How Much Does an ADU Cost in Cupertino? (2026)
Cupertino ADUs cost $130,000-$500,000+ in 2026 depending on type and scope. Garage conversions start at $130K. Attached ADUs run $175K-$325K. Detached ADUs cost $290K-$500K+. Cupertino's high property values and premium finish expectations push ADU costs 10-20% above the South Bay average, but the city's compliance with California's streamlined ADU laws keeps the permitting process manageable.
How much does an ADU cost in Cupertino?
ADU costs in Cupertino range from $130,000 for a garage conversion to $500,000+ for a large detached unit in 2026. The average detached ADU costs $290K-$450K. Attached ADUs average $175K-$325K. Cupertino's premium market and high finish expectations add 10-20% above the broader South Bay average.
ADU Costs in Cupertino: What to Expect in 2026
Cupertino is one of the most sought-after residential communities in the Bay Area. With Apple Park as its anchor employer, top-rated schools, and a median home price approaching $3 million, the city commands premium pricing for virtually every type of construction, including accessory dwelling units. But even at Cupertino’s price point, an ADU remains one of the best investments a homeowner can make: rental income, family housing, or long-term property value.
This guide breaks down 2026 ADU costs specific to Cupertino, covering what each type costs to build, what you will pay in permits and fees, what drives costs up or down, and how to plan your budget effectively.
All pricing is approximate, reflects 2026 Bay Area market conditions, and is subject to change. Every project is unique. Final costs are determined on a project-by-project basis during our design phase.
For Bay Area-wide ADU pricing, see our ADU cost guide.
Cost by ADU Type
The type of ADU is the single biggest factor in your total investment. Here is what Cupertino homeowners are paying in 2026:
| ADU Type | Cost Range | Cost/Sqft | Timeline | Typical Size |
|---|---|---|---|---|
| Garage Conversion | $130,000-$165,000 | $175-$375 | 4-6 months | 400-500 sqft |
| Attached ADU | $175,000-$325,000 | $325-$475 | 6-10 months | 400-800 sqft |
| Detached ADU | $290,000-$500,000+ | $375-$525 | 8-14 months | 500-1,200 sqft |
| Junior ADU (JADU) | $90,000-$165,000 | $225-$375 | 3-5 months | 200-500 sqft |
These ranges cover construction costs. Permits, design fees, and utility connections are additional expenses covered below.
Garage Conversions
Garage conversions are the most affordable ADU option because the shell already exists. The investment covers insulation, drywall, flooring, a kitchen, a bathroom, plumbing, electrical, and HVAC. In Cupertino, where homes sell for $2.5-$4 million, homeowners converting garages typically invest in finishes that match the main home’s quality level.
A one-car garage conversion (250-400 sqft) runs $90,000-$130,000. A two-car garage (400-600 sqft) costs $130,000-$165,000. Cupertino’s premium adds 10-15% compared to similar conversions in San Jose or Santa Clara.
Attached ADUs
Attached ADUs share at least one wall with the main home, simplifying utility connections and reducing foundation costs. In Cupertino, attached ADUs are common on tighter lots where a detached structure would struggle to meet setback requirements.
Expect to pay $175,000-$325,000 for an attached ADU. The range reflects differences in size (400-800 sqft), integration complexity, and finish level.
Detached ADUs
Detached ADUs are standalone structures offering maximum privacy and the highest rental potential. In Cupertino, a detached ADU costs $290,000-$500,000+. The higher cost reflects new foundation work, full framing, roofing, independent utility connections, and site work.
Cupertino’s lot sizes (typically 6,000-10,000 sqft) accommodate detached ADUs on most properties, though setback calculations are critical for determining the maximum footprint.
Junior ADUs (JADUs)
JADUs are created within the existing footprint of the primary home, up to 500 sqft. They require a cooking facility (a small kitchenette counts) and a separate entrance. At $90,000-$165,000, JADUs are an affordable way to add a rental unit or family suite without new construction.
