A vacant lot in Berkeley's Northbrae neighborhood is now the subject of preliminary plans for a small duplex infill project, with a two-story residence and an attached two-level basement accessory dwelling unit proposed for the steep parcel at 824-826 Indian Rock Avenue. The property sits between Marin Avenue and San Luis Road, within walking distance of both Grotto Rock Park and Cragmont Elementary School, and would bring two units to the vacant lot.
The preliminary application was filed by a Cupertino-based family trust, according to San Francisco YIMBY, whose reporter Andrew Nelson detailed the filing. The project as described would include an on-site garage, though bedroom counts and other architectural details have not yet been published. The site last sold for just over half a million dollars in April 2026, and Zillow listing records show the parcel closed for $565,000 on April 7 after being listed in February with panoramic San Francisco Bay views, per Zillow listing records.
A Hillside Lot With Strict Building Limits
The vacant lot is subject to the city's Hillside Overlay, a designation that comes with its own set of construction rules. Under Berkeley Municipal Code Chapter 23.306, accessory dwelling units built inside the Hillside Overlay face a 20-foot height limit and maximum unit sizes of 850 to 1,000 square feet, compared with 25 feet and 1,200 square feet allowed elsewhere in the city, according to the ADU Zoning Hub. The filed design pairs a modestly sized two-story residence with a basement-level ADU.
The City of Berkeley's Evacuation Time Estimate Study found that maximum permissible ADU development within the Hillside Overlay zone could increase emergency wildfire evacuation times by up to 102 percent. That evacuation concern has been part of discussions about Berkeley's Middle Housing Ordinance, which allows multifamily buildings of up to eight units in residential neighborhoods, as reported by SFGATE.
State Law Still Opens A Path For Small-Scale Density
With the hills excluded from Berkeley's broader middle-housing expansion, projects like the Indian Rock Avenue duplex can also rely on older state tools. California's Senate Bill 9, enacted in 2022, permits property owners in single-family zones statewide to ministerially split lots or build up to two housing units per parcel, a mechanism Hoodline also detailed in its report on a San Pablo Park lot split. Once an application is filed, the clock starts ticking: under state housing law, including Senate Bill 543 effective January 1, 2026, local planning departments must act on complete ADU permit applications within a 60-day ministerial review window or the application is deemed approved, per the ADU Zoning Hub.
Newly constructed accessory dwelling units on the site will also have to meet Berkeley's Electrification Reach Code, which requires all newly built accessory dwelling units and residential additions to be 100 percent electric, banning natural gas hookups in favor of electric heat pumps and induction appliances, the ADU Zoning Hub notes. Construction costs for ADUs in Berkeley in 2026 average between $250,000 and $500,000, or roughly $400 to $700 per square foot, with the city also charging a $250 zoning plan check fee and a $500 neighbor noticing fee for submittals, according to the same source.
A Neighborhood Defined By Rock Outcrops And Steep Streets
Grotto Rock Park is a volcanic rhyolite rock park in Berkeley, prized locally for its panoramic views and urban bouldering, according to East Bay Magazine. The surrounding corridor also includes single-family homes on Indian Rock Avenue.
Whether the current design ultimately fits within the Hillside Overlay's 20-foot height ceiling, and how neighbors along the narrow, steep street will respond to new construction near the rock park, remain open questions as the preliminary application moves forward. No estimated construction cost or timeline for the project has been shared publicly to date.
