Existing Buildings and the “10% Rule”: Survey Results, Opinions, and Recommendations

Additions, alterations, and voluntary seismic improvements to existing buildings can be challenging to implement in California. Our 2018 paper presented this issue and surveyed engineers throughout the state to determine if there is uniformity in the way engineers currently interpret the California Existing Building Code provisions related to modifications and additions to buildings. Preliminary results were presented at the 2018 SEAOC Convention and those results clearly indicate that the profession is not in agreement.

This paper presents the 2018 survey results in detail including differentiation of responses by practicing engineers and building officials, licensed structural engineers and licensed civil engineers, younger engineers and seasoned engineers. Data is analyzed to correlate the survey questions to California Existing Building Code provisions and highlights common themes of uniformity and disagreement among the profession. The authors provide their opinion on individual questions as well as overall themes and offer commentary on the intent of the code compared to how it is actually implemented in practice. Finally, the paper concludes with remarks that may help both practicing engineers and building officials by providing a path forward to resolve issues with varied interpretation and implementation of these code sections including recommendations for code language improvements.

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