336-340 12th Ave, San Francisco, CA 94118

The property at 336-340 12th Avenue is a 2-unit, 2-story multi-family residential building constructed in 1914, currently owned by Calvin Chun Mau Lam. The building has undergone several significant modifications and improvements over the years, with the most recent being a completed rear yard stair installation to the second floor in June 2023, costing $6,000. Notable safety improvements include the 2009 installation of fire sprinklers in the rear building ($3,500), and the building underwent soundproofing enhancements in 2015 with the addition of resilient channels and new sheetrock ($2,800). The property has a concerning pattern of unauthorized modifications, particularly regarding a disputed roof deck installation, with multiple complaints filed between 2020 and 2024 about work being conducted without proper permits or inspections.

The building's history includes one major compliance issue from 2000-2004 regarding an unauthorized conversion of ground floor spaces into living areas, though this violation was eventually abated. The property has experienced periodic maintenance issues typical of older buildings, including multiple sewage backup incidents (recorded in 2010 and 2021), as well as exterior maintenance concerns such as a collapsed sidewalk (2012) and various reports of loose garbage (2015, 2020). Historical records indicate attempts to convert the garage space into a childcare center and the addition of exterior stairs, though it's unclear if these projects were fully realized. The most recent planning records show ongoing interest in expanding the building envelope, with previous proposals for significant additions including a new two-story-over-garage structure with roof deck, though it's important to note that such proposals were only informational and not confirmed as executed.

The building also retains some historical commercial use, having housed "Dong Dong Day Care" in 2012, though this operation appears to have been addressed and resolved. The property has undergone various modifications and improvements, including interior changes (2009) such as converting living spaces between study rooms and play areas, window modifications, and utility updates. An extension of fire safety features in 2009 and electrical improvements in 2009 demonstrate some level of maintenance attention to safety systems. However, the recurring pattern of unpermitted modifications, particularly regarding the roof deck, raises ongoing concerns about adherence to building codes and proper permitting procedures.