How to Find a Good ADU Contractor in California: 15 Questions to Ask Before You Sign

If you are trying to find a good ADU contractor in California, do not begin with reviews or the lowest price. Begin by verifying the exact company through the California Contractors State License Board (CSLB), then compare recent ADU experience, local permitting knowledge, bid completeness, payment terms, and references using the same standard.

Building an ADU is not a normal remodel. Your contractor may need to coordinate design revisions, multiple trades, trenching, utility providers, city inspections, and final approval before the unit can be used. A polished sales presentation tells you very little about whether the company can manage that chain of work.

The safest choice is not automatically the lowest bid, the largest company, or the contractor with the most five-star reviews. It is the contractor whose identity and credentials you can verify, whose recent ADU work resembles yours, and whose written contract makes scope, risk, payments, changes, and closeout unmistakably clear.

This guide gives you 15 questions to ask before signing. Each includes the answer you want to hear, the red flags to notice, and an independent way to verify what you are told.

QUICK ANSWER
Before hiring, verify the exact contracting business in the California Contractors State License Board (CSLB) database; compare at least three bids against the same plans and scope; speak with recent ADU clients; confirm insurance directly; identify all exclusions and allowances; and insist on a California-compliant written contract. For most ADU home-improvement contracts, the down payment cannot exceed $1,000 or 10% of the contract price, whichever is less, and later payments should not exceed the value of work performed or materials delivered.

In this guide

Use this guide in three stages

1. Shortlist: Find candidates with recent, permitted ADUs similar to yours and experience in your city or county.
2. Verify: Check the exact CSLB entity, license classification and status, insurance, personnel, references, permits, and completed work.
3. Compare and score: Normalize three bids, ask the same 15 questions, apply the 100-point scorecard, and negotiate the contract—not just the price.

What this guide covers

• how to shortlist qualified ADU contractors in California
• CSLB license, classification, personnel, bond, and complaint checks
• insurance and workers’ compensation verification
• ADU-specific and local permitting experience
• design, engineering, Title 24, and plan-check responsibilities
• allowances, change orders, utility work, and hidden exclusions
• California payment-schedule and deposit red flags
• 15 questions to ask every ADU contractor
• an original 100-point ADU Contractor Scorecard
• deal-breakers, excessive deposit steps, and frequently asked questions

Why ordinary contractor advice is not enough for an ADU

Most contractor checklists say to verify a license, insurance, references, price, and schedule. Those are sensible starting points, but ADU owners usually need more precision.

A low bid may exclude the electrical service upgrade, sewer connection, long trench, demolition, grading, drainage, permit fees, plan-check corrections, or finish selections. A “fixed price” may contain large allowances that can still move. A contractor can have an active license yet have little experience with ADUs in your jurisdiction. And paying the general contractor does not by itself prove that subcontractors and suppliers were paid.

California’s CSLB specifically advises ADU owners to confirm who handles underground utilities, keep payments from getting ahead of the work, verify charges for plans and permits, and put all change orders in writing. Use those issues as a minimum—not the finish line—for your vetting.

Before you interview contractors: make the bids comparable

Ask at least three contractors to price the same drawing set, specifications, finish level, and responsibility list. CSLB recommends at least three written bids based on identical plans, specifications, and scope. If one contractor prices a permit-ready set while another prices a sketch, their totals tell you almost nothing.

Give each bidder a one-page scope sheet covering:

• ADU type, size, address, and current design/permit stage
• demolition, access, staging, tree protection, and debris removal
• foundation, structure, roofing, windows, exterior, and interiors
• plumbing, sewer, electrical service/panel, gas if any, HVAC, solar if applicable, and utility trenching
• grading, drainage, retaining work, survey, soils/geotechnical work, and fire-access requirements
• design, engineering, Title 24 energy documentation, plan-check corrections, permits, fees, inspections, and utility coordination
• finish allowances with brands, models, quantities, or realistic dollar amounts
• landscaping and restoration disturbed by construction
• final inspection, punch list, lien releases, warranties, manuals, and keys

Then ask the following questions in the same order at every interview.

