Seismic Retrofit

Seismic Retrofitting is the modification of existing buildings to make them more resistant to seismic activity and earthquakes

 

The Long Beach earthquake of 1933 alerted Californians of the need to engineer earthquake safe buildings and reinforce existing buildings with seismic retrofitting.

Homes built before 1933 in Los Angeles were built without being bolted to their foundations. Houses built between 1933 and 1940 may or may not have bolting as this is when bolting was starting to become common building practice.

One of the reasons the San Fransico Earthquake of 1906 was so devastating was because it left an estimated 300,000 bay area residents homeless after the quake. With no place to live, and no access to food and water, these earthquake victims had to rely on temporary housing shelters and emergency aid.

San Fransico House destroyed by 1906 earthquake

San Fransico House destroyed by 1906 earthquake

Homes with seismic retrofitting are much more likely to stay on their foundation during a major earthquake and therefore remain habitable after an earthquake. Houses that are shaken off their foundations from the lateral and vertical forces during an earthquake may collapse, or be a safety hazard to enter because they are no longer structurally sound.

Lateral and Vertical Earthquake forces

Lateral and Vertical Earthquake forces

Seismic retrofitting costs approx $5,000 to $10,000.

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Cripple Wall or 'Raised Foundation'

Cripple Wall or ‘Raised Foundation’

Foundation Bolts

foundation-anchor-bolts

attaches the mudsill of the houses framing to the concrete foundation. The strength of the fastening is affected by the type of washer, the size and the type of bolt, as well as the location and spacing of the bolt on the mudsill.

Shear Wall

Shear-walls-in-crawlspace

Plywood paneling that prevents cripple walls from collapsing.

Foundation Anchors

foundation-seismic-anchors

Homes with low-clearance where traditional bolting may not be possible can be bolted with a special hardware known as foundation anchors.

 

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