How Much Does an ADU Cost in Los Gatos? (2026)
Los Gatos ADUs cost $140,000-$520,000+ in 2026 depending on type and scope. Garage conversions start at $140K. Attached ADUs run $185K-$340K. Detached ADUs cost $300K-$520K+. Los Gatos's premium housing market, hillside lot challenges, and high finish expectations push costs 15-25% above the broader South Bay average. The town's Architecture and Site Review process applies to most ADU projects that affect the exterior appearance.
How much does an ADU cost in Los Gatos?
ADU costs in Los Gatos range from $140,000 for a garage conversion to $520,000+ for a large detached unit in 2026. The average detached ADU costs $300K-$460K. Attached ADUs average $185K-$340K. Los Gatos's Architecture and Site Review process and premium market expectations add 15-25% above the South Bay average.
ADU Costs in Los Gatos: What to Expect in 2026
Los Gatos is one of Silicon Valley’s most desirable residential communities. Nestled at the base of the Santa Cruz Mountains with a walkable downtown, highly rated schools, and a distinct small-town atmosphere, the town commands premium property values. With a median home price near $2.8 million, Los Gatos homeowners who add an ADU are making a high-value investment on high-value land.
This guide breaks down 2026 ADU costs for Los Gatos specifically: pricing by ADU type, permit and soft cost details, what drives costs up, and how to build smart.
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 you choose is the primary cost driver. Here is what Los Gatos homeowners are paying in 2026:
| ADU Type | Cost Range | Cost/Sqft | Timeline | Typical Size |
|---|---|---|---|---|
| Garage Conversion | $140,000-$170,000 | $185-$385 | 4-7 months | 400-500 sqft |
| Attached ADU | $185,000-$340,000 | $340-$490 | 6-11 months | 400-800 sqft |
| Detached ADU | $300,000-$520,000+ | $385-$540 | 9-15 months | 500-1,200 sqft |
| Junior ADU (JADU) | $95,000-$170,000 | $230-$380 | 3-5 months | 200-500 sqft |
These ranges represent construction costs. Permits, design fees, and utility connections are additional.
Garage Conversions
Los Gatos homes often have attached or detached two-car garages that convert into functional ADU space. Because the structure already exists, garage conversions skip foundation, framing, and roofing costs. The investment covers insulation, interior walls, flooring, kitchen and bathroom installation, plumbing, electrical, and HVAC.
In Los Gatos, garage conversions cost more than in San Jose or Sunnyvale primarily because of finish expectations. Homeowners here want ADU interiors that reflect the quality of their main home. A two-car garage conversion (400-600 sqft) runs $140,000-$170,000 with mid-range to premium finishes.
Attached ADUs
Attached ADUs connect to the primary home, sharing at least one wall. This reduces foundation and utility connection costs compared to detached structures. In Los Gatos, attached ADUs work well on properties where the rear yard slopes or where setbacks constrain a detached footprint.
Expect $185,000-$340,000 for an attached ADU. The range covers size variations (400-800 sqft), the complexity of tying into the existing structure, and finish quality.
Detached ADUs
Detached ADUs are standalone structures offering the most privacy and highest rental income potential. In Los Gatos, detached ADUs cost $300,000-$520,000+. The premium over other cities reflects:
- Higher foundation costs, especially on sloped lots
- Premium exterior materials to complement Los Gatos’s architectural character
- Longer utility runs on larger lots
- Higher finish expectations from the local market
Los Gatos’s lot sizes (many 8,000-15,000+ sqft) can accommodate substantial detached ADUs, though hillside properties face additional constraints.
Junior ADUs (JADUs)
JADUs are carved from existing space within the primary home (up to 500 sqft). They need a kitchenette and a separate entrance. At $95,000-$170,000, JADUs offer the lowest entry cost for adding a living unit. In Los Gatos, where homes are often 2,000-4,000 sqft, there is frequently underused space that lends itself to a JADU conversion.
Los Gatos 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-$30,000 | Plans, engineering, Title 24 compliance |
| Utility connections | $5,000-$18,000 | Water, sewer, electrical; detached costs more |
| Impact fees (750+ sqft) | $5,000-$14,000 | Schools and parks for units over 750 sqft |
| Impact fees (under 750 sqft) | $0 | Waived under California law |
| Survey and soils report | $2,500-$6,000 | Required for detached structures, especially hillside |
| Geotechnical report (hillside) | $4,000-$8,000 | Required for sloped properties |
| Landscaping and site restoration | $4,000-$15,000 | Yard restoration, retaining walls, fencing |
Total soft costs typically add $25,000-$75,000 on top of construction, with hillside properties trending toward the higher end.
