Multifamily and Duplex Properties for Sale in Loma Mar: Zoning and Rent Rules

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What multifamily in Loma Mar looks like

In Loma Mar, "multifamily" usually means a cabin or house with a second unit, two homes on one larger parcel, or a small rental on rural land. Apartment buildings are essentially absent. The community is unincorporated and sits in the redwoods along Pescadero Creek Road beside Memorial Park, and the real limits on adding units are water, septic, slope and fire access. For two to four units, see financing 2-4 unit properties; for larger buildings, apartment building loans.

Where the zoning allows it

San Mateo County zones Loma Mar under Title 8; its districts are listed in Chapter 8.08. We did not verify which districts are mapped on Loma Mar parcels, and you should confirm whether a parcel lies in the Coastal Zone.

District	Two or more units	Notes
RM Resource Management	Single-family and multi-family residences listed as permitted uses, within density credits	One unit per 5 acres by default; one per 10, 20 or 40 acres on steeper, flood-prone, remote or unstable land
RM bonuses	Up to 10% more density for permanent open space over 80% of the parcel, and up to 10% more for listed design or housing criteria	Conservation easements follow land divisions
TPZ Timberland Preserve	Not reviewed	Timber-focused district listed in Section 8.08.010
ADUs and JADUs	One main home plus accessory units	County ADU rules in Chapters 8.392 (inland) and 8.396 (Coastal Zone)

How RM density works. The RM chapter assesses each part of a parcel in order and assigns it a density. Slopes over 50%, floodplains, active fault zones and remote land count at one unit per 40 acres. Slopes of 30 to 50% count at one per 20, and 15 to 30% slopes at one per 10. Fractions of half a unit or more round up. On steep redwood parcels like those around Loma Mar, the result is often one home, whatever "multi-family" the use list allows. Parcels of five acres or more that were legal when RM took effect remain legal; smaller parcels stay legal only under listed conditions.

ADUs. The County’s ADU page places inland ADU rules in Chapter 8.392 and Coastal Zone rules in Chapter 8.396. On a Loma Mar lot the practical questions are septic capacity and a water source for the second unit. See our ADU investment guide.

SB 9. SB 9 lot splits and two-unit projects apply to single-family residential zones in urban areas, so they are unlikely to reach resource-zoned parcels. Confirm with the County. See our SB 9 lot split guide.

Rent rules: state law only

The Attorney General’s rent cap page, updated July 16, 2026, puts San Mateo County in the San Francisco area, with increases on covered units capped at 8.8% from August 1, 2026 through July 31, 2027. Loma Mar has no local rent ordinance. Many rural rentals here are single-family homes, which can be exempt from AB 1482’s cap if the owner is not a corporation and gives the required notice. Read our AB 1482 guide and just cause eviction guide.

Loma Mar rental property rules

Development review. RM treats new structures and land divisions as development needing a County permit. That review involves the County Engineer on roads and geology, the Health Officer on water and sewage, and fire authorities. Adding a rental unit goes through all three.

Short-term rentals. The County’s Coastal Zone short-term rental permit covers only R-1 and R-3 parcels in the Coastal Zone, so it does not fit typical resource-zoned Loma Mar land. We did not verify inland County short-term rental rules; ask County Planning before marketing a cabin for short stays. Hosts in unincorporated areas owe transient occupancy tax.

Transfer tax. The County’s documentary transfer tax is 55 cents per $500, paid at recording. There is no city tax.

Water, septic and creek issues

The mutual water company. The Loma Mar Pipeline Replacement and Water Plant Upgrade Project, filed in June 2022, describes the Loma Mar Mutual Water & Improvement Company as a 36-hookup system relying on Pescadero Creek diversions. The filing calls its lines leaky and at risk of catastrophic failure. Four 4,995-gallon tanks were installed in 2019 to replace a failing 40,000-gallon tank. The project would replace about 1.2 miles of pipe with new HDPE lines and meters, upgrade the intake and plant, and add backup power. We did not confirm that the work is complete. A buyer should confirm membership, shares, service to each unit and any assessments.

Creek and fish. The project aims to cut diversions in summer low flows to protect steelhead and coho salmon. That makes added water demand a sensitive question.

Septic. We found no public sewer for private parcels. Memorial Park operates its own wastewater plant, which the County planned to rebuild under a 2019 environmental review. For a rental, the septic permit’s bedroom count is often the true unit limit.

Older cabins. Older wood-frame cabins on slopes deserve a seismic retrofit review, and any building of three or more units with elevated decks needs SB 721 balcony inspections.

Underwriting a Loma Mar multifamily purchase

Confirm the zoning, Coastal Zone status and the parcel’s density credits.
Verify every dwelling was permitted, and match bedrooms to the septic permit.
Confirm water service for each unit with the mutual water company, or test the private source.
Classify units under AB 1482 and model covered increases at or below 8.8%.
Collect leases and estoppel certificates.
Rebuild expenses with reassessed taxes, water assessments, fire-hardening and insurance in our rental property analysis.

Questions people ask

Can I build a duplex in Loma Mar?

Only if the parcel’s district and density credits allow a second dwelling, and water and septic can serve it. On steep land, density is often one home.

Is there rent control in Loma Mar?

No local rent control. AB 1482 applies to covered units.

Who provides water in Loma Mar?

The Loma Mar Mutual Water & Improvement Company serves 36 hookups; other parcels may use private sources.

Can I add an ADU?

County ADU rules apply, but septic capacity and water supply decide whether a second unit is practical.

Is Loma Mar in the Coastal Zone?

Check each parcel with County Planning; we did not verify the boundary here.

What is the transfer tax?

The County documentary transfer tax, 55 cents per $500. No city tax applies.

Water-system project records

The 2022 Loma Mar water-project notice describes approximately 1.2 miles of replacement pipeline, meters, four storage tanks installed in 2019, treatment improvements and backup power. It identifies 36 existing hookups and a goal of reducing losses affecting Pescadero Creek. This is a project description, not confirmation of completion or spare capacity. Ask the mutual company for the parcel’s membership, connection rights, current project status and capacity for the proposed use.

Sources & notes

Note: We did not confirm parcel zoning, the Coastal Zone boundary, inland short-term rental rules, TPZ rules, County septic standards or completion of the water project.

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

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