SB 1211 for Fourplex / 4-unit in Napa
Own a fourplex / 4-unit in Napa? SB 1211 lets you stack 5 new units on top of your existing 4: 4 detached + 1 interior. At Napa's median rent of $2,400/mo, that's ~$144K in additional gross annual rent.
The Napa scenario
Picture the typical case: a 4-unit fourplex / 4-unit on a Napa block built between 1955 and 1975, with surface parking that hasn't been fully utilized in years. SB 1211 turns that parking into 4 detached units plus 1 interior conversion — 5 new doors that didn't exist before 2024.
Local tip for Napa: Ag preserve does not restrict ADUs in residential zones.
Small multifamily (2–4 unit) design playbook
Small multifamily lots are usually constrained on width before they're constrained on count. With a 4-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 | 4 |
| Detached ADUs (SB 1211) | 4 |
| Interior conversions | 1 |
| Total new units | 5 |
| Median 1BR rent in Napa | $2,400/mo |
| Est. additional gross rent | $144K/yr |
| Estimated total project cost | ~$1,344K |
| Year-1 NOI estimate | ~$108K |
| Stabilized cap rate at cost | 8.0% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in Napa | 75-120 days |
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