Enabling Cost-Effective Retrofits for More Types of Houses
Houses built before 1979 have many conditions that make them more vulnerable to earthquake damage than newer houses. Many of these older houses have a short wood-framed wall ("cripple wall") surrounding the crawl space under the house, which needs to be reinforced to help prevent the house from toppling during an earthquake. Bolting the house's frame to its foundation will help keep the house from sliding off the foundation during an earthquake.
- Even a moderate earthquake can severely damage a house that has not been retrofitted according to modern seismic building codes.
To address this challenge, CEA is working to develop 'prestandards' for the evaluation and retrofit of a variety of single-family, wood, light-frame houses. Once completed, a prestandard may be adopted into the California Existing Building Code and support development into a standard plan set.
How could this help with your retrofit?
When a community approves the use of a standard plan set, homeowners and contractors can more easily retrofit older houses, likely eliminating the need for a design professional to come up with site-specific plans and design calculations. A standard plan set provides a low-cost method way to help older houses better survive an earthquake.
What is a standard plan set?
Today, only one California building code exists to seismically retrofit a very specific kind of single family home—a wood-frame house with a raised concrete foundation and cripple walls less than four feet tall. Known as Chapter A3, this code is the basis for Plan Set A, adopted by many cities. You can use this plan set to get consistent bids from contractors, or, if experienced, do the work yourself.
However, no plan sets exist to seismically retrofit houses with other vulnerabilities, like houses:
- With a living space over the garage,
- Built on a hillside, or
- Built with post-and-pier construction (a raised house supported on posts).
If you want to retrofit your house and it does not meet Plan Set A criteria, you will need site-specific seismic retrofit plans and calculations prepared by a registered design professional (architect or engineer). The Department of Consumer Affairs Contractors State License Board has information on how to hire a licensed contractor.