Building a Custom Home in Atherton: What Makes It Different

Why Atherton Is Different

Atherton is not just another affluent Bay Area city. It occupies a category entirely its own. For eight consecutive years, Atherton’s 94027 zip code held the title of the most expensive in the United States, and it continues to rank among the top two nationally with a median home sale price above $8 million. Homes here regularly sell for $10 million, $20 million, and occasionally above $50 million.

What makes Atherton truly distinct is not the price tag. It is the character of the place itself. The Town of Atherton has no commercial zoning whatsoever. There are no shops, no restaurants, no office buildings. The entire municipality is dedicated to residential living on large, wooded estate lots. This deliberate choice creates the privacy, quiet, and natural beauty that attract homeowners willing to invest at this level.

For anyone considering building a custom home in Atherton, this character comes with a specific set of requirements. Heritage tree protections, design review processes, estate-scale setbacks, and a permitting environment shaped by the community’s commitment to preserving its wooded, residential identity all require careful planning. This guide covers what you need to know.

The Estate-Scale Lot: Starting Point for Everything

Atherton’s zoning requires a minimum lot size of one acre for most residential properties, and many parcels are significantly larger. This is not a community of subdivided quarter-acre lots. When you build in Atherton, you are building on an estate.

This scale affects every aspect of the project:

• Building placement. With front yard setbacks of 30 to 60 feet (depending on zoning district and building height), side yard setbacks of up to 50 feet on wider lots, and comparable rear yard requirements, the buildable envelope must be carefully mapped before design begins.
• Driveway and access. Long driveways, gated entries, and motor courts are common. Site planning must account for emergency vehicle access, utility routing, and grading across the full parcel.
• Landscape integration. On a one-acre-plus lot, the relationship between the home and its landscape is a design decision, not an afterthought. Mature trees, topography, and views shape where the home sits and how it faces.
• Floor Area Ratio (FAR). Atherton limits the maximum floor area to 0.45 of the lot size. This ratio can increase to 0.55 if all resident parking is placed below grade. On a one-acre lot, this allows a home of roughly 19,600 to 24,000 square feet, though most custom homes range from 5,000 to 10,000 square feet.

Understanding these constraints before purchasing a lot, or before designing on a lot you already own, prevents the expensive surprises that come from discovering mid-design that your floor plan does not fit the buildable area.

Heritage Tree Protections: A Defining Factor

Atherton’s Heritage Tree Ordinance is one of the most consequential regulations affecting custom home construction. The town places a high value on its wooded character, and this ordinance is the primary mechanism for preserving it.

What Qualifies as a Heritage Tree

Under Atherton’s municipal code, a heritage tree is defined as:

• Any oak tree with a trunk circumference of 48 inches or more (approximately 15.2 inches in diameter), measured at 54 inches above grade, located anywhere on the lot
• Any other tree species with the same minimum circumference, located outside the main buildable area

This definition is broader than many Bay Area cities, where heritage tree protections often apply only to specific native species or trees above a larger size threshold.

Impact on Design and Construction

Heritage tree protections affect your project in several concrete ways:

1. Tree protection plans are mandatory. Every new construction, remodel, or demolition project must submit a tree protection plan showing the location and protection details for all heritage trees on site. This plan is reviewed before permits are issued.
2. Protection zones are generous. Tree protection fencing must be placed at a distance of 8 times the trunk diameter from the base of each heritage tree. For a tree with a 20-inch diameter trunk, this creates a protection zone extending over 13 feet in every direction.
3. Building footprint constraints. Heritage trees can effectively reduce your buildable area. A cluster of protected oaks near the center of a lot may force the home’s footprint to shift, split, or shrink.
4. Removal requires approval. Removing a heritage tree requires a permit and can involve mitigation requirements, including replacement plantings. Unauthorized removal carries significant penalties.

The practical implication: your architect and builder must survey existing trees early in the process and design around them. At Custom Home, we coordinate arborist assessments during our Phase 1 design process so that tree constraints are incorporated into the design from the start, not discovered after plans are drawn.

Design Review: Building for Community Character

Unlike many Bay Area cities where building permits are primarily a code-compliance exercise, Atherton layers a design review process on top of standard building code enforcement. The Town’s Planning Department evaluates new construction for compatibility with neighborhood character.

What Design Review Covers

The review process considers factors including:

• Building mass and scale relative to the lot and neighboring properties
• Exterior lighting. Atherton requires all exterior and landscape lighting to be directed downward with shielded light sources. Up-lighting of trees and permanent lighting within trees is specifically prohibited.
• Architectural compatibility with the surrounding neighborhood
• Impact on adjacent properties, including views and privacy

Navigating the Process

Design review adds time to the permitting process, typically 4 to 8 weeks beyond standard plan review. However, it also protects property values. The review ensures that no single project disrupts the aesthetic standard of the neighborhood, which is one of the reasons Atherton properties hold and appreciate their value so effectively.

Working with a builder who has experience in Atherton’s review process makes a significant difference. Understanding what the Planning Department looks for, and designing to those expectations from the beginning, avoids the resubmittals and revisions that delay projects by months.