If your plans are still moving through the city, review the ADU Project Planner guide to the California ADU permit process before relying on a contractor’s schedule. Permit stage and plan completeness materially affect whether bids are comparable.

The California checks that matter most

Verify the CSLB license, classification, and status

The first screen is not “Does the contractor have a license number?” It is “Does this exact company have the right active license for this work?” Match the legal business name, personnel, address, classification, bond, and workers’ compensation information to the proposal and contract. A typical multi-trade site-built ADU is commonly handled by a B General Building contractor; manufactured-home installation can involve a C-47 contractor. Review disclosed disciplinary or complaint information and ask for an evidence-backed explanation of anything material.

Confirm insurance and workers’ compensation

Workers’ compensation and commercial general liability cover different risks. Ask for both, verify policies directly with the carrier or agent, and make sure the named insured is the same entity signing your contract. Do not confuse California’s contractor license bond with liability insurance or a completion guarantee.

Distinguish ADU experience from general remodeling

An attractive kitchen portfolio does not prove the contractor can manage a new dwelling. Look for recently completed, permitted projects comparable in type: detached ADU, attached ADU, garage conversion, or manufactured unit. Ask what went wrong, how the team handled corrections, and whether each project reached final approval.

Test experience with your permitting jurisdiction

The most valuable local knowledge is specific, not boastful. The contractor should be able to describe your city or county’s submittal process, likely inspection sequence, utility interfaces, common plan-check corrections, and realistic lead times. Verify those claims with permit records, the building department, and recent local clients.

Identify who prepares plans and engineering

Design-build does not always mean every discipline is in-house. Identify the architect or designer, structural and civil engineers where needed, Title 24 provider, surveyor, soils consultant, and the party responsible for plan-check corrections. State who owns and may reuse the plans if the contractor relationship ends.

Make allowances and change orders auditable

Every allowance should state a dollar amount, what it buys, whether tax/delivery/installation are included, the contractor markup, selection deadline, and how savings or overruns are credited. Every change order should state the reason, scope, price or credit, markup, schedule effect, and require written approval before changed work begins.

Inspect the full payment curve

An apparently lawful deposit does not make a front-loaded schedule safe. Compare each milestone with the value of visible completed work and delivered materials. Keep meaningful leverage through final inspection and punch-list completion, and pair payments with conditional and unconditional lien releases.

Require an ADU-ready contract

The contract should do more than satisfy a form. It should incorporate the plans/specifications, precise inclusions and exclusions, permit responsibilities, start and completion assumptions, payment milestones, change-order procedure, cleanup, insurance, warranties, dispute terms, lien releases, and a detailed closeout definition. California CSLB guidance says important promises and changes belong in writing.

Assign utilities and site work explicitly

State who investigates, designs, coordinates, pays for, and installs water, sewer, electrical, gas if any, trenching, service/panel upgrades, utility meters, grading, drainage, and restoration. “Utilities by owner” is not a scope—it is an invitation to disagreement unless every boundary is defined.

Compare three bids properly

Normalize the bids before comparing totals. Use the same plans and scope, separate base price from allowances and alternates, add known owner-paid items, and flag every unknown. The most useful comparison is expected all-in cost plus risk—not the bold number on page one.

What a useful answer sounds like

Topic	Weak answer	Useful, verifiable answer
License	“We are fully licensed.”	“This exact legal entity and license number will sign the contract. Here is the CSLB record; verify its status and classification independently.”
ADU experience	“We build lots of small homes.”	“These three permitted ADUs reached final approval in comparable jurisdictions. Here are the permit references and owners you may contact.”
Scope	“Everything required is included.”	“The bid identifies plans, engineering, utilities, site work, finishes, permit responsibilities, allowances and exclusions line by line.”
Changes	“We will work it out if something comes up.”	“No changed work starts until you receive the written scope, price, markup and schedule impact and approve it.”

