Commercial Real Estate in Emerald Hills: Hillside Zoning, Use Permits and What Business Use Is Possible

By Matthew Martinez, Founder, CEO & Managing Broker, Diamond Real Estate Group. California DRE #01869679.

Emerald Hills, also known as Emerald Lake Hills, is an unincorporated hillside neighborhood west of Redwood City, and it is almost entirely residential. Commercial property in the usual sense, such as retail strips and office buildings, sits just outside it in Redwood City and Woodside. Inside the community, business use comes down to what the County’s hillside zoning allows: home occupations, a few institutional and recreational uses by use permit, and small lodging. Confirm the zoning and permit history of any parcel with San Mateo County Planning and Building.

Who controls the parcel

Emerald Hills is not a city. San Mateo County zones it under Title 8, the Zoning and Development Code, and the County Board of Supervisors governs it directly. Sewer service in the core of the community comes from the Emerald Lake Heights Sewer Maintenance District. That district was formed on November 4, 1947 under the Health and Safety Code, is governed by the Board of Supervisors and is run by County Public Works. The County’s LAFCo listing puts the district’s population at about 3,300 as of 1990.

Because Redwood City surrounds much of the area, many Emerald Hills parcels carry Redwood City mailing addresses. A Redwood City address does not mean Redwood City zoning, so confirm whether a property sits in the city or in unincorporated County land before you assume a commercial use is possible. For city parcels, see our Redwood City commercial guide.

Emerald Hills zoning for business and institutional use

The County’s RH Residential Hillside district carries the Emerald Lake Hills permit limit, and its purpose is to provide hillside parcels mainly for single-family homes, with a compatible mix of institutional and recreational uses.

Use type under RH	Permit	Notes
Home occupations	No permit listed	Accessory to a residence
Small hostelries	Use permit	The district’s only lodging use
Schools, religious facilities, clubs, some care facilities	Use permit	Institutional uses
Fire stations and cemeteries	Use permit	Public and quasi-public uses
Parks, trails, outdoor sports facilities, golf courses	Use permit	Recreational uses
Most residential care facilities	No permit listed	Residential uses
Retail, office, restaurant, industrial	Not listed	Not allowed in RH

The chapter’s use list was last amended by Ordinance 4844 on May 4, 2021.

What business use is realistic in Emerald Hills

Home-based businesses. For most buyers, commercial activity in Emerald Hills means a professional or creative business run from a home. RH lists home occupations as an accessory residential use. Check County home occupation standards on employees, customer visits and signs before buying a home for a business.

Institutional and club properties. Schools, places of worship, clubs and recreation facilities exist across many hillside communities, and RH allows them by use permit. If you are buying or leasing one, get the use permit and its conditions, because the permit, not the base zone, sets hours, enrollment, events and parking. Expanding or changing that use generally means amending the permit.

Lodging. A small hostelry needs a use permit. Unincorporated operators register and file transient occupancy tax through the County’s contractor, HdL.

Site limits that apply to any building. RH applies the same physical limits to every building on a lot:

Floor area. All buildings together may not exceed 30% of the site or 2,400 square feet, whichever is greater, counting garages, carports and large covered decks.
Coverage. Lot coverage tops out at 25%.
Height. 28 feet.
Setbacks. 20 feet front and rear, with side yards totaling 20 feet and at least 7.5 feet each. One side must give the Fire Marshal access to the rear.
Grading. No more than 1,000 cubic yards per building site.

These rules cap how large an institutional or club building can grow.

Hillside rules: the permit cap, design review and roads

The 55-permit limit. RH caps new residential building permits in Emerald Lake Hills at 55 per calendar year. The limit, carried from Ordinance 3194 of October 31, 1989, exempts rebuilding after a disaster, remodels under 50% of replacement value and deed-restricted affordable housing. A buyer planning to add a caretaker unit or a residence alongside an institutional use should ask Planning where the year’s count stands.

Design review. The County has a dedicated Emerald Lake Hills Design Review Officer. In June 2026 the Board adopted an updated design review ordinance, and for design review areas outside the Coastal Zone review became ministerial, at staff level, on July 23, 2026. Projects submitted before that date may still go to hearing as needed.

Frontage and lots. New RH parcels need at least 50 feet of frontage and width, and lots that were legal building sites when the district was adopted remain buildable.

Transfer tax, business tax and property tax

The San Mateo County Assessor-County Clerk-Recorder collects documentary transfer tax at 55 cents per $500, or $1.10 per $1,000, when the deed records. Unincorporated Emerald Hills has no city transfer tax. Assumed liens may be deducted, and exempt transfers need a transfer tax affidavit. We did not verify a County business license tax for unincorporated areas. A sale generally triggers Proposition 13 reassessment.

Due diligence that matters in Emerald Hills

Start with our commercial due diligence checklist, then add:

Confirm County or Redwood City jurisdiction from the parcel map, not the mailing address.
Confirm the RH district and any combining district on the County zoning map.
For a school, church, club or recreation property, pull the use permit and every amendment.
Check floor area and coverage against RH limits before planning additions.
Confirm sewer service through the Emerald Lake Heights district or septic status, and narrow-road access for fire apparatus.
For any new residential unit, ask about the 55-permit annual count.

Questions people ask

Can I open a shop or office in Emerald Hills?

Not in the RH district, which lists no retail, office or restaurant uses. Commercial space nearby is in Redwood City.

Can I run a business from my Emerald Hills home?

RH lists home occupations as an accessory use. Check County standards on employees, visitors and signs.

What uses need a use permit?

Small hostelries, schools, religious facilities, clubs, some care facilities, fire stations, cemeteries, parks, outdoor sports facilities and golf courses.

Is there a limit on new homes in Emerald Lake Hills?

Yes, 55 new residential building permits per calendar year, with exceptions for disaster rebuilds, smaller remodels and affordable housing.

Who handles design review now?

County staff. Since July 23, 2026, design review outside the Coastal Zone is ministerial.

Who provides sewer service?

The Emerald Lake Heights Sewer Maintenance District, run by County Public Works under the Board of Supervisors.

Does Diamond handle commercial property in Emerald Hills?

Contact Matthew Martinez to discuss buying, selling or leasing commercial property in Emerald Hills.

Sources & notes

Note: We did not review the zoning map, so some Emerald Hills parcels may carry other County districts. We did not review County home occupation standards, the fire hazard maps or the County’s design review ordinance text.

This page is general information, not legal or tax advice. Last reviewed October 2026 by Matthew Martinez.

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