AWARD WINNING SEISMIC ENGINEERS

Soft-Story Retrofits Against Earthquakes

multi story residential building

Creating awareness, education, and solutions for soft-story retrofits against earthquakes is something essential particularly in the area of East Coast as long as soft-story structures are popular on the West Coast, and are typically multi-story residential buildings built above a ground-level garage, tuck-under parking garage or a storefront. Their mixed-use design often means wider openings and fewer partition walls on the first story than on the upper stories, leaving soft-story buildings structurally vulnerable in the event of a major earthquake. During the 1971 San Fernando, 1989 Loma Prieta and 1994 Northridge earthquakes, soft-story buildings sustained major damage or collapsed entirely.


Laws Require a Mandatory Retrofit

For years, cities on the West Coast have recommended soft-story retrofits for thousands of residential structures to increase building resiliency. Cities such as San Francisco, Berkeley, as well as Los Angeles have already passed laws that require a mandatory retrofit for certain soft-story residential buildings, and many other cities are following suit.

The soft-story retrofitting process may seem complicated, but we have provided information for each step along the way. Whether you are a building owner, engineer, architect, contractor or inspector, we have useful information to help you navigate your soft-story retrofit from the beginning stage of receiving a mandate letter to the latter stage of implementing a soft-story retrofit solution.

San Francisco’s Mandatory Soft Story Retrofit Program

The Mandatory Soft Story Retrofit Program was created in 2013 as a multi-year community-based effort led by the Earthquake Safety Implementation Program and enforced by the Department of Building Inspection to ensure the safety and resilience of San Francisco's housing stock through the retrofit of older, wood-framed, multi-family buildings with a soft-story condition.

As part of this program, all affected property owners were noticed beginning in September 2013 and were required to have submitted their screening forms to DBI by September 15, 2014. DBI has achieved over a 99% response to the program. Buildings that have not complied with this requirement have been placarded and issued Notices of Violation.
We encourage property owners of soft-story buildings to take the necessary steps to comply with program requirements by filing for a permit to ensure their properties are seismically safe in anticipation of the next big quake. Read one of our articles for more information about the program’s compliance timeline and tiers.

The City of Berkeley | Soft-Story Program

The City of Berkeley requires owners of soft, weak, or open-front buildings with five or more dwelling units to retrofit their buildings per Berkeley Municipal Code Chapter 19.39. Owners were required to apply for a building permit by December 31, 2016, and have two years to complete the work after submitting their permit application. The law took effect on January 4, 2014, and applies to wood-frame buildings constructed prior to 1978.   

Read about our new Retrofit Grants available for owners of soft-story buildings.

SWOF building owners must also post an earthquake warning sign and notify their tenants of the building's potentially hazardous condition. Under the first phase of the soft story program, starting in 2005, SWOF building owners were required to submit an engineering evaluation report identifying their building's weaknesses and ways to remedy those weaknesses.

LA Soft-Story Program

The destruction caused by the Northbridge earthquake in 1994 had a big impact on the creation of the program. The beginning of the LA soft-story retrofit program originally was started in San Francisco in 2013. This program is created to prevent loss of human lives and create better resiliency for the city in the event of a major earthquake. But in 2015 the city of Los Angeles started to roll out its own program and passed the two ordinances about Los Angeles Retrofit, according to which the following types of buildings were applied by:

  • Most of the Multistory wood-framed buildings, which have one or more sides of the ground floor open, typically for tuck-under parking. This applies to buildings constructed before about 1980.

  • Most concrete buildings constructed before about 1980.

Los Angeles retrofit ordinance 183893, with the amendments 184081, is a city law that mandates the seismic retrofit of buildings in case they can not be proven to meet specific safety standards. The ordinance mostly is intended to promote public welfare and safety by reducing the risk of injury and loss of life that may result from the effects of earthquakes on existing buildings. Have more information here.

Multi-Story Residential Buildings

Many properties, commercials, and apartments, as well as multi-story residential buildings have what is called a soft-story condition. The term is used to describe any building that has a habitable rooms or rooms above a garage, carport, or porch area that was specifically designed to transmit shear lateral forces to the story above. Failures of these types of buildings or structures with soft-story conditions can lead to loss of lives in an earthquake. Many counties in California are currently drafting ordinances to require retrofitting of all soft-story buildings.

open garage building

Residential Retrofit Program Design Guide

This residential retrofit program design guide focuses on the key elements and design characteristics of building and maintaining a successful residential retrofit program. For the purposes of this Design Guide, “residential retrofit” is loosely defined as installing measures or equipment in existing homes in order to increase the energy efficiency of these buildings. A high level of focus has been placed on existing buildings recently, and for good reason, as existing residential and commercial buildings account for approximately 40% of energy consumption in the United States. Additionally, work that addresses residential energy retrofits is inherently local, building local economies and providing local jobs. The design guide is intended to be a living document, focusing first on providing basic context and guidance, and later building additional content and linking to helpful resources as they are identified and/or developed. The information presented will mostly be common to all those interested in retrofit programs. However, successful program design and implementation will likely generate questions and issues that require a focus on the specific location and circumstances, so seeking outside expertise can help the reader work through those specific issues.