ABAG Shaken Awake! Report -
Wood-Frame Multifamily Buildings

4-7 Stories, Built After 1939

Typical Building Damage

In these wood-frame-over-parking buildings, the parking level, whether it is reinforced concrete or reinforced masonry, will usually perform in accordance with its design and detailing. Any full or partial collapse of this underlying structure will result in damage similar to ground failure under more typical wood buildings. Although the shaking of the wood portion of the construction will be amplified by the base shaking, this portion of the building will otherwise perform in accordance with other wood dwellings.


This building type includes wood frame structures built over a first-story concrete podium used entirely for parking. As was mentioned earlier, this is a common design formula for many apartment buildings in the Bay Area, and California in general. The podium structure usually consists of walls or columns of either reinforced concrete or concrete masonry units (CMUs) supporting a concrete slab. The wood frame sits on the reinforced concrete slab, and as the building increases in height, so does the use of steel within the wood frame.

Bearing CMU walls are generally identified with the 1960's. This construction system involves the use of concrete blocks to form walls which are reinforced with steel bars and then filled with concrete. During the 1960s, but to a lesser degree after that, these walls were usually bearing. CMU walls can also serve as shear walls in the parking structure.

Occurrence of This Building Type in the San Francisco Bay Area

A significant percentage of the Bay Area's multi-family housing stock falls within this category. This generalized building type includes a high number of the multi-family structures built in the Bay Area during a period of intense urban growth. Over the total Bay Area, 7.1% of the multi-family housing stock falls within this category. San Mateo County has the highest percentage of dwelling units within this category: 5.4% of the total units and 17% of the multi-family units. In an older region such as the County of San Francisco, they represent only 5.7% of the multi-family stock. This type of building represents 2.3% of the total Bay Area housing stock.

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.