A confident answer is not enough by itself. Ask for the document, public record, reference or contract clause that lets you verify it.

The 15 questions to ask an ADU contractor

1. What exact CSLB-licensed business will sign my contract, and who is authorized to sign for it?

Do not verify only the license number printed on a proposal. Verify the legal entity attached to it. California licenses can belong to an individual, partnership, corporation, LLC, or joint venture, and the company name in your contract should match the CSLB record.

A strong answer: “ABC Builders LLC, license number XXXXXXX, will be the prime contractor. The contract, invoices, insurance certificate, and payment recipient will all use that entity. I am an officer/personnel member shown on the license record.”

Red flags: The proposal uses a different business name; checks must be made to an individual; the salesperson says the company “works under” someone else’s license; or the name and address keep changing.

Verify: Search by license number and business name in CSLB’s Check a License tool. Compare the entity name, address, personnel, status, and classification with the proposal, contract, insurance certificate, and payee.

2. Is the license active and appropriately classified for this ADU, and what complaints or discipline should I know about?

A typical site-built ADU involves several unrelated trades, so a B General Building contractor is commonly the appropriate prime contractor. CSLB says a B contractor can build or install ADUs and supervise properly licensed specialty subcontractors. A manufactured-home installation may involve a C-47 General Manufactured Housing contractor.

A strong answer: The contractor gives you the number without hesitation, explains the classification, and invites you to check its full history.

Red flags: An expired, suspended, inactive, or wrong-class license; a recently reissued entity with unexplained history; undisclosed disciplinary actions; or a request to ignore a mismatch because “the permit office knows us.”

Verify: Review the CSLB record on the day you sign and again before work starts. Look at license status, classifications, bond, workers’ compensation information, personnel, and any complaint or disciplinary disclosure. A disclosed complaint is not automatically proof of wrongdoing, but it deserves a clear explanation and supporting documents.

3. Who sold me this project, and are they properly connected to the licensed company?

The person making promises may be a salesperson rather than the qualifier, project manager, or company owner. In California, a person who solicits, sells, negotiates, or executes home-improvement contracts for a contractor generally must be registered as a Home Improvement Salesperson (HIS), unless an exemption applies.

A strong answer: The person identifies their role, registration or exemption, employer, and who has authority to bind the company. Every promise they make will appear in the final contract.

Red flags: “I’m independent, but they let me use their license”; pressure to sign before meeting the construction team; or assurances that do not appear in writing.

Verify: Use CSLB’s license/HIS lookup and compare the salesperson’s relationship with the contracting company. Ask an officer of the company to confirm unusual promises in writing.

4. What insurance and bonds cover this project, and may I verify them directly?

“Licensed, bonded, and insured” is a slogan, not an insurance analysis. California contractors with employees generally must carry workers’ compensation insurance. CSLB does not universally require commercial general liability insurance, although it can protect against accidental property damage. The standard contractor license bond is $25,000; CSLB cautions that it is not proof of competence and may be insufficient for multiple claims or a six-figure project.

A strong answer: The contractor supplies current workers’ compensation and general liability certificates, names the carriers and agent, explains coverage and exclusions, and permits direct verification. Subcontractor coverage is managed and documented.

Red flags: A workers’ compensation exemption despite crews appearing on site; an expired or altered certificate; refusal to let you contact the carrier; or the claim that the license bond guarantees completion.

Verify: Call the insurer or agent using independently obtained contact information. Confirm the named insured matches the contracting entity, policy dates cover the project, and the described operations fit the work. Ask your homeowner insurer what evidence and limits it recommends.

5. Which permitted ADUs have you completed recently in my city or county?

General remodeling experience is not the same as delivering an ADU through final inspection. Local experience matters because building departments, fire authorities, utility providers, and inspectors can have different processes and recurring correction issues.

A strong answer: The contractor provides several recent, comparable ADUs, their jurisdiction, approximate scope, permit number or address with owner permission, contract-to-final timeline, and the person who managed each job.

