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

What multifamily in Ross looks like

Ross is almost entirely single-family. Its zoning has no duplex or apartment district, so "multifamily" here usually means one of three things. The first is an estate with an ADU, a JADU or both. The second is a two-unit project under SB 9. The third, and rarest, is a building with apartments over shops in the small C-L commercial district. Each route has its own limits. For financing an existing small multi-unit property, see financing 2-4 unit properties. For anything larger, see apartment building loans.

Where the zoning allows it

Two-unit projects. Chapter 18.43, adopted in 2022, carries out the state two-unit law in all single-family zones. A project is ineligible if it would demolish or alter housing that a tenant occupied in the past three years, or affordable or rent-controlled units. It is also ineligible on a parcel withdrawn from the rental market under the Ellis Act in the past 15 years, or in a historic district or on a listed landmark. Units of 800 square feet or less with 4-foot side and rear setbacks must be allowed even if other standards would block them. Each unit needs its own water, sewer and electric connections. See our SB 9 lot split guide.

ADUs. Under Chapter 18.42, last amended in 2025, a by-right ADU may be 850 square feet with one bedroom or 1,000 with more, and a JADU up to 500. The Town Council may approve an ADU of up to 1,200 square feet if it is rented to a very low-income household, at or below 50% of Marin median income. That requires a recorded rent restriction for at least 20 years and an annual rent certification, and it does not apply on hillside lots. Two detached ADUs need a council exception and at least an acre. On a lot with an existing multifamily building, Ross allows ADUs in non-livable space and up to eight detached ADUs, capped at the number of existing units. See our ADU investment guide.

Rent rules: state law only

We found no rent stabilization, just cause or mediation chapter in the Ross code. Marin County’s just cause and mediation ordinances apply only in unincorporated areas such as neighboring Kentfield, not in Ross. Confirm with the town that nothing newer has been adopted.

Rent caps. AB 1482 applies to covered units. The Attorney General’s rent cap page sets the San Francisco Area maximum at 8.8% for increases from August 1, 2026 through July 31, 2027. Single-family homes and ADUs owned by individuals are often exempt if the owner gives the required notice. A property with two or more units on one parcel generally is not. See our AB 1482 guide.

Just cause. State just cause rules apply after 12 months of tenancy for covered units. Ross’s two-unit chapter adds a related limit: a unit a tenant occupied in the past three years cannot be demolished or altered for a two-unit project. See our just cause eviction guide.

Ross rental property rules

• No short stays in added units. ADUs and JADUs may not be rented for fewer than 30 consecutive days, and two-unit development units must be rented for more than 30 days. With no short-term rental chapter in the code, plan on long-term tenants.
• JADU owner occupancy. The owner must live in either the main house or the JADU. No owner occupancy is required for an ADU.
• Parking. Single-family homes need two spaces, one enclosed, plus one for an ADU. Two-unit projects need one space per unit, with exceptions near transit.
• Transfer tax. The town’s documentary stamp tax is $0.275 per $500, excluding liens. The county’s is $0.55 per $500, per the Recorder, which lists only San Rafael as having an added city tax, so confirm the split with escrow.

Sewer laterals, creek flooding and hillsides

The Ross Valley Sanitary District requires a lateral Certificate of Compliance at sale, for remodels over $75,000 and when a bathroom is added. That means a video inspection, a permit and a witnessed pressure test. A two-unit project with separate sewer connections may need new laterals entirely. Properties near Corte Madera Creek fall under the town’s Floodway (F) district and FEMA flood zones. Hillside lots are governed by Chapter 18.39, and the large council-approved ADU is not available there. Older homes converted to hold several units deserve a seismic retrofit review. Any building with three or more units and elevated decks needs SB 721 inspections.

Underwriting a Ross multifamily purchase

1. Confirm the zoning district and :B suffix, and check that each existing unit has a permit as a primary home, ADU or JADU.
2. For a two-unit plan, check tenant history for the past three years and any Ellis Act withdrawal in the past 15 years.
3. Classify each unit under AB 1482 and confirm whether the exemption notice has been given.
4. Model rents on 30-day-plus tenancies only.
5. Order the sewer lateral inspection and flood zone check at the start of escrow.
6. Collect leases and estoppel certificates, then rebuild expenses with reassessed taxes in our rental property analysis.

Questions people ask

Sources & notes

1. Ross Municipal Code Chapter 18.16, R-1 District (GoCodebook, October 2026)
2. Ross Chapter 18.43, Two-Unit Housing Developments
3. Ross Chapter 18.42, Accessory Dwelling Units
4. Ross Chapter 18.20, C-L District
5. Ross Chapter 3.12, Documentary Stamp Tax and Marin County Recorder, transfer tax
6. Ross Valley Sanitary District, lateral compliance
7. California Attorney General, Rent Caps

Note: We did not read the :B suffix standards in Chapter 18.32, the hillside chapter, the Floodway district or the Housing Element. Ross’s Housing Element sites may carry rezonings not reflected here.

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

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