Multifamily and Duplex Properties for Sale in Half Moon Bay: Zoning and Rent Rules

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What multifamily in Half Moon Bay looks like

Half Moon Bay’s rental housing is a small-town mix: duplexes and triplexes in older neighborhoods near downtown, small apartment buildings, units over Main Street shops, homes with second units, and a few larger complexes. Two local rules set it apart from the rest of the Peninsula: every parcel is in the Coastal Zone, and new homes, ADUs included, compete for a limited number of annual allocations under Measure D. Existing legal units are therefore scarce and hard to add to. For financing, see financing 2-4 unit properties and apartment building loans.

Where the zoning allows it

The city’s residential chapter sets minimum as well as maximum densities, and any use it does not list is prohibited.

District	Two-family	Multifamily	Key standards
R-2 Two-Family	Permitted, no use permit	Not listed	10–17.42 units/acre. 28 ft multistory. 35% coverage multistory. FAR 0.5
R-3 Multiple-Family	Permitted	Permitted	15–29.04 units/acre. 1,500 sq ft of lot per unit. 40 ft multistory. 45% coverage. 75 ft lot width
C-D Commercial-Downtown	Not listed separately	Permitted, except on Heritage Main Street ground floors	36 ft, 3 stories
C-R Commercial-Residential	Not listed separately	Permitted	28 ft. Two parking spaces per new unit
C-G Commercial-General	Not listed separately	Permitted	36 ft. Multifamily coverage 35%
C-VS Visitor Serving	—	Not allowed	Mixed-use housing only by use permit, secondary to a permitted use

R-2 and R-3 details.

Setbacks. 20 feet front and rear, 5-foot interior sides and 10-foot street sides, with combined side yards equal to 20% of lot width.
Open space. Multifamily projects must provide usable open space equal to 15% of floor area per unit.
Parking. At least one of the two required spaces per unit must be in a garage. Duplexes and triplexes need one guest space.

The use rules were last amended by Ordinance C-2023-02.

Downtown housing. In C-D, single-family and multifamily housing is allowed without a use permit. Multifamily is barred only in the first 50 feet of ground-floor frontage on Heritage Main Street, between Pilarcitos Creek and Correas Street. Residential parking is one space for a studio or one-bedroom and 1.5 for larger units, plus guest spaces.

ADUs and SB 9. ADUs are covered by Chapter 18.33. Under Chapter 18.20, an ADU built inside an existing home or accessory structure is exempt from a coastal development permit if it expands the structure by no more than 10% and adds no new habitable space. Other ADUs generally need a CDP. State SB 9 rules apply to qualifying single-family lots. See our ADU investment guide and SB 9 lot split guide.

Measure D: the residential unit allocation system

Half Moon Bay’s allocation chapter says it implements Measure D, the residential growth initiative. The base ordinance is C-8-09 from 2009.

Annual cap. New units each year may not exceed what would grow the population by 1%. Chapter 18.04 lets the downtown share rise by 50%, and the City Council sets the year’s maximum by resolution before December 31.
Timing. Applications are due January 1–31, with later filings allowed until September 1 or until the cap is reached. Allocations are set by April 1 and ratified by the Planning Commission in April.
Scoring. Projects are scored on factors such as infill, affordability, home size and household diversity. When demand is high, one applicant may receive up to five units in the initial period.
Exemptions. One-for-one replacement units and state-required affordable density bonuses are exempt. The code text lists ADUs as covered projects, and they earn points in the household-diversity category. State ADU law limits how cities may restrict ADUs, so ask the city how it currently applies the system to them.
Deadlines. A complete building permit application is due within one year of an award. Extensions are limited, and an unused allocation becomes void.

For investors, the takeaway is that an approved allocation or a finaled unit has real value, and a plan to add units should be built around the January filing window.

Rent rules: state law only

Half Moon Bay has no local rent control ordinance; the Attorney General’s rent cap page lists East Palo Alto as the only San Mateo County city with one. Updated July 16, 2026, the AG page puts San Mateo County in the San Francisco Area, with a 6.3% cap for increases from August 1, 2025 and 8.8% from August 1, 2026 through July 31, 2027 for covered units. Owner-occupied duplexes and qualifying single-family homes can be exempt. See our AB 1482 guide and just cause eviction guide.

Half Moon Bay rental property rules

Coastal permits. All of the city is in the Coastal Zone. Repairs and maintenance that don’t expand a structure are exempt, but additions, new units and work near bluffs, wetlands or creeks generally need a coastal development permit. Projects near the shoreline may be appealable to the Coastal Commission.
Findings. A CDP for new housing requires a finding that it is consistent with the annual population limitation system and has adequate services.
Hotel tax. Short stays are subject to the city’s transient occupancy tax under Chapter 3.12; we did not confirm the rate or any short-term rental permit rules.
Transfer tax. The County Recorder’s documentary transfer tax is $1.10 per $1,000. We found no Half Moon Bay tax; confirm on the escrow estimate.

Coastal hazards and older buildings

Under Chapter 18.20, a CDP is required for development within 100 feet of sensitive habitat, riparian corridors, bluffs or wetlands, and Coastal Commission appeal areas extend 300 feet from the beach or bluff top. Pilarcitos Creek marks one end of Heritage Main Street, so check flood zone status for parcels near it. Older wood-frame duplexes and apartment buildings warrant a seismic retrofit review, and salt air is hard on decks, so budget for SB 721 balcony inspections at three or more units.

Underwriting a Half Moon Bay multifamily purchase

Confirm the district and that the unit count fits the R-2 or R-3 density range; extra units may be nonconforming.
Pull permits and any Measure D allocation history for each unit.
Classify units under AB 1482 and model covered increases at or below 8.8%.
Treat added units or ADUs as contingent on an allocation and, usually, a CDP.
Collect leases and estoppel certificates.
Rebuild expenses with reassessed taxes, coastal maintenance and insurance in our rental property analysis.

Questions people ask

Where can I build a duplex in Half Moon Bay?

Two-family homes are permitted without a use permit in R-2 and R-3. Multifamily is also allowed in C-D, C-R and C-G.

What density does R-3 allow?

15 to 29.04 units per acre, with 1,500 square feet of lot per unit.

What is Measure D?

The residential growth initiative behind the city’s allocation system, which limits new units to 1% population growth a year, with more allowed downtown.

Do ADUs need a Measure D allocation?

The code text treats ADUs as covered projects, but state ADU law constrains local limits. Ask the city how it applies the rule today.

Is there rent control in Half Moon Bay?

No local ordinance. AB 1482 applies to covered units at 8.8% for increases from August 1, 2026.

Do I need a coastal permit to add a unit?

Usually. An ADU inside an existing structure that adds no new habitable space and expands it by no more than 10% is exempt.

Sources & notes

Note: We did not review the ADU chapter (18.33), the current annual allocation resolution, the hotel tax chapter or the zoning map. The online R-2 table is partly ambiguous; confirm figures with the city.

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

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Matthew Martinez

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