Earthquake Hazard Reduction
The City of Richmond Planning & Building Services Department is preparing an inventory of potential soft-story buildings in the City. A soft-story building is a multi-story building with one or more floors that are “soft” due to structural design. These floors can be especially dangerous in earthquakes because they can not cope with the lateral forces caused by the swaying of the building during an earthquake. As a result, the soft story may fail, causing what is known as a soft-story collapse. Soft-story buildings are characterized by having a story that has a lot of open space. Parking garages, for example, are often soft stories, as are large retail spaces or floors with a lot of windows in the walls. While the unobstructed space of the soft story might be aesthetically or commercially desirable, it also means that there are fewer opportunities to install shear walls, specialized walls which are designed to distribute lateral forces so that a building can cope with the swaying characteristic of an earthquake. If a building has a floor that is 70% less stiff than the floor above it, it is considered a soft-story building.
The purpose of the inventory being developed is to identify potential soft-story buildings and to alert the property owners and tenants of the potential risk of damage and/or loss of life in an earthquake, in addition to assisting owners of soft-story buildings in locating funding to retrofit the building. Furthermore, it is the goal of the inventory to promote public safety by identifying those buildings in the city which exhibit structural deficiencies, and by accurately determining the severity and extent of those deficiencies in relation to their potential for causing loss of life or injury.
Resources for Earthquake Hazard Reduction
What is Standard Plan Set A?
This plan set is a standard template for strengthening homes to better withstand earthquake shaking. When approved by the local building official, the plan set may be used to strengthen older homes without the need for an engineer to develop costly site-specific plans and design calculations. This plan set provides a low-cost method to help improve an older home’s chances of surviving an earthquake.
Who can use this plan set?
If your home meets all of the following criteria, your house qualifies to use this plan set. If your home does not meet one of these criteria, you should contact an engineer.
- One or two family residential structure
- Two stories or less
- Wood-framed construction
- Has a continuous perimeter foundation (ignoring the immediate areas surrounding the fireplace and porches)
- All of the cripple walls are less than four feet in height (see top left picture for an example of a cripple wall)
- If home has brick or stone veneer along the exterior walls (excluding the chimney), it is less than four feet in height above the foundation
- Roofing is a material other than clay tile
What does the plan set say needs to be done to my house?
The three main components of this plan set are demonstrated in the pictures at the top of the page in ABAG link page. They include:
- Bolting the cripple wall mudsill to the foundation
- Installing plywood brace panels to the cripple walls
- Connecting the cripple wall to the floor above
- Plan Set for Crawlspace Dwellings FEMA P-1100-2A / October 2019
- Plan Set for Living-Space-Over-Garage Dwellings FEMA P-1100-2B / October 2019
- Plan Set for Masonry Chimneys FEMA P-1100-2C / October 2019