Tiburon, California Zoning Map

The RO-1 (Residential Open 40,000 square feet, ~158 acres) and RO-2 (Residential Open 20,000 square feet, ~402 acres) zones establish large minimum lot sizes that strongly restrict subdivision and limit density to one home per lot or larger. These designations preserve the open, hillside character of Tiburon's residential neighborhoods. Investors evaluating existing homes in these zones should note that lot splits are constrained and ADU options are the primary tool for adding units under state law.

Tiburon has designated two AHO overlay parcels: NC/AHO (Neighborhood Commercial and Affordable Housing Overlay, 6.6 acres) and RMP/AHO (Residential Multiple Planned and Affordable Housing Overlay, 2.7 acres). These overlays allow higher residential density when a project includes affordable housing units as required by the overlay. Developers pursuing these sites can potentially achieve greater unit counts than the base zone would allow, subject to affordability set-asides and design review.

Tiburon's commercial land base is extraordinarily limited: Village Commercial (VC) covers only 7 acres on the waterfront, Neighborhood Commercial (NC) covers 14 acres, and Office (O) covers 1.3 acres. This amounts to roughly 22 acres of commercial-zoned land for the entire town. The small commercial footprint reflects the community's strong preference for preserving residential character and the waterfront village aesthetic. New commercial uses typically require a use permit, and expansions of existing commercial are closely scrutinized.

The RPD zone at 389 acres governs a large portion of Tiburon's hillside residential communities and applies planned development standards rather than standard lot-by-lot zoning. Most of this land is already developed with the planned residential communities for which the RPD was created. Remaining RPD opportunities - if any - would typically require processing a planned development amendment through the town, which involves substantial discretionary review given the sensitivity of hillside and bay-view properties.

California state ADU law supersedes local restrictions in all residential zones, meaning that owners of parcels in R-1, RO-1, RO-2, R-2, R-3, RMP, and RPD zones can add ADUs subject only to state-mandated ministerial standards. In a high-value market like Tiburon, ADUs can command premium rents and meaningfully improve property cash flow. Junior ADUs attached to the primary structure are also permitted by right. The town's design review process may still apply to ADU design even where state law requires ministerial approval of the use.