JURISDICTION:
The Mobilehome Parks Act, HSC, Division 13, Part 2.1, is applicable to the installations of manufactured homes both in and outside of mobilehome parks. HSC Section 18613 and related regulations prescribe requirements for the installations of manufactured homes without foundation systems. The Mobilehome Parks Act provides for the preemptive regulation of manufactured home installations and further provides for a local government option to assume enforcement responsibility for parks within their jurisdiction. Presently, the Department has enforcement responsibility in approximately 3,600 of California's 5,800 mobilehome and special occupancy parks with local governments having enforcement jurisdiction in the remaining parks as well as all manufactured home installations outside of parks.
SUPPORT SYSTEM DEVICES:
Under current regulations, several types of support devices are approved by the Department for use with manufactured homes. To gain Department approval, the regulations require a manufacture of a support device to first have the load bearing support device listed by an approved listing and/or testing agency. Generally, these devices are either steel piers, concrete blocks, or concrete piers. These various support devices are installed on wood or concrete footings located under the chassis beam at approximately 6' on center, and at concentrated load points, as specified in the home manufacturer's installation instructions.
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Steel Piers:
This type pier is typically of a triangular shape with a 9" X 9" to 12" X 12" base. The vertical "legs" of the steel pier extend upward 12 to 30 inches in height and are welded at the base and at the top. The top of the steel pier is usually a hollow cylinder having a hole large enough for an adjusting bolt to slide through. The bolt is used to adjust the finished height and to level the manufactured home. Welded to the top of the adjusting bolt is a thin, flat piece of steel which provides the bearing surface upon which the manufactured
home chassis rests. This thin, flat piece of steel at the top of the pier is approximately 2" X 3", providing a very small bearing surface for each support device. The steel pier is favored by many manufactured home installers because of its relatively light weight and triangular shape which allows these supports to be stacked one on top of the other requiring very little space during transportation. The steel pier has a significant capacity to resist vertical loads in relationship to its relatively light weight and low cost.
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Concrete Piers:
The concrete pier type support, like the steel pier, is triangular in shape having a base dimension of 9" X 9" to 12" X 12". It also comes in varying heights from 12 to 30 inches and has significant load bearing capacity. Normally, the lower two thirds of these devices are hollow to allow stacking during transportation as well as to reduce the weight. The top surface of these piers can be flat to accept a wedge leveling method consisting of two wedges cut 12 inches long from 2" X 4" lumber. However, the concrete cones or piers are normally manufactured with a hole through the top and a leveling bolt is used in the same manner as with a steel pier.
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Concrete Blocks:
This load bearing device consists of field assembled, 8" X 8" X 16" hollow core concrete blocks stacked vertically one on top of the other. Although the use of 1" X 8" X 16"wood blocks or spacers between the concrete blocks is recommended to distribute the loads between the concrete blocks it is not required. A 1 inch wooden cap block or 4 inch concrete cap block is also recommended to assure proper weight distribution although not required. Height adjustment and leveling are obtained by using wood wedges, between the top of the support device and the manufactured home chassis.
Note: Any support device that is in excess of 36 inches in height must be laterally braced in two directions at right angles to each other. When more than one forth of the manufactured home is supported at a height of three or more feet, the manufactured home must be installed on a permanently-constructed and approved support structure. A support structure must be designed to resist both seismic and wind loads for the area in addition to the vertical load to be supported.
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Footing Materials
All three of the load bearing support devices described above require the use of an approved footing. Department regulations specify the materials and minimum sizes of footings. Generally, each footing for a load bearing support is either pressure treated lumber or three and one-half inch thick concrete which is precast or poured in place. The length to width ratio of a footing may not exceed 2.5 to 1. Therefore, if a piece of 2" X 12" treated lumber is used as footing material, the maximum length would be 30 inches. Department regulations provide the method for calculating the total footing area and that all soil is presumed to have 1000 pounds per square foot of bearing capacity unless data to substantiate higher values is submitted to and approved by the enforcement agency.
