SB 1211 for 10-unit apartment in San Mateo
San Mateo's SB 1211 math for 10-unit apartment owners: 8 detached ADUs (the §66323 cap), plus 2 interior conversions. Total: 10 new homes. At San Mateo's median rent of $3,000/mo, that's ~$360K in additional gross annual rent.
The San Mateo scenario
Run it as a sequence: stabilize existing 10 units → permit 8 detached ADUs ministerially under §66314 → convert 2 interior spaces into rentable units → re-tenant at San Mateo medians.
Local tip for San Mateo: Peninsula tech rents; very strong upside.
Large multifamily (10+ unit) design playbook
A 10-unit complex is capped at 8 detached ADUs by statute, so the play shifts toward interior conversions: max(1, ⌊units × 25%⌋) = 2 additional units carved from common rooms, oversized lobbies, basement storage, or laundry rooms.
Pro-forma snapshot
| Existing units | 10 |
| Detached ADUs (SB 1211) | 8 |
| Interior conversions | 2 |
| Total new units | 10 |
| Median 1BR rent in San Mateo | $3,000/mo |
| Est. additional gross rent | $360K/yr |
| Estimated total project cost | ~$2,016K |
| Year-1 NOI estimate | ~$270K |
| Stabilized cap rate at cost | 13.4% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in San Mateo | 75-130 days |
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