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DBI adopts AB 111 to tighten geotechnical guidance for tall‑building foundations
Summary
The Building Inspection Commission unanimously approved Administrative Bulletin AB 111, a set of geotechnical guidelines aimed at improving foundation design and post‑construction settlement monitoring for tall buildings (defined in the study as over 240 feet). Staff said the bulletin closes a gap in guidance and will be updated regularly.
The San Francisco Building Inspection Commission voted unanimously on June 17 to approve Administrative Bulletin AB 111, "Guidelines for preparation of geotechnical and earthquake ground motion reports for foundation design and construction of tall buildings." The bulletin is intended to provide a consistent set of expectations for geotechnical investigations and foundation design for buildings taller than 240 feet, and to require early engagement of a geotechnical member of the engineering design review team (EDRT).
DBI senior staff presented the bulletin as the outcome of a multi‑year, multi‑stakeholder review process tied to an Applied Technology Council tall‑building study dating to 2017. Gary Ho summarized the study background and the need for city‑specific guidance for the Bay Area’s unique soils and seismic setting. "The purpose of this study is examining the appropriate performance of city tall buildings and to come up with recommendations to adjust building code requirements," staff said during the presentation.
Shao (Shao Watani), who led technical drafting, said AB 111 sets out recommended content for geotechnical reports and work plans — including number, depth and spacing of borings, cone penetration tests when used, piezometer locations to monitor groundwater, and methods for ground‑motion and foundation design development. The document also requires mandatory post‑construction settlement monitoring; Richard Tan of DBI said applicants for tall‑building permits will need to submit a 10‑year settlement monitoring program before final completion is issued.
Commissioners asked whether stakeholders and developers had participated in drafting; staff said the bulletin was peer reviewed by local geotechnical engineers and a special review panel and was intended as a consensus document from major local technical practices. Staff also explained AB 111 is written to be updated as practice and code evolve.
Commissioner Kevin Clinch moved to approve the bulletin when the commission took action; Vice President Moss seconded. The commission carried the motion by unanimous roll call vote.
DBI said it will post AB 111 to its website, provide in‑house training for tall‑building plan reviewers, and notify professional groups including the Structural Engineer Association of Northern California, the American Institute of Architects and the Building Owners and Managers Association.
Implementation steps outlined by DBI include posting the bulletin, outreach to professional organizations, training for reviewers, and continuing periodic updates as codes and technical practice evolve. The commission’s approval directs DBI to proceed with publication and implementation.
