ABAG Shaken Awake! Report -
Wood-Frame Single-Family Homes

1-3 Stories, Built After 1939

Typical Building Damage

Although the post-1940 house does not present widespread problems with foundation anchorage and foundation reinforcing, there often is a lack of proper reinforcement of the masonry chimneys. A significant number of post-1940 dwellings can be yellow-tagged because of some type of chimney damage. The second major source of damage is damage (or even collapse) of garages with living area above in two-story or split-level homes due to long spans over the garages.

Typical Damage to Post-1939 Single-Family Home

Source -- Courtesy of Degenkolb Associates


This category accounts for the suburban California house that is familiar to most of us. Built after WW II with increasingly larger garages, our single family house has increased in square foot size over the years. A common design formula for post WW II single family house has been locating the living spaces above a two car garage that faces the street. This strategy often produces long spans for the floor and roof diaphragms making the structure more vulnerable during an earthquake.

Occurrence of This Building Type in the San Francisco Bay Area

The post-1940 house accounts for 53.6% of the total Bay Area housing stock. Its relative numbers are most significant in the more recently urbanized counties of the Bay Area: Contra Costa County 68.3%, Marin County 59.9%, Napa County 62.6%, San Mateo County 58.6%, Santa Clara County 61.2%, Solano County 67.3%, and Sonoma County 64.9%.

ABAG, the Association of Bay Area Governments, is the regional planning and services agency for the nine-county San Francisco Bay Area.

This page is based on a 1996 ABAG report. It was last updated 9/29/03 by jbp.