Multifamily and Duplex Properties for Sale in St. Helena: Zoning and Rent Rules

What multifamily in St. Helena looks like

St. Helena’s income property is mostly small-scale: duplexes, triplexes and cottage groupings in the medium-density neighborhoods off Main Street, a limited number of apartment buildings, units above downtown storefronts, homes with ADUs, and a mobile home park or two. Under the zoning code adopted as Ordinance 23-4, new density is aimed at the MR, HR and Mixed-Use districts. For financing, see financing 2-4 unit properties and apartment building loans.

Where the zoning allows it

Small lots and mobile homes. New small-lot development needs a CUP in LR, MR and HR. Single-room occupancy housing is permitted in HR. Mobile homes need a CUP in every residential district, and new parks require a rezoning to the Mobile Home Park overlay filed together with a CUP. Densities existing on January 1, 2023 may remain.

ADUs. Under Section 17.22.030, amended by Ordinance 25-2:

• Size. Up to 850 square feet for a studio or one-bedroom and 1,000 for a two-bedroom, with no more than two bedrooms.
• Existing multifamily. At least one converted ADU and up to 25% of the existing unit count, plus up to eight detached ADUs, but never more than the number of primary units.
• Rental term. No ADU or JADU may be rented for less than 30 days.

See our ADU investment guide.

SB 9. The city implements state two-unit rules in Chapter 17.31, and LR-1A allows greater density only under those rules. Confirm eligibility for the specific lot. See our SB 9 lot split guide.

Inclusionary rules. Chapter 17.30, last amended by Ordinance 25-1, requires at least 20% of new units in a residential project to be affordable. Projects of four or fewer units may pay an in-lieu fee instead, and new units under 850 square feet are exempt. For rental projects of one to three units, the first required unit is very low income. Rental restrictions last in perpetuity; ownership restrictions run at least 45 years and restart on each resale.

Rent rules: state law only

Rent caps. The Attorney General’s rent cap page, updated July 16, 2026, places Napa County in All Other Counties. Covered units may rise up to 7.7% for increases from August 1, 2025, and 8.6% from August 1, 2026 through July 31, 2027. No Napa County city appears on the AG’s list of local apartment rent ordinances, and we found no St. Helena rent stabilization chapter. See our AB 1482 guide and just cause eviction guide.

St. Helena rental property rules

• Managers and lease terms. Chapter 5.32 requires an on-site resident manager for complexes of 16 or more units. Properties of five to 15 units must post the owner’s or agent’s name and address. Leases must address tenant responsibility for guests and illegal activity and must be in English or Spanish, or explained through an interpreter.
• Code-enforcement relocation. If repairs ordered through code enforcement force tenants out, Chapter 8.32 requires the owner to give 30 days’ notice and pay a $500 dislocation allowance plus moving costs ($800 flat with storage, $400 without) and a replacement housing payment. Tenants keep the right to move back. Willful nonpayment can bring treble damages.
• Vacation rentals. Section 17.22.200 limits short-term rentals to single-family homes, one per lot, with an owner-held permit that cannot transfer. Only 25 permits may exist citywide. Do not underwrite an apartment or duplex on short-stay income.
• Transfer tax. The city’s transfer tax is 27.5 cents per $500, administered by the County Recorder. The County’s transfer tax page shows a combined $0.55 per $500 with half to the city.

Flood, historic and building issues

The flood plain overlay covers the FEMA 100-year flood plain. It sets no-build setbacks of 50 feet from the Napa River and 20 feet from Sulphur Springs Creek and measures height from flood elevation. Parcels on the Historic Preservation map need design review, and listed buildings must follow the Secretary of the Interior’s standards, which affects window, siding and porch work on older rentals.

Older wood-frame buildings warrant a seismic retrofit review, and buildings of three or more units with elevated decks need SB 721 balcony inspections.

Underwriting a St. Helena multifamily purchase

1. Confirm the zone and density. More than 16 units per acre requires HR zoning.
2. Underwrite long-term rents only; vacation rental permits are capped and limited to single-family homes.
3. Classify units under AB 1482 and model increases at or below 8.6% for covered units.
4. For added units, budget for the 20% inclusionary requirement or the in-lieu fee.
5. Collect leases, the rent roll and estoppel certificates, and check that leases contain the Chapter 5.32 terms.
6. Rebuild expenses with reassessed taxes, insurance and city utility charges in our rental property analysis.

Questions people ask

Sources & notes

1. St. Helena Chapter 17.16, Residential Districts (GoCodebook)
2. St. Helena Chapter 17.17, Commercial and Mixed-Use and Chapter 17.18, Business and Industrial
3. St. Helena Chapter 17.21, Overlay Districts
4. St. Helena Chapter 17.22, Specific to Uses (ADUs, short-term rentals)
5. St. Helena Chapter 17.30, Affordable Housing Program
6. St. Helena Chapter 5.32, Residential Rental Units
7. St. Helena Chapter 8.32, Relocation Services and Payments
8. St. Helena Chapter 3.20, Real Property Transfer Tax
9. California Attorney General, Rent Caps
10. Napa County, Document Transfer Tax

Note: We did not review the text of Chapter 17.31 (two-unit projects), the ADU permit type by district, current in-lieu fee amounts, or the full short-term rental section, which was cut off in the published copy. Confirm with the city.

General information, not legal or tax advice. Last reviewed October 2026 by Matthew Martinez.

Related: St. Helena real estate guide · Commercial real estate in St. Helena · Multifamily investing guide · Investor services