SB 1211 for Duplex in Napa
A 2-unit duplex in Napa qualifies for up to 3 new homes under SB 1211 — 2 detached ADUs and 1 interior conversions. At Napa's median rent of $2,400/mo, that's ~$86K in additional gross annual rent.
The Napa scenario
The scenario most Napa duplex owners face: an existing building, mature trees, and a back lot that's currently doing nothing. SB 1211's 4-ft setback and 18-ft height envelope fits 2 detached units behind that primary structure with room for fire-access in front.
Napa watch: 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 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 Napa | $2,400/mo |
| Est. additional gross rent | $86K/yr |
| Estimated total project cost | ~$806K |
| Year-1 NOI estimate | ~$65K |
| Stabilized cap rate at cost | 8.1% |
| Replacement parking required | No (§66313) |
| Approval pathway | Ministerial · §66314 |
| Typical permit timeline in Napa | 75-120 days |
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