Contra Costa County Luxury Homes for Sale

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

Contra Costa County’s estate homes are concentrated in the hills of Lamorinda (Orinda, Lafayette and Moraga) and the San Ramon Valley (Alamo, Danville, Diablo and Blackhawk), with waterfront homes out at Discovery Bay. Two checks matter most: whether the parcel is inside a city or unincorporated, since Alamo, Diablo and Blackhawk follow county rules while Danville and Lafayette run their own hillside and design review, and whether the home sits in a mapped High or Very High fire hazard severity zone, which shapes insurance and the seller’s defensible space paperwork.

This page explains where estate homes are and what to check. It gives no prices or market statistics; ask us for a current comparable-sales review.

At a glance

Where to look in Contra Costa County

Lamorinda. Orinda real estate, Lafayette real estate and Moraga real estate are three cities of wooded and hillside single-family lots off SR 24, inside EBMUD’s water service area and served by Central San for sewer. Orinda and Lafayette have BART stations; Moraga does not. Our Lafayette hillside home due diligence and Orinda hillside home due diligence guides list what to request on a slope.

San Ramon Valley. Alamo real estate is unincorporated, with larger lots and estate parcels along I-680. Danville real estate is an incorporated town with subdivisions, planned communities and estate parcels. Diablo real estate and Blackhawk real estate are unincorporated areas near Danville, and San Ramon adds planned communities to the south. EBMUD’s service area includes the San Ramon Valley, and Central San collects wastewater for Alamo, Danville and San Ramon. For Diablo’s private roads and utilities, see Diablo private roads and site access.

Walnut Creek and Clayton. Walnut Creek real estate and Clayton include larger homes on hillside lots within city limits.

Delta waterfront. Discovery Bay real estate is unincorporated and includes waterfront homes on the Delta; see our Discovery Bay flood, levee and insurance records guide.

Mailing addresses blur the city line: a Walnut Creek or Danville address can belong to an unincorporated parcel. Confirm jurisdiction by assessor’s parcel number; our unincorporated Contra Costa County page explains the check.

What to check before you buy

Hillside and design review

Lafayette. The city requires a Hillside Development Permit for projects in its Hillside Overlay District that erect, modify or relocate a structure, grade the site, remove native riparian vegetation, change density or intensity of use, subdivide or adjust lot lines. Work that needs no building or grading permit, stays inside an existing structure or doesn’t change exterior appearance is exempt. On vacant land, a new house goes through two phases: the Planning Commission reviews siting and massing, then the Design Review Commission reviews final design. Development within a protected ridgeline setback goes to the Planning Commission, and every project must substantially comply with the city’s Residential Design Review Guidelines.

Danville. The town’s Design Review Board reviews site design, architecture, signs and landscaping for consistency with the General Plan, ordinances and design standards. It is advisory, assisting the Town Council and Planning Commission.

Unincorporated areas. In Alamo, Diablo and Blackhawk, county planning and building rules apply, and many planned communities also have association architectural rules. Ask for the CC&Rs and any architectural approvals with the HOA documents. Orinda, Moraga and Walnut Creek have their own review processes, which we did not verify for this page.

What this means for a buyer: if you plan to add on, rebuild or regrade, ask the seller for prior hillside or design approvals and confirm the current process with the city or county before you remove contingencies. Our guides to Alamo renovation feasibility records and Danville hillside due diligence cover the records.

Fire hazard zones and insurance

The State Fire Marshal’s fire hazard severity zone maps classify land as Moderate, High or Very High. State Responsibility Area maps took effect April 1, 2024, and Local Responsibility Area maps, which cover incorporated cities, were released in four phases between February 10 and March 24, 2025. The maps measure hazard, not risk. Check the exact parcel on the map viewer, including in-city hillside lots.

In a High or Very High zone, Civil Code 1102.19 requires the seller, since July 1, 2021, to provide documentation of compliance with defensible space rules, or a written agreement under which the buyer obtains it. See our AB 38 defensible space inspection guide.

