the unit, the live and dead loads, the type of construction, I-beam size, soil bearing capacity, footing size, and such other factors as the location of doors or other openings.

b. Mate-line and column pier supports, unless the pier support and footing configuration is designed by a registered professional engineer or registered architect.

c. Piers supporting the frame shall be no more than 24 inches from both ends and not more than 120 inches center to center under the main rails.

d. Pier support locations and spacing shall be presented, as applicable, unless alternative designs are provided by a professional engineer or registered architect in accordance with acceptable engineering practice.

e. Piers may be offset up to 6 in. in either direction along the supported members to allow for plumbing, electrical, mechanical, equipment, crawlspaces, or other devices.

f. Single-stack concrete block pier loads shall not exceed 8,000 lbs.

7. Required Perimeter Supports

a. Perimeter pier or other supports shall be located as follows:

(1) On both sides of side wall exterior doors (such as entry, patio, and sliding glass doors) and any other side wall openings of 48 inches or greater in width, and under load-bearing porch posts, factory installed fireplaces, and fireplace stoves).

(2) Other perimeter supports shall be:

i. Provided by other means such as additional outriggers or floor joists. When this alternative is used, consider the additional loads in sizing the pier and footing supports under the main chassis beam.

ii. For roof live loads of 40 psf or greater, a professional engineer or architect shall determine the maximum sidewall opening permitted without perimeter pier or other supports.

b. The location and installation of any perimeter pier support shall not take the unit out of compliance with the Manufactured Home Construction and Safety Standards.

8. Typical Blocking Diagram for Single Section Unit

a. Framed piers shall be single, closed cell concrete block, 8x8x16, install at right angle to support I-beams, mortar is not required.

b. End piers under main I-beams may be set back a maximum of 24 inches, as measured from the outside edge of the floor to the center of the pier.

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c. Place piers on both sides of sidewall exterior doors, patio doors, and sliding glass doors;

under porch posts, factory-installed fireplaces, and fireplace stoves; under jamb studs at multiple window openings; and at any other sidewall openings 48 inches or greater in width.

For roof loads of 40 psf or greater, a professional engineer or registered architect shall determine the maximum sidewall opening permitted without perimeter supports.

9. Ground Anchor Installation

a. Provide ground anchor assembly designs tested to meet or exceeded a working load of 3,150 pounds and sustained an ultimate load of 4,725 pounds in the weakest soil classification for which the anchors were tested and certified.

b. Specifications for tie-down straps and ground anchors

c. Ground anchors shall 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. The ultimate load and working load of ground anchors and anchoring equipment shall 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.

d. Tie-down straps. A 11⁄4 inch × 0.035 inch or larger steel strapping conforming to ASTM D 3953—97, Standard Specification for Strapping, Flat Steel and Seals, 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.) shall be used. The tie-down straps shall 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.

e. The requirements in paragraph (c) of this section shall be used to determine the maximum spacing of ground anchors and their accompanying anchor straps, based on the soil classification:

(1) The installed ground anchor type and size (length) shall 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

(2) All ground anchors shall be installed in accordance with their listing or certification and the ground anchor manufacturer installation instructions; and

f. 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 shall 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.

g. Anchor per manufacturer’s recommendations

h. Maximum Diagonal Tie-Down Strap Spacing, Wind Zone I

(1) Nominal floor width, single section: 12/24 ft., 144 in. nominal section(s)

(2) Max. height from ground to diagonal strap attachment: 25 in

(3) I-beam spacing: 14 ft. 2 in