Quick answer
A planning department is the city or county office that applies the zoning code and general plan, checking where a project goes, what it is used for and how big it is.
For an ADU, it reviews the site plan against zoning rules such as setbacks and height. The building department then checks that the unit is built safely. Some cities call it community development.
Quick facts
- Also called
- Planning division, community development, planning and zoning
- In California
- Each city and county has a planning agency; its tasks may go to a planning department 1
- Main ADU job
- Zoning review of the site plan
- California ADU review
- Ministerial: no discretionary review or hearing 4
- Not the same as
- The building department, which checks construction
Key takeaways
- The planning department applies zoning. It checks location, use and size.
- The building department is a separate office that checks construction safety.
- In California, every city and county has a planning agency, and many assign its work to a planning department 1.
- For a California ADU, planning staff review the plan ministerially, with no hearing 4.
- The planning counter is the best first stop before you design.
What a planning department is, in plain English
City hall has many offices. The planning department is the one that knows the zoning map and rule book.
Its staff answer: can this go here, and how big can it be? They do not inspect framing or wiring. That is the building department’s job.
Small towns may have one person doing planning and building. Large cities have whole divisions. The name on the door also varies.
Planning staff also look ahead. They help write the general plan, update the zoning code and track housing goals. That long-range work is why ADU rules in a city can change from one year to the next.
Counties have planning departments too. If your home is outside city limits, the county office handles your ADU instead of a city one.
Why the planning department matters to you
It is the first public office to look at your ADU plan. If zoning is wrong, the project stops there.
Staff can tell you your zone, overlays and the local ADU rules before you spend on design. Many cities offer a free counter visit or call.
Later, the same office signs off the zoning part of your permit. A clear, complete site plan speeds that up.
Who does what at city hall
| Office or body | What it does | When an ADU meets it |
|---|---|---|
| Planning department | Applies zoning and the general plan | Site plan and zoning review |
| Building department | Checks plans and inspects construction | Plan check, permits, inspections |
| Planning commission | Hears discretionary cases and code changes | Rarely, for a compliant California ADU |
| Zoning administrator or board of zoning adjustment | Decides variances and conditional uses | Only if a variance or use permit applies 3 |
| Public works | Streets, sewers, some utilities | Sewer, driveway or frontage items |
| Fire department | Fire access and sprinklers | Access and fire review in some cities |
Three kinds of decision a planning department makes
| Kind | What it means | Example |
|---|---|---|
| Ministerial | Staff check fixed rules; no judgment calls and no hearing | A compliant California ADU 4 |
| Discretionary | A person or body weighs the project and may add conditions | A variance or conditional use permit 3 |
| Legislative | Elected officials change the rules themselves | Adopting a new zoning code or general plan |
Second example: reading a correction letter
A hypothetical set of planning comments, for illustration only. The owner’s first ADU submittal comes back with three notes.
| Comment | What it means | Fix |
|---|---|---|
| “Show all setback dimensions on the site plan.” | The reviewer cannot check distances | Add a dimension from each wall to each lot line |
| “Identify existing easements.” | A recorded easement may cross the yard | Add easements from the title report or survey |
| “Provide height to the highest point of the roof.” | Height is measured to a defined point | Add the measurement the code defines |
None of these comments says no. Each one asks for missing facts. A complete ADU site plan avoids most of them on the first try.
How to get the most from a counter visit
Go with a short list. Three to six clear questions get better answers than a long story.
Bring your parcel number and a simple sketch. Mark the house, the yard and where you hope to build.
Ask staff to point you to the code section behind each answer. Write it down. Section numbers let your designer check the rule later.
If an answer matters a lot, ask for it by email. A written reply is easier to rely on than a memory of a talk.
Be polite and patient. Counter staff handle many cases a day, and a calm visit tends to go further.
Use the checklist below as your packing list. Each item answers a question staff are likely to ask before they can answer yours.
- Your parcel number (APN) from the property tax bill
- The zoning district from the city’s online map, if you found it
- A simple sketch of the lot with the house, yard and planned ADU spot
- Your survey or any map showing property lines, if you have one
- Easements listed in your title report
- Photos of any garage or structure you plan to convert
- Three to six written questions, with space to note each code section
- An email address, so staff can confirm key answers in writing
Get the code section, not just the answer
A spoken “yes” at the counter is not an approval. The code section number is what lets your designer check the rule and what you can point to if plan check later reads it differently.
How the planning department handles an ADU
- You ask questions at the counter or online, often before applying.
- You submit the application and plans, often through one city portal.
- Planning staff check that the application is complete.
- They check the site plan against zoning: setbacks, height, size, parking.
- They send corrections if something does not meet the code.
- They sign off zoning, and the building department finishes its review.
- The permit issues once all departments clear it.
Worked example: a California ADU timeline with the planning department
A hypothetical project, for illustration of the state clock only. A homeowner in California submits a detached ADU application on a lot with an existing house.
| Event | State rule | What it means here |
|---|---|---|
| Application received | The clock starts | Day 0 |
| Completeness notice | Written notice within 15 business days 4 | The city says whether the file is complete |
| If the city misses that notice | The application is deemed complete 4 | The review clock runs anyway |
| Decision | Approve or deny within 60 days of a complete application 4 | Planning and building together must meet this |
The state sets the clock for the whole permitting agency, not just planning. A complete first submittal is the best way to stay on it. See ADU approval time statistics for measured results.
