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 Seismic retrofit is a highly specialized field.
Approximately one-third of the retrofits we do involve repairs or redo´s of jobs done by well-meaning contractors who did not understand the engineering principles involved in retrofit. Here are three questions
you can ask a contractor to determine if he is qualified to retrofit your home.
1. Does the contractor have a structural engineer he consults, and will that engineer verify that the contractor is competent to design a retrofit? If he
does, call the engineer for a reference. If he doesn´t, don't hire him.
2. Why does the most recent building code require large square plate washers be used on foundation bolts rather than the small round washers allowed by previous codes?
During the Northridge earthquake, many mudsills were destroyed when they split lengthwise at bolt locations. Engineers discovered that oversized bolt holes
allowed excessive play between the bolts and mudsills, causing the bolts to ram against the mudsills, splitting the wood like an ax. Large square plate washers
secure the bolts to the mudsills with greater force and decrease movement between the two.
3. Is the contractor aware of the two seismic retrofit codes, and can he name them? They are:
1. The Uniform Code of Building Conservation (UCBC)
2. The City of Los Angeles Retrofit Code
If the contractor cannot name at least one of these retrofit codes, he is not
using current standards and has not researched basic information in the retrofit field. DO NOT HIRE HIM.
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