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RE: California Earthquake Problems

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I believe that this statement in regards to residential construction is
incorrect. There are over 1.5 million residential structures (single family
only - and even more multi-family residential structures) built prior to
1969 that are not in compliance with post 1933 seismic provisions. Although
these structures are not required to be retrofit or made to comply, the
state passed a disclosure law around 1992 or 1993 that required real-estate
agents to provide prospective home buyers of the possible inadequacy that
may result in the collapse of cripple walls and the possibility that a home
may be inadequately anchored to its foundation.
There are not requirements for the upgrade, however, Los Angeles and Los
Angeles Country led the way to provide a prescriptive retrofit suggestion
sheet which is available to anyone interested in doing the work.
I worked for one company in the early '90's who specialized in this work -
which became even more popular after the Northridge earthquake.
The need to respond to the publics desire to have some kind of standard for
the retrofit of residential homes (wood framed) prompted the California
Seismic Safety Commission to establish an Ad-hoc committee appropriately
named the RRR or Residential Retrofit and Repair committee. Although I
worked for a construction company that specialized in this work - I was the
chair of a new sub-committee for SEAOSC (Structural Methods Sub-committee
now chaired by Robert Sonntag) under the control of the then Hazardous
Building Committee which was chaired by Dave Brieholtz.The purpose of our
committee was to test anchor installation on existing concrete foundations.
A church in the Silverlake area of LA donated three foundations on the site
of a demolished structure for our use. At the time there was a number of
considerations for the guidelines of the retrofit. One side wanted to work
from the code minimum requirements that 1/2" diameter anchor bolts were
required to be installed at a minimum of 6'-0" on center (by UBC). However,
manual calculations supplied by Ben Schmidt showed compelling reasons why
the 6' minimum spacing of anchors is insufficient for homes constructed with
a raised floor. The need to resist two diaphragms in shear caused a
difference of opinion as how to proceed in the retrofit suggestions.
This was easier solved in the RRR committee which was represented by members
of other concerns besides structural. If I recall, the members represented
the AIA, the Pest Industry, Insurance Industry as well as the structural
 On one occasion when Ben Schmidt was unavailable for the RRR meeting, I sat
in as representative of SEAOC.
The outcome of the RRR's work was the publication of the Uniform Code for
Building Conservation Appendix Chapter 5 which provided a prescriptive
method with details as to suggested methods to accomplish this retrofit
work. At the same time, companies like Simpson, Harlen and Redhead became
active with the Structural Methods sub-committee and our results were issued
to the City of Los Angeles and to the County of Los Angeles representatives.
I believe the results of the testing - which was paid for by Harlen, Simpson
and even MEC Labs who provided the labor for testing - was used by both
Simpson and Harlen to launch their retrofit hardware.
Remember, there was no (and is none at this time) ordinance or code that
requires homes to be upgraded. The insurance industry been the primary
driving force behind this work - in hopes that retrofit homes will greatly
reduce their liability -which was extensive in both Loma Prieta and

A long around explanation, but as far as I know - there was never any
requirement for residential compliance to post 1933 seismic provisions other
than those in non-complying conventional framed structures. The majority of
homes constructed prior to 1969 were not engineered and were built to the
minimum conventional framing standards which, in as we have argued on this
list - does not meet minimum engineered solutions.

Others involved with the RRR committee that may have more to offer include
Fred Turner who chaired the RRR for Cal. Seismic Safety Commission, Frank
Lew who was very active on the committee and is still floating around with
some of the members of our list, Rick Ranous who is a freqent participant in
this list (and who represented the State of California Office of Emergency
Services) and Ben Schmidt SE who is active with SEAOSC (seaosc(--nospam--at) I'm
sure they can offer more recent information to this discussion.

Dennis S. Wish PE

-----Original Message-----
From: Ricardo Rafael Hernandez [mailto:rik(--nospam--at)]
Sent: Tuesday, January 12, 1999 8:14 AM
To: seaint(--nospam--at)
Subject: Re: California Earthquake Problems

Where can this article be found? Who wrote it?

At 05:18 AM 1/12/99 -0500, you wrote:
>For those who are interested in the subject matter it is suggested that
>five-page (plus) long document be printed out for easier reading.
>January 1999
>California Earthquake Problems
>All structures built in California since 1933, including residential
>are built (or are supposed to be built) to comply with seismic code
>requirements so they do not collapse, or partially collapse, under seismic

Ricardo Rafael Hernandez
89A Escondido Village
Stanford, CA   94305

Phone: 650.497.3865
Fax: 650.497.3865
email: rik(--nospam--at)