County of San Diego ADU Permit Process: 2026 Fees, Checklist & Timeline

Last updated: May 15, 2026 · Last verified against County PDS and California Government Code sources: May 15, 2026

Sources: County PDS ADU page; PDS-611; PDS-613 (FY 2025–26); PDS-441A; PDS-658; County Zoning Ordinance § 6156; Cal. Gov. Code §§ 66311.5, 66317, 66322, 66342; Cal. Educ. Code § 17620; AB 1033; AB 2533. Verified May 15, 2026.

Do County of San Diego rules apply to your property?

San Diego County PDS governs ADUs only on parcels in unincorporated San Diego County — not inside any of the 19 incorporated municipalities. Communities commonly confused for incorporated cities but actually in unincorporated County include: Ramona, Fallbrook, Bonsall, Alpine, Jamul, Spring Valley, Bonita, Lakeside, Santee (some fringe parcels), Rancho Santa Fe, Julian, Valley Center, and Pauma Valley, among others.

The single most expensive mistake in San Diego ADU planning

Researching City of San Diego rules for a parcel that is actually in unincorporated County — or vice versa — is the single most common and expensive mistake we document in San Diego ADU projects. The two jurisdictions have different zoning codes, different permit forms, different fee schedules, and different review processes. City advice applied to a County parcel produces a permit denial, a redesign, and weeks of lost time.

The fix takes five minutes: pull your Assessor’s Parcel Number (APN) from your property tax bill and run it through the County’s Accela Citizen Access portal to generate a Property Summary Report. The report states your jurisdiction, zoning, and community plan area.

County PDS vs. City of San Diego — quick decoder

How to confirm your jurisdiction in five minutes

1. Find your APN on your property tax bill, the County Assessor portal, or your title documents.
2. Go to publicservices.sandiegocounty.gov (Accela Citizen Access).
3. Search your APN and pull the Property Summary Report.
4. Confirm the jurisdiction field reads County of San Diego — unincorporated. If it reads any city name, stop and use that city’s permit process.

What can you build on a County parcel?

On an eligible single-family lot in unincorporated San Diego County, you can get ministerial (no public hearing) approval for one detached or attached ADU plus one JADU, when standards are met. California Government Code § 66323 allows a qualifying single-family lot to host one ADU created from existing space, one JADU, and one newly constructed detached ADU up to 800 sq ft. Multifamily lots have their own rules.

Five ADU types in unincorporated County

County ADU size matrix

Sources: County PDS-611; County ADU Handbook (April 2024); Cal. Gov. Code §§ 66311.5, 66321, 66323. Verified May 15, 2026.

ADU rules at a glance — unincorporated County

Step-by-step: the County PDS ADU permit process

The County ADU Handbook describes a 14-step process; the 11 steps below consolidate those into the practical phases that determine timeline and outcome. The sequence is not optional — skipping or reordering steps (especially outside-agency clearances) is the primary cause of permit delays in the mid-project range.

What to submit: the PDS-658 checklist in plain English

PDS-658 divides submittal items into always-required and conditionally-required categories. A clean first submittal means every always-required item is present and every conditional item that applies to your parcel is included — signed by the appropriate licensed professional.

Always-required plan items

• PDS Form #291 — Residential Building Permit Application
• Plot plan (survey-grade: setbacks, easements, existing structures, utilities, driveway, drainage, north arrow, scale)
• Floor plan with room labels and dimensions
• All four exterior elevations
• Building cross-sections
• Foundation plan
• Roof framing plan
• Wall sections
• Structural calculations (engineer-stamped)
• Soils report (engineer-stamped, when triggered)
• Energy compliance — Title 24 Part 6 (CF1R, CF2R, CF3R forms re-run for your climate zone and orientation)
• Solar PV plan (new detached non-manufactured ADUs)
• Stormwater BMP documentation

Conditionally-required items — triggered by parcel

What County Plans A–F do not replace

The County’s free Dwelling Unit Plans A–F handle the architectural and structural skeleton — but they’re explicitly approximately 85% complete per the County’s Dwelling Unit Building Plans page. You still need: site-specific plot plan, foundation design tied to your actual soils, utility connection plan, Title 24 forms re-run for your climate zone and orientation, and any WUI / fire / septic / grading documentation triggered by your parcel.

A clean first submittal includes every required item that applies, signed by the appropriate licensed professional, with the County’s plan-check template followed exactly. PDS reviewers will return a submittal as incomplete if any required item is missing — and the state-law 15-business-day completeness clock restarts when you resubmit.