Red flags: A portfolio made entirely of renderings, kitchens, or projects outside California; no completed ADU reached final approval; or repeated claims that permit records are confidential when the contractor cannot provide any verifiable alternative.

Verify: Check public permit portals or call the building department. Confirm the project existed, the contractor was associated where records show it, and final inspection/approval occurred. Compare detached ADUs with detached ADUs and conversions with conversions.

6. May I speak with three recent clients and visit or drive by completed and active sites?

Do not ask references only, “Were you happy?” Ask questions that reveal budget control, communication, and closeout performance.

Ask each reference:

• What was the original contract price and final amount, excluding owner-requested upgrades?
• Which exclusions or assumptions surprised you?
• How many change orders occurred, and were they explained before the work?
• Did payments ever get ahead of progress?
• Who was actually on site and who solved problems?
• How accurate were the start and completion promises?
• Did the contractor pass final inspection and finish the punch list promptly?
• Did any subcontractor or supplier claim nonpayment?
• Would you hire this same legal entity and project manager again?

A strong answer: A mix of recent completed clients and an active project, not only one carefully selected fan.

Red flags: References with the same surname or business ties that are not disclosed; no active site; reluctance to let you see workmanship; or references who report unexplained cost jumps and weak closeout.

Verify: Independently confirm the project address or permit. Respect homeowner privacy and never enter a site without permission and safety arrangements.

7. Who will manage my site every day, and which trades will you self-perform versus subcontract?

The salesperson may disappear after signing. Find out who owns the schedule, inspects subcontractor work, communicates with you, and attends inspections.

A strong answer: A named project manager or superintendent with a realistic project load, defined site-visit frequency, regular written updates, and an escalation contact. The contractor can identify major subcontractors and explain how their licenses and insurance are checked.

Red flags: “We all pitch in”; no named supervisor; an unreachable owner managing many scattered projects; cash-paid labor with unclear employment; or refusal to identify major trades.

Verify: Meet the proposed project manager before signing. Ask current references how often that person was present. Check specialty licenses when a trade contracts directly with you or when classification questions arise.

8. Who is responsible for plans, engineering, Title 24, plan-check corrections, permits, inspections, utilities, and final approval?

“We handle permits” can conceal gaps. Separate responsibility for preparing documents, paying fees, responding to corrections, scheduling inspections, coordinating utility applications, and fixing failed inspections.

A strong answer: A written responsibility matrix names the party responsible for each deliverable, the included number of plan-check cycles, fees included or excluded, and how utility-company delays affect the schedule. The contractor pulls the construction permit in the proper capacity.

Red flags: The contractor asks you to pull the permit as owner-builder while promising to run the whole job. CSLB warns that an owner-builder assumes responsibility for project supervision and may face employment, safety, insurance, compliance, and lien risks.

Verify: Call the local building department to confirm permit costs and process. Confirm design professionals’ licenses where applicable. Ask the utility provider what applications and lead times may be required. Never sign an owner-builder declaration unless you knowingly intend to act as the general contractor.

9. Exactly what is included, excluded, or carried as an allowance in this price?

The missing-scope page is often more valuable than the total-price page. Require a line-item schedule of values and a written list of exclusions.

At minimum, locate these items in the bid: demolition and hauling; access/staging; temporary facilities; survey and soils work; excavation; foundation; grading and drainage; retaining work; water, sewer, electrical and gas runs; main-panel or service upgrades; utility fees; permit and school/impact fees where applicable; fire requirements; solar; appliances; cabinets; fixtures; finishes; landscaping restoration; cleaning; testing; and closeout.

A strong answer: Each item is included with a defined quantity/specification, excluded explicitly, or carried as a transparent allowance.

Red flags: “Standard finishes” without brands or budgets; “utilities by owner” with no scope boundary; large unallocated contingencies; or a short lump-sum proposal that depends on verbal explanations.

