Code Provisions for Unreinforced Masonry Bearing Wall Buildings in California

Prior to the Long Beach earthquake of 1933, unreinforced masonry (URM) construction was usual in California, as it still is in many areas of the United States. The poor performance of these URM buildings in that earthquake led to State legislation regulating first new construction, then existing buildings. In addition, various cities have enacted seismic retrofit ordinances. Ultimately, seismic strengthening of existing URM bearing wall buildings was covered in a model building code, the Uniform Code for Building Conservation. This paper discusses the hazards presented by unreinforced masonry structures and presents a history of code development for their strengthening.