ADU builders
ADU architect: when you need one
By the HyreADU research desk. Last checked .
The short answer
An ADU architect is not required for most ADUs in California. Bus. & Prof. Code § 5537 lets an unlicensed person prepare plans for a wood-frame house of up to two stories and a basement, and for garages and structures that go with it.
Anything outside conventional framing needs plans or calculations stamped by a licensed architect or engineer.
What the law requires
Section 5537 exempts plans for single-family wood-frame dwellings of no more than two stories and basement, multiple dwellings of up to four units, and garages or structures that go with them.
If any part departs from conventional wood framing, the building official must require plans or calculations from a licensed architect or registered engineer for that part.
Your city can still ask for more on a hillside, a hazard zone or an unusual structure. Ask the permit counter before you hire.
When an architect is worth it anyway
A small unit leaves little room for error. An architect earns the fee on a tight or sloped lot, a design that must meet a historic district’s rules, or a unit built for aging in place. They can also run the permit and answer plan check comments.
How to check one
Look up the license on the California Architects Board site. Ask for ADUs they took through your city’s plan check, and whether the fee covers permit corrections and construction questions.
If you do not need an architect, see ADU designer.
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
Do I need an architect for a garage conversion?
Usually not, if the work is conventional wood framing. Structural changes need an engineer’s stamp.
Can an architect pull the permit?
Many architects submit and manage the permit for you. The builder still needs a contractor license to build.
What is the difference between an architect and a designer?
An architect holds a state license. A designer may not. Both can draw an exempt ADU in California.
Does an ADU architect guarantee approval?
No one can. California requires ministerial review of a compliant application, but the drawings must meet the code.
Sources
- Bus. & Prof. Code § 5537 (plans exempt from architect licensing). Checked October 27, 2026.
- California Architects Board, license verification. 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.