Verify: Create a bid-comparison matrix. Mark every row included, excluded, allowance, unit price, or unknown. Do not select a contractor until the unknowns are resolved in writing.

10. What site and utility assumptions could change the price, and what investigation will you complete before signing?

ADU cost surprises often live underground or at the connection point: sewer depth and route, electrical capacity, long trenches, rock, unsuitable soil, drainage, slope, retaining walls, tree roots, restricted access, or hazardous materials in a conversion.

A strong answer: The contractor lists assumptions, reviews available utility records, walks the route, identifies exploratory work or professional reports needed, and provides unit prices or a defined decision process for genuinely unknown conditions.

Red flags: A guaranteed price before reviewing plans or visiting the property; no discussion of sewer and electrical capacity; or a contingency that the contractor can spend without documentation or approval.

Verify: Cross-check assumptions with the designer, civil/structural engineer, surveyor, building department, and utility providers. For a conversion, ask whether asbestos or lead testing is appropriate before demolition.

11. Is this fixed price, cost-plus, or an estimate, and how are overhead, profit, allowances, and contingency handled?

The label matters less than the mechanism. A “fixed price” with undefined allowances and broad exclusions may be less certain than a carefully administered cost-plus contract.

A strong answer: The contractor explains what can change the price, how actual costs are documented, what markup applies to labor/materials/subcontracts, who controls contingency, how unused allowances are credited, and when selections must be made.

Red flags: “The final number depends”; undisclosed markup; allowances far below the finish level shown in sales materials; no credit for unused allowance; or a clause allowing unilateral price changes.

Verify: Test the proposal with three scenarios: a fixture exceeds allowance, concealed damage appears, and the owner deletes work. Ask the contractor to calculate each adjustment in writing before you sign.

12. What are the start assumptions, critical milestones, completion definition, delay rules, and communication cadence?

A single “six to eight months” promise is not a schedule. Separate preconstruction, permit issuance, mobilization, foundation, framing, rough trades, enclosure, finishes, inspections, utility energization, punch list, and final approval.

A strong answer: The contract has approximate start and completion dates, dependencies, a milestone schedule, selection deadlines, a process for documenting excusable delays, and weekly written updates showing progress, upcoming work, decisions, risks, and payment status.

Red flags: A start date that ignores permit status and long-lead materials; many simultaneous projects with no staffing plan; no definition of “substantial” or final completion; or pressure to accept a verbal schedule.

Verify: Compare the promised duration with recent references and permit records. Ask who owns utility and inspection appointments and how missed inspections or correction work affect payment.

13. How do change orders work, including documentation, pricing, markup, schedule impact, and prior written approval?

California’s CSLB says changes to a home-improvement contract must be written and signed before the changed work. A good change-order system distinguishes owner upgrades, plan/code requirements, and contractor estimating or coordination errors.

A strong answer: No changed work proceeds without a written description, reason, itemized price or credit, markup, time impact, and both signatures—except a genuine emergency addressed by a narrowly written procedure.

Red flags: Blank change-order forms; “we settle up later”; verbal authorization by text without a price; markup on correction of the contractor’s own defective work; or a clause treating silence as approval.

Verify: Ask for a redacted change-order log from a comparable completed ADU. Review whether the causes and approvals are clear and whether the original bid omitted predictable scope.

14. Does the payment schedule follow California rules, and how will lien releases be exchanged?

For most California ADU home-improvement contracts, the down payment cannot exceed $1,000 or 10% of the contract price, whichever is less. CSLB says there is no general special-order-material exception. Later payments should not exceed the value of work performed or materials delivered.

Do not stop at the deposit. A legal deposit can be followed by an unsafe front-loaded schedule. Tie each payment to observable, inspectable completion—not a date or vague percentage.

A strong answer: The contractor uses a detailed schedule of values, invoices only after milestones are reached or identified materials are delivered, permits reasonable verification, and keeps meaningful money for final inspection and punch-list closeout. The contract explains conditional and unconditional lien releases from the prime contractor and relevant subcontractors/suppliers.

