ADU Design & Build
ADU Builder in the Bay Area
Backyard homes that pay for themselves: feasibility, design, 60-day permits, financing, and fixed-price construction from one team.
The ADU is the best risk-adjusted investment most Bay Area homeowners will ever have access to: build a $300K asset on land you already own, rent it for $2,500–$4,500 a month in the nation's strongest rental market, and add appraisable value at resale. State law has cleared the path — cities must approve compliant units within 60 days and can't impose impact fees under 750 square feet.
What separates a smooth ADU from an 18-month ordeal is execution: a design that fits your lot's setbacks and utilities the first time, a complete permit package, and a builder who prices the whole job upfront. That's the BARC system, and it starts with a feasibility check on your actual parcel.
What's included
Lot Feasibility Check First
Setbacks, utility routing, tree constraints, and buildable envelope — answered before you spend a dollar.
Detached New-Construction ADUs
400–1,200 sq ft backyard homes, studio to 3-bedroom, designed for rental durability.
Attached ADUs & Conversions
Additions and interior conversions that create separate-entrance units economically.
Garage Conversion ADUs
The fastest path: existing structure becomes a studio/1BR for $125K–$220K.
Financing & Pro Forma
Cost, rent, and payback modeled upfront; HELOC/renovation-loan structuring in-house.
Fixed-Price Contracts
Locked construction pricing with milestone payments — no cost-plus roulette.
How it works
- 1
Feasibility
Parcel review and budget range — a clear go/no-go with numbers.
- 2
Design & Engineering (6–10 wks)
Floor plan, elevations, Title 24, structural — tuned for first-pass approval.
- 3
Permits (≤60 days)
Complete submittal triggers the state-mandated 60-day review clock; we manage corrections.
- 4
Construction (5–8 months)
Foundation, framing, trades, and finishes with weekly photo reports.
- 5
Rental-Ready Handover
Final inspection, address assignment, and rent-pricing guidance from our brokerage.
What it costs
| Project | Typical Range | Notes |
|---|---|---|
| Garage conversion (≈400 sq ft) | $125K – $220K | Studio or 1BR |
| Detached studio/1BR (400–600 sq ft) | $220K – $330K | $350–$550/sq ft |
| Detached 2BR (750–1,000 sq ft) | $320K – $480K | Best rent-per-dollar for families |
| Attached ADU | $300 – $450 / sq ft | Shares structure; saves foundation cost |
Utility distance, slope, and finish level move totals. Units under 750 sq ft are exempt from city impact fees statewide.
Frequently Asked Questions
How much does an ADU cost in the Bay Area in 2026?+
All-in (design, permits, fees, construction): garage conversions $125K–$220K; detached 400–600 sq ft units $220K–$330K; detached 2-bedrooms $320K–$480K. Per-square-foot costs run $350–$550 for detached new construction in Santa Clara County.
What rent will a Bay Area ADU earn?+
2026 Santa Clara County typical: studios $2,200–$2,800; 1-bedrooms $2,600–$3,400; 2-bedrooms $3,200–$4,500, with Palo Alto/Mountain View/Cupertino at the top of ranges. Most BARC ADUs gross 10–15% of construction cost annually.
Can my city really not block my ADU?+
Compliant proposals must be approved ministerially — no public hearings, no discretionary denial — within 60 days under state law (Gov. Code §66314 et seq.). Cities retain building-code and objective-standard review, which is why a clean, code-annotated submittal matters.
How big can I build?+
State law guarantees at least an 800 sq ft ADU on virtually any single-family lot regardless of lot coverage limits; most cities allow 1,000–1,200 sq ft for detached units. Two-story ADUs are allowed in many cities subject to height limits (16–25 ft). Your feasibility check pins down your parcel's exact envelope.
Do you handle everything, including utilities?+
Yes — trenching, panel upgrades, sewer connection or e-one systems, separate sub-metering where wanted, fire-sprinkler determination (usually not required if the main house doesn't have them), and solar compliance for new detached units.
Is an ADU the same as an in-law unit, guest house, or granny flat?+
Yes — accessory dwelling unit (ADU) is the legal term; in-law unit, guest house, granny flat, backyard cottage, and casita all describe the same thing: a permitted, self-contained second home on your property. Whatever you call it, the same California rules apply — ministerial approval within 60 days and impact-fee exemption under 750 sq ft.
Available by city
ADU Design & Build in Sunnyvale
Backyard homes built by the contractor down the street — feasibility, design, 60-day permi…
ADU Design & Build in San Jose
San Jose has the biggest lots and one of California's most ADU-friendly cities — we turn t…
ADU Design & Build in Palo Alto
The strongest ADU rents in our service area, built to Palo Alto's exacting standards — fea…
ADU Design & Build in Mountain View
Backyard homes that earn elite rents near Google and Microsoft — feasibility, design, 60-d…
ADU Design & Build in Santa Clara
Standard ranch lots, strong chip-industry rents, and the cheapest electricity in the South…
ADU Design & Build in Fremont
Fremont's bigger lots make backyard homes genuinely feasible — feasibility, design, 60-day…
ADU Design & Build in Milpitas
Milpitas pairs value entry prices with BART-boosted rents — which is why ADU yields here a…
ADU Design & Build in Los Gatos
Guest-house ADUs built to the 95030 standard — on larger in-town parcels and in the hills …
ADU Design & Build in Saratoga
Estate-grade guest houses on Saratoga's generous lots — feasibility, design review, 60-day…
ADU Design & Build in Cupertino
Multigenerational in-law suites today, premium rentals tomorrow — feasibility, design, 60-…
ADU Design & Build in Los Altos
Real guest houses, not squeezed-in rentals — Los Altos' quarter-acre lots host 1,000–1,200…
ADU Design & Build in Campbell
Walkable downtown, light rail, near-zero vacancy — Campbell ADUs rent fast and pencil hard…
ADU Design & Build in Menlo Park
The strongest ADU rents on the Peninsula — Meta one mile away, Stanford next door — built …
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