California's Build-Side ADU Partner for Your Project
ADUscale is a build-side ADU partner for California homeowners, including Los Angeles, San Diego, San Francisco, San Jose, and Orange County. We do not build. We verify your contractor against six independent data sources, including 11 million inspection records from our sister product InspectPilot, going back to 2013. We oversee every milestone from feasibility through certificate of occupancy, and protect your budget through Verified Milestone Payouts: your money releases only after each construction milestone passes independent inspection. Sometimes the right answer is not to build, and we say that clearly, before any money moves.
Start with a free ADU Reality Check.
Before you talk to a contractor. Before you pay an architect. Before you sign anything. We pull your county parcel data, run your lot against current state ADU law and your city's local rules, and give you a one-page answer in under two minutes.
- Whether your lot qualifies for an ADU
- What types are allowed (detached, attached, garage conversion, JADU)
- The maximum size your lot supports
- A realistic cost band based on your ZIP and 2026 California construction data
- It is not a soils report
- It is not a structural plan
- It is not a permit submittal
- It is the first answer, not the last word
Who this is for. And who it's not.
We say no to as many homeowners as we say yes to. Read this honestly before you click.
- California homeowners planning an ADU on their residential property
- People who want independent oversight, not a sales pitch from a contractor
- Homeowners who want their construction budget protected by Verified Milestone Payouts
- First-time builders who need a clear process, not a gut decision
- Owners of properties with low-rate mortgages who want to keep them
- Commercial developers or multi-unit investors
- Properties outside California (Massachusetts, Oregon, Washington, Colorado are next)
- Homeowners looking for the cheapest possible build with no oversight
- DIY builders who want to self-manage end-to-end
What type of ADU fits your property?
Five paths — your lot, zoning, budget, and timeline decide which one is right, not the contractor selling it to you.
Garage Conversion
Turn your garage into a legal living space.
Why ADU projects go wrong.
Most projects do not fail in construction. They fail in the spaces between architect, contractor, city, lender, and homeowner, where no one is in charge of the homeowner's interest. The five failure patterns we see most often:
The contractor takes the deposit and disappears.
California's CSLB contractor license bond pays at $25,000 maximum total for all claims combined, under 10% of a typical $300,000 ADU project. The 2024–2025 collapses left hundreds of California homeowners with half-finished ADUs: Anchored Tiny Homes (Roseville — 450+ projects abandoned, Chapter 7 bankruptcy with $12.8M liabilities) and Multitaskr Construction (Chula Vista — license revoked June 2025, four officers banned from contracting for 5 years).
Subcontractors file mechanic's liens against the homeowner's property even when the homeowner has paid the GC in full.
California Civil Code §8400 et seq. permits direct liens against the property, and §8200 preliminary notice protects sub claim rights from day one of work. Common pattern in recent California ADU company failures.
Plan check correction loops quietly add months.
ADU plans commonly go through 2–3 correction rounds at LADBS, San Diego DSD, and most Bay Area planning departments, and an incomplete submission resets the 60-day approval clock under California ADU streamlining law (Gov Code §65852.2). Each round adds weeks plus architect re-work fees. Staffing backlogs in 2025–2026 are documented in city permit reporting.
Mid-project change orders inflate the budget without independent review.
California construction labor runs $65–$120/hour, material costs are up 18% since 2023, and on failed California ADU projects, bids have doubled mid-build. Without an independent reviewer, change orders ride on the GC's word.
Inspections fail in sequence, and each re-inspection costs money.
A typical ADU passes through 5–7 inspections (foundation → framing → mechanical, electrical, plumbing → final). Each failed inspection adds $600–$1,000+ in fees plus re-work labor (LADBS reinspection schedule plus InspectPilot field tracking). Without independent pre-inspection verification, the homeowner only learns there is a problem after the work is already done, and paid for.
A build-side ADU partner is the answer to all five. Not a different builder. A different role.
The ADUscale Method: Decide. Verify. Protect. Build.
We work in four stages. Hire us for one stage, or for all four.
Decide
We assess feasibility, build the cost model, and walk through the financing options for your specific situation. You get a written Feasibility & Risk Assessment for $199 that tells you whether to proceed and how, including the right loan path for your specific mortgage. If you hire us for the full ADUscale engagement, the $199 credits against your contract.
Verify
We run every contractor bid through six data sources: CSLB license status, state complaint history, court filings (mechanic's liens and prior lawsuits), city inspection records, inspection-pass-rate data from our sister brand InspectPilot (11 million records going back to 2013), and contract review. You do not pick the contractor on a gut feeling. You pick on 11 million data points.
Protect — Verified Milestone Payouts
Your project budget moves only when work passes independent inspection. We define milestones with the contractor (foundation, framing, mechanical, finishes, final inspection). At each milestone we verify the work in person before any payout is triggered. If the work does not meet standard, the money does not move.
Build
We coordinate with the contractor, your lender, the city, and the inspectors. You get a single point of contact. We catch the problems before they become $40,000 problems.
What ADU projects look like across California.
Three typical paths, fact-checked against 2026 California market data. Bay Area projects, custom finishes, hillside or coastal lots, and projects requiring soils-related foundation work typically add 25–50% to the base figures.
Garage Conversion
up to $225K with structural upgrades or premium finishes
Backyard Detached
premium builds run $400K+
Prefab
up to $300K with full site work
Cost-band sources: industry cost-benchmark data and California HCD permit fee benchmarks. Worst-case outliers in LA County and Saratoga have hit $420K–$650K for large premium-finish builds.
I started ADUscale because I watched homeowners lose budget on the predictable change-order categories: $15K–$30K sewer-lateral upgrades, $20K–$60K hillside soils work, $5K–$25K structural retrofits on pre-1970 garages. None of these are random. All of them are documented. And every other party on the project — contractor, prefab seller, even the lender — was on the other side. So we built the verification and the payment-control system to put a real weight on the homeowner's side.
What ADUscale costs.
Here is the catch on the $199 Feasibility & Risk Assessment: there is not one. If you hire us for the full ADUscale engagement, the $199 credits against your contract. You are effectively paying for the report only if you decide not to work with us. Even then, you keep the analysis.
Free ADU Reality Check
- Pulls your parcel data
- Runs eligibility against state and city rules
- Returns a one-page answer
- No phone call required
ADU Feasibility & Risk Assessment
- Full lot analysis
- Cost model with current 2026 inputs
- Financing-path recommendation
- Contractor-market read for your city
- Written risk register
Full ADUscale Engagement
- Full Decide → Verify → Protect → Build service
- $199 Feasibility deposit applies on day one
- Verified Milestone Payouts on Stripe Connect rail (no fund-control fee)
- Optional DFPI-licensed escrow rail (partner fee 0.5–1.0%)
- Coordination through certificate of occupancy
Three ways to run an ADU project. Only one works for you.
A $250K commercial build would not run without a build-side partner. A $250K residential build runs with the contractor on both sides of the table.
We are not a contractor. And that is the point.
We do not pour foundations. We do not frame walls. We do not broker loans. We do not sell prefab kits.
What we do is simpler: read every contractor bid against six independent data sources. Verify the work in person at every milestone. Refuse to release money until the work passes. That is the role.
Your side of the scale.
Frequently
asked questions.
The questions homeowners ask before they sign.
Start with clarity. It is free.
And the right time to run it is before you spend on architectural plans, which is typically the first 5–10% of the budget out of pocket.