Red flags: 10% of a six-figure job requested as a deposit instead of the lesser-of calculation; cash-only payments; a large “mobilization” payment unsupported by delivered value; payments triggered merely by ordering materials; or refusal to provide lien releases.

Verify: Compare each invoice with site progress, delivered materials, preliminary notices, and the schedule of values. CSLB advises obtaining conditional releases before payment and unconditional releases after payment; paying the prime contractor alone does not guarantee that every claimant has been paid. Use California’s statutory waiver forms and ask a construction attorney about project-specific payment controls when the stakes justify it.

15. What do I receive at closeout, and what written warranties and dispute process apply?

“Done” should mean more than the crew leaving. Define the documents, approvals, corrections, and physical condition required for final payment.

A strong answer: Closeout includes passed final inspection and applicable occupancy/final approval, completed punch list, unconditional final lien releases, paid permit status, warranties, manuals, product information, keys/remotes, final photos or as-builts where promised, cleanup, and correction of contractor-caused damage. Labor and manufacturer warranties identify coverage, duration, exclusions, response time, and contact procedure in writing.

Red flags: Final payment due before final inspection; warranty promises only in sales literature; no deadline for punch-list completion; broad waiver of known defects; or a dispute clause the contractor cannot explain.

Verify: Attach a closeout checklist to the contract and make the final payment milestone depend on it. Review mediation, arbitration, attorney-fee, venue, and notice clauses with a qualified California attorney before signing if you do not understand their effect.

ADU contractor evidence checklist

Use one record per bidder. Mark each item verified, unresolved, or does not meet the requirement. Record the source, date, responsible person and next action. These are evidence statuses, not predictions of contractor performance.

Check	Evidence to request
Licensed entity	Exact company, license status and applicable classification; date checked
Comparable ADUs	Permit records, final approvals and owner references for similar work
Local experience	Projects in the actual city or county—not just the same region
Scope and exclusions	Same drawings, allowances, utility boundaries and unresolved conditions
Staff and schedule	Named supervisor, dependencies, selections and delivery dates
Contract and payment	Applicable contract rules, milestones, written changes and release process
Insurance	Correct entity, relevant coverage and direct verification
References and workmanship	Independent answers about completion, changes and defects

How to use the evidence

Do not average away a material license, insurance, scope or contract concern. Resolve it before signing. Compare prices only after identifying the same scope and all outstanding costs.

Open the editable contractor interview worksheet. Save or print a separate copy for each bidder.

The five-minute CSLB check that catches common mismatches

Before signing, open CSLB’s license lookup and record or save a PDF/screenshot of:

• exact business name and license number
• current license status and expiration
• B, C-47, or other relevant classification
• personnel and qualifier names
• business address
• contractor bond status and surety
• workers’ compensation status
• disclosed disciplinary action or complaints

Now compare those fields with the proposal, contract, insurance certificate, invoice name, payment instructions, salesperson, and building-permit application. Any mismatch needs a written, verifiable explanation before money changes hands.

Seven deal-breakers before you sign

Walk away or pause for professional advice if the contractor:

1. will not identify the exact licensed entity;
2. asks you to pull an owner-builder permit while it controls the job;
3. demands an ordinary down payment above California’s lesser-of limit;
4. wants cash, payment to a different person/entity, or progress money ahead of work;
5. will not state utilities, site work, exclusions, allowances, and change-order markup in writing;
6. refuses direct insurance verification, recent references, or permit-record checks; or
7. pressures you to sign immediately or leave blanks in the contract.

What to do if a contractor asks for an excessive deposit

For an ordinary California ADU home-improvement contract, CSLB states that the down payment generally cannot exceed $1,000 or 10% of the contract price, whichever is less. On a $250,000 ADU, the ordinary ceiling is therefore $1,000—not $25,000. CSLB also says special-order materials are not a general exception. A rare contractor with a blanket performance and payment bond filed with CSLB may fall within an exception; verify that directly with CSLB rather than relying on a salesperson’s statement.

