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EVALUATION OF MANUFACTURED HOUSING SUPPORT SYSTEM PERFORMANCE IN THE LOMA PRIETA EARTHQUAKE: (Attachment A)

Following the October 17, 1989 Loma Prieta Earthquake, personnel from the Department's Division of Codes and Standards responded with assistance to local governments, park operators and homeowners. As in several previous earthquakes, Department inspectors reported significant differences in the performances of the various type support systems. However, for the first time, detailed information on the performance of the different types of manufactured home installation systems was gathered and published in a Department report.

This report centered around 27 mobilehome parks in three counties within the designated disaster area. Those counties were Santa Cruz, Santa Clara, and San Benito. The total number of spaces within the parks surveyed numbered 2,434 and the number of homes within these parks that fell from their supports totaled 592. That represents slightly more than 24 percent of the total homes surveyed. Two manufactured homes were destroyed by fire and two others were structurally damaged beyond repair.

FACT FINDING HEARINGS:

Oral and written comments were sought from the manufactured home and related industry leaders, contractors, associations, local enforcement agencies, other government departments concerned with earthquake safety, the insurance industry, as well as manufactured home owners and the general public.

During the course of the six hearings, there were a total of 119 interested parties in attendance and 56 offered testimony and multiple recommendations. Nearly all of the recommendations received at the hearings fell within one of the following thirteen categories, listed in order of preference, based on the comments received.

"Pro" indicates the number of persons speaking in support of the recommendation, while "Con" indicates the number of individuals speaking in opposition.

1. Support devices need to be attached to the manufactured home and the support footing. Pro 13 - Con 1.
2. Manufactured home support systems need to be designed and constructed to resist lateral forces. Pro 10 - Con 0.
3. Any replacement or alteration of a manufactured home's support device or system needs to be done under benefit of permit and inspection from the enforcement agency. Pro 8 - Con 0.
4. All certified earthquake resistant bracing systems (ERBS) should be subjected to actual testing and the results published in a consumer report comparing each ERBS with the others. Pro 8 - Con 0.
5. Mandatory requirement of ERBS installation, primarily as a retrofit for existing manufactured homes. Pro 7 - Con 3.
6. Reevaluate statistics reported in the Department's report on the Loma Prieta Earthquake to determine any differences between manufactured homes installed prior to and after the July 1974 regulation changes. Pro 5 - Con 0.
7. Request that Community Development Block Grant funds, tax incentives and/or low-interest loans be made available to manufactured home owners to purchase and install ERBS. Pro 5 - Con 0.
8. Require the use of heavy duty piers with n the design of all support systems. Pro 5 - Con 1.
9. Require all manufactured homes be installed with the wheels and axles remaining attached to the home. Pro 4 - Con 3.
10. Identify seismic zones based on the likelihood of an earthquake happening and vary the requirements for support systems by zone. Pro 3 - Con 0.
11. Require anchorages or tiedowns to be installed at the same time the manufactured home is installed. Pro 2 - Con 1.
12. Allow noncertified ERBS to be marketed within California. Pro 1 - Con 0.
13. Require all manufactured homes to be installed on foundation systems Pro 2 - Con 5.

Damage and Costs

Although two manufactured homes were structurally damaged beyond repair during the Loma Prieta Earthquake, structural damage to manufactured homes in earthquakes is normally light or nonexistent. Even when the home falls completely to the ground the structural integrity of the home itself is most often not affected.

This is not to imply that piers will not penetrate the floor, or that interior as well as exterior wall coverings may not pop loose from the wall framing members. These as well as other forms of damage may and do occur. However, the repair of this type of damage is relatively minor and generally can be completed for a few hundred dollars. The major expense occurs when the home has to be lifted up and placed back on its support system, the utility connections have to be repaired and accessory structures replaced.

Following the Loma Prieta Earthquake, manufactured home setup contractors charged an average of $1500 per transportable section just to raise and reset manufactured homes. This did not include any repair work required to be done to the home or its accessories. The average doublewide manufactured home owner, whose home fell to the ground, spent an additional $14,400 repairing the accessory structures, utilities and home.

Note: All replacement costs were indicated to include a labor charge to remove the damaged accessory structure prior to installing the new item.

Damage Caused By Fire:

Fire is always a primary concern during and after an earthquake, especially when a manufactured home is involved. Immediately following the Loma Prieta Earthquake, two manufactured homes in Watsonville were completely destroyed by fire. According to an official with the Watsonville Fire Department, there was no investigation conducted by their department to determine the exact cause of those two fires. It is suspected, however, that the gas piping to either the home itself or one of the home's gas appliances was ruptured and the escaping gas ignited.

