Signing a contract with the wrong ADU builder is how a $6,000 design package turns into a stalled framing job and a lien on your house. The vetting sequence below is what separates a licensed, ADU-experienced crew from a contractor who's learning on your lot in 2026.
- Verify license, insurance, and ADU-specific permit history before requesting a single bid in 2026.
- A bid 15-20% below the median usually means cut corners on rebar, insulation, or panel upgrades, not savings.
- Tie draw schedules to inspection milestones, not calendar dates, so a stalled builder can't drain your budget.
- Cap the upfront deposit at your state's legal limit and put every change order in writing before work continues.
Why this matters
An approved permit doesn't guarantee a good build. California, Texas, and Arizona have all seen ADU permit volume climb going into 2026, and rising demand pulls in contractors who've never framed a detached unit before. Build With A Plan handles the design and permit side of an ADU project — feasibility, drawings, permit submission — but the day you sign a construction contract, you're evaluating a business, not a drawing set.
Get that evaluation wrong and the math flips fast. A rejected permit costs you weeks. A bad contractor costs you a half-finished structure on a lot you can't legally rent out until it's fixed. The vetting steps below are the same ones that separate a $6,000 design fee well spent from a $180,000 lot with nothing sellable on it.
What you'll need
- The contractor's license number and the exact business name on the bid
- Proof of general liability insurance and a workers' comp certificate
- Three to five completed ADU references — not general remodels
- An itemized bid broken down by line item, not a single lump sum
- A written draw schedule tied to inspection milestones
- 30 to 60 minutes per candidate for a reference call
The steps
1. Confirm the license is active and matches the business name
Pull the license through your state's lookup tool — CSLB in California, TDLR in Texas, ROC in Arizona. Check the expiration date and any disciplinary history, then cross-reference the business name against the one printed on the bid. A license that belongs to a different LLC than the one signing your contract is a hard stop. This happens more often than homeowners expect when a builder subcontracts the ADU to a crew operating under a separate entity.
2. Pull ADU-specific permit history, not general contracting history
Kitchen remodels and additions don't translate to detached ADU experience — foundation type, egress, and utility separation are different problems. Ask for addresses of ADUs the builder has pulled permits for in the last 24 months, then verify with the local building department that the permits were issued under that builder's name. If you're converting an existing structure instead of building new, the cost and code differences change your bid comparisons — see how to convert your garage into an ADU for rental income for what shifts.
Common mistake: accepting "similar projects" that turn out to be additions or garage remodels, not standalone or attached ADUs.
3. Get itemized bids from at least three builders
Compare line items — foundation, framing, electrical panel upsize, sewer lateral tie-in — not just the bottom-line number. Flag any bid more than 15-20% under the median. That gap gets absorbed somewhere, usually in rebar spacing, insulation R-value, or finish-grade materials the homeowner never sees inspected.
Common mistake: picking the lowest number without asking why it's lower.
4. Match the draw schedule to inspection milestones, not the calendar
A sound draw schedule releases payment at foundation pour, framing sign-off, rough-in inspection, and final — never on fixed dates regardless of progress. If you're financing the build with a HELOC, your draw requests should mirror the same milestones the builder is invoicing against; see how a HELOC works for ADU construction for how draw-based lending typically structures those releases.
Common mistake: agreeing to a 50% deposit before any inspection has happened.
5. Call at least two references not on the builder's hand-picked list
Ask the building department for two addresses where the builder pulled ADU permits, then call those homeowners directly. Ask how many change orders hit the final invoice, whether the final cost matched the contract price, and how many weeks the project ran past schedule.
Common mistake: only calling references the builder selected, who are statistically the happiest customers by design.
6. Read the contract for permit responsibility and warranty terms
Confirm in writing who pulls the building permit, who pays if an inspection fails and the plan needs resubmission, and how long the workmanship warranty runs. A contract silent on failed-inspection costs means you're the one paying for a resubmission the builder should have gotten right the first time.
Common mistake: signing a contract that never names a warranty period at all.
7. Cap the upfront deposit at your state's legal limit
California law (Business and Professions Code §7159) caps home improvement contract deposits at 10% of the contract price or $1,000, whichever is less. Texas and Arizona don't set the same statutory cap, so negotiate a deposit tied to material procurement, not a flat percentage demanded on day one.
