The permit clock
Completeness, approval, issuance, and occupancy are four different gates.
California's March 2026 ADU Handbook says a permitting agency must tell you whether an ADU application is complete within 15 business days. If it is incomplete, the written notice must identify the missing items and explain how to complete the application.
Once the application is complete, the agency generally has 60 days to approve or deny it when an existing primary dwelling is already on the lot. That does not mean a permit will be in hand 60 days after you first call a designer. Property research, drawings, agency corrections, fee payment, and project-specific reviews sit before or around that clock.
Read California HCD's March 2026 ADU Handbook-
01 · Jurisdiction
Find the agency
A mailing address can sit outside city limits. Confirm whether the city, county, or another agency issues the permit.
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02 · Feasibility
Screen the property
Check legal structures, lot constraints, access, utilities, easements, trees, fire conditions, and any coastal or historic review.
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03 · Drawings
Build one coordinated set
Align the site plan, architecture, structure, energy documents, and utility assumptions before intake.
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04 · Intake
Earn completeness
Submit every required form, plan, calculation, and agency document in the current local format.
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05 · Review
Close corrections
Keep one response log so comments from planning, building, fire, and utilities do not conflict or disappear.
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06 · Closeout
Issue, build, inspect
Pay the current fees, pull permits, schedule required inspections, and obtain final approval before occupancy.
Permit packet
Start with eight coordinated parts, then use your agency's checklist.
California does not use one universal ADU application packet. Local staff review the application, site plan, building plans, and other documents against objective standards. Ask for the current checklist before paying for a complete drawing set.
The list below is a coordination tool, not a substitute for your city or county's forms.
01
Application and project contacts
Owner, applicant, designer, contractor when known, project address, scope, valuation, and declarations.
02
Property and zoning facts
Parcel boundaries, existing legal structures, use, lot coverage, easements, setbacks, overlays, and recorded constraints.
03
Scaled site plan
Existing and proposed buildings, dimensions, setbacks, access, parking when applicable, grading, drainage, and utility routes.
04
Architectural drawings
Floor plans, roof plan, exterior elevations, building sections, room uses, doors, windows, and life-safety information.
05
Structure and foundation
Structural plans, details, calculations, foundation design, and existing-condition verification for conversions.
06
Energy documents
The applicable California Energy Code compliance package for a detached new build, addition, or alteration.
07
Utility plan
Electrical load and service, water, sewer or septic, gas if used, meters, trenching, and agency approvals.
08
Site-specific studies
Fire access, grading, soils, protected trees, flood, coastal, historic, or other documents only when the property triggers them.
Project type changes the packet
Existing permitted space
Garage or interior conversion
Prove what was legally built, then document how the existing structure, fire separation, ceiling height, light, ventilation, access, and utilities will support a dwelling.
Main risk: hidden or unpermitted existing conditions.
New building
Detached ADU
Coordinate a full foundation, building envelope, structure, energy package, drainage, utility connections, site access, and any required solar or battery-ready provisions.
Main risk: site and utility scope left out of the design proposal.
Repeatable building design
Preapproved plan
Reuse the approved building-design set, then add the property-specific title sheet, site plan, foundation, drainage, utility, access, and local application documents.
Main risk: treating plan approval as site approval.
Energy treatment also changes by project type. The California Energy Commission treats a new detached ADU as new construction, attached ADUs and conversions of unconditioned space as additions, and conversions of conditioned space as alterations.
Fees and utility charges
There is no dependable statewide permit price.
Ask your agency for a written estimate that separates plan review, permit issuance, impact fees, school fees, utility review, connection or capacity charges, and any property-specific review.
Impact fees
An ADU with 750 square feet or less of interior livable space is exempt from impact fees. Larger ADUs may be charged proportionately under state law.
Permit and plan review
The impact-fee exemption does not erase plan review, building permit, or project-specific agency charges. Current local schedules control.
Water and sewer
Existing-space ADUs and JADUs receive specific protection from being treated as a new residential use for connection-fee calculations, with exceptions and proportionality rules. Get the utility's determination in writing.
School fees
School districts may levy impact fees on ADUs larger than 500 square feet. Confirm whether the district charges them before finalizing the budget.
Responsibility map
Most delay starts in the handoff between people.
Before signing, put one name next to every permit task. A design agreement that stops at drawings and a construction agreement that starts after permits can leave no one responsible for intake, corrections, or agency coordination.
| Task | Name the owner | Evidence to request |
|---|---|---|
| Property research | Owner, designer, or feasibility consultant | Written zoning, permit-record, easement, overlay, and utility assumptions |
| Permit drawings | Designer plus required engineers | Sheet list, included calculations, exclusions, and revision rounds |
| Agency intake | Named applicant or permit coordinator | Submission receipt, completeness notice, fee invoice, and permit number |
| Corrections | Designer, engineer, builder, and utility contacts by topic | Comment log, response letter, revised-sheet index, and resubmittal date |
| Inspections and closeout | Builder and owner | Inspection record, approved changes, finals, and certificate of occupancy |
Choose the project team
Compare permit scope before comparing price.
Give every bidder the same property facts, intended unit type, utility assumptions, and finish level. Then compare what each proposal includes for drawings, engineering, fees, corrections, construction, inspections, and closeout.
- 01
Verify the contractor license
Check the current CSLB record, classification, bond, workers' compensation information, and available complaint disclosure.
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Call recent local references
Ask what changed during plan review, who answered corrections, how utilities were handled, and whether final inspection closed cleanly.
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Compare exclusions and allowances
A lower proposal may simply omit permit coordination, utility work, site conditions, fees, finishes, or correction rounds.
Local permit starting points
Move from statewide rules to the agency that controls your address.
Permit FAQ
Five answers to use before you buy plans.
Do you need a building permit for an ADU in California?
Yes. An ADU is a dwelling unit, so the project needs approval from the local permitting agency before construction and a certificate of occupancy before anyone moves in. The exact forms and reviews depend on the property, project type, and local agency.
How long does a California ADU permit take?
The permitting agency must generally determine whether an ADU application is complete within 15 business days and approve or deny a completed application within 60 days. Feasibility, design, corrections, permit issuance, construction, inspections, and special reviews can make the full project much longer.
What plans do I need for an ADU permit?
A typical package includes an application, site plan, floor plans, elevations, sections, structural information, energy documents, and utility details. Your city or county sets the exact checklist and may require additional documents for grading, fire access, trees, historic resources, septic systems, or coastal review.
Are California ADUs exempt from permit fees?
Not from every fee. State law exempts an ADU with 750 square feet or less of interior livable space from impact fees, but plan review, building permit, utility, school, and project-specific charges may still apply. Ask the permitting agency for a written fee estimate for your exact scope.
Does a preapproved ADU plan skip the permit process?
No. A preapproved plan can reduce review of the repeatable building design, but the local agency still reviews the property-specific site plan, zoning, foundation, drainage, utilities, access, and other applicable conditions before issuing a permit.
Your next step
Turn the permit checklist into one project brief.
When suitable builders are available, your shortlist may include up to three evidence-backed matches. We manually compare your city, ADU type, project stage, and budget with builder-published local-service evidence, ADU focus, and a dated check of the current CSLB record. We follow up by email after review. We share your brief only with your consent. A request does not guarantee a match, a specific match count, a builder response, response time, price, or project outcome.
Official resources
State law, building codes, energy requirements, fees, and local procedures change. Confirm the current rules for your property with the permitting agency before relying on a schedule, design, or budget.