Multifamily and Duplex Properties in Green Valley: Zoning and Rent Rules

What multifamily in Green Valley looks like

Unincorporated Green Valley is a valley of large-lot homes, vineyards and ranches north of Cordelia. Apartment buildings and duplexes are essentially absent from the county-zoned part of the valley, and the zoning mapped there does not allow them. For an investor, "multifamily" in Green Valley usually means one of three things: adding an ADU, JADU or secondary dwelling to a home or farm, buying into the clustered neighborhoods planned under the Middle Green Valley Specific Plan, or looking south to apartment-zoned land inside the City of Fairfield, whose residential districts allow multifamily in RM, RH and RVH. For financing small income property, see financing 2-4 unit properties; for larger buildings in Fairfield, apartment building loans.

Where the zoning allows it

County Section 28.32 maps three Residential-Traditional Community districts in Green Valley: R-TC-1AC, R-TC-20 and R-TC-15. The suffix signals the minimum parcel size. Farmland around them is in the Exclusive Agricultural districts.

The specific plan allows up to 400 new homes in compact clusters with more than 1,400 acres of farmland and open space protected. Its housing types and standards are set by the plan itself, so get the current plan text from county planning before assuming any attached or multi-unit product is allowed.

ADUs. Under Section 28.72, ADUs and JADUs are allowed by right in R-TC and rural residential districts and expressly in the residential districts of the Middle Green Valley Specific Plan area. A detached ADU in an R-TC district can be 850 square feet, or 1,000 with more than one bedroom; an attached ADU up to half the home’s floor area, capped at 1,200 square feet; a JADU up to 500. If a lot has both, the detached ADU is capped at 800 square feet. See our ADU investment guide.

Secondary dwellings on farms. On agricultural land the county uses the secondary dwelling instead: one per lot, up to 2,400 square feet, with the lot generally meeting the district’s minimum parcel size unless it was created before January 1, 1984 or qualifies for another exception. The owner must show water and wastewater capacity for both homes.

SB 9. SB 9 is aimed at single-family zones in urbanized areas, and we found no county SB 9 provisions in the sections reviewed. Rural Green Valley parcels may not qualify; ask the county. See our SB 9 guide.

Rent rules: state law only

The Attorney General’s rent cap page shows no local cap anywhere in Solano County and places the county in All Other Counties. For covered units the maximum increase is 7.7% for increases starting August 1, 2025 through July 31, 2026, and 8.6% for those starting August 1, 2026 through July 31, 2027. The AG notes that its chart may not list every local rule. Many single-family homes owned by individuals are exempt from the cap if the required notice was given, but ADUs and homes owned by corporations or certain LLCs may be covered. See our guides to AB 1482 and just cause eviction.

Green Valley rental property rules

• ADU rentals. An ADU can be rented separately but never sold separately from the main home.
• JADU limits. A JADU cannot be rented for 30 days or less, and if a lot has both an ADU and a JADU, neither can. The owner must live in either the main home or the JADU, backed by a deed restriction recorded before construction.
• Secondary dwellings. Rentals must be for more than 30 days and the unit cannot be sold apart from the main home. A secondary dwelling is not allowed on a lot that already has a duplex, multifamily building or similar accessory unit.
• Hosted rentals. A short-stay room rental in the owner’s primary residence needs an administrative permit in R-TC-1AC and R-TC-20, one guest room, no events, a TOT registration and a business license.

Wells, septic and fire

Many rural Green Valley parcels rely on private wells and septic systems, so confirm the service for any lot. Under Section 28.72, an ADU or JADU on a private septic system cannot be occupied until county Environmental Health approves it, and a secondary dwelling application must show enough water and wastewater capacity for two homes. Hillside lots in the valley also raise wildfire and access questions, so check the state fire hazard map and insurance availability early. Older outbuildings converted to living space should be checked for permits.

Underwriting a Green Valley income property

1. Confirm county or Fairfield jurisdiction and whether the lot is inside the Middle Green Valley Specific Plan.
2. Pull the district: R-TC-1AC and R-TC-20 rule out duplexes, so plan around an ADU and JADU.
3. On farmland, confirm parcel size and creation date before counting a secondary dwelling.
4. Get septic records and a well test, and confirm Environmental Health approval for any added unit.
5. Check AB 1482 coverage for each unit and whether the exemption notice was given.
6. Collect leases and estoppel certificates and run our rental property analysis.

Questions people ask

Sources & notes

1. California Attorney General, Rent Caps
2. Solano County, Middle Green Valley Specific Plan
3. Solano County Code Section 28.32, Residential-Traditional Community Districts (GoCodebook)
4. Solano County Code Section 28.72, Residential Uses
5. Solano County Code Section 28-21, Exclusive Agricultural Districts
6. Fairfield Municipal Code Section 25.20, Residential Districts

Note: R-TC-15 use rules and the specific plan’s housing standards were not in the text we reviewed. Fire hazard and AB 1482 exemption points are general state-law guidance.

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

Related: Green Valley real estate guide · Commercial real estate in Green Valley · Multifamily investing guide · Investor services