509-511 21st Ave, San Francisco, CA 94121

The two-unit residential building at 509-511 21st Avenue in the Central Richmond neighborhood is a two-story flats and duplex structure built in 1922, currently owned by Benjamin C. Owyoung.

The building has undergone several significant improvements over the years, with the most recent major work being the installation of new fiber cement siding at the rear of the building in 2015, a project that cost $5,000. Other notable improvements include a garage door replacement in 2007 ($750), a complete reroofing in 2007 ($5,000), and substantial electrical upgrades in 2003-2004, including the installation of a new electrical panel and additional circuits throughout the unit. A possible illegal basement unit was reported in 1997 but was resolved by January 1998.

The property has experienced recurring issues with the sidewalk in recent years, with multiple reports of defects including tree root damage (2024) and collapsed conditions (2023), though one similar complaint from December 2023 was resolved with no action described. There have been several incidents of sidewalk parking reported between 2019-2021, though in each case, responding officers were unable to locate the offending vehicles. The building's location and infrastructure have been actively managed, with street space permits issued in 2008 and 2015, and a sidewalk permit in 2010, suggesting ongoing attention to public space maintenance.