Cupertino ADU Permit Fees and Soft Costs
| Cost Category | Typical Range | Notes |
|---|---|---|
| Building permit fees | $4,000-$18,000 | Based on project scope and valuation |
| Architectural/design fees | $10,000-$28,000 | Plans, engineering, Title 24 compliance |
| Utility connections | $5,000-$18,000 | Water, sewer, electrical; detached costs more |
| Impact fees (750+ sqft) | $5,000-$15,000 | Schools and parks for units over 750 sqft |
| Impact fees (under 750 sqft) | $0 | Waived under California law |
| Survey and soils report | $2,500-$5,500 | Required for new detached structures |
| Landscaping and site restoration | $3,000-$12,000 | Yard restoration, fencing, hardscape |
Total soft costs typically add $25,000-$70,000 on top of construction.
What Drives ADU Costs in Cupertino
Premium Finish Expectations
In a market where homes sell for $2.5-$4 million, builder-grade finishes will look out of place. Cupertino homeowners typically specify:
- Quartz or stone countertops
- Engineered hardwood or premium LVP flooring
- Semi-custom or custom cabinetry
- Upgraded appliances (stainless steel, energy-efficient)
- Quality fixtures and hardware throughout
These choices add $20,000-$60,000 compared to a standard-finish ADU. For rental units, mid-range materials offer the best balance between cost and rental income potential.
Lot Configuration and Access
Cupertino’s residential lots vary from compact 6,000 sqft parcels to larger 10,000+ sqft properties. On tighter lots, site access for construction equipment can be limited. If materials need to be carried by hand through a narrow side yard, labor costs increase. Lots with alley access or wider side yards save on construction logistics.
Utility Infrastructure
Older Cupertino homes (1960s-1980s) may need electrical panel upgrades before an ADU can be connected. Upgrading from 100-amp to 200-amp service costs $3,000-$6,000. Detached ADUs require independent utility trenching (water, sewer, electrical) at $10,000-$18,000. California law requires a separate electrical panel for ADU metering.
Apple Park Effect
Cupertino’s proximity to Apple creates intense housing demand. Rental rates for well-finished ADUs range from $2,500-$4,000+ per month. This strong rental market means homeowners can justify higher construction budgets, knowing the investment will generate meaningful income.
Cupertino ADU Regulations
- Lot zoning: ADUs are permitted on any residential lot with an existing single-family home
- Maximum size: Detached ADUs up to 1,200 sqft. Attached ADUs up to 50% of primary home area, maximum 1,200 sqft
- Setbacks: 4 feet from side and rear property lines for detached ADUs (per state law)
- Height: Detached ADUs up to 16 feet (single-story) or 18 feet (two-story, where allowed)
- Parking: No additional parking required (per state law)
- One ADU plus one JADU per single-family lot
- Owner occupancy: Not required for ADUs (state law preempts local requirements through 2030)
Cupertino’s residential zoning is predominantly R1, and the city complies with California’s ADU laws, which streamline the approval process.
How Cupertino Compares to Other Bay Area Cities
| City | Estimated Cost (600 sqft Detached) | Permit Timeline | Key Difference |
|---|---|---|---|
| Cupertino | $290,000-$400,000 | 8-12 weeks | Premium finishes expected, strong rental market |
| San Jose | $250,000-$350,000 | 6-10 weeks | Lower costs, ADU Ally program, fee waivers |
| Sunnyvale | $270,000-$380,000 | 8-12 weeks | Comparable market, standard processing |
| Mountain View | $275,000-$385,000 | 8-12 weeks | Similar costs, Eichler lots add complexity |
| Palo Alto | $320,000-$450,000 | 10-16 weeks | Design review, highest finish expectations |
Cupertino sits in the upper tier of South Bay ADU pricing but below the most premium Peninsula markets.
