Soft Story Retrofit: The Complete Guide for Property Owners
Property owners in LA and other first and second tier municipalities are often confused about the process involved in the seismic retrofit.
In areas that are more prone to seismic activity, certain types of construction are more dangerous than others.
“Soft story” buildings must be reinforced in order to preserve the building itself and the safety of the people living in it. The retrofitting process addresses the construction oversights that may have occurred when the structure was built, creating a much safer building for future residents.
Here is your complete guide to the soft story retrofit:
What is a soft story building?
A soft story building is one that is considered unstable according to modern earthquake engineering design. The soft story is a multistory building that is in many cases an apartment building or parking deck.
Many of these soft story designs were built before massive earthquakes in the 1980s and 1990s showcased their weaknesses. They experienced massive damage because of their lack of a shear wall to stabilize windows, doors and wide open spaces. The official definition of a soft story building is one that has a level that is less than 70% as rigid as the story immediately above it, or less than 80% as rigid as the level three floors up.
In an earthquake situation, the soft story building is vulnerable to collapse because of the excess flexibility in these soft floors. Lateral earthquake motion causes a disproportionate percentage of the lateral shift in the building to focus on these floors during an earthquake. The floor collapses, causing the floors above it to cave in in a phenomenon that is known as “soft story collapse.”
The soft story retrofit was first mandated in San Francisco in 2013 to address this problem. Even the Loma Prieta earthquake of 1989 in California was not enough to cause many property owners to invoke soft story solutions that would stabilize the buildings described above. As a result, other events created much more damage than they perhaps should have in subsequent earthquakes around the area.
Soft story buildings in Los Angeles
There are nearly 9000 soft story buildings in Los Angeles that are still in need of earthquake retrofits, even after the 1994 Northridge earthquake that caused many politicians to begin moving forward initiatives to mandate soft story building Los Angeles upgrades. Seismic retrofitting companies began to proliferate during this time, with many forward thinking developers moving to create buildings that would be more resistant to earthquakes in the future.
The one advantage of major earthquake activity is the data we receive about buildings that are placed under those conditions. The Northridge earthquake moved forward our technological prowess in terms of seismic force resistance, seismic modeling software, testing systems, design, structural forms and structural connections. As a result, LA soft story retrofit efforts are more successful than ever.
We now know that certain seismic retrofitting in Los Angeles will not work. One example is the so-called “soft story multifamily apartment” that was so popular before smart business and government regulation took over. These buildings looked like three-story boxes on extremely narrow lots, with the upper two floors hanging over the lower floor. The building would be supported on pipe columns, allowing for cars to be parked underneath. The ground level of these floors is soft relative to the upper floors, meaning that the upper part of the building can sway and fall into the carport.
New research has helped us conclude that no wood floors should be allowed to extend more than an additional 15% beyond the sheer wall or other lateral load resisting element of the floor directly beneath it. This would usually result in a maximum 4 foot overhang compared to the 20 to 40 foot range that could be expected in previous iterations. Architects who still looked to this design technique must refer to themselves to soft story retrofit contractors in LA to help replace the traditional pipe column design with a laterally stiff steel “moment frame.” This mitigates the problem of LADBS soft story structures by stiffening the soft ground floor.
Seismic retrofitting for soft-story buildings
Seismic retrofitting is the sum total of our positive takeaways from previous seismic activity. Retrofitting means to modify existing structures to improve their resistance to seismic activity, ground motion or soil failure in an earthquake situation.
Mandatory soft story program
The city of Los Angeles mandatory soft-story retrofit program, referred to by Ordinance 183893, is the new standard that must be applied to all existing buildings within the municipality. Specifically, the city of Los Angeles retrofit requirements apply to buildings with the following characteristics:
- Two or more stories wood frame construction wood frame construction
- Built under the building code standards enacted before January 1, 1978
- Contains ground or other similar open floor space that causes soft, weak or open wall lines
The above criteria do not apply to residential buildings with three units or less.
Soft story retrofitting process in LA – step-by-step
So how long does a soft story retrofit take? This depends on the current way in which Los Angeles building and safety ordinances apply to the structure and the talent and experience of the licensed retrofitting architect undertaking the project. Let’s take a look at the steps that all building owners must take in Los Angeles to ensure compliance with the current building standards.
First, the owner of the property must hire a duly licensed (meaning licensed from the state of California) architect or engineer to evaluate the current strength of the building. This professional will then develop plans in compliance with current ordinances. The property owner has the responsibility of notifying any current tenants of the changes to be made under HCIDLA regulations.
Second, the owner must submit to the Department of Building and Safety proof to retrofit or demolish the building. If a previous retrofit has been administered, the building owner must also submit that information as well. These plans will be checked against current regulations. LADBS will then guide the process of obtaining the retrofit permit, which includes obtaining clearances from all relevant agencies.
Retro Experts are familiar with every aspect of the retrofitting process and will help you work with LADBS requirements. Retro Experts has been in business for X years with Y projects completed alongside LADBS standards. Availing yourself of the structural engineering, financing, construction, cost recovery, tenant habitability plan and consulting expertise of Retro Experts will save you time and money.
Story Story retrofit cost
How much does it cost a seismically retrofit a house?
Retrofitting costs vary widely depending upon the level of hazard and the necessary work to upgrade a property to current standards. The total cost can best be predicted through a consultation with a licensed architect or civil/structural engineer. This professional should specialize in seismic retrofitting and planning for seismic retrofits. Property owners are also advised to obtain bids from licensed contractors.
The general range that a property owner can expect to pay for seismic retrofitting is between $60,000 and $130,000 depending on the size of the building. These numbers come from the Community Action Plan for Seismic Safety (CAPSS). However, extenuating circumstances may cause costs to rise in certain situations.
Retro Experts can provide property owners with a full suite of retrofitting services, including in-house steel manufacturing and access to experts in property management, code compliance, structural engineering, construction and financing.
Soft story financing is available for property owners who are in need of assistance to fully comply with municipal standards. Because retrofitting is a time sensitive process that must be completed on a certain schedule, you should not let monetary concerns hold up the process. Attempting to wait for cash funds without financing may stunt the entire retrofitting effort, causing the you to lose even more time and money in the long run.