San Mateo County Unincorporated, California Zoning Map

Dozens of zone designations in unincorporated San Mateo County carry a /CD suffix indicating the parcel is within the California Coastal Zone and requires a Coastal Development Permit in addition to standard planning approvals. The county's Local Coastal Program (LCP) governs what the CDP process entails, and coastal zone projects face additional review for impacts on visual resources, public access, habitat, and shoreline processes. Developers evaluating coastal-zone parcels should budget for the CDP entitlement track, which runs parallel to but separate from the standard discretionary review process.

San Mateo County uses an /S suffix on its C-1 and H-1 commercial and highway-frontage base zones to specify the maximum residential density tier permitted on that parcel, with higher numbers generally corresponding to higher density. For example, C-1/S-7 allows more dwelling units per acre than C-1/S-1. This system means that two adjacent commercial-zoned parcels with different /S designations can have very different residential development capacities, so investors cannot rely on the base zone alone to determine housing yield.

The M-1 Light Industrial district at 4,611.18 acres encompasses the county's major industrial and logistics zones, concentrated in Burlingame-adjacent and Bayshore locations near San Francisco International Airport. The M-1/AO/DR/CD subvariant adds Airport Overlay and Design Review requirements for parcels within flight path zones. Industrial investors should identify whether a target site carries the /AO airport overlay, which can restrict building height and certain uses related to aviation interference or noise compatibility.

CMU-1 (16.13 acres), CMU-2 (3.65 acres), and CMU-3 (70.74 acres) are the county's mixed-use commercial designations, found in community plan areas including El Granada on the Coastside and North Fair Oaks in the mid-Peninsula. CMU-3 is the largest and accommodates the broadest range of ground-floor commercial uses with upper-floor residential potential. These districts are small relative to the county's industrial land base but represent the most active opportunities for neighborhood-scale mixed-use investment in the unincorporated areas.

Several zone designations in the county carry /GH (Geologic Hazards) or /WO (Wetland Overlay) suffixes that trigger additional environmental review. The CCR/DR/GH/CD designation, for example, combines coastal recreation base zoning with design review, geologic hazards, and coastal development requirements - a four-layer entitlement process. Parcels near coastal bluffs, unstable slopes, or tidal wetlands are candidates for these overlays, and investors should obtain a geotechnical report and consult with the county's planning and building departments early to assess feasibility before committing capital.