Top image: Colma from the air. Photo: Dicklyon / CC BY-SA 4.0 via Wikimedia Commons
For years, many inclusionary housing rules on the Peninsula came with a way out. A developer could pay a fee, build the affordable units somewhere else, or aim them at moderate incomes. San Mateo County has now closed those options in the three areas it recently upzoned for dense housing, a test of whether land-use policy can produce deeply affordable units on the same sites as market-rate ones.
What changed
On Oct. 6, the San Mateo County Board of Supervisors amended its inclusionary housing ordinance for three new zoning districts (R3-MD, PC-HD, and TS-MU) in unincorporated Colma, Broadmoor, and the Harbor Industrial Area near Belmont, according to the county staff report and the San Mateo Daily Journal. Projects in those districts must make at least 20% of units affordable at low, very-low, and extremely-low income levels, and those units must be built on site.
The Daily Journal reported that the previous ordinance let affordable units in some projects go to moderate-income households. It also allowed alternatives to building them on site, such as paying fees or providing the units elsewhere. The amendments remove the moderate-income option and all of those alternatives in the new districts.
Where the density goes
The county created the districts earlier this year as part of a Housing Element rezoning program. According to the Daily Journal, the largest upzoning is in unincorporated Colma, on parcels along Hillsdale Boulevard near the BART station and Reiner Street. In Broadmoor, a small area near Edgeworth and Sullivan avenues along 87th Street was upzoned. In the Harbor Industrial Area, parcels between Elmer Street and Old County Road were included.
“What we’re doing today is amazing,” Supervisor David Canepa said of the Colma upzoning, according to the Daily Journal. “I always looked at unincorporated Colma as what could potentially be the Redwood City of the north.”
The numbers behind it
Under its state-mandated Regional Housing Needs Allocation, the county must plan for 2,833 units across income levels by 2031, the Daily Journal reported: 1,121 at market rate, 433 for moderate-income households, 468 for low-income households, and 811 for very-low-income households. The very-low and low-income categories, nearly half the total, are the hardest to finance, and they are the ones the new rule targets.
The long view
The amendments are a bet on mixed-income density near transit. The goal of a strict on-site rule is to keep affordable homes in the same buildings, near the same transit, as market-rate ones. The open question with any deep-affordability mandate is whether projects can still pencil out without subsidy. The county has chosen where to run that experiment: a BART-adjacent corridor in Colma and two smaller districts. If developers apply and build, the Peninsula gets a working model of integrated, transit-oriented housing. If applications stall, the debate will return to subsidies. In either case, the results should be clear within this housing cycle, which ends in 2031.
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