Many mobilehomes and manufactured homes are built on support piers, often steel jacks or masonry piers, that were designed just for gravity loads—and these gravity support systems were not built to withstand earthquake shaking.
In California, laws were enacted after the 1994 Northridge earthquake that require new or relocated mobilehomes and manufactured homes to have earthquake bracing but, unfortunately, the standards in place allow for inadequate seismic bracing systems to be installed. Recent earthquakes including the 2014 South Napa and the 2019 Ridgecrest earthquakes have shown that unbraced and inadequately braced homes can sustain extensive earthquake damage, with many sliding off their support systems onto the ground or sliding enough to disrupt habitability.
Mobilehomes and manufactured homes can be improved by installing an Earthquake Resistant Bracing System (ERBS), designed to prevent or minimize home movement during earthquake shaking. In California, the State of California Department of Housing and Community Development (HCD) requires that all of the bracing systems offered to residents be certified. Most of these systems can be installed as part of new home’s overall installation.
Homeowners are required to submit an Application for Permit to Install Manufactured Home/Mobilehome Earthquake Resistant Bracing System to HCD prior to installing an ERBS. The application must be filled out either by the licensed contractor hired to perform the work or signed by the owner as an owner-builder if they choose to do the work themselves. This permit and other related information can be found on HCD’s website.
Strengthen Your House
CEA encourages owners of mobilehomes and manufactured to have an ERBS properly installed on their homes to strengthen them against earthquake damage.
One way that a homeowner can ensure that the ERBS is installed properly is to require that the installation is in accordance with Federal House and Urban Development standards. HUD installation standards are found in the Code of Federal Regulations (CFR) Title 24, Model Manufactured Home Installation Standards.
Additional information on effective seismic bracing systems can be found in two documents available online:
Homeowners are cautioned that seismic bracing that is supported only on plywood or wood blocks directly on the ground have not performed well in earthquakes.
Once the ERBS has been installed and certified, CEA policyholders with properly retrofitted eligible homes can receive a premium discount of 21% from CEA.