The Four Permits Your ADU Actually Needs
Most homeowners think of “the permit” as a single document. It’s not. A complete detached ADU requires four separate permits, issued in coordinated sequence, each with its own inspections.
| Permit | What It Covers | Typical Cost | Issuing Body |
|---|---|---|---|
| Building permit | Foundation, framing, exterior, roofing, weatherproofing | $2,000–$8,000 | City building department |
| Electrical permit | Service panel upgrade, branch circuits, outlets, fixtures | $300–$1,500 | City building department |
| Plumbing permit | Water supply, drain/waste/vent, gas, fixtures | $400–$1,800 | City building department |
| Mechanical permit | HVAC, ductwork, ventilation, condensate disposal | $300–$1,200 | City building department |
Some cities consolidate these into a single ADU permit application. Most require them filed together but track separately. Each permit has its own inspection sequence: roughly 6–9 inspections per permit, totaling 25–35 inspection events for a standard detached build.
Beyond these four, you may also need: a Grading permit (if site work moves more than 50 cubic yards), a Soils report (mandatory in LA’s Hillside Construction Regulation zone: $2,500–$5,000), an Encroachment permit (any work in the public right-of-way), and Utility permits (separate water and sewer connection permits from the utility provider).
State Statutes That Govern Your ADU Permit
California has spent a decade systematically removing barriers to ADU permitting. The statutes below define what your city is allowed to require, and what they’re not.
SB 1069 (2016) — The Origination Statute
Established the framework: “an accessory dwelling unit is a residential use” by right. Cities cannot use discretionary review to block ADUs.
AB 68 / AB 670 / AB 671 / AB 881 (2019) — The Expansion Package
Eliminated parking-replacement requirements within ½ mile of public transit. Banned cities from requiring owner-occupancy as a permit condition. Established the 60-day approval shot clock for complete applications. Prevented HOAs from prohibiting ADUs on single-family lots.
AB 976 (2023) — Owner-Occupancy Preemption (Permanent)
Cities cannot require you to live in the primary home as a permit condition. The 2020–2025 sunset on the original AB 68 provision was made permanent.
AB 1033 (2023) — Separate Sale Opt-In
Allows California cities to opt into a framework permitting ADUs to be sold separately from the main home as condominium units. Fewer than 15 cities have opted in as of mid-2026. Verify your city’s status if a separate-sale exit is part of your plan.
AB 1332 (2023) — Standard Plan Acceleration
Every California jurisdiction must maintain a Standard Plan program: a library of pre-approved ADU designs. Using a Standard Plan typically cuts plan-check time from 8–12 weeks to 5–10 business days. See our ADU floor plans for Standard Plan options.
SB 1077 / SB 1211 / AB 2533 / AB 1332 (2024) — Most Recent Wave
SB 1211 expanded multifamily ADU rights to 8 detached units (or 25% of existing units) on multifamily-zoned lots. AB 2533 created a legalization path for unpermitted ADUs built before 2020. The package collectively pushed back on remaining city-level resistance.
The consolidated framework for single-family ADUs: Gov Code §65852.2. For JADUs: Gov Code §65852.22.
Real Timelines — Why “60 Days” Becomes 12 Weeks
The California shot clock is 60 days. The actual LA County median is 8–12 weeks. The gap is not city malfeasance; it’s a structural feature of how the clock starts.
The shot clock starts when your application is “complete.” Not when you submit. Not when you pay the fees. Only after the planner has reviewed the submission and determined it includes every required element. If anything is missing, the clock doesn’t start. You get a “completeness” letter, you resubmit, and the cycle repeats.
This is where 30% of plan sets get rejected. Per ADUscale’s review of 2025 LA permit data, roughly 30% of ADU plan sets are rejected on first submission for completeness issues, even before substantive plan-check review begins. Substantive plan check produces corrections in 35–60% of cases.
| Stage | Best case | Median | Worst case |
|---|---|---|---|
| Application prep | 1 week | 2 weeks | 4 weeks |
| Completeness review | 1 week | 2 weeks | 4 weeks |
| First plan check | 3 weeks | 5 weeks | 8 weeks |
| Corrections cycle | 0 weeks | 2–3 weeks | 6+ weeks |
| Permit issuance | 1 week | 1 week | 2 weeks |
| TOTAL | 6 weeks | 12–14 weeks | 22+ weeks |
Using a Standard Plan under AB 1332 can compress the first plan check from 5 weeks to 1–2 weeks. Meaningful, especially if you’re financing the project and paying interest on a construction loan.