Federal construction standards for manufactured homes require gas appliances within a manufactured home to be secured in place; however, previous experience indicates that homeowner replacement of gas appliances often overlook this requirement of Department and federal regulations. Another requirement of Department regulations is that the gas piping connector to the home itself be flexible and of a six-foot (6') length. The purpose of this unusual connector, listed and tested specifically for manufactured homes, is to accommodate movement of the home without fracture of the connector.

Chassis Damage

Unlike previous earthquakes, several chassis under manufactured homes in Hollister had to be replaced after the Loma Prieta Earthquake. Apparently, the first movement of the earth was in an upward motion then the ground shifted laterally. As a result, the homes came back down, slightly off center of the concrete block supports, crushing the blocks and forcing the chassis girders to bend against the concrete debris below. Mike Terrian, General Manager of the Champion Home Builders manufacturing plant in Lindsay, California, commented during the Fresno Fact Finding Hearing that his firm manufactured three new chassis that were used to replace ones damaged in Hollister. The cost of replacing each chassis ran about $1000 including installation.

Damage to Manufactured Home Utility Systems

The manufactured home installation regulations require flexible utility connections for manufactured homes to allow for some movement associated with this type of structure. However, due to the violent nature of the Loma Prieta Earthquake, many manufactured homes came to rest as much as four feet away from their original location. This caused extensive damage to sewer and water piping located beneath the homes and utility connectors between the homes and the park utility systems. The electrical feeder assemblies typically have an additional 10' to 15' of conductors enclosed with flexible metal conduit between the home and the electrical pedestal. This allowed homes to move farther than did the water and sewer lines without causing major damage to either the home or park electrical systems. However, some electrical feeder assemblies were damaged when the homes fell on the flexible metal conduit and crushed the conductors inside the conduit, In addition, several park electrical pedestals were knocked over when the homes fell against the equipment, resulting in damage to the park electrical system.

Effectiveness of Wheels and Axles

Prior to January 1, 1980, wheels and axles were required to be left on the manufactured homes upon installation. However, Chapter 1160 of the 1979 Statutes, added Section 18550.5 to the Health and Safety Code allowing the removal of these items at the homeowner's discretion for recycling.

When a manufactured home is installed and the wheels and axles are left on the home, the tires naturally deflate and rot within a few years. The axis have no further purpose and pose more of an obstacle than advantage to the setup contractor when attempting to properly place the load bearing supports in the area beneath the running gear.

Wheels and axles used to transport manufactured homes are normally recycled. The average price typically paid for recycled axles is $200 per axle. Wheels and tires are recycled for approximately $40 each. For the typical doublewide manufactured home having three axles under each half, this could represent as much as a $1,680 reduction in the cost of the home to the manufactured home buyer.

There is no evidence that leaving the wheel hubs and axles on a manufactured home provides any reasonable protection against earthquake damage.

RESULTS OF THE QUESTIONNAIRE:

A questionnaire was sent to all city and county building officials throughout the State and manufactured home manufacturers holding current manufacturing licenses from the Department. Responses were sought for 11 questions relating to their experiences with manufactured home support devices during earthquakes as well as their ideas for improving the support devices performance. The Department received 91 responses to the questionnaire representing 16.8 percent of those questioned. The actual breakdown of responses is as follows: 71 of the nearly 450 cities, 19 of the 58 counties, and 3 of 46 manufacturers responded.

Damage Found By Those Responding:

The primary form of damage to manufactured homes reported by building officials was support devices penetrating the floor when the homes fell to the ground. In addition, they reported severe damage to awnings, decks, skirting and other accessory structures. Little or no structural damage to the homes was noted. This is similar to the Department's observations in the Loma Prieta and previous earthquakes where manufactured homes were damaged.

Recommendations From Those Responding:

1. All future installations of manufactured homes in California should be anchored to the ground by use of tiedowns or similar devices.
2. All manufactured home support systems should be designed and constructed to resist the lateral loads.
3. Design requirements for the support systems should be based on the criteria specified in the Uniform Building Code (UBC) for the seismic zone the manufactured home is being installed in.
4. Support devices should have some type of physical connection to the manufactured home to prevent separation during earthquakes and/or high winds.
5. Several responses recommended mandatory installation requirements for ERBS. Particularly for those manufactured homes being installed in the UBC Seismic Zone 4. UBC Seismic Zone 4 is that area of California with historically high seismic activity.