Commercial Real Estate in Diablo: County Zoning, Private Roads and What Business Uses Are Possible

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

Diablo is a small, almost entirely residential community northeast of downtown Danville, set around the Diablo Country Club at the foot of Mount Diablo. It has no shopping district and no commercial zoning that we could find, so "commercial" here means the club, institutional uses that a county land use permit can allow in a residential zone, and home-based work. Before you plan any business use, confirm the zoning, the road situation and the permit path with Contra Costa County and the Diablo Community Services District.

Who controls the parcel

Diablo is unincorporated, so three bodies matter:

Contra Costa County. The Department of Conservation and Development sets zoning and issues permits under the county’s Division 84 land use districts.
Diablo Community Services District (DCSD). The county’s Diablo page describes it as an independent special district formed in September 1969. It provides security services, maintains roads, culverts and bridges, and keeps up Kay’s Trail. Its five-member board is elected at large. Contra Costa LAFCO’s 2023 directory lists it at 1.17 square miles serving about 1,158 people, with a sphere of influence matching its boundary.
Diablo Municipal Advisory Council (DMAC). Created by the Board of Supervisors on June 25, 1996, through Resolution 96/314, it advises the county on Diablo matters. Its members are the same five people as the DCSD board, and it meets after the DCSD meeting when there are applications to review. The county page directs zoning and permit questions to the DCSD general manager.

The Town of Danville borders Diablo, and its zoning is entirely separate. Confirm which side of the line a parcel is on. See our Danville commercial guide.

Diablo zoning for commercial, industrial and mixed use

There is no mapped retail, office or industrial district inside Diablo that we could verify. Recent parcels reviewed by the DMAC were zoned R-20 single-family with the -UE combining district, and LAFCo’s 2011 report on parcels along upper Mt. Diablo Scenic Boulevard listed them as A-2 General Agricultural. The table shows what those districts allow beyond a home.

District	Intended uses	Notes
R-20 Single-Family	One house per lot, ADUs, crop farming, short produce stands	20,000 sq ft lots, 120 ft wide; 25 ft front setback; 15 ft side yards
R-district uses by land use permit	Golf, tennis and swimming clubs; churches and private schools; medical and dental offices; child care centers; commercial nurseries	R-20 picks up the R-6 permit list, except greenhouses over 300 sq ft
A-2 General Agricultural	Agricultural and related uses	Mapped on some outer parcels; check the use list
-UE Urban Farm Animal Exclusion	Overlay limiting farm animals	Shown on DMAC-reviewed parcels
P-1 Planned Unit	Uses set by a development plan	Confirm whether any Diablo parcel uses it

What business uses are realistic in Diablo

The country club. The R-6 permit list, which R-20 incorporates, names golf, tennis and swimming clubs as uses that need a county land use permit. A club property’s value depends on its existing permit and conditions, so request them early.
Institutional and professional uses. Medical and dental offices, child care centers, churches and private schools are possible only with a land use permit, which means a hearing, neighbor notice and DMAC review. In a community this small, expect close scrutiny.
Home-based work. We did not verify the county’s home occupation rules for Diablo, so confirm them before marketing a property for business use.
Short-term rentals. Rentals of under 30 days need a county permit under Chapter 88-32, adopted in 2020. The operating rules ban events such as weddings, cap gatherings at 20 people and require a county business license and transient occupancy registration first. ADUs cannot be used.
Cannabis. Diablo is not one of the nine areas in the county’s -CE Cannabis Exclusion district, though neighboring Blackhawk is. The residential zoning still leaves little room for it.

Private roads, access and small lots

Diablo’s road network is the biggest practical constraint on any non-residential use:

LAFCo’s 2011 report says most Diablo roads are private, with Caballo Ranchero the exception, and that DCSD maintained 8.5 miles of improved road at that time.
The same report describes upper Mt. Diablo Scenic Boulevard as privately owned by the adjoining owners and below county private road standards, with heavy use by park visitors.
Encroachments and traffic from any business use are a DCSD matter as well as a county one. Ask the district about its road rules before you plan customer or delivery traffic.

Many lots are older and smaller than today’s standards. The DMAC’s May 13, 2024 agenda, for example, reviewed a setback variance for a substandard R-20 lot on El Centro and a lot line adjustment that left one parcel under the 20,000 square foot minimum. Expect variances for most expansions.

Transfer tax, business tax and property tax

Diablo has no city government and no city transfer tax. The Contra Costa Clerk-Recorder charges the county documentary transfer tax of $0.55 per $500, and posts city taxes only for El Cerrito and Richmond. Under Proposition 13, a sale generally resets assessed value to the price paid. The county code requires a county business license under Chapter 64-14 before a short-term rental can operate; confirm whether it applies to your business with the county Treasurer-Tax Collector. Ask too about any DCSD charges on the tax bill.

Due diligence that matters in Diablo

Start with our commercial due diligence checklist, then add:

Confirm the parcel is in unincorporated Diablo, inside the DCSD boundary, and not in the Town of Danville.
Pull the zoning and any land use permit or conditions for a club, school, church or office use.
Ask DCSD about road ownership, maintenance and encroachment rules for the parcel’s access.
Check lot size and width against R-20 standards before planning any addition.
Confirm sewer or septic service with the provider before adding any use.
Plan for a DMAC hearing on any discretionary permit.

Questions people ask

Is there commercial zoning in Diablo?

We found none. Diablo is residential, with business uses possible mainly through county land use permits.

Who approves a business use in Diablo?

Contra Costa County, after review by the Diablo Municipal Advisory Council.

Who maintains Diablo’s roads?

The Diablo Community Services District maintains most roads, which LAFCo describes as largely private.

Can a medical office open in a Diablo house?

The county R-district rules list medical and dental offices as needing a land use permit, so it would take a discretionary approval.

Can I host weddings at a Diablo property?

Not as a short-term rental. The county’s short-term rental rules prohibit events. Other event uses would need their own approval.

Is there a Diablo transfer tax?

No. Only the county’s $0.55 per $500 applies.

Does Diamond handle commercial property in Diablo?

Contact Matthew Martinez to discuss buying, selling or leasing property in Diablo.

Sources & notes

Contra Costa County, Diablo
Contra Costa LAFCO, Directory of Local Agencies, Section 3 (July 2023) and LAFCO 11-02 staff report (May 2011)
Diablo MAC agenda, May 13, 2024
County Ordinance Code via GoCodebook: Division 84, R-20, R-6 uses, -CE, Chapter 88-32 permits and requirements
Contra Costa Clerk-Recorder, Documentary Transfer Tax

Note: The county page dates DCSD to 1969, while the 2011 LAFCo report says 1968. The LAFCo directory’s 1.17 square miles differs from the 1.56 in the 2011 report. We did not verify the zoning of the country club parcel, home occupation rules, the A-2 use list, or Diablo’s sewer provider.

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

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