ADU builders
ADU design-build: one contract for design and construction
By the HyreADU research desk. Last checked .
The short answer
ADU design-build means one firm both designs and builds your unit under one contract. You gain a single point of contact and a design priced as it is drawn. You give up an easy way to compare bids, because no other builder priced those drawings. The contract should say you can take the drawings elsewhere.
Design-build vs design-bid-build
In design-bid-build, you hire a designer, get permit drawings, then ask several builders to bid them. In design-build, one firm does both. The first gives you competing bids on the same scope. The second gives you one team that answers for both the drawings and the build.
What to put in the contract
Split the contract into a design phase and a build phase, with a price for each. State who owns the drawings if you stop after design.
Name every allowance in the build phase. California caps the deposit on a home improvement contract at $1,000 or 10 percent, whichever is less (Bus. & Prof. Code § 7159).
Check that the firm holds a B General Building license for the build. Design work on a wood-frame house of up to two stories does not need an architect license in California (Bus. & Prof. Code § 5537), but anything outside conventional framing needs stamped engineering.
A way to keep a price check
Even under design-build, you can ask a second builder to price the permit drawings. Use the ADU bid comparison to see which lines differ.
What to do next: read the questions to ask an ADU builder, check what decides ADU cost, then tell us about your project. Matching is not live yet, so we reply with information, not a quote.
Get ADU optionsQuestions
Is design-build faster for an ADU?
It can be, because design and pricing happen together. The permit clock is the same: a 60-day decision on a complete application in California.
Can I leave a design-build firm after design?
Only if the contract allows it. Get that right before you sign.
Who is responsible for design errors?
Under design-build, usually the firm. Read the contract for how it handles them.
Does HyreADU offer design-build?
No. HyreADU designs and builds nothing.
Sources
- Bus. & Prof. Code § 7159 (home improvement contracts). Checked September 5, 2026.
- Bus. & Prof. Code § 5537 (plans exempt from architect licensing). Checked October 27, 2026.
- CSLB Fast Facts: Accessory Dwelling Units (2025). Checked October 27, 2026.
- Gov. Code § 66317 (ministerial review, 60-day decision). Checked September 5, 2026.
HyreADU is a publisher. It does not design, permit or build ADUs, has no partner builders, and gives no legal, tax or engineering advice. Rules vary by state and city; California rules are labeled as such.