Multifamily and Duplex Properties for Sale in San Lorenzo: Zoning and Rent Rules

What multifamily in San Lorenzo looks like

San Lorenzo was built mostly as a postwar planned community of single-family homes. Its multifamily stock is smaller and sits in a few places:

• Duplexes and small apartment buildings along and behind Hesperian Boulevard, Lewelling Boulevard and East 14th Street
• Garden apartments on R-S and higher-density land near the Hayward and San Leandro borders
• New mixed-use rentals in the San Lorenzo Village Center
• Single-family homes rented out, which can fall under county eviction rules

Because San Lorenzo is unincorporated, Alameda County sets both its zoning and its tenant rules. For financing, see financing 2-4 unit properties and apartment building loans.

Where the zoning allows it

The county’s west county zoning map (a 2009 draft) covers San Lorenzo and its neighbors. Its legend shows densities for each residential district:

R-S standards. Under Chapter 17.12, R-S sites need a 5,000 square foot lot and a median width of 50 feet. Buildings are limited to two stories and 25 feet. Each unit needs 600 square feet of usable open space. Site development review applies once a site is large enough for five units.

Village Center housing. The 2004 specific plan caps housing at 580 units: 450 across Subareas 2, 4 and 5A to 5D, and 130 in Subarea 6. It requires at least 150 square feet of open space per unit and two parking spaces per unit, or more if a study requires it. A 2021 county hearing reviewed 138 rental units with ground-floor retail on the former Mervyn’s site at Hesperian and Paseo Grande, at about 26.9 units per acre gross.

ADUs and SB 9. County ADU rules are in Chapter 17.55, and state SB 9 law applies on single-family lots. See our ADU investment guide and SB 9 lot split guide.

Rent rules: state cap plus county mediation and just cause

Unincorporated Alameda County has no local apartment rent cap, so covered units follow the statewide cap. The Attorney General’s chart puts the county in its San Francisco Area region: 6.3% for increases from August 1, 2025, and 8.8% from August 1, 2026 through July 31, 2027. Two county ordinances add to state law. See our AB 1482 guide.

Rent mediation, Chapter 3.68. The Board adopted a new Rental Housing Dispute Resolution chapter by Ordinance 2024-35 on November 12, 2024. Its main rules:

• Trigger. Either side may request mediation within 21 days of an increase that takes rent more than 5% above base rent, or that follows another increase within 12 months.
• Effect on the increase. If a tenant requests mediation over an increase above 5% in 12 months, the increase does not take effect until mediation ends.
• Good faith. An increase is not effective unless the landlord takes part in good faith for the whole process.
• Outcome. Mediation is nonbinding unless the parties sign an agreement, which the county can enforce as a third-party beneficiary.

In practice, that 5% trigger is lower than the state cap, so expect mediation requests on larger increases.

Just cause, Chapter 3.70. The county’s just cause ordinance was adopted February 4, 2025, and took effect March 6. Its provisions, from the Board agenda text:

• Single-family rentals. Covered when the landlord owns five or more rental units in the unincorporated county.
• Relocation. No-fault evictions require relocation pay, raised in the adopted text to two months’ rent and capped at $10,000 per household.
• Longer notice. Households with children, disabled members, seniors 62 and older or lower-income members get at least 90 days’ notice of a no-fault eviction.
• Return right. Tenants displaced by an owner move-in or substantial remodel can return if the unit is re-rented within a year.
• Filing. Every termination notice must be filed with the Community Development Agency within three days of service. Skipping the filing can give the tenant a defense.

See our just cause eviction guide.

San Lorenzo rental property rules

Business license. Under Chapter 3.04, apartment owners in unincorporated areas pay $1.25 per $1,000 of gross receipts. Owners of a single-family home, or of a property with no more than two units not counting one they live in, are not covered. Units under a rent-limitation agreement are exempt.

Help for owners. The county’s Housing & Community Development Department points landlords to a Housing Provider Resource Center and to ECHO Housing’s mediators and landlord training.

Sewer laterals and building issues

Oro Loma Sanitary District serves San Lorenzo. For escrows opened on or after August 1, 2026, it requires a Sewer Lateral Compliance Certificate before title transfers. Adding an ADU or another unit also triggers the requirement. The certificate fee is $450, plus any repair cost. Postwar buildings often have original clay laterals, so get the inspection early.

Many duplexes and small apartment buildings date from the 1950s and 1960s. They warrant a seismic retrofit review, though we found no mandatory county soft-story program. Buildings of three or more units with elevated balconies need SB 721 inspections. With no city transfer tax, only the county’s $0.55 per $500 applies.

Underwriting a San Lorenzo multifamily purchase

1. Confirm the parcel is unincorporated and get its district and D suffix from County Planning.
2. Model increases at or under the state cap, and expect mediation requests on anything above 5%.
3. Ask for copies of every termination notice filed with the county and any mediation agreements.
4. Price relocation exposure of two months’ rent, up to $10,000, for any no-fault move-out.
5. Collect leases, the rent roll and two years of statements, and get estoppel certificates.
6. Add the Oro Loma lateral work, county license tax and reassessed property tax to your rental property analysis.

Questions people ask

Sources & notes

1. Alameda County Ordinance Code Chapter 3.68, Rental Housing Dispute Resolution, Article III (GoCodebook)
2. Board of Supervisors, Just Cause Eviction ordinance, Feb. 4, 2025, and County HCD, Tenant Protections
3. County HCD, Rental Property Providers & Owners
4. Chapter 3.04, Business License Tax, Chapter 17.12, R-S Districts and Chapter 17.55, ADUs
5. County zoning Map 1, San Lorenzo area (draft 2009)
6. San Lorenzo Village Center Specific Plan (2004) and PLN2021-00044 presentation
7. Oro Loma Sanitary District, Private Sewer Lateral Program
8. California Attorney General, Rent Caps and Alameda County Clerk-Recorder

Note: The just cause text we reviewed was a redline; confirm the codified relocation terms with the county. We did not open Chapter 17.55 for this page.

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

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