Construction Costs: What to Budget

Custom home construction in Atherton commands some of the highest per-square-foot costs in the Bay Area. Here is what to expect in 2026:

Build Tier	Cost Per Sqft	6,000 Sqft Home	8,000 Sqft Home
Premium Standard	$500-$650/sqft	$3.0M-$3.9M	$4.0M-$5.2M
High-End	$650-$850/sqft	$3.9M-$5.1M	$5.2M-$6.8M
Ultra-Luxury	$850-$1,000+/sqft	$5.1M-$6.0M+	$6.8M-$8.0M+

These figures cover construction costs only. Additional budget items include:

• Land acquisition: $3M to $10M+ depending on lot size, location, and existing improvements
• Demolition (if replacing an existing home): $50,000-$150,000+
• Architecture and engineering: 8-12% of construction cost
• Permits and fees: Atherton’s building permit fees are calculated on a service requirement of $509 per square foot. For an 8,000 sqft home, the service requirement value is over $4 million, and permit fees are calculated as a percentage of this figure.
• Landscaping: On an estate lot, professional landscaping commonly runs $200,000-$500,000+
• Interior design and furnishing: Varies widely based on scope

What Drives Atherton Costs Higher

Several factors push Atherton construction costs above Bay Area averages:

• Finish expectations. Atherton homeowners typically specify imported stone, custom millwork, designer fixtures, and materials that require specialized installation. Standard builder-grade finishes are rarely appropriate for this market.
• Estate-scale infrastructure. Longer utility runs, larger HVAC systems, and more extensive site work on one-acre-plus lots add costs that do not exist on smaller parcels.
• Below-grade construction. Basements, underground garages, wine cellars, and below-grade entertainment spaces are common in Atherton and add significantly to foundation and excavation costs.
• Resort-style amenities. Pools, pool houses, tennis courts, outdoor kitchens, and guest houses are standard expectations for Atherton estates.
• Heritage tree accommodation. Designing around protected trees sometimes requires structural modifications, specialized foundations, or adjusted building footprints that add engineering and construction complexity.

For a broader view of Bay Area custom home pricing, see our complete custom home cost guide.

The Permitting and Approvals Timeline

Building in Atherton involves multiple review processes that run sequentially and sometimes in parallel. Here is a realistic timeline for new custom home construction:

Phase	Duration
Design and Architecture	3-6 months
Arborist Assessment and Tree Protection Plan	2-4 weeks
Engineering and Structural Plans	1-3 months
Planning/Design Review	4-8 weeks
Building Plan Review	6-12 weeks
Total Pre-Construction	8-14 months
Active Construction	14-24 months

Atherton enforces the California Building Code (Title 24) and adds local requirements that often exceed state standards. The Building Department reviews plans for compliance with both the California Building Standards Code and the Atherton Municipal Code.

Construction Hours and Neighbor Considerations

Atherton has specific regulations regarding construction hours to minimize disturbance to residents. These restrictions are strictly enforced, and violations can result in stop-work orders. Planning your construction schedule around these limitations from the start prevents delays and maintains positive relationships with neighbors, which matters in a community this close-knit.

Privacy: The Core Expectation

Privacy is not just a preference in Atherton. It is the defining expectation. Homes are set far back from the road, often behind gates, walls, and mature landscaping. The town’s wooded character, large setbacks, and prohibition on commercial activity all contribute to a level of seclusion that is difficult to find anywhere else on the Peninsula.

When designing a custom home in Atherton, privacy considerations include:

• Siting the home to maximize distance from property lines and road frontage
• Landscape buffering with mature plantings that provide immediate screening
• Window placement and glazing that balances natural light with visual privacy from adjacent properties
• Security systems and entry design integrated architecturally rather than added as an afterthought
• Downward-directed exterior lighting that meets code requirements while preserving the neighborhood’s dark-sky character

These elements should be part of the initial design conversation, not addressed after the floor plan is set.

Why Design-Build Matters More in Atherton

The complexity of building in Atherton makes the choice of delivery method especially important. The traditional approach, where a homeowner hires an architect separately from a builder, creates coordination gaps that are costly in any market but particularly expensive in Atherton.

When heritage tree constraints, design review feedback, or zoning limitations require changes, a design-build firm can adapt the design and adjust the construction plan simultaneously. With separated architect and builder contracts, every change triggers a chain of revisions, re-pricing, and potential disputes about scope.

Custom Home’s two-phase process is built for exactly this kind of complexity:

Phase 1 (Design): We survey the site, map all heritage trees, analyze zoning constraints, and develop complete 3D visualizations of your home. You see every room, every material, every angle before construction begins. The budget is itemized and locked in. Heritage tree protections, design review requirements, and setback constraints are all resolved during this phase.

Phase 2 (Build): Construction proceeds from fully-approved plans with no surprises. Because every constraint was addressed in Phase 1, there are no mid-construction redesigns, no budget overruns from tree discoveries, and no schedule delays from planning department feedback.

This approach is especially valuable in Atherton, where a single overlooked heritage tree or a design review revision can add months and hundreds of thousands of dollars to a project.

Building in Atherton: The Bottom Line

Atherton offers something no other Bay Area community can match: true estate living, with large wooded lots, complete residential character, and a level of privacy that technology executives, venture capitalists, and established families have valued for decades. Building a custom home here is the opportunity to create a residence that matches the setting.

It is also a process that rewards preparation. Understanding the heritage tree ordinance, the design review process, the zoning constraints, and the cost dynamics before you begin is the difference between a project that runs smoothly and one that stalls in permitting or balloons in budget.

Custom Home Design and Build has guided homeowners through the Bay Area’s most demanding construction environments. Our two-phase process gives you complete clarity on design, budget, and timeline before any construction begins.

Ready to explore what is possible on your Atherton lot? Contact our team for a consultation. We will walk through your site, your vision, and the specific requirements that will shape your project.