Soft story retrofitting is the process of reinforcing a building's quake-vulnerable floor/floors to make the entire structure more resistant to the shear forces present during an earthquake.
Soft-story buildings are multi-story buildings characterized by a ground floor or lower floors that are significantly "less stiff" (thus they're called "soft stories") than the upper floors they support. In a soft-story building, the lower levels do not have enough shear walls or other elements (e.g. steel frames) to help the structure withstand lateral (side-to-side) earthquake movements.
Examples of soft stories:
In Los Angeles, according to a Caltech survey, there are more than 19,000 soft-story buildings in need of soft-story retrofitting. If you own an old, multi-story residential or commercial building, you might need a soft-story retrofit.
Request a soft-story inspection.
Soft stories are an earthquake hazard and they could lead to a very substantial loss of investment, profit and lives. If the sideways movement during an earthquake is particularly strong, the weak supports in the soft stories could give way. This, in turn, would cause the upper floors to fall onto the lower floors, thereby crushing whatever or whoever is on those lower levels. This type of structural failure is known as "pancake collapse."
The risk of soft-story-induced pancake collapse during an earthquake became glaringly obvious when the 6.7-magnitude earthquake struck Northridge in 1994. At that time, more than 20,000 soft-story buildings were gravely damaged or went down like a house of cards and 33 persons lost their lives.
If your building has soft stories, get it retrofitted as soon as possible. The following are some of the reasons why prompt action is advised:
Once soft-story retrofit becomes compulsory (as it already is in some parts of California), expect soft-story retrofitting prices to become a lot higher than they are now.
Earthquake scientists predict that there is a 99.9% chance of a 7-magnitude quake hitting Los Angeles in the next decade or so. If this earthquake strikes before you've had a chance to retrofit your residential or commercial building, many lives could be lost and massive property damage could result. Since Los Angeles codes state that building owners are liable for any loss of life and damage to property within their buildings, you could end up facing enormous liability losses.
One may argue, of course, that insurance exists to protect a building owner from liability in case his or her building collapses during an earthquake and injures people and damages tenants' property. Even so, doesn't it make sense to retrofit and thus prevent major losses instead of simply waiting for the worst and then relying on insurance to make things right?
In the midst of post-earthquake chaos, with building owners clamoring for insurance coverage right after the quake, you'd be very glad you decided to retrofit.
If you retrofit your soft-story building, the lower your earthquake insurance premiums are likely to be. Your earthquake insurance underwriter will probably decide you have low potential exposure (i.e. that you're a low-risk client) because your building has been reinforced to protect it from earthquake damage.
A loan taken out on a soft-story building is likely to have a higher interest rate than a loan taken out on a properly reinforced building. The logic is simple. Structurally sound buildings make good collateral, while structurally weak ones pose a great risk to the lender. What if an earthquake demolishes or seriously damages the building before the loan is paid off? The lender will be left with a worthless (or nearly worthless) piece of property as security.
Building owners are required by law to disclose their buildings' seismic vulnerability to prospective tenants — so if you don't retrofit, you could scare tenants away. On the other hand, if you retrofit, the fact that your building has been retrofitted may be used as an additional marketing/selling point. You could also command higher rent prices.
In the end, it's all about ROI. According to Caltech's survey, the benefit-to-cost ratio of a soft story retrofit could be as much as 7:1 — and since there's a 99% probability of a big quake happening in the next 10 years — you should really get your soft stories retrofitted NOW.
To the Sinai Construction Crew,
Thank you very much for all the hard work you have done these past several weeks to make our home's foundation & den ceiling more structurally safe & sound! We truly appreciate your efforts in doing a thorough job as well as accommodating the extra things we've requested along the way.
The Valdez Family, Los Angeles