ABAG Shaken Awake! Report -
Non-Wood-Framed Buildings

Over 7 Stories, Built Before 1940

Building Damage Varies by Construction Type

Similar to the pre-1940 buildings under seven stories , pre-1940 non-wood buildings over seven stories consist primarily of cast-in-place concrete bearing wall structures or steel frame with unreinforced masonry infill wall structures.

Construction and Performance of Buildings with Concrete Bearing Walls

Concrete bearing-wall construction can have good seismic force resisting characteristics. Walls are poured to the level below the floor, then a floor slab is poured, and finally the next portion of the wall is poured. Typically, pre-1940 concrete bearing wall buildings are under 10 stories. Examples of this building type exist in the older cities of the Bay Area, particularly San Francisco, Oakland and Palo Alto.

Since the older concrete bearing-wall structures were constructed before the use of plywood, the impression of the horizontal form boards are often left on the exterior walls of the building. Older concrete buildings with cast-in-place concrete walls have performed very well in earthquakes even though they may not have been intentionally designed to resist them. However, non-structural damage to elevators and plumbing may occur in all concrete buildings.

Construction and Performance of Buildings with Steel Frames

Steel frame with unreinforced masonry infill walls generally perform well in avoiding collapse. However, the unreinforced infill walls present life safety risk in the form of falling hazards. The infill walls may be difficult to identify as they may be covered with plaster. Large cracks in them indicates a potentially unsafe situation.

Buildings in the San Francisco Bay Area

Units in buildings within this category represent only 0.1% of the total Bay Area housing stock. In San Francisco County they represent 1% of the total and 1.5% of the multi-family stock. This building type is non-existent in Contra Costa, Marin, Napa, San Mateo, Solano and Sonoma counties.

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 9/26/03 by jbp.