Complete ADU Permit Checklist for Los Angeles & Orange County (2025)

Whether you’re planning a garage conversion, a detached ADU, or an attached addition, one thing is guaranteed:
You cannot start construction until your permits are fully approved.

And in Los Angeles and Orange County, the permit process is detailed — but very predictable when you know exactly what’s required.

This guide gives you a clear, step-by-step ADU permit checklist so you can submit confidently, avoid corrections, and shorten the timeline from design to approval.

Why Permits Matter So Much for ADUs

ADUs are regulated at both the state level (California) and local level (city/county). A complete permit set ensures:

• your project meets Title 24 energy standards

• your ADU complies with zoning rules

• structural and safety codes are correctly followed

• inspectors can verify work during construction

• your project is legally rentable and insurable

Missing even one required document can delay your project weeks or months — especially in LA City, Long Beach, Irvine, and Santa Ana.

ADU Permit Checklist (What Every City Requires)

Below is the complete checklist used for most ADU projects in Los Angeles, LA County, Orange County, and surrounding cities.

1. Site Documentation

✔️ Property Survey (Recommended / Sometimes Required)

Shows:

• property lines

• easements

• utility locations

• slopes

• setbacks

Some cities (Irvine, Huntington Beach, Long Beach) require it.

✔️ Property Profile / ZIMAS Sheet (LA City)

Confirms zoning, fire zones, overlays, and parcel info.

✔️ Utility Maps (if available)

Water, sewer, electrical.
Helps plan accurate utility routes and budget.

2. ADU Architectural Plans (Full Plan Set)

Every ADU submission must include a complete architectural package:

✔️ Cover Sheet

• project description

• zoning information

• ADU size

• occupancy type

• scope of work

✔️ Site Plan

Shows:

• existing structures

• ADU location

• parking (if required or existing)

• grading

• utility paths

• required setbacks

✔️ Floor Plan (existing + proposed)

✔️ Roof Plan

✔️ Exterior Elevations (4 sides)

✔️ Building Sections

Minimum 1–2 required.

✔️ Door & Window Schedule

✔️ Electrical Plan

Lighting, outlets, smoke/CO detectors.

✔️ Plumbing Plan (usually simplified)

✔️ Mechanical Plan (if required by the city)

Some cities accept a simple notation of HVAC system.

✔️ Title 24 Energy Compliance Sheets

Required statewide.

3. Structural Engineering Requirements

Most cities require structural plans for:

• foundations

• framing

• roof structure

• wall load calculations

• lateral bracing / shear walls

• hold-downs

✔️ Structural Plans + Structural Calculations

Prepared and stamped by a licensed engineer.

4. Additional Documents Often Required

Depending on the city and property characteristics, you may also need:

✔️ Soils Report

Only for:

• hillside lots

• poor soil conditions

• major additions

• heavy structures

✔️ Grading Plan

For slopes or drainage-heavy sites.

✔️ Sewer Capacity Letter

Some OC cities request this.

✔️ Arborist Report

If construction affects protected trees.

✔️ Fire Sprinkler Plans

Only if required by local ordinance or if the main home has sprinklers.

✔️ HOA Approval (if applicable)

Not mandatory from a city perspective — but essential for HOA-governed communities.

5. Permit Fees You Should Expect (2025)

Permit fees vary significantly by city.

Typical ADU Permit Fee Range:

💰 $4,000 – $10,000

Breakdown may include:

• plan check fees

• building permit fees

• electrical permit

• plumbing permit

• mechanical permit

• impact fees (waived for <750 sq ft)

Majority of LA and OC cities do not charge impact fees for ADUs under 750 sq ft.

6. How Long Do ADU Permits Take in 2025?

Average ADU Permit Timeline

• Los Angeles City: 8–14 weeks

• LA County: 6–12 weeks

• Orange County Cities: 6–16 weeks

• Fastest Cities: Anaheim, Glendale, Santa Clarita

• Slowest Cities: Long Beach, Pasadena, Irvine, Santa Monica

A complete and accurate plan set can reduce revisions dramatically.

7. Tips to Speed Up ADU Permit Approval

✔️ Submit a complete plan set

90% of delays come from missing sheets or calculations.

✔️ Use an architect experienced with ADUs

Familiarity with local code = fewer corrections.

✔️ Keep utility routes simple

Cities inspect utility planning closely.

✔️ Avoid zoning variances

ADUs bypass most zoning rules, but not all.

✔️ Respond quickly to plan check comments

Cities pause your application until you resubmit.

Final Thoughts

Getting an ADU permit in Los Angeles or Orange County doesn’t have to be overwhelming. With the correct documents, professional plans, and a clear checklist, you can navigate the process with confidence — and start construction faster.

If you want expert help preparing accurate ADU drawings, engineering, and permit submissions, ADU Studio specializes in turning ideas into fully approved ADU projects.