ALL YOU NEED TO KNOW ABOUT AN ACCESSORY DWELLING UNIT (ADU)
Soft-story buildings are multi-story dwellings with one or more lower stories with significantly less rigidity relative to upper stories. An example of such buildings is an apartment complex with tuck-under parking. Soft-story buildings performed poorly during earthquakes and have collapsed in the past. Many cities in California, including Los Angeles, West Hollywood, and Santa Monica, require a Mandatory Soft-Story Retrofit. This program creates a guide for property owners, engineers and contractors to reinforce the structure and improve the performance of buildings during earthquakes.
SOFT-STROY RETROFIT PROCESS
This picture captures the results of the Northridge earthquake on soft-story buildings in 1994. In the earthquake, many wood-frame soft-story buildings caused loss of life, injury, and property damage.
Soft-story retrofit process. There are several solutions to improve the building by altering or adding structural elements. The process can take up to 16 weeks.
Retrofitted soft-story. The building is reinforced with steel moment frames and will perform congruously during an earthquake.
SOFT-STROY RETROFIT SOLUTIONS
STEEL MOMENT FRAME
The most common and cost-effective solution. Moment frames are easy and quick to install. The benefit of the moment frames is the possibility of preserving the parking spaces.
SHEAR WALL
Shear walls can be used in soft-story buildings to resist lateral load during an earthquake. It is a simple solution that will strengthen the entire building and prevent collapse during major earthquakes.
BRACING DAMPERS
Viscous dampers act similarly to shock absorbers in a car - they transform kinetic energy of the building caused by an earthquake into heat. These dampers are usually installed in the areas that experience large displacements - this is the most efficient way to capture the energy. However, due to the complexity of analysis and construction costs, this method is rarely used for residential buildings.
BASE ISOLATION
Seismic base isolation systems enhance performance of structures and minimize any interruptions of use of facility. Isolation devices reduce damaging deformations in structural/nonstructural components and minimize forces experienced by the building. However, similarly to viscous dampers, this methodology is more frequently used in infrastructure projects rather than residential properties.
SOFT-STORY RETROFIT PROGRAM
Los Angeles Department of Building and Safety has created a Mandatory Soft-Story Retrofit Program to reduce structural deficiencies by the most economical and feasible method. Ordinance 183893 and Ordinance 184081 were issued to identify Soft-Story buildings that must comply with the Mandatory Seismic Retrofit Program and define the time limits for compliance.
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Ordinance 183893
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Retrofit Program applies to buildings that:
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1. Are of wood frame and was permitted or built before January 1, 1978
2. The ground floor portion of the structure contains parking or any other similar open space.
3. The building contains four or more dwelling units.
Ordinance 183893 also applies three different priority designations as follows:
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Priority I - Buildings with 16 dwelling units or more.
Priority II - Buildings with three or more stories, but contain less than 16 units.
Priority III - All buildings not falling within Priority I or Priority II
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Ordinance 184081
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The language in ordinance 184081 identifies the Time Limits for Compliance for the Soft Story Retrofit program.
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1. Within two years, the owner should submit a structural analysis for review and approval to:
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Submit structural analysis to demonstrate existing compliance
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Submit a structural analysis to demonstrate a proposed structural alteration to meet seismic retrofit requirements
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Plans for demolition of the building
2. Within three and a half (3.5) years after service of the order, obtain all necessary permits for rehabilitation or demolition.
3. Within seven (7) years after service of the order, complete construction or demolition work under all necessary permits.
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Verification
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To verify if your building is within the scope, please refer to the Permit & Inspection Report (Property Activity Report).
To obtain the inventory list of buildings, please contact the LADBS Custodian of Records.
(213) 482-6770
LADBS.custodianofrecords@lacity.org