Earthquake (Seismic) Retrofitting

If you’re a homeowner in Alameda, Albany, Moraga, El Cerrito, Kensington, Oakland, Orinda, Piedmont, and San Leandro, CA.

Most Older Homes Should Have Basic Seismic Upgrades

Basic seismic upgrades should be installed in the basement and crawlspaces of most older homes. When bolts are absent they should be installed, or additional bolts added when they are not sufficient for current engineering standards. Plywood sheerwalls should be installed along with clips, holdowns for cripple walls taller than 4 feet, and post-beam hardware added for pier supports if they are present.

Small Piers Should Be Upgraded

Older pier supports are often small, shallow and in poor condition. Newer piers should ideally be about 2’ square, around 18” embedded into soil. Post base brackets should be installed in the concrete and new t-straps added at the post-beam connections.

Room Add-Ons Are Often Seismically Weak

This second story room addition had settled and cracked, poorly supported with small piers and beams. We installed a new welded steel support structure resting on new piers.

The New Supports are Trimmed for a Finished Look

The steel beams were wrapped in wood, and a new patio slab was installed to give this retrofit a finished appearance that blends in with the existing house.

Tall Brick Walls are Seismically Weak

These tall brick walls in the basement of this 3 story building were beginning to fail. With no practical way to replace them due to their proximity to the property line, the answer was to build a reinforced concrete retaining wall adjacent to them to act as a secondary foundation.

Shotcrete Simplified the Concrete Installation

Instead of forming the walls, we shotcreted them. This process involves blasting a very thick concrete mix at the walls, which sticks to the rebar and can then be finished with floats and trowels. The process is more expensive, but it more than makes up for the costs of forming the walls.

Beefing Up the Basement Structure

Additional retrofitting measures were installed after the shotcrete was completed, including below grade interior peirs, ,upgraded support beams and hardware, and sheerwalls.