A soft-story building has a ground floor that is much weaker sideways than the floors above it. The classic example is a wood-frame apartment building with parking tucked under the units, where the ground level is mostly open on one or more sides. In a strong earthquake that open level can lean and collapse, with the floors above coming down onto it.
This checklist is for owners who have received a retrofit notice, or who own a building that looks like it fits the description. We are a licensed builder based in Long Beach and work on seismic retrofits across Los Angeles and Ventura Counties.
What makes a building soft-story
Check your building against these features:
- Wood-frame construction, two or more stories.
- A ground floor with large openings: tuck-under parking, garage doors, a storefront or a wide lobby that leaves few solid walls on that level.
- Older building code. The Los Angeles ordinance targets buildings built under codes in effect before January 1, 1978.
The weakness comes from the difference between floors. The upper floors have many walls that brace them, and the ground floor does not, so the movement concentrates at the bottom.
City ordinances and notices
The City of Los Angeles adopted a mandatory retrofit program for these buildings through Ordinance 183893, later amended. LADBS identifies buildings that fit its criteria, lists them on its website and sends owners an order to comply. The program covers wood-frame buildings of two or more stories, built under code standards from before January 1, 1978, with ground-floor parking or similar open space. LADBS states that residential buildings with three or fewer units are outside its scope.
Under the program, the owner hires a California-licensed engineer or architect to prepare the structural analysis and plans. Those go to LADBS for plan check, and a permit is issued once they show compliance. Deadlines run from the date of the order, so read yours carefully and check the current LADBS soft-story page for any changes before you plan around a date.
Other cities have their own programs and rules. Long Beach, Santa Monica, West Hollywood, Culver City and others have adopted or studied soft-story programs of their own, with different scopes and timelines. Your notice names the city and the code section that applies.
Steel frames, plywood and foundations: typical fixes
The engineer chooses the fix based on the building's layout and how it will be used. The common approaches are:
- Steel moment frames. Placed at the parking openings, a steel frame resists sideways force while leaving the opening clear for cars. These need new footings, which often means cutting and repouring sections of the slab.
- Plywood shear walls. Where a solid wall can be added or an existing one strengthened, plywood nailed to the studs in a set pattern, with hold-downs at the ends, adds sideways strength at lower cost.
- Cantilevered columns. Steel columns set into deep footings can work in some layouts where a frame does not fit.
- Foundation work. The new frames and walls have to deliver their force into the ground, so the plans often include new or enlarged footings and grade beams.
- Connections. Straps, ties and anchors connect the new elements to the floor framing above.
Each building usually ends up with a combination of these. The engineer balances strength, cost and how much of the parking or storefront has to change.
Tenants, access and schedule
Soft-story work happens mostly at ground level, in parking areas and storage rooms, so tenants can usually stay in their units. Plan for these items early:
- Notices. In the City of Los Angeles, tenant notification rules for the work are set by the housing department (LAHD, formerly HCIDLA). Follow its current requirements for written notice before work starts.
- Parking. Steel frames and footings take parking spaces out of use for part of the job. A phased schedule keeps some spaces open.
- Utilities. Gas, water and electrical lines often run through the ground floor. The plans should show which need to move.
- Noise and dust. Concrete cutting and drilling are loud. Working hours follow the city's rules.
How a retrofit is quoted
What moves the cost of a soft-story retrofit is the building itself: how many lines of open wall need strengthening, whether the fix is steel or plywood, how much foundation work the frames need, and what has to be removed and restored around them, such as stucco, utilities and paving.
We quote from the engineer's plans. The written quote lists each frame or wall line, the foundation work for it, the utility relocations and the restoration work separately, along with the permit and inspection items. If you do not have plans yet, we can begin with a feasibility visit and work with your engineer as the design develops. The full range of retrofit work sits under structural work, and owners of commercial buildings can read about our commercial construction service.