Commission approves ADU and modest expansion at 49120 Third Avenue, 4–2, with condition severing internal living‑space connection

The San Francisco Planning Commission on March 31 approved a conditional use authorization to alter and expand a single‑family dwelling at 49120 Third Avenue, allowing an increase in the main unit to about 2,342 square feet and creation of a one‑bedroom accessory dwelling unit (ADU) of approximately 644 square feet.

Planning staff presented the project as code‑compliant and compatible with the surrounding RM1 neighborhood. Staff noted the ADU would occupy an unfinished basement area with access via a tunnel from the street; the project adds two Class 1 bicycle parking spaces, a private deck and shared rear yard. Architect David Marlotte said the modest expansion aims to keep the current family in place while adding rental income and improving safety and energy performance.

Commissioners asked detailed questions about ADU independent access and about an internal door and open stair that could allow the two units to function as a single home. To address that concern, staff recommended a condition of approval that the internal living‑space connection between the units be eliminated — converting the direct internal door to a solid wall — to preserve unit separation and comply with ADU controls.

The commission voted on the motion to approve the conditional use authorization with the staff condition. Commissioner Diamond voted aye; Commissioner Fung voted aye; Commissioner Imperial voted no; Commissioner Coppell voted aye; Commissioner Moore voted no; Commission President Tanner voted aye. The motion carried 4–2.

Committee discussion referenced the interim controls that prompted conditional review of modest expansions, and several commissioners observed that the interim policy may have different implications for new construction versus alterations to older buildings. Staff told the commission there were few other similar applications in the pipeline and that the interim controls typically last 18 months.

The approval included the condition read into the record by staff to eliminate the internal living‑space connection; commissioners noted the condition can be refined in permit language before issuance. No appeal or implementation date was announced at the hearing.