Common mistake: wiring a large deposit before a single permit has been pulled.
8. Confirm the change-order process before you sign anything
Require every change order in writing with cost and schedule impact, signed by both parties before the work proceeds. A verbal "we'll just add that" is how homeowners end up disputing charges on a final invoice with no paper trail to point to.
Common mistake: treating verbal agreements on-site as binding.
“A license number that belongs to a different LLC than the one signing your contract is a hard stop.”
Skip the builder-vetting guesswork
Get matched with vetted ADU builders after a free feasibility check.
Troubleshooting
- Builder won't share a license number upfront. Walk away — this is non-negotiable in every state with ADU permitting in 2026.
- The lowest bid sits 20-25% below the rest. Ask for the same line-item breakdown the other bidders gave you; if they can't itemize, the number isn't real.
- Builder suggests skipping permits to save time. Decline immediately. Unpermitted ADUs can't legally be rented and create title problems at resale.
- Contract has a vague "scope of work" paragraph instead of specs. Don't sign until square footage, materials, and fixture counts are listed line by line.
- References go unanswered. Request the permit number and call the building department directly to confirm the builder actually pulled it.
- Builder demands more than your state's deposit cap. Cite the legal limit and negotiate down; refusal to adjust is a red flag on its own.
Tools and resources
- State license lookup tool (CSLB, TDLR, or ROC depending on location)
- Local building department permit records — public and searchable by contractor name
- A written, itemized bid template with line items for foundation, framing, electrical, and plumbing
- Financing pre-approval so builders quote against a real budget, not a guess — compare options in best ADU financing options for homeowners in 2026
What to do next
Line up financing before you start interviewing builders — a pre-approved budget changes which bids are realistic and which are padded to fit whatever number you mention first. Once you've verified license, permit history, and references, the contract review in step 6 is the last gate before you sign. Builders who balk at any single step above are telling you something about how the next six months will go.
FAQ
What's the best way to verify an ADU builder's license in 2026?
Search the builder's license number through your state's official lookup tool — CSLB in California, TDLR in Texas, ROC in Arizona — and confirm the business name matches the bid exactly. Check for expiration dates and disciplinary actions before requesting a proposal.
Is a lower bid always a red flag when vetting an ADU builder?
Not always, but a bid 15-20% below the median usually means something got cut — rebar spacing, insulation grade, or panel capacity. Ask for the same itemized breakdown every other bidder gave you before assuming it's a deal.
How much can an ADU builder legally ask for a deposit?
In California, home improvement contract deposits are capped at 10% of the contract price or $1,000, whichever is less, under Business and Professions Code Section 7159. Texas and Arizona don't set the same statutory cap, so negotiate deposit terms tied to material procurement instead.
Should I hire the same contractor who did my home addition for an ADU?
Only if they can show completed ADU permits in the last 24 months, not just additions or remodels. Detached ADUs involve foundation and utility separation work that addition experience doesn't cover.
How many references should I call before signing an ADU contract?
Call at least two, and pull one address yourself from the building department's permit records rather than relying only on names the builder hand-picked. Ask specifically about change orders and final cost versus contract price.
What's the difference between vetting a builder and vetting a design or permit company?
A design and permit service produces drawings and manages the permit submission; a builder physically constructs the ADU and carries the licensing, insurance, and warranty obligations for the build itself. Vetting each requires checking different credentials.
How long does ADU builder vetting typically take?
Plan on one to two weeks to collect bids, run license checks, and complete reference calls before signing. Rushing this step is the most common reason homeowners end up with unresolved change-order disputes mid-build.
Can I switch builders after permits are approved?
Yes — approved permits stay tied to the property, not the builder, in most jurisdictions, though some cities require a permit amendment to update the contractor of record. Confirm with your local building department before terminating a contract.
One last thing
Most homeowners never ask, but the building department that issued your permit will usually tell you, over the phone, every address a contractor has pulled ADU permits for in the last two years. That single call does more vetting in ten minutes than a stack of glowing references a builder handed you directly.
