Retrofitted homes are safer to live in, easier to sell and lower home insurance costs.

If you are planning to reinforce your home against earthquakes, it is essential to understand the basic concepts of retrofitting.

Seismic retrofitting is the modification of existing structures to make them more resistant to seismic activity, ground motion or soil failure due to earthquakes.

With better understanding of seismic demand on structures and with our recent experiences with large earthquakes near urban centers, the need of seismic retrofitting is well acknowledged.

Prior to the introduction of modern seismic codes many structures were designed without adequate detailing and reinforcement for seismic protection.

Older buildings were mainly designed to withstand one type of load - a gravity load, which is an up-and-down force. However, most earthquake forces are from side to side, producing what engineers call a lateral load.

Thus, older buildings that were adequately designed to support gravity loads may collapse because of the lateral forces of an earthquake.

Current practice of seismic retrofitting is predominantly concerned with structural improvements to reduce the seismic hazard of using the structures, it is similarly essential to reduce the hazards and losses from non-structural elements.

It is also important to keep in mind that there is no such thing as an earthquake-proof structure, but undoubtedly retrofitted homes are safer to live in.

If you are planning to reinforce your home against earthquakes, it is essential to understand the basic concepts of retrofitting.

Retrofitting is a process that ties a home together. It increases the resistance to earthquake damage and the risk of injury and it significantly strengthens your home.

A safe home is one that can withstand a sideways pull and is built on firm foundations. By securely fastening the house to the foundation, and securely connecting the house components together, your chances of having an earthquake permanently affect your home become less possible.

A safe home is achieved by installing and bolting the structure to the foundation with varying styles of foundation anchors and straps.

There are four basic types of seismic retrofitting.

The most basic is known as “public safety retrofitting.”

This type of seismic retrofitting consists of reinforcing a structure in order to help prevent death and injury during an earthquake.

For structures which are not very valuable, this type of seismic retrofitting is a reasonable option, if the owner does not want to rebuild the structure altogether.

The next level of seismic retrofitting is “structure survivability,” designed to ensure that the structure will endure the earthquake, although it may need significant repairs.

The next level up is “primary structure undamaged” is a type of seismic retrofitting in which the majority of damage done to a structure as a result of an earthquake will only be cosmetic.

Finally, “structure unaffected” is the highest level of seismic retrofitting, chosen for buildings of high economic, social or cultural value.

Some of these terms are a bit misleading, as no structure can be made entirely safe.

A major concern for companies that handle seismic retrofitting is historic buildings. It is important to preserve historic buildings with seismic retrofitting, but it is also important to ensure that the integrity of the building is not compromised. This takes extensive work and cooperation with companies which specialize in restoration of historic buildings.

With all that said, people who live in earthquake prone regions should not rely on seismic retrofitting for safety, however; they should regularly review earthquake safety materials and make sure that they have an evacuation plan in place.

Serving the Southern California community Unique Home Design & Remodeling has been helping homeowners for over 26 years.

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