Where you will meet the planning department
- The planning counter, in person or by video.
- The city permit portal, where you upload plans.
- A completeness letter after you apply.
- Correction comments on your site plan.
- The zoning sign-off on your permit record.
California’s rules for planning departments and ADUs
California Government Code section 65100 says each city and county has a planning agency. The local legislative body assigns its tasks by ordinance. It can give them to a planning department, a planning commission, hearing officers, itself, or a mix 1.
Each planning agency prepares a general plan, which the council or board adopts 2. Zoning then carries out that plan.
For ADUs, section 66317 sets the review rules. An ADU application must be approved ministerially, without discretionary review or a hearing.
The agency must say whether the application is complete within 15 business days.
It must approve or deny within 60 days of a complete application when there is an existing home on the lot 4.
These rules bind the permitting agency as a whole. Planning staff often run the ADU process, but the building department shares the clock. The ministerial approval page explains what “no discretion” means.
Planning departments in other states
Every state lets cities plan and zone. The American Planning Association traces the shared structure to 1920s model laws 5.
Review rules for ADUs differ. Some states require ministerial review; many do not. Some ADUs elsewhere still need a hearing. See ADU laws by state.
Costs and what drives them
Many planning departments charge for zoning review as part of the permit. Some charge for pre-application meetings. Amounts differ by city.
Correction rounds are the hidden cost. Each one adds designer time and delay.
See California ADU fees by city and the guide to ADU permit fees for how fees are set.
Benefits and limits of working with planning early
What it does well
- Confirms your zone and rules before design.
- Flags overlays and easements you may not know about.
- Often free at the counter.
Where it falls short
- Counter answers are often informal, not binding.
- Staff time can be limited in busy cities.
- Advice may change if the code is updated.
Planning department compared with building department
| Question | Planning department | Building department |
|---|---|---|
| Main rule book | Zoning code and general plan | Building, fire and energy codes |
| Core question | Can it go here, and how big? | Is it built safely? |
| Checks | Setbacks, height, use, parking | Structure, wiring, plumbing, energy |
| Site visits | Rare for an ADU | Inspections during construction |
| California ADU rule | Ministerial review 4 | State building codes as adopted |
Common misreadings
- Myth Planning and building are the same office.
- Reality They are usually separate, with separate reviews, even if one portal handles both.
- Myth A planning commission must approve my ADU.
- Reality In California, a compliant ADU is approved ministerially with no hearing.
- Myth What the counter told me is final.
- Reality Counter advice is usually informal. Get key answers in writing.
- Myth Planning only looks at the outside.
- Reality It also checks use and unit count, which shape what you can build.
What to ask the planning department
- What is my zoning district, and are there overlays?
- Where is your ADU checklist or handout?
- Do you offer a pre-application meeting?
- Which departments review an ADU here?
- How do I submit, and what makes an application complete?
- Can you confirm key answers in writing?
Checklist for your project
- Find your city’s planning department page and ADU handout.
- Book a counter visit or call with your parcel number ready.
- Bring a rough lot sketch with the house and yard.
- Write down every rule they name and its code section.
- Use the timeline planner to map review steps.
- Submit a complete package to start the state clock cleanly.
Related guides and research
Questions about planning department
What does a planning department do?
It applies the zoning code and general plan. It checks where a project goes, what it is used for and how big it is. It also drafts plans and code changes for the city or county.
What is the difference between planning and building departments?
Planning checks zoning: location, use and size. Building checks construction: structure, wiring, plumbing and energy. An ADU needs sign-off from both.
Do I need planning approval for an ADU?
Yes, a zoning review is part of almost every ADU permit. In California it must be ministerial, so there is no hearing for a compliant ADU.
Should I talk to the planning department before designing?
Yes. A short counter visit can confirm your zone, overlays and the ADU rules. It can save a redesign later. Get key answers in writing.
How long does the planning department take to review an ADU?
In California, the permitting agency must say if the application is complete within 15 business days and decide within 60 days of a complete application when a home is on the lot. Actual times vary by city.
What is a planning commission?
It is an appointed body that hears discretionary cases and advises on code changes. A compliant ADU in California does not go to the planning commission.
What is community development?
Many cities group planning, building and sometimes housing into one community development department. The planning work is the same; only the name differs.
Can the planning department deny my ADU?
It can deny an application that does not meet objective standards. In California, a denial must come within the state timeline, and the review must be ministerial.
What should I bring to the planning counter?
Bring your address, parcel number and a rough sketch of the lot, house and where you want the ADU. Photos help. Have a list of questions ready.
Who is above the planning department?
The city council or county board of supervisors. They adopt the general plan and zoning code, and set who does the planning work.
Sources
- California Legislature, Government Code §65100, local planning agency, retrieved .
- California Legislature, Government Code §65300, general plan, retrieved .
- California Legislature, Government Code §65901, board of zoning adjustment and zoning administrator, retrieved .
- California Legislature, Government Code §66317, ministerial review of ADU applications, retrieved .
- American Planning Association, Standard State Zoning Enabling Act and Standard City Planning Enabling Act, retrieved .
Expert review
Written by the HyreADU Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Government Code §§65100, 65300, 65901 and 66317 were read on leginfo.legislature.ca.gov on 8 October 2026. The 15-business-day and 60-day figures were confirmed in the current §66317 text. The office roles table describes common patterns, not any one city.
Suggest a correction. We fix errors and say what changed.