Riley Act of 1933

• In 1933, the Long Beach earthquake devastated numerous public schools and was the catalyst for the creation of the Riley Act. The act required all California local governments to have a building department and to inspect new construction, mandating that all structures in the state be designed to withstand a horizontal acceleration of 0.02 times the acceleration due to gravity. These requirements pertained only to structures built after 1933.
  
  

California Construction Patterns 1933-1950

• Many homes built in California before 1940 did not have their frames bolted to the foundation. After the 1933 quake, however, new seismic design codes arose that required wood-framed walls to be bolted to reinforced concrete or masonry foundations. Between 1940 and 1960, construction patterns evolved to include anchored stem walls, reinforced masonry and still bolts to two-by-four mud sills and let-in bracing. The building materials used in the walls of structures in 1950 was primarily a combination of gypsum, lath and plaster.
  
  

1950 Building Patterns

• The shower landing, or floor area directly under and around the shower, in 1950 would have been typically been built on unreinforced concrete, if built prior to 1940, and on reinforced concrete if built in 1950 or later. It may have included an additional top layer of ceramic tile or rubber flooring. The shower landing would typically be at least as wide and deep as the bottom floor area of the shower cavity to retain water, with a central drain. Building standards at this time were not well-regulated, resulting in a wide variation in construction patterns.
  
  

Current Standards

• Most older buildings do not meet today's building codes. The California Historical Building Code provides the owners of older buildings some flexibility in meeting code requirements if the structures meet the established criteria. As of 2007, the top layer of a shower landing or floor must be constructed out of vitrified china, earthenware, ceramic tile, porcelain or enameled material, according to the California Building Code. The shower floor must slope from the sides of the shower toward the drain, not less than one-quarter inch per foot or more than a half-inch per foot. Thresholds shall be of sufficient width to accommodate a minimum 22-inch opening. All shower compartments, regardless of shape, are required to have a minimum finished interior of 1,024 square inches, according to the current code.