If a contractor asks for more:

1. Do not pay or sign under pressure.
2. Ask the contractor to identify the legal basis for the request in writing.
3. Recheck the exact license and any blanket performance and payment bond in CSLB records or contact CSLB.
4. Save the proposal, messages, invoice, and payment request.
5. Ask for a corrected contract and milestone schedule tied to completed work or delivered materials.
6. If the contractor refuses or you suspect a violation, contact CSLB and consider advice from a California construction attorney.

Do not solve an excessive-deposit demand by relabeling advance money as “mobilization,” “design,” or “materials” without confirming the arrangement is lawful and matches actual separately delivered value.

A practical hiring sequence

Step 1: Define the project

Complete enough design and site investigation to let contractors price the same work. List unresolved assumptions instead of hiding them.

Before setting a construction budget, compare the expected project cost with the likely use and value of the finished unit. ADU Project Planner’s California property-value analysis explains why added value rarely equals construction cost dollar for dollar.

Step 2: Build a longlist

Use referrals from recent ADU owners, designers, building departments where they provide neutral resources, trade associations, and local searches. A referral is a lead, not proof.

Step 3: Screen credentials

Check the exact CSLB entity, classification, history, personnel, bond, workers’ compensation, salesperson relationship, and insurance before investing time in a full interview.

Step 4: Issue the same bid package

Request itemized bids using the same plans, finish assumptions, and responsibility matrix. Require bidders to list exclusions and qualifications.

Step 5: Interview and verify

Ask all 15 questions, speak with clients, examine an active and completed site where possible, and check permits. Record verified evidence and unresolved issues.

Step 6: Negotiate the contract—not just the price

Resolve allowances, exclusions, permit duties, site assumptions, milestones, change orders, lien releases, schedule, insurance, warranties, and closeout. Have a California construction attorney review a six-figure contract if appropriate.

Step 7: Recheck before mobilization

Confirm the license and insurance remain active, the permit is issued correctly, the job file is complete, and the first payment complies with the signed contract and California law.

Final takeaway

The right ADU contractor will not be threatened by careful verification. Good builders benefit when the plans are clear, bids are comparable, owner decisions are timely, and payment rules are understood. Your goal is not to eliminate every unknown—construction always has some—but to expose the important ones before they become expensive surprises.

If a promise matters to your budget, schedule, property, or final approval, put it in the contract.

Frequently asked questions

How do I find a good ADU contractor in California?

Start with referrals from owners who completed permitted ADUs and local searches for your city, then screen the exact company through CSLB before requesting a detailed bid. Compare at least three contractors using the same plans and scope. Verify recent permitted ADUs, local jurisdiction experience, insurance, references, site supervision, utility responsibilities, payment terms, and closeout. Use the evidence checklist above to compare documented facts.

What contractor license should an ADU builder have in California?

A typical site-built ADU uses multiple unrelated trades and is commonly contracted by a B General Building contractor. A C-47 General Manufactured Housing contractor may install an ADU that is a manufactured home. The correct classification can depend on the exact scope and contracting arrangement, so verify it with CSLB.

How many ADU contractor bids should I get?

CSLB recommends at least three written bids based on identical plans, specifications, and scope. Three incomparable lump sums are not enough; normalize allowances, exclusions, owner-paid costs, and unknowns.

How much can a California ADU contractor ask for upfront?

For most home-improvement/ADU contracts, CSLB states the down payment cannot exceed $1,000 or 10% of the contract price, whichever is less. A narrow exception can apply when a qualifying blanket performance and payment bond is on file with CSLB. Verify current rules and any claimed exception directly.

Should the homeowner pull the ADU permit?

The contract should state who obtains permits. Be cautious if a contractor wants you to sign as owner-builder while it manages the job: CSLB warns that the owner-builder assumes broad responsibility and potential employment, safety, insurance, compliance, and lien exposure.

Is a fixed-price ADU contract always better?

