Certain types of homes are more likely to need a retrofit than others. If you answer yes to any of these questions, you should consider retrofitting your home.
Find out if you live in a moderate or high seismic area. Call your local building department and ask if you are in Seismic Design Category D, E or F. You also can visit the U.S. Geological Survey website and review its seismic hazard maps at http://earthquake.usgs.gov/hazards/products/.
Homes built prior to 1985 are typically more vulnerable to earthquake damage. Most homes built after 1985 were designed to conform to stricter building codes and are most likely better equipped to resist the force of an earthquake.
If your house is not built on a concrete slab, chances are it's built on a raised foundation (these homes typically have a crawl space). This supporting structure under the house may not have been built to resist seismic forces and can be highly susceptible to structural failure in an earthquake.
Homes built on a hillside typically have raised foundations and tend to have more severe failures because the structural framing supporting the house – posts and cripple walls – are built at different heights.
Garage door openings create vulnerable areas in a house. The narrow walls on either side of the garage door must be carefully designed to resist earthquake forces. This is extremely important if there is a living space above the garage because these rooms add weight that the garage framing must support. (Note: if you live in an older home with a living space above the garage or on a hillside, you'll need to consult with a licensed structural engineer for design solutions.)