J. David Ford Construction offers a full range of seismic retrofitting services to East Bay residents. Many homes in the Bay Area were built before Building Codes had provisions for seismic safety. Many of these homes are at risk of sustaining severe damage in the event of a strong earthquake. Depending upon the strength of the earthquake and the proximity to the epicenter, many East Bay homes risk complete structural failure. A sound seismic retrofit will prevent this from happening in the event of an earthquake.
Installation of Prescriptive Seismic Retrofits (Plan Set A)
This is simply a pre-approved plan set that can be used as a blueprint for earthquake retrofitting. It has 3 main components: Bolting the cripple wall mudsill to the foundation, installing plywood brace panels to the cripple walls and connecting the cripple wall to the floor diaphragm above.
In the City of Oakland, use of this plan set qualifies the homeowner for Oakland’s $250.00 flat fee permit program. Other East Bay cities also offer reduced or no fee permits for Plan Set A work. In the City of Berkeley, new homeowners can receive transfer tax rebate funds for Plan Set A seismic work.
In order to qualify to use the Plan Set A the house must meet the following criteria:
- One or two family residential structures
- Two stories or less
- Wood framed construction
- Continuous perimeter foundation (excluding fireplaces and porches)
- Cripple walls less than four feet in height
- Any stone or brick exterior veneer must be less than four feet above foundation
- Roof must not be clay tile
J David Ford has installed 100’s of Plan Set A retrofits. We use the Plan Set A guidelines as minimum requirements and always install extra hardware and shear panel, where appropriate, to further strengthen the building.
Engineered Seismic Retrofits
If the house does not meet Plan Set A, an earthquake retrofitting plan should be designed by an engineer. J. David Ford works with many engineers who are experienced in designing seismic retrofits. We will refer and or coordinate the design process with the engineer, who will design a plan for the retrofit.
Engineered seismic retrofits can qualify the homeowner for Oakland’s $250.00 flat fee permit program. Other East Bay cities also offer reduced or no fee permits for engineered designed seismic work. In the City of Berkeley, new homeowners can receive transfer tax rebate funds for engineered seismic work.
If a house has been built under the new Code and already has some seismic strengthening in place, J. David Ford will review and evaluate whether it would benefit from additional supplemental work. In those cases, bolts, shear panel, shear transfer ties and/or other appropriate hardware can be added to the existing work.
Soft Story Retrofits
A “Soft Story” is a condition where living space, most often a bedroom, has been built over a large opening such as a garage, patio door or large span of windows. A large span such as this provides little or no structural strength to protect the room above from lateral movement. The term “soft story” refers to this area built over a wall that is “soft”.
Soft stories can be retrofitted in different manners including an engineered designed steel frame around the opening or a “Hardy Frame” that is manufactured for this purpose. A large percentage of the failures seen in the San Francisco Marina neighborhood after the Loma Prieta earthquake were the result of soft stories.
J. David Ford Construction is an expert in the installation of soft story retrofits. We have been part of a team of inspectors, contractors and engineers working with the City of Oakland to identify soft stories in the City. To learn more about soft story retrofitting, check out the following links:
- David Bonowitz – Earthquake Risk in Residential Buildings (PDF, 4.4Meg)
- Tom Tobin – Consequences of Earthquake Damage to Soft Story Buildings (PDF, 81k)
- Joan MacQuarrie - A Hard Look at Soft Stories (PDF, 1.7Meg)
- Jeanne Perkins – Berkeley and the Bay Area Earthquake Nightmare (PDF, 800k)