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

What multifamily in Windsor looks like

Windsor’s rental housing is mostly newer than in older Sonoma County towns: apartment complexes and townhomes from the past few decades, mixed-use buildings around the Town Green, duplexes and small multiplexes in established neighborhoods, houses with ADUs, and several mobile home parks. Zoning changes now allow two to four units by right across most residential zones, which opens up small infill on single-family lots. For two to four units, read financing 2-4 unit properties; for five or more, see apartment building loans.

Where the zoning allows it

Chapter 17.10 sets Windsor’s residential zones. Its use table lists two-to-four-unit buildings separately from five-plus projects.

Zone	2 to 4 units	5+ units	Density (units per acre) and height
RR Rural Residential	Not allowed (SB 9 two-unit permitted)	Not allowed	Up to 0.2; 35 ft
ER Estate Residential	Permitted	Not allowed	0.2 to 3; 35 ft
SR Surrounding Residential	Permitted	Minor use permit	3 to 6; 35 ft
VR Village Residential	Permitted	Minor use permit	5 to 8; 35 ft
MDR Medium Density Residential	Permitted	Permitted	8 to 16; 35 ft
CR Compact Residential	Permitted	Permitted	16 to 32; four stories
TC, BMU, NCMU, CC	—	Mixed-use housing	TC and BMU 16 to 32; NCMU 8 to 16; CC up to 16
SC, GC, RC	—	Not allowed	No housing

Mobile home parks. Windsor has no separate park zone. A new park needs a conditional use permit in SR, VR or MDR, and MDR matches the General Plan’s mobile home park designation.

SB 9. The table lists SB 9 two-unit dwellings as permitted in RR, SR and VR. See our SB 9 lot split guide.

ADUs. ADUs are exempt from growth control allocations, but they cannot be used as short-term rentals. See our ADU investment guide.

Rent rules: state cap plus mobile home space stabilization

AB 1482. The Attorney General’s rent cap page, updated July 16, 2026, puts Sonoma County under "All Other Counties," with covered units allowed up to 8.6% for increases from August 1, 2026 through July 31, 2027. Windsor has no local apartment rent cap, and the code index we reviewed shows no general just cause chapter. Sonoma County’s tenant ordinance is addressed to unincorporated areas, so it generally does not reach parcels inside town limits.

Mobile home space rent. Title VIII, Chapter 1 was first adopted by Ordinance 92-25 in October 1992. Its increase formula was amended in December 2022 and February 2023.

Space rent may rise once in 12 months by the lesser of 75% of the CPI change or 4%.
Owners must give 90 days’ written notice.
A higher increase requires notices, a meet-and-confer within seven working days and, if tenants holding at least 51% of affected spaces petition within 21 days, arbitration.
Increases above 300% of the CPI change go to mandatory arbitration.
The increase cannot be collected while a petition is pending.
Prospective residents must be offered a month-to-month or 12-month tenancy.
Leases exempt under Civil Code Section 798.17 are outside the cap.

See our AB 1482 guide and just cause eviction guide.

Windsor rental property rules

Short-term rentals. Chapter 23, from Ordinance 2023-379 and amended by Ordinance 2025-400, allows only hosted short-term rentals, with the owner or primary occupant in residence. Non-hosted rentals in residential districts had to stop by July 1, 2025. Only individual owners or their family trusts may hold licenses, up to three per host. Stays are capped at two guests per bedroom and eight in total, and licenses do not transfer on sale.
Growth control. Title XVI, Chapter 4, last amended in 2017, targets average growth of 1.5% a year and limits phased projects to 50 units a year. Projects of four or fewer units, ADUs, deed-restricted lower-income units and core downtown projects are exempt.
Transfer tax. The County Recorder lists only the County’s $0.55 per $500 for Windsor.

Newer buildings, older parks and balconies

Much of Windsor’s apartment stock is recent, but older complexes and mobile home parks need the usual checks. Budget SB 721 balcony inspections for three or more units with elevated decks or walkways, and order a seismic retrofit review for any tuck-under or raised wood-frame building. In parks, ask for capital improvement records, since pass-throughs must be claimed within 12 months of completion.

Underwriting a Windsor multifamily purchase

Confirm the zone and whether the existing unit count fits it, or is legal nonconforming.
Classify units under AB 1482 and model increases at or below 8.6% for covered units.
For a mobile home park, model space rent at the lesser of 75% of CPI or 4%, and check for pending petitions.
Remove any planned non-hosted nightly income; it is no longer allowed in residential districts.
For added units, check whether growth control allocations apply; collect leases, the rent roll and estoppel certificates.
Rebuild expenses with reassessed taxes, insurance and SB 721 in our rental property analysis.

Questions people ask

Is there rent control in Windsor?

Not for apartments beyond AB 1482. Mobile home space rents are limited to the lesser of 75% of CPI or 4% a year.

Can I build a fourplex on a single-family lot in Windsor?

Two to four units are permitted by right in ER, SR, VR, MDR and CR, subject to development standards.

Where are five-plus unit buildings allowed?

By right in MDR and CR, with a minor use permit in SR and VR, and in the mixed-use zones.

Can I Airbnb a Windsor ADU?

No. ADUs cannot be used as short-term rentals, and only hosted rentals are licensed.

Do small projects need growth allocations?

Projects of four or fewer units are exempt, as are ADUs and deed-restricted lower-income units.

What notice do mobile home park owners give for increases?

At least 90 days’ written notice, with tenant petitions due within 21 days for increases over the cap.

Sources & notes

Note: We read the code through GoCodebook’s October 2026 edition. We did not read the town’s ADU standards, the mobile home definitions and administration articles, or the Station Area/Downtown Specific Plan, and did not confirm whether Windsor has adopted any tenant protections after that edition. The housing stock description is a general observation. See also our Sonoma County multifamily guide and Sonoma County commercial guide.

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

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