One of these houses looks like yours, see what kind of seismic retrofit you need.

seismic retrofit contractor retrofits an older house

Retrofitting a Home built before 1940

Seismic retrofit contractors such as Bay Area Retrofit mostly do seismic retrofit work on homes built before 1940 that have a structural weakness called a cripple wall.  Homes built on hillsides after 1940 also have cripple walls and their retrofits must be addressed in the exact same way.  At least 95% of the damage to homes is caused by cripple wall collapse but it has been proven that seismic retrofit techniques are a proven method of preventing this kind of damage.

Without exception these older homes need to be bolted to their foundations.  These homes are found in the older neighborhoods of Bay Area cities and were built before any seismic protection regulations were part of the building code.  Even San Jose and places like Burlingame and San Mateo have their older neighborhoods where you will find homes with cripple walls that need to be strengthen with cripple wall retrofits.

If you have more than 3 steps leading into your front door you almost for sure have a cripple wall that once it collapses can create a terrible disruption in your life.  Not only will you need to clean up the mess and be displaced for who knows how long but losing a home has a terrible financial impact.  A retrofit usually costs 1-3% of a home’s value and is probably a good investment relative to the prices of Bay Area homes.

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Seismic retrofit of house without cripple walls.

Retrofitting a Home on a flat Lot built after 1940

After approximately 1940 houses were no longer built with cripple walls unless they were on a slope and a seismic retrofit contractor needs to address these homes in .  This is especially true in newer cities such as San Jose, Sunnyvale, Fremont, Burlingame,Walnut Creek, Santa Clara, and practically anywhere where house are built on flat lots.  After being retrofitted these houses do extremely well in earthquakes because the floor can be attached directly to the foundation with steel.

Cripple wall retrofits on the other hand only allow a steel connection to the cripple wall which is much weaker than the concrete.  These retrofits are usually 25% cheaper and 100% more effective than cripple wall retrofits.  If you have less than three steps leading into the front door this is the kind of retrofit you will need.

What makes these retrofits so effective is that the floor is very close to the foundation.  This allows the retrofit contractor to make a direct firm connection from the floor to the foundation with steel.  Nothing in your home is more stable than the foundation and to the extent you can attach to the house to it directly with steel the greater resistance against earthquakes your home will have.

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Cripple wall retrofit terminology and diagram

A Review of Seismic Retrofit Design and Installation Principles

The purpose of this website is to help you understand what you need, why you need it, and how to get it for the best price.  In this case knowledge is power and the more you know the better able you will be to evaluate bides from seismic retrofit contractors and engineers and if you are willing to put in the time use this information to design your own retrofit.  If you take the time to study this material and review it a few times you will be better informed about the subject than most engineers and contractors.  Instead of being at the mercy of a retrofit professional you will be able to speak to them as someone as knowledgeable if not more knowledgeable than they are.  It will take some time.  I am still learning after 21 years but have made every effort to make this information available to the general prublic. Read more

Soft story home with living area above a garage needing a seismic retrofit

Retrofitting a Housewith Living Area above the Garage

Homes with living areas above a garage are known as a soft story and they almost always need retrofit work.  A soft story is defined as a structure where the first story, in this case the garage door opening, is 75% more flexible that the story above.  Open air, such as the garage door opening is as flexible as you can get.

Seismic retrofits for soft story building are done in several ways.  Some use bolting and shear walls, some use a principle called rotation where the back and two sides are braced with plywood, and sometimes a large vertical steel beam is embedded in concrete and attached to the floor above the garage door.  All of these methods work and it is up to the retrofit contractor or structural engineer to figure out which is the best approach.

Bay Area Retrofit usually uses the steel pole method which will be discussed later on.  It is not only extremely effective but the patent pending system we use is fully serviceable after an earthquake so it can be used again and again.  Prior designs could only be used once and the mangled and bent pole would need to be removed after the earthquake at great expense.

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Typical hillside home on a foundation with serious earthquake damage hazard

Retrofitting a House Built on a steep Hillside

Home built on steep lots are very dangerous in earthquakes, in fact, they are life threatening.  The Northridge earthquake have showed that standard seismic retrofit techniques found in the California Building Code that use plywood and bolts do not work on hillside homes.

After the Northridge Earthquake it was discovered that a house that should have collapsed survived the earthquake just fine.  It turns out a brilliant architect thought earthquake damage like this might occur so he designed this house will all the components which are now part of the Los Angeles Steep Hillside Home retrofit code.  It is the only retrofit building code that once should even consider.

These retrofits are very expensive, usually costing in the tens of thousands but certainly a good investment relative to the danger.  The require large steel braces that must be welded, an analysis of the existing foundation to make sure it can take the force, and the steepness of the slope makes working on these homes very difficult.  If you are concerned with your safety, probably best to live somewhere on flat ground. Read more

Emergency carrying a stretcher after an earthquake

When the shaking starts what do you do?

The first thing you will hear in any earthquake preparedness class is “Don’t Panic!”  That is excellent advice.  However, you can be sure you will panic.  Earthquakes are very frightening.  I was at the center of a very large Northern California 7.2 earthquake in 1992 in a house that had not been retrofitted.  It felt as if King Kong had lifted up the house and was shaking it violently.  My wife and I were both knocked to the living room floor.  Standing was out of the question because the shaking was so violent.  Your Office of Emergency Services can help you with this. Read more

Headquartered

Bay Area Retrofit
427 San Pablo Ave
Albany, CA 94706
Field offices in San Jose & Hayward

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License Info

Works' Comp RWCC64393236
Contractors Lic #558462
Bond #SC6334450
Liability Ins PCA 1045011
Link to Contractor's License Board