Get insurance quotes during your contingency period. The California FAIR Plan covers residential property up to $3 million per location, per the Department of Insurance, as a limited fire policy; water damage, liability and theft need a separate difference-in-conditions policy. For a large estate, compare the limit with the rebuild estimate. See our FAIR Plan guide for homebuyers.

Wells and septic on estate parcels

Most Lamorinda and San Ramon Valley homes are on public water and sewer, but some hillside and rural parcels rely on a well and septic system. Contra Costa Environmental Health requires a permit at each step of a new septic system and a monitoring program for alternative systems. Existing wells need a bacteriological test; new wells need a four-hour pump test showing at least 3.0 gallons per minute sustained, and must sit at least 100 feet from the septic tank and leach field. Ask the seller for permit records and test results; see also Diablo rural water and wastewater.

Owning and financing an estate home

Transfer tax. California counties may levy a documentary transfer tax of $0.55 per $500 of value under Revenue and Taxation Code 11911, and some Contra Costa cities add their own tax. We could not open an official county or city rate page for this guide, so ask your title officer for the rates on your parcel. See California transfer tax.

Jumbo financing. Contra Costa’s 2026 one-unit conforming loan limit is $1,249,125, per FHFA, the national high-cost ceiling. Above that, a loan is jumbo and follows the lender’s own rules. Limits reset each year. See our jumbo loans guide.

Private and off-market sales. Some estate owners sell without public marketing. We handle private and off-market sales and can explain the trade-offs.

Questions people ask

Is Alamo a city?

No. Alamo is unincorporated, so county planning and building rules apply. Central San provides its wastewater collection and treatment.

Are Blackhawk and Diablo part of Danville?

No. Both are unincorporated areas near Danville and follow county rules, even with a Danville mailing address. Confirm by parcel number.

When does Lafayette require a Hillside Development Permit?

For new, modified or relocated structures, grading, riparian vegetation removal, subdivisions and lot line adjustments in the Hillside Overlay District, unless the work needs no building or grading permit.

Does Danville’s Design Review Board approve projects?

It advises. The board reviews site design, architecture and landscaping and assists the Town Council and Planning Commission.

What does a seller have to provide in a High or Very High fire zone?

Documentation of compliance with defensible space rules, or a written agreement that the buyer will obtain it, under Civil Code 1102.19.

Is the FAIR Plan enough for a large estate?

Its residential limit is $3 million per location, and it is a limited fire policy. Most owners also need a difference-in-conditions policy.

What does Contra Costa require for a new well?

A four-hour pump test of at least 3.0 gallons per minute and at least 100 feet of separation from the septic tank and leach field.

Where does a jumbo loan start in Contra Costa County?

Above $1,249,125 for a one-unit home in 2026, per FHFA.

Sources & notes

1. City of Lafayette: Hillside Development Permit.
2. Town of Danville: Design Review Board.
3. CAL FIRE Office of the State Fire Marshal: Fire hazard severity zones.
4. Civil Code 1102.19 (read via the california.public.law mirror).
5. California Department of Insurance: California FAIR Plan.
6. Contra Costa Health, Environmental Health: Land use (septic systems and wells).
7. EBMUD: Service area and Central San.
8. Revenue and Taxation Code 11911 (Justia mirror; official text at leginfo.legislature.ca.gov).
9. FHFA: 2026 county conforming loan limits.

Notes: Contra Costa County’s recorder transfer tax page and any city transfer tax rates could not be verified, so no city rates are given. Lafayette’s numeric slope and ridgeline setback standards (Municipal Code Chapter 6-20), Danville’s board guidelines, and design review in Orinda, Moraga, Walnut Creek and the unincorporated county were not reviewed. HOA architectural rules in Blackhawk and other planned communities vary; read the association documents. Rules change; verify before you buy.

General information, not legal, tax or lending advice. Updated November 2026. Primary sources are linked in this guide.

Related: Contra Costa County homes · Where to live in Contra Costa County · Buying a luxury home · Private sales · Jumbo loans