ADU builders
ADU feasibility study: what it should cover
By the HyreADU research desk. Last checked .
The short answer
An ADU feasibility study answers one question before you pay for drawings: can this lot take an ADU, and what will make it hard? A good study covers zoning, setbacks and lot coverage, utility routes, access for equipment, hazard overlays and the fees that apply. You can check much of it yourself first.
What a study should cover
Zoning and size: the zone, the allowed size and height, and setbacks. In California, Gov. Code § 66321 bars rules that prevent an 800 square foot unit with four-foot side and rear setbacks.
Utilities: where water, sewer and power would run, and whether capacity exists. Access: whether a crew and equipment can reach the build spot. Overlays: flood, fire, coastal, historic. Fees: which apply at your planned size.
What you can check yourself
Our ADU feasibility checker lists the questions your planning counter will ask. The size calculator works out the pad left after setbacks. Many planning departments will tell you the zone and overlays for a parcel over the phone.
When to pay for a study
Pay for a study on a sloped lot, a lot with a septic system, a corner or flag lot, or any site with an overlay. Ask what the deliverable is: a written report with sources, or a sales call.
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
Who does ADU feasibility studies?
Designers, architects and some ADU builders. A builder’s study may be part of a sales process, so read it with that in mind.
Does a feasibility study guarantee a permit?
No. Only a permit does.
Do I need a survey for a feasibility study?
Not always, but setbacks near a lot line need one. See land survey.
Can my city stop me building an ADU?
In California, it must approve a compliant ADU ministerially (Gov. Code § 66317), but your lot still has to meet the rules.
Sources
- Gov. Code § 66321 (size and height floors). Checked September 5, 2026.
- Gov. Code § 66317 (ministerial review, 60-day decision). Checked September 5, 2026.
- Gov. Code § 66311.5 (ADU fees and utility connections). 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.