What Drives ADU Costs in Los Gatos
Hillside vs. Flatland
The single biggest cost variable in Los Gatos ADU construction is terrain. Properties in the flatland neighborhoods near downtown (Almond Grove, Belwood, Blossom Manor) have straightforward site conditions. Hillside properties above town face:
- Engineered foundations. Stepped or pier foundations on slopes cost $25,000-$50,000+ compared to $12,000-$20,000 for standard slab foundations on flat ground.
- Retaining walls. Slopes often require retaining walls to create a level building pad, adding $15,000-$40,000.
- Access challenges. Narrow driveways, steep grades, and limited staging areas increase labor costs by 10-20%.
- Grading and drainage. Managing water flow on sloped sites requires engineered drainage plans and grading work at $5,000-$15,000.
A detached ADU on a hillside lot in Los Gatos can cost 15-30% more than the same ADU on a flat lot.
Premium Market Expectations
Los Gatos homeowners expect quality. An ADU with builder-grade finishes will feel out of place on a property valued at $2-$5 million. The local market sets a higher baseline for:
- Exterior materials that complement the main home’s architecture
- Interior finishes including hardwood or engineered hardwood flooring, quartz or stone countertops, and quality cabinetry
- Thoughtful landscaping that integrates the ADU into the existing yard
- Architectural details that reflect Los Gatos’s character
These expectations add $25,000-$60,000 compared to a standard-finish ADU in a more moderate market.
Lot Size and Configuration
Los Gatos lots are generally larger than in Sunnyvale or Mountain View (many are 8,000-15,000+ sqft), which gives more flexibility for detached ADU placement. However, larger lots also mean longer utility runs. Trenching water, sewer, and electrical lines 50-100 feet from the main house to a detached ADU costs $12,000-$20,000, compared to $5,000-$10,000 for closer placements.
Heritage Trees
Los Gatos has a heritage tree ordinance that protects significant trees. If your proposed ADU site is within the drip line of a heritage tree, you will need an arborist report ($1,500-$4,000) and potentially a tree protection plan. Relocating the ADU to avoid protected trees is often the most cost-effective approach.
Los Gatos ADU Regulations
- Lot zoning: ADUs permitted on residential lots with an existing single-family home
- Maximum size: Detached ADUs up to 1,200 sqft. Attached up to 50% of primary home, max 1,200 sqft
- Setbacks: 4 feet from side and rear property lines for detached ADUs (state law)
- Height: Up to 16 feet (single-story) or 18 feet per state allowances
- Parking: No additional parking required
- One ADU plus one JADU per single-family lot
- Architecture and Site Review: May apply to visible ADU projects, though state law limits discretionary delays
- Hillside Development Standards: Additional requirements for properties on slopes exceeding 10%
How Los Gatos Compares to Other Bay Area Cities
| City | Estimated Cost (600 sqft Detached) | Permit Timeline | Key Difference |
|---|---|---|---|
| Los Gatos | $300,000-$420,000 | 8-14 weeks | Premium market, hillside lots add cost |
| Saratoga | $310,000-$440,000 | 10-16 weeks | Similar premium tier, Design Review process |
| San Jose | $250,000-$350,000 | 6-10 weeks | Lower costs, streamlined permitting |
| Campbell | $255,000-$355,000 | 6-10 weeks | More moderate market, straightforward process |
| Monte Sereno | $320,000-$460,000 | 10-16 weeks | Most exclusive, highest finish expectations |
Los Gatos sits in the premium tier of South Bay ADU pricing, comparable to Saratoga and above the broader San Jose market.