No. A fixed price can still contain broad exclusions, unrealistic allowances, or clauses allowing price changes. Compare the mechanism: scope completeness, documented assumptions, allowance reconciliation, change-order rules, markup, and credits.

How can I reduce change orders?

Complete the design and site investigation before bidding; use specifications and realistic allowances; identify utility and site unknowns; compare bids line by line; and require written, priced, signed change orders before changed work. Unknown conditions cannot be eliminated, but vague scope can.

How do I protect against mechanics liens?

Track preliminary notices, compare invoices with work and delivered materials, and use California’s statutory conditional and unconditional waiver/release forms. CSLB warns that paying the prime contractor alone does not ensure subcontractors and suppliers were paid. Obtain project-specific legal advice when needed.

Sources and further reading

1. California Contractors State License Board, “Fast Facts: Tips for Building a Residential ADU,” revised November 2025. https://www.cslb.ca.gov/Resources/GuidesAndPublications/2025/FastFacts_ADU.pdf
2. California Contractors State License Board, “How do I find the right licensed contractor?” https://www.cslb.ca.gov/Consumers/Hire_A_Contractor/Finding_The_Right_Contractor.aspx
3. California Contractors State License Board, “What is a Contract?” https://www.cslb.ca.gov/Consumers/Hire_A_Contractor/Home_Improvement_Contracts/What_Is_A_Contract.aspx
4. California Contractors State License Board, “Homeowner Checklists.” https://www.cslb.ca.gov/Consumers/Hire_A_Contractor/Home_Improvement_Contracts/Homeowner_Checklists.aspx
5. California Contractors State License Board, “Check a Contractor License or Home Improvement Salesperson Registration.” https://web.cslb.ca.gov/OnlineServices/CheckLicenseII/CheckLicense.aspx
6. California Contractors State License Board, “B – General Building Contractor.” https://cslb.ca.gov/About_Us/Library/Licensing_Classifications/Licensing_Classifications_Detail.aspx?Class=B
7. California Contractors State License Board, “Owner-Builder Risks.” https://www.cslb.ca.gov/Consumers/Know_Risks_Of_Owner_-_Builder/The_Downside_Of_Being_An_Owner_-_Builder.aspx
8. California Contractors State License Board, “How to Prevent a Mechanics Lien.” https://www.cslb.ca.gov/consumers/legal_issues_for_consumers/mechanics_lien/How_To_Prevent_A_Mechanics_Lien.aspx
9. California Contractors State License Board, “Conditional and Unconditional Waiver and Release Forms.” https://cslb.ca.gov/Consumers/Legal_Issues_For_Consumers/Mechanics_Lien/Conditional_And_Unconditional_Waiver_Release_Form.aspx
10. California Contractors State License Board, “Before You Apply for Home Improvement Salesperson Registration.” https://www.cslb.ca.gov/Contractors/Applicants/Home_Improvement_Registration/Before_Applying_For_HIS.aspx
11. California Contractors State License Board, “Warnings and Exceptions” (cancellation rights). https://www.cslb.ca.gov/Consumers/Hire_A_Contractor/Home_Improvement_Contracts/Warnings_And_Exceptions.aspx
12. California Contractors State License Board, “Terms of Agreement: A Consumer Guide to Home Improvement Contracts.” https://www.cslb.ca.gov/Resources/GuidesAndPublications/HomeImprovementContractsConsumerGuide.pdf

Research note

Competitor articles from California ADU firms and guides were reviewed to identify common coverage and gaps. Public homeowner discussions were used only to surface recurring questions about utilities, site work, allowances, supervision, change orders, and schedule risk. Legal and consumer-protection statements in this article are grounded in CSLB sources above. Rules and local processes can change; verify current requirements before signing. This article is general education and not legal, insurance, or financial advice.

Evidence standard: this checklist does not assign a performance score or predict who will deliver successfully. Resolve material concerns individually. Then compare bids on the same scope.

Ready to compare prices? Use the California ADU bid-comparison example and fillable checklist.