Custom homes & residential design in Diablo

A Diablo project often begins with an established property: a house, generous grounds and a landscape with its own history. The goal may be a more welcoming arrival, a better relationship between rooms and garden, or a complete rethink of the home. Start with the parcel and existing conditions. Diablo's postal name does not put a property under the Town of Danville's planning rules.

ZIP 94528

Kitchen with a pale island and tall timber cabinetry. — Kitchen with a pale island and tall timber cabinetry · From our residential portfolio

Start with the right address

Diablo 94528 is an unincorporated Contra Costa County postal locality. Confirm the parcel in the County's CCMAP and use County, not Danville, planning guidance unless the mapped jurisdiction shows otherwise.

Establish county planning requirements

Diablo is an unincorporated Contra Costa County community. The County's permit information page says its Department of Conservation and Development handles planning in unincorporated areas and recommends checking jurisdiction through CCMAP. It also notes that many projects need planning approval before building permits, including residential units. Confirm zoning and the proposed approval path before treating a preliminary sketch as a buildable plan.

A property study should locate the existing house, accessory structures, drives, easements, grades and major trees. County guidance says work within the dripline of some protected trees may require a permit. This makes landscape preservation part of early feasibility, especially when new rooms, parking or a pool compete for the same ground. Ask the Planning Division about the actual parcel rather than applying a general estate formula.

Verify the parcel and jurisdiction in the County mapping system.
Request zoning and permit history before defining scope.
Mark protected tree candidates and their drip lines on the survey.

Plan the grounds and the house together

An estate's exterior sequence can be as important as its living room. Walk from street to entry, from kitchen to outdoor dining, and from bedrooms to quiet garden spaces. Identify where service vehicles, guests and residents overlap. Then test whether a renovation can simplify those paths or whether a more substantial change is justified.

Keep the landscape in the drawings throughout the process. A detached structure may appear small in floor area while consuming a valuable view corridor or requiring a longer drive. Similarly, an expanded house can create beautiful rooms but leave fragmented outdoor spaces. Study the property in plan and section so that usable shade, privacy and circulation survive the new program.

Map the everyday arrival and service routes separately.
Compare several locations for outdoor rooms and secondary structures.
Evaluate the quality of remaining open space, not just its area.

Kitchen with an island and a view toward the dining area. — Kitchen with an island and a view toward the dining area · From our residential portfolio

Choose a scope that solves the right problem

Before choosing replacement, inspect the existing structure and its thermal and spatial performance. A renovation may keep mature landscape and recognizable proportions while correcting weak circulation. A new home may offer a clearer plan if the original structure severely limits the brief. Compare both with the same site diagram, costs and permitting assumptions.

The County's planning application overview lists possible paths including development plans, tree permits and variances, but it does not say every Diablo property needs each one. Build a project team around the actual constraints and request agency guidance at concept stage. That makes later design decisions more deliberate and avoids attaching architectural ambition to an uncertain permit premise.

Document structural and building-system conditions.
Separate essential room needs from optional amenities.
Check whether each option changes trees, grading or access.

You asked, we answered

Is Diablo under Danville planning?

Diablo is generally an unincorporated Contra Costa County community. Verify the parcel in CCMAP; the County reviews projects within its unincorporated jurisdiction.

Does an exterior remodel need county approval?

County guidance says changes to the size, height, dimensions or exterior of a building can require planning approval. Confirm the permit path for the exact scope.

Can I build near a mature tree?

Some trees are protected and work within their drip lines may need a permit. Have the site surveyed and ask County Planning before locating foundations or trenches nearby.

Local planning resources

Sources reviewed October 28, 2026. Confirm the current requirements for your parcel and scope with the reviewing authority.

Make the next conversation concrete

Share your property address, available plans and the changes you are considering. We can discuss the scope, site and the right next step for your home.

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