SB 1211 for Duplex in Costa Mesa
Costa Mesa's SB 1211 math for duplex owners: 2 detached ADUs (the §66323 cap), plus 1 interior conversions. Total: 3 new homes. At Costa Mesa's median rent of $2,700/mo, that's ~$97K in additional gross annual rent.
The Costa Mesa scenario
Run it as a sequence: stabilize existing 2 units → permit 2 detached ADUs ministerially under §66314 → convert 1 interior space into rentable units → re-tenant at Costa Mesa medians.
Costa Mesa watch: OC infill market.
Small multifamily (2–4 unit) design playbook
Small multifamily lots are usually constrained on width before they're constrained on count. With a 2-unit existing footprint, the binding constraint becomes side-yard setbacks (4 ft min) and the 18-ft height limit. Two-story stacked-flat ADUs over surface parking are the highest-yield typology.
Pro-forma snapshot
| Existing units | 2 |
| Detached ADUs (SB 1211) | 2 |
| Interior conversions | 1 |
| Total new units | 3 |
| Median 1BR rent in Costa Mesa | $2,700/mo |
| Est. additional gross rent | $97K/yr |
| Estimated total project cost | ~$806K |
| Year-1 NOI estimate | ~$73K |
| Stabilized cap rate at cost | 9.1% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in Costa Mesa | 75-120 days |
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