Sample ADU Budgets for Cupertino
Budget Example: 450 sqft Garage Conversion
| Line Item | Cost |
|---|---|
| Construction | $125,000 |
| Building permits | $5,000 |
| Design and engineering | $10,000 |
| Utility upgrades | $6,000 |
| Landscaping/site restoration | $4,000 |
| Total | $150,000 |
Budget Example: 800 sqft Detached ADU
| Line Item | Cost |
|---|---|
| Construction | $340,000 |
| Building permits | $12,000 |
| Design and engineering | $22,000 |
| Utility connections | $14,000 |
| Impact fees (over 750 sqft) | $10,000 |
| Survey and soils report | $4,000 |
| Landscaping/site restoration | $8,000 |
| Total | $410,000 |
How to Control Your Cupertino ADU Budget
Stay Under 750 sqft
Keeping your ADU under 750 sqft eliminates impact fees ($5,000-$15,000 savings) and reduces construction costs proportionally. A well-designed 700 sqft ADU can include a full kitchen, bathroom, living area, and separate bedroom. Rental income for a 700 sqft unit is typically only $200-$400/month less than a 1,000 sqft unit.
Choose Mid-Range Finishes for Rentals
If your ADU will be a rental unit, mid-range finishes deliver the best return on investment. Quartz countertops, LVP flooring, and quality (not luxury) fixtures look clean and professional while being durable enough for tenant use. Save premium materials for an ADU built for family.
Lock in Pricing During Design
Custom Home’s two-phase process separates design from construction. During Phase 1, every material, fixture, and finish is selected and priced. You approve a final number before construction begins. This eliminates the change orders and budget creep that cause most ADU projects to exceed their original estimates.
Consider a JADU First
If your primary goal is rental income and your home has an underused space (a large bedroom, a den, a section of the garage), a JADU at $90,000-$165,000 may accomplish your goal at a fraction of the cost of a detached ADU. JADUs do not require new foundation, roofing, or exterior work.
Why Cupertino Homeowners Choose Custom Home
Custom Home Design and Build has been building ADUs in Cupertino since 2005. We understand the local market’s expectations, the permitting process, and the level of quality that Cupertino properties demand.
Our process for ADU projects:
- Free consultation. We assess your lot, discuss your goals, and provide a realistic budget range.
- Phase 1: Design. Full architectural plans, 3D renderings, material selections, and a locked-in construction price.
- Phase 2: Build. Permitted construction with weekly progress updates and a dedicated project manager.
Every detail is finalized before we build. No surprises, no change orders, no budget overruns.
Start Your Cupertino ADU Project
Cupertino’s combination of strong rental demand, premium property values, and California’s ADU-friendly laws makes it one of the best cities in the Bay Area for an ADU investment. Whether you are building for rental income, housing a family member, or adding long-term value to your property, the right plan starts with accurate numbers.
Ready to explore what an ADU would cost on your specific Cupertino property? Contact Custom Home for a free consultation. We will visit your site, discuss your goals, and give you a realistic budget based on your lot, your neighborhood, and your vision.
Frequently Asked Questions
What is the maximum ADU size allowed in Cupertino?
Cupertino follows California state ADU law. Detached ADUs can be up to 1,200 sqft for properties with an existing single-family home. Attached ADUs can be up to 50% of the primary residence floor area, with a maximum of 1,200 sqft. JADUs are capped at 500 sqft and must be within the existing footprint of the primary home.
How long does it take to get an ADU permit in Cupertino?
Cupertino processes ADU building permits in approximately 8-12 weeks. California law requires cities to act on ADU applications within 60 days of receiving a complete submission. In practice, plan check corrections and resubmittals can extend the timeline. Budget 9-14 months total from initial design through completed construction.
Can I rent out an ADU in Cupertino?
Yes. Cupertino allows ADUs to be rented as long-term rentals (leases of 30 days or longer). Short-term rentals of ADUs are restricted. The strong rental market in Cupertino, driven by proximity to Apple and other tech employers, supports monthly rents of $2,500-$4,000+ for well-finished ADUs depending on size and amenities.
Does Cupertino charge impact fees for ADUs?
ADUs under 750 sqft are exempt from impact fees under California state law. For ADUs 750 sqft and larger, Cupertino may assess proportional impact fees for schools, parks, and traffic. These fees typically range from $5,000-$15,000 depending on the unit size. Keeping your ADU under 750 sqft is one of the most effective ways to reduce total project costs.