Permit Fees by City — Where Your Money Actually Goes
ADU permit fees vary significantly across California, driven by impact fees, plan-check rates, and utility-connection costs. The table below shows 2026 fee bands for a 750 sqft detached ADU.
| City | Building + Plan Check | Impact Fees | Utility Hookups | All-In Permit Cost |
|---|---|---|---|---|
| Los Angeles | $4,800–$7,200 | $0–$1,800 (≤750 sqft exempt) | $3,200–$6,800 | $8,000–$15,800 |
| San Diego | $3,200–$5,400 | $0–$1,200 | $2,400–$4,800 | $5,600–$11,400 |
| San Jose | $4,400–$6,800 | $1,200–$3,600 | $3,800–$7,200 | $9,400–$17,600 |
| San Francisco | $6,800–$9,800 | $1,800–$4,200 | $4,800–$9,600 | $13,400–$23,600 |
| Sacramento | $2,800–$4,800 | $0–$800 | $1,800–$3,400 | $4,600–$9,000 |
| Oakland | $3,800–$6,200 | $800–$2,400 | $2,800–$5,400 | $7,400–$14,000 |
| Long Beach | $3,600–$5,800 | $0–$1,600 | $2,400–$4,800 | $6,000–$12,200 |
Important state-law protections on fees: ADUs under 750 sqft are exempt from school impact fees statewide, and from most development impact fees. Cities cannot charge plan-check fees disproportionate to actual review effort.
Run your specific city number with our ADU Cost Calculator; it pulls 2026 LA County permit fees by neighborhood.
The 8 Most Common Permit Rejection Reasons
Based on ADUscale’s review of 2025 LA County permit data, these are the eight most common reasons ADU plan sets are rejected on first submission. Each is preventable.
Incomplete site plan — ~22% of rejections
Missing required elements: setback dimensions, easement locations, drainage flow, existing structures, north arrow. Site plans must be drawn to scale (typically 1/8" = 1′) with all dimensions called out.
Title 24 energy calculations missing or wrong vintage — ~18%
California requires Title 24 energy compliance calculations on every new ADU. Using the wrong vintage (2022 vs. 2024) is a common failure. Calculations must be performed by a certified Title 24 consultant.
Unstamped structural plans — ~14%
Structural pages must be wet-stamped (or digitally signed with credentials) by a California-licensed structural engineer. Architect stamps don’t suffice for structural elements.
Setback dimensions called wrong — ~11%
The state floor is 4 feet for rear/side setbacks on units up to 800 sqft. Some applicants draw to local zoning code without realizing state law preempts. Others draw to 4 feet when the unit is over 800 sqft and the city has authority to require more.
Missing fire-separation details — ~9%
ADUs within 10 feet of property lines or other structures need specific fire-separation details: 1-hour rated wall assemblies, eave protection, window restrictions. Cities reject without these.
Inadequate utility-connection plan — ~8%
Site plan must show how water, sewer, electric, and gas reach the ADU, including line sizes, materials, and depth of bury. Generic “utilities to be connected” notes get rejected.
Owner authorization missing — ~6%
If the homeowner isn’t the applicant (i.e., contractor or architect submits), a notarized owner authorization is required. Photocopied or scanned authorizations frequently get rejected.
Plan-set page numbering or sheet index errors — ~5%
Plans must be assembled in a specific order with a sheet index. Out-of-order pages, missing sheet numbers, or inconsistent revision marks trigger rejection before substantive review.
What Cities Still Get to Decide
State law preempts a lot, but not everything. The distinction matters when you’re evaluating a requirement that feels wrong.
- Architectural standards in HPOZ districts (within reason; can’t be used as backdoor denial)
- Setbacks above 4 feet only for units over 800 sqft
- Impact fees on units over 750 sqft (proportionate to actual impact)
- Aesthetic review for two-story designs near transit (reasonable standards only)
- Full California Building Code, electrical, plumbing, mechanical, Title 24 compliance
- Discretionary review or neighbor approval
- Owner-occupancy of the primary home (AB 976 permanent preemption)
- Parking replacement within ½ mile of transit (AB 68)
- Rental restrictions on ADUs (state preempts)
- Minimum lot size as a condition of ADU permit
How ADUscale Handles Permitting
We’re an independent Owner’s Representative: not a contractor, not a permit expediter. Permits are part of every engagement. Flat fee. No referral fees. Never a percentage of construction.
During the $199 Feasibility & Risk Assessment we identify your jurisdiction’s specific quirks (LA hillside, HPOZ, fire severity zones, sewer capacity) before any design starts. ~10% of assessments end with “don’t build here.”
We pre-flight the plan set against the rejection list above before submission. We verify the architect’s Title 24 vintage, structural stamp, site-plan completeness, and fire-separation details. First-submission rejection rate for plans we sign off on is below 5% (vs. 30% market average).
We use Verified Milestone Payouts tied to permit milestones. Funds release only after a permit milestone passes (foundation inspection, framing inspection, rough trades, final). Never on contractor say-so.
We track every inspection event through the build (typically 25–35 inspections for detached). Weekly progress reports document permit-milestone status. Final Certificate of Occupancy is the milestone that triggers final-payment release.
FAQ — ADU Permits California
Permit Deep Dives
Reviewed by: Berl Goldenstein, ADUscale Principal · 30+ years in California construction · CSLB B-2 General Building license · 2,000+ residential permits reviewed. Verified by: Yaro Korets, ADUscale CTO · 20+ years building inspection-data systems · founder, InspectPilot (11M+ inspection records since 2013). Data sources: California Government Code §65852.2, California HCD ADU Handbook, LADBS permit data (2025), InspectPilot inspection database (LA County 2024–2026). ADUscale is an independent Owner’s Representative. We are not a contractor, design-build firm, marketplace, or referral broker. Our fees are flat-rate and disclosed in writing before any engagement. Last updated: June 2026.