A guide to seismic retrofitting in San Francisco — what it is, which homes benefit, what the engineer does, what construction is involved, permits, disruption and cost drivers.
A seismic retrofit connects a house properly to its foundation, braces weak walls and ties the framing together so the structure resists earthquake forces as one unit. A structural engineer determines what is required and issues stamped drawings; the contractor builds it, coordinates the permit and the inspections, and makes good afterwards.
A house that is not properly tied together tends to fail where its parts meet. The frame slides off the foundation. The short cripple walls in the crawl space rack over. The ground floor of a building with a wide garage opening deflects while the floors above keep moving.
A retrofit addresses those connections so the load path from roof to foundation is continuous. It is targeted work, not general strengthening.
Anchor bolts or plates tying the mudsill to the concrete so the framing cannot slide off it.
Structural sheathing on the short walls between foundation and first floor.
Steel hardware resisting the uplift that tries to lift a braced wall off its footing.
Engineered panels carrying lateral load. Where these land in finished rooms, the room is opened and made good.
Steel frames used where a wide opening — typically a garage — has to stay open while carrying lateral load.
Rot, previous alterations and undersized members corrected before new structure is attached to them.
Structural work of this kind is permitted and inspected. The work holds at defined points so an inspector can see the connections and hardware before anything is covered. Leafair coordinates that rather than covering work that has not been signed off.
A straightforward bolting and bracing job in an accessible crawl space is measured in weeks. A soft-story solution involving steel and finished rooms being opened runs considerably longer. The engineering and permit stages come first and are their own timeline.
See seismic retrofitting with Leafair for how the construction is run, and foundations and structural work for foundation replacement, underpinning and retaining walls.
Structural work that improves how a building resists earthquake forces — connecting the house to its foundation, bracing weak walls, and tying the framing together so the structure moves as one unit rather than coming apart at the joints.
Older San Francisco homes built before modern seismic requirements, houses with unbraced cripple walls in the crawl space, and buildings with living space over a wide garage opening are the categories most often identified. Only an engineer can tell you about your specific building.
The engineer assesses the building, determines what is required and produces stamped drawings and calculations. The contractor builds exactly that, coordinates the permit and the inspections, and makes good afterwards. Leafair does the second, not the first.
Much of the work is in the crawl space, garage or at the ground floor perimeter, so many households stay in the property. Where shear walls land in finished rooms, those areas are opened, worked and made good.
Access to the work areas, how much finished space has to be opened and restored, what is found in the existing framing once exposed, and whether the engineered solution is prescriptive bracing or something more involved such as a steel moment frame.
Leafair will walk the site, talk through what is realistic, and give you a written estimate priced line by line. Estimates are free.
