SB9 in San Mateo

San Mateo earns a C grade for SB9 implementation, indicating moderate progress with room for improvement. For investors, this means the city is beginning to allow more SB9 projects but still shows limited overall uptake. The environment is cautiously optimistic but not yet robust enough to rely on for consistent SB9-driven development.

San Mateo’s SB9 ordinance follows a standard Peninsula city model with no unusual restrictions or incentives. It complies with state SB9 requirements, allowing lot splits and duplexes on qualifying parcels. Setbacks, parking, and design standards align with typical local zoning rules, without additional barriers or facilitation. The city does not impose minimum lot sizes beyond state law, nor does it add discretionary review beyond ministerial approval.

San Mateo’s SB9 activity started slowly in 2022 with a single application and approval. The absence of applications in 2023 suggests initial caution or lack of awareness among property owners and developers. However, activity picked up in 2024 and 2025, with three applications and two approvals over those two years. This pattern indicates growing familiarity and comfort with SB9 processes. The approval rate of 75 percent shows the city is generally cooperative with SB9 projects once submitted. No charter city litigation has affected San Mateo, so the trajectory reflects organic growth rather than legal pressure. Uptake remains low relative to the city’s size, but the trend is clearly upward.

There is no record of any HCD enforcement action against San Mateo related to SB9 compliance. The city remains in good standing with state housing authorities.

San Mateo is a wait-and-see market for SB9 investment. The city is compliant and approvals are occurring, but overall volume remains low. Investors should monitor whether the upward trajectory continues and if the city streamlines processes further. For now, SB9 projects can succeed but require patience and careful navigation of local standards. This is not a high-velocity market, but it is improving steadily and could become more attractive over time. For the grading methodology, see the SB9 City Guide post.