Disaster Highlights 2007 0709 v2

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I Establishing Retrofit Standards ] What is involved in a proper retrofit? Not all retrofits are created equal. For a typical older house with a crawl space Depending on the city, somewhere between 15% and 80% of underneath the home, a retrofit consists of no the homes have had any retrofit work done. Unfortunately, less than three separate actions. just because a house has been retrofitted does not First the ba necessarily mean that the home has been properly retrofitted of th~ housese and is therefore protected against earthquakes. In a 1999 (mudsill) 's survey of 341 homes, ABAG found that anywhere from 1/3 to se d tl th 2/3 of retrofitted homes were not adequately prepared for fo~~~:tio~ e a future quake (the percentage varied by city). In a 2006 using bolt t survey of 35 homes published in the Contra Costa Times on prevent th~ 0 March 5, 2006, 2/3 of retrofitted homes were not adequately house from retrofitted to prevent collapse and limit damage. slipping off of the foundation. Contractors may be untrained in retrofits and may therefore be Second, if the house has a cripple wall (which unaware of p.roper retrofit procedure. The work they do may forms the perimeter of the crawl space), it is therefore be I~adequate (for example, they may on~y add bolts strengthened by adding plywood panels (shear to t~~ foundation and not ~erfor.m the other .two ~ctlons). In. walls) along the interior of all perimeter walls. addition, contractors may Inten,tlonally deceive clients even If The unbraced cripple wall is the most likely part they are aware of proper retrofit p.rocedure, as few of the home to collapse in an earthquake. homeowners would know how to Inspect the work. Finally, the floor framing is secured to the cripple Home inspec~ors ~nd loc~1 government building insp~ctors walls to prevent the floor from slipping off these may be untrained In retrofits and therefore unable to Judge walls. If the home does not have cripple walls, wh~t~er the co~tractor has performed a pro~er retrofit. In then the floor framing is secured to the mudsills. addition home Inspect?rs may be unable to Judge whether a home needs a retrofit In the first place. If anyone of these actions does not occur, then. . . " there remains a large risk that the house will still Llce~sed profes~/onals (engme~rs or architects Wlt~ . collapse applicable expenence) are required for homes on hillSides or . with living spaces above garages. If these professionals are Therefore, if all three of the above not included in the design process when retrofitting these actions occur in a retrofit, the home will homes, it is unlikely that the home will be protected against much better prepared for the next collapse. earthquake. If a home is on a hillside or has living space above a garage, the retrofit is likely to be more complex and will require the services of an engineer in addition to those of a qualified contractor. Current California building codes for new construction are adequate to protect new homes from collapse due to earthquakes. It is essential that local governments properly enforce these codes for all new construction to guarantee that new buildings can withstand earthquakes without collapse and to limit damage. April II, 2006 Local governments should playa strong role in promoting retrofits as well as increasing the quality of retrofits by establishing a retrofit standard and enforcing that standard. A retrofit standard clearly establishes the requirements for a retrofit, and gives local governments the power to enforce the standard. The standard applies not only to what is done in the retrofit, but also who is involved in the retrofit. Local governments can also require that engineers be involved in complex retrofits of homes on hillsides or on split-level homes with living spaces above a garage.