Sample ADU Budgets for Los Gatos
Budget Example: 450 sqft Garage Conversion (Flatland)
| Line Item | Cost |
|---|---|
| Construction | $132,000 |
| Building permits | $5,000 |
| Design and engineering | $10,000 |
| Utility upgrades | $6,000 |
| Landscaping/site restoration | $4,500 |
| Total | $157,500 |
Budget Example: 800 sqft Detached ADU (Flatland)
| Line Item | Cost |
|---|---|
| Construction | $340,000 |
| Building permits | $12,000 |
| Design and engineering | $22,000 |
| Utility connections | $14,000 |
| Impact fees (over 750 sqft) | $8,000 |
| Survey and soils report | $4,000 |
| Landscaping/site restoration | $8,000 |
| Total | $408,000 |
Budget Example: 700 sqft Detached ADU (Hillside)
| Line Item | Cost |
|---|---|
| Construction (hillside premium) | $350,000 |
| Building permits | $11,000 |
| Design and engineering | $24,000 |
| Geotechnical report | $6,000 |
| Utility connections (long run) | $18,000 |
| Retaining walls | $25,000 |
| Survey and soils report | $5,000 |
| Landscaping/site restoration | $12,000 |
| Total | $451,000 |
How to Control Your Los Gatos ADU Budget
Choose Your Site Carefully
On larger Los Gatos lots, ADU placement choices can swing costs by $30,000-$60,000. Placing a detached ADU closer to the main home reduces utility trenching costs. Avoiding heritage tree drip lines eliminates arborist requirements. Selecting a flat area of the lot (even on hillside properties) avoids retaining wall expenses.
Stay Under 750 sqft
The impact fee exemption for units under 750 sqft saves $5,000-$14,000 in Los Gatos. A 700 sqft ADU with a well-designed one-bedroom layout provides excellent livability and commands strong rent in this market.
Invest in Quality Where It Shows
For Los Gatos ADUs, spend on the features tenants and family members experience daily: countertops, flooring, kitchen appliances, and bathroom fixtures. Save on elements hidden from view: utility-grade plumbing behind walls, standard insulation, and basic framing materials. The visual quality of the ADU drives rental value and resale appeal.
Lock Your Budget Before Construction
Custom Home’s two-phase design-build process means you approve a fixed construction price before any work begins. Every material, fixture, and finish is selected and priced during Phase 1. This prevents the change orders and budget creep that push most ADU projects 10-20% over their initial estimates.
Why Los Gatos Homeowners Choose Custom Home
Custom Home Design and Build has been building in Los Gatos since 2005. We understand the town’s unique characteristics: hillside construction, heritage tree protections, premium finish expectations, and the Architecture and Site Review process.
Our ADU process:
- 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.
Start Your Los Gatos ADU Project
Los Gatos’s premium rental market, large lot sizes, and strong property values make it one of the best communities in the Bay Area for an ADU investment. Whether you are building for rental income, housing a family member, or adding long-term property value, the key is working with a team that knows this market.
Ready to explore what an ADU would cost on your specific Los Gatos property? Contact Custom Home for a free consultation. We will visit your site, evaluate your lot and terrain, and provide a realistic budget based on your property, your goals, and the specific conditions of your neighborhood.
Frequently Asked Questions
Does Los Gatos require design review for ADUs?
Los Gatos may require Architecture and Site Review for ADU projects that alter the exterior appearance of the property, particularly detached ADUs visible from the street. However, California's statewide ADU laws limit the ability of cities to impose discretionary reviews that would delay ADU approvals beyond 60 days. The exact requirements depend on the visibility and scale of the ADU. Consult with the town's Community Development Department for your specific property.
Can I build an ADU on a hillside lot in Los Gatos?
Yes, but hillside lots add cost and complexity. Los Gatos's Hillside Development Standards may apply to ADU projects on sloped parcels, requiring geotechnical reports, engineered foundations, retaining walls, and grading plans. Hillside ADU construction typically costs 15-30% more than flatland projects. Access challenges on steep driveways also increase material delivery and labor costs.
What rent can I charge for an ADU in Los Gatos?
Los Gatos ADU rental rates range from $2,500-$4,200+ per month in 2026 depending on size, finishes, and location. Studio and one-bedroom ADUs (400-600 sqft) rent for $2,500-$3,200/month. Larger one- or two-bedroom units (700-1,200 sqft) command $3,200-$4,200/month. Los Gatos's walkable downtown, excellent schools, and small-town character make it one of the highest-rent ADU markets in the South Bay.
How long does it take to build an ADU in Los Gatos?
Los Gatos ADU construction timelines range from 4-6 months for garage conversions to 9-15 months for detached ADUs. Permitting takes 8-14 weeks. Properties in hillside areas or near heritage trees may face additional review time. Plan for 10-16 months total from initial design through completed construction for a detached ADU.