Multifamily and Duplex Properties for Sale in Penngrove: Zoning and Rent Rules

What multifamily in Penngrove looks like

Penngrove is a small unincorporated village, so "multifamily" there usually means a house with an ADU, a duplex or small cluster of older units near the village center, an apartment over a Main Street storefront, or a rural property with a second home. Larger apartment buildings are rare. Because Penngrove is outside Petaluma, the city’s tenant ordinance and transfer tax do not apply, but Sonoma County’s own tenant protection ordinance does. For two to four units, read financing 2-4 unit properties; for anything larger, see apartment building loans.

Where the zoning allows it

The Penngrove Area Plan, adopted in 1984 and last modified by Resolution 08-0808 on September 23, 2008, sets residential densities that depend on whether a parcel is inside the sewer district.

Area under the plan	Density or minimum lot	Multifamily potential
Urban residential areas east and west of Oak Street	Multifamily up to six units per acre	The plan’s main location for multi-unit housing
Main Street, Limited Commercial	Apartments as a secondary use	Units over or behind shops
Single Family Residential north of Woodward Avenue	6,000 sq ft lots	ADUs; SB 9 if eligible
Single Family Residential south of Woodward Avenue	10,000 sq ft lots	ADUs; SB 9 if eligible
Rural Residential inside the sewer district	1- to 2.5-acre density, varying by location	Second units and ADUs
Rural Residential outside the sewer district	1.5 to 5 acres	Limited by septic and wells
Diverse Agriculture outside the sewer district	20 acres, or 10 south of East Railroad Avenue	Farm and agricultural housing rules

Public services first. The plan requires public sewer and water for its Single Family and Low Density Residential designations, and outside sewer service it sets a 1.5-acre minimum for lots using septic and private wells.

Older homes. The plan lets existing homes built before 1960, or legally permitted, and larger than 840 square feet be split onto their own parcels without an area plan amendment, which can matter for a lot with two older houses.

Second units. The plan calls for monitoring second units and referring applications to the City of Petaluma; today state ADU law governs most ADU approvals.

SB 9. In the unincorporated county, Permit Sonoma’s SB 9 page limits eligibility to single-family zones inside a U.S. Census urban area, with ministerial review and an owner occupancy affidavit for lot splits. Whether a Penngrove parcel qualifies must be confirmed by a planner. See our SB 9 lot split guide and ADU investment guide.

Rent rules: state cap plus county just cause

State rent cap. The Attorney General’s rent cap page, updated July 16, 2026, places Sonoma County in the "All Other Counties" group, with covered increases capped at 8.6% from August 1, 2026 through July 31, 2027. No local rent cap applies in Penngrove.

Sonoma County tenant ordinance. Ordinance No. 6496, passed September 17, 2024 and effective 30 days later, applies in unincorporated areas such as Penngrove.

Just cause from move-in. Protection starts when lawful occupancy begins, not after 12 months.
Relocation. For no-fault terminations, the owner pays the greater of the county’s HUD Fair Market Rent for the unit size or the actual monthly rent.
Filing. For notices served on or after January 1, 2025, a copy must be filed through the county’s Tenant Protections Portal within three days, and the landlord page says termination information is due within three days whatever the reason.
Sale is not a cause. Notices must state that selling the property is not a valid reason to evict.
Affordable units. Deed-restricted affordable units lose the state exemption.

See our AB 1482 guide and just cause eviction guide.

Penngrove rental property rules

Vacation rentals. Under Permit Sonoma’s rules, whole-home vacation rentals are not allowed in R1, R2 or R3 districts, in ADUs, or on Williamson Act or LIA land, so a village duplex or ADU should be underwritten as a long-term rental.
Transfer tax. The County Recorder collects $0.55 per $500 after assumed loans; the Petaluma city tax does not apply to unincorporated Penngrove.

Sewer, water and older buildings

The Penngrove Sanitation Zone covers about 475 acres and pipes sewage through a lift station to Petaluma for treatment, so adding units on a sewered lot depends on Sonoma Water connection approval and fees. The area plan names the Penngrove Water Company as the village water supplier and describes a past connection moratorium; ask the company about current capacity in writing. Older wood-frame units should be checked for seismic retrofit needs, and any building of three or more units with elevated balconies needs SB 721 balcony inspections.

Underwriting a Penngrove multifamily purchase

Confirm the parcel is in unincorporated Penngrove and whether it is inside the sanitation zone.
Check the unit count against the area plan density and county zoning; extra units may be unpermitted.
Treat every tenancy as covered by county just cause from day one, and budget the greater of Fair Market Rent or actual rent for any no-fault move-out.
Model covered increases at or below 8.6% through July 2027.
Collect leases, the rent roll and estoppel certificates, plus county portal filings for any recent notices.
Rebuild expenses with reassessed taxes, septic or sewer costs and insurance in our rental property analysis.

Questions people ask

Does Petaluma’s tenant ordinance apply in Penngrove?

No. Penngrove is unincorporated, so Sonoma County’s Ordinance No. 6496 applies instead.

When does just cause start for a Penngrove tenant?

When the tenant lawfully moves in, under the county ordinance.

How much relocation is owed in Penngrove?

The greater of the HUD Fair Market Rent for the unit size in Sonoma County or the actual monthly rent.

Where does the Penngrove plan allow apartments?

In urban residential areas east and west of Oak Street at up to six units per acre, and as a secondary use on Main Street.

Can I rent a Penngrove ADU on Airbnb?

No. County rules bar vacation rentals in ADUs and in R1, R2 and R3 districts.

Is there sewer in Penngrove?

Part of the village is in the Penngrove Sanitation Zone, which sends sewage to Petaluma; outlying parcels use septic.

Sources & notes

Note: The area plan is an archived county document and parts of it, such as the water moratorium and second-unit referrals, may be superseded. We did not confirm current zoning on specific parcels, Census urban area status for SB 9, or Penngrove Water Company capacity. Housing types described are general observations.

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

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