SB 1211 for 5-unit apartment in San Mateo
San Mateo's SB 1211 math for 5-unit apartment owners: 5 detached ADUs (the §66323 cap), plus 1 interior conversions. Total: 6 new homes. At San Mateo's median rent of $3,000/mo, that's ~$216K in additional gross annual rent.
The San Mateo scenario
Run it as a sequence: stabilize existing 5 units → permit 5 detached ADUs ministerially under §66314 → convert 1 interior space into rentable units → re-tenant at San Mateo medians.
San Mateo-specific note: Peninsula tech rents; very strong upside.
Mid-size multifamily (5–8 unit) design playbook
This is SB 1211's sweet spot. A 5-unit existing building maxes out the 8-detached cap (or comes close), so design moves are about packing detached ADUs efficiently around the existing structure and converting underutilized parking.
Pro-forma snapshot
| Existing units | 5 |
| Detached ADUs (SB 1211) | 5 |
| Interior conversions | 1 |
| Total new units | 6 |
| Median 1BR rent in San Mateo | $3,000/mo |
| Est. additional gross rent | $216K/yr |
| Estimated total project cost | ~$1,478K |
| Year-1 NOI estimate | ~$162K |
| Stabilized cap rate at cost | 11.0% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in San Mateo | 75-130 days |
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