Katherine Roberts says a six inch shortfall in ceiling height has trapped two long running in law apartments in her Cole Valley Edwardian in a kind of housing purgatory, and fixing it could run as high as $1 million. For decades she has rented the two ground floor studios to students and young professionals, but San Francisco’s stricter ceiling rules mean the units are officially “unwarranted” and cannot be legalized without heavy structural work. Her situation puts a sharp point on a familiar contradiction in San Francisco housing policy, where officials talk up adding units while narrow technical requirements can make modest retrofits financially impossible.
Roberts purchased the house in 2003 for about $1.17 million and still rents the two studios, roughly 650 and 450 square feet, for about $2,500 a month each. She has done so while operating under unresolved Department of Building Inspection violations that date back to 2004 and 2008, plus a lien that briefly appeared in 2013. The paper trail and her years of back and forth with inspectors are detailed in reporting that tracks Roberts’ two decade effort to legalize the units, as reported by the San Francisco Chronicle.
Why six inches changes everything
Under San Francisco’s Building Code, habitable rooms must have ceilings of at least 7 feet 6 inches, which is a half foot taller than the 7 foot minimum in some state rules. That gap means a basement or split level space that would squeak by under statewide standards can still flunk locally and trigger costly fixes. The city’s room dimension provisions spell out those limits in precise terms, so plan reviewers do not have much discretion when a drawing comes in short. As set out in the San Francisco Building Code, ceilings under 7 feet 6 inches are not normally accepted as is for legalized dwelling units.
What the city requires before a permit
Owners who want to legalize an accessory dwelling unit have to start with a feasibility check, then bring in a licensed design professional and pull together floor plans, leases and other documents for a multi agency review. The city spells out specific requirements for glazing, egress and ceiling height, and warns that some projects will have to rely on waivers or alternate means to satisfy the intent of the code. Those early screening steps and the basic ceiling rules are laid out in the city’s ADU guidance. According to SF.gov, these initial tasks must be completed before any construction can begin.
Structural fixes can blow the budget
Two architects Roberts consulted estimated that digging down and underpinning the foundation, adding waterproofing, providing new egress and likely tackling related seismic work would cost from about $750,000 up to $1 million. For an owner collecting current rents, that sort of price tag wipes out any plausible return and tends to halt the project before it starts. ADU architect Steve Edrington has described underpinning as “an extensive and expensive process” that often sets off a chain reaction of additional requirements, which helps explain why some homeowners drop legalization once they see the full scope. Those feasibility and retrofit numbers are drawn from reporting by the San Francisco Chronicle, which also notes that feasibility studies often cost around $3,000, with another $20,000–$30,000 for architectural plans before any construction starts.
State amnesty does not erase building code limits
California’s AB 2533 sets up a retroactive permitting track for many unpermitted ADUs built before 2020 and offers owners some protection from specific fines and fees. The law, however, is aimed at violations of the Health and Safety Code rather than granular Building Code issues like ceiling height. The bill was chaptered in 2024 and amended Government Code section 66332 to broaden eligibility, and the legislative text and summaries spell out what the law does and does not cover. For the statutory language and bill history, see the chaptered bill text and Government Code section 66332. (LegiScan; Justia.)
What this means for small scale housing
Roberts says she would rather see a genuine amnesty that grandfathered long standing units than a system that forces prohibitively expensive retrofits and effectively removes relatively affordable rentals from the market, a sentiment echoed by many owners in older neighborhoods. Her case highlights a basic policy split in the city’s housing story. On one side, developers put up new and expensive apartments. On the other, some of the city’s existing and well used smaller units remain legally off limits because of technical gaps between codes. For homeowners thinking about legalization, the practical first move is still the city’s feasibility process and, when it applies, seeking relief through the state’s AB 2533 program.