How much does a County of San Diego ADU permit cost in 2026?

The County’s FY 2025–26 PDS-613 fee schedule lists ADUs with their own dedicated fee lines: standard plan review is $1,865 plus $0.394 per square foot, the permit fee is $1,596 plus $0.537 per square foot, and the OTC path lowers plan review to $1,084 plus $0.304 per square foot. For a 600 sq ft detached ADU using the standard path, that calculates to $4,019.60 in County PDS base fees — before school, fire, septic, grading, water, sewer, and utility-agency fees. The County’s trial impact-fee waiver ended January 9, 2024.

County PDS base fees by ADU size — calculated from PDS-613

Source: County of San Diego PDS-613 Fee Schedule, FY 2025–26 (effective July 1, 2025). Standard plan-review formula: $1,865 + $0.394/sf. OTC plan-review formula: $1,084 + $0.304/sf. Permit-fee formula: $1,596 + $0.537/sf. These are PDS-only base fees. They do not include the $87 Land Development counter screening fee, resubmittal fees, or any outside-agency fees.

What state law says about ADU local impact fees

California Government Code § 66311.5 limits when local agencies, special districts, and water corporations can charge impact fees on ADUs:

• No local agency, special district, or water corporation impact fee is allowed on ADUs of 750 sq ft or smaller, or on JADUs of 500 sq ft or smaller.
• For ADUs over 750 sq ft, any local impact fee charged must be proportionate to the burden the ADU places on the agency’s services.
• Utility connection and capacity fees are treated differently than impact fees and may still apply.

School fees are handled separately. School developer fees are governed by California Education Code § 17620 — not by the 750 sq ft local impact-fee exemption above. When the resulting increase in assessable space exceeds 500 sq ft, school developer fees may apply. So an ADU of 600 sq ft is exempt from local impact fees (under 750 sq ft) but may still owe school fees because it exceeds the 500 sq ft school-fee threshold. Treat school fees and local impact fees as two separate questions with two separate thresholds.

School developer fees — verify your district

Because unincorporated County parcels fall under many different school districts, you must verify your specific school district by address or APN. As of May 2026:

How long does the County ADU permit process take?

California Government Code § 66317 gives the County 15 business days from submittal to issue a completeness determination, and 60 days from a complete application to approve or deny — when an existing primary dwelling is on the lot. In practice, most County ADU projects take several weeks for plan review on a clean first submittal, with full project timelines (design, permitting, construction) running roughly 10–18 months. The state-law clock pauses every time the County issues corrections and waits for your resubmittal.

Realistic timeline by path

These ranges are Dwelling Index editorial estimates based on industry observation and verified County data on plan-check cycles; they are not County-published guarantees.

What will delay your County ADU permit?

The most common County PDS ADU delays are: wrong-jurisdiction research that wastes weeks; incomplete plan submittals that fail the 15-business-day completeness check; outside-agency conditions (fire, septic, school, water/sewer) that lag plan check; WUI and fire-district review on rural parcels; and grading triggers that surface after design is locked. None of these are dealbreakers. All of them are avoidable when caught early.

What unincorporated overlays can delay a County ADU permit?

Three constraints define unincorporated ADU permitting and rarely appear on City-focused pages: septic systems requiring DEHQ review, Wildland-Urban Interface (WUI) construction with defensible-space requirements, and grading triggers on sloped or large-earthwork projects. Each can add weeks of process and material cost. Getting ahead of these in the design phase is the single highest-leverage move a homeowner in Alpine, Ramona, Fallbrook, Bonsall, Jamul, Rancho Santa Fe, Julian, Valley Center, or any unincorporated community can make.

Septic systems and the DEHQ pathway

Many unincorporated parcels aren’t on public sewer. If your main house is on septic and you’re adding an ADU, the existing system has to accommodate the new bedroom count and fixture units. DEHQ reviews:

1. Existing capacity — can the disposal field absorb the additional load?
2. Tank sizing — does the existing septic tank meet the County’s standards for the new combined fixture count?
3. Setbacks — where on the property does any new system or tank go?

The first step is contacting a licensed OWTS Professional (On-site Wastewater Treatment System designer) listed on the DEHQ website. They prepare an OWTS Layout Application; DEHQ performs a field inspection; if everything aligns, DEHQ provides terms of approval. Email lwqduty.deh@sdcounty.ca.gov for correspondence and document submittals.

Septic costs vary widely by parcel — from tank supplement only (lowest cost) to full system replacement or engineered systems (sometimes the largest line item outside of construction itself). These are Dwelling Index editorial estimates based on