Choosing the right ADU builder is the most consequential decision in your ADU project. The right builder delivers on time, on budget, and with quality that maximizes your investment. The wrong builder can turn your ADU dream into a costly nightmare of delays, change orders, and subpar work.
The 10 Essential Questions
1. Are you licensed, bonded, and insured?
Why it matters: Unlicensed contractors are illegal in most states and leave you with no recourse if problems arise.
What to verify:
- Active contractor license (Class B minimum in California; check CSLB)
- General liability insurance ($1 million minimum)
- Workers' compensation insurance
- Bond coverage
2. How many ADUs have you completed?
Why it matters: ADU construction has unique permitting, design, and utility connection challenges distinct from general contracting.
What to look for:
- Minimum 10 completed ADU projects
- Experience with your specific ADU type (detached, garage conversion, attached)
- Familiarity with your local building department
- Photos and addresses of completed projects
3. Can I visit a completed ADU and speak with the owner?
Why it matters: Photos only tell part of the story. Visiting a completed project reveals build quality, and speaking with the homeowner reveals communication and process quality.
Red flag: A builder who cannot provide 3-5 references is either new or hiding problems.
4. Is your pricing fixed-price or cost-plus?
Why it matters: ADU projects average 10-20% over initial estimates. A fixed-price contract protects you from overruns.
Fixed-price advantages:
- You know the total cost before signing
- The builder absorbs cost overruns (within scope)
- Easier to compare bids between builders
Cost-plus risks:
- Final cost is uncertain until completion
- Builder has less incentive to control costs
- Change orders can spiral
5. What is included in your price — and what is not?
Why it matters: The most common source of ADU budget overruns is discovering that items you assumed were included are actually excluded.
Ensure the bid includes:
- Design and engineering fees
- Permits and fees (city, utility connection)
- Site preparation (grading, demolition, tree removal)
- Foundation and utility trenching
- All construction (framing, roofing, plumbing, electrical, HVAC)
- Interior finishes (flooring, cabinets, countertops, fixtures)
- Exterior finishes (siding, paint, landscaping restoration)
- Final inspections and certificate of occupancy
Common exclusions to ask about:
- Utility upgrades (panel upgrade, sewer lateral)
- Soil testing and geotechnical reports
- Survey costs
- Landscaping beyond restoration
- Appliances and window coverings
- Furniture and furnishings
6. What is your realistic timeline?
Why it matters: Many builders understate timelines to win contracts. Understanding realistic expectations prevents frustration.
Typical timelines (2026):
- Design: 1-3 months
- Permitting: 1-3 months
- Construction: 3-8 months
- Total: 6-14 months
Ask about their current project load and when they can realistically start your project. See our ADU construction timeline guide.
7. How do you handle change orders?
Why it matters: Change orders are the #1 source of budget overruns and disputes.
What to establish:
- Written change order process required before any additional work
- Pricing method for changes (fixed or time-and-materials)
- Who can authorize changes (you only, not a spouse or family member without authorization)
- How changes affect the timeline
- Maximum allowable change order percentage before contract renegotiation
8. Who will be my primary point of contact?
Why it matters: Communication breakdowns cause more dissatisfaction than any other factor in construction projects.
What to establish:
- A dedicated project manager (not the owner juggling 10 projects)
- Expected communication frequency (weekly updates minimum)
- Communication method (email, app, phone)
- How quickly they respond to questions
- Process for escalating concerns
9. What warranty do you provide?
Why it matters: Quality builders stand behind their work. Weak warranties suggest a builder who expects problems.
What to expect:
- Structural: 10 years minimum
- Mechanical (plumbing, HVAC, electrical): 2-5 years
- Finishes (paint, trim, flooring): 1-2 years
- Workmanship: 1-2 years
- Manufacturer warranties on appliances and equipment: varies
10. What happens if the project goes over budget or over time?
Why it matters: Understanding how a builder handles adversity reveals their character and professionalism.
Good answers include:
- "We absorb cost overruns within the fixed scope"
- "We provide liquidated damages for late completion" (uncommon but excellent)
- "We communicate delays immediately and provide recovery plans"
- "Our typical project completes within X% of the original budget"
Red flag answers:
- "That rarely happens" (it always happens sometimes)
- "Change orders are just part of construction"
- "We'll figure it out as we go"
Additional Due Diligence
Check Online Reviews
- Google Business: Look for 4.5+ stars with 50+ reviews
- Yelp: Check for consistent quality feedback
- Houzz: View portfolios and client reviews
- BBB: Check for complaints and rating
Verify Past Projects
- Visit completed ADUs in person if possible
- Ask references about budget accuracy, timeline adherence, and communication
- Check if permits were properly closed with the city
Review the Contract Carefully
Before signing, ensure the contract includes:
- Detailed scope of work
- Fixed-price total with payment schedule tied to milestones
- Timeline with start and completion dates
- Change order process
- Warranty terms
- Dispute resolution mechanism
- Cancellation terms
For ADU financing options, see our dedicated guide.
Frequently Asked Questions
How many bids should I get for an ADU project?
Get at least 3 bids from different builders. More is better, but diminishing returns set in after 5. Ensure each bid covers the same scope so you are comparing apples to apples.
Should I hire a design-build firm or separate architect and builder?
Design-build firms (one company handles both design and construction) offer simplicity, faster timelines, and single-point accountability. Hiring a separate architect gives you more design independence but adds coordination complexity. For most ADU projects, design-build is the more efficient approach.
What is a reasonable deposit for an ADU builder?
Standard deposit is 10% of the contract value. Never pay more than 10% upfront. Subsequent payments should be tied to milestones (foundation complete, framing complete, rough-ins complete, etc.), not calendar dates. The final 10% should be held until all inspections pass and punch list items are completed.
How do I verify a contractor's license?
In California, check the CSLB website (cslb.ca.gov). In Oregon, check the CCB (ccb.state.or.us). In Washington, check L&I (lni.wa.gov). Enter the contractor's license number or business name to see license status, insurance, bond, and any complaints or disciplinary actions.
What should I do if problems arise during construction?
Document everything in writing (email). Refer to the contract for dispute resolution procedures. Communicate concerns to your project manager promptly. If issues are not resolved, escalate to the company owner. If necessary, file complaints with your state's contractor licensing board and consult a construction attorney.
Related Reading
- Questions to Ask Before Hiring an ADU Builder
- ADU Builder Timeline Expectations
- ADU Builder Warranty Standards
- How to Hire the Right ADU Builder
- How to Vet ADU Builder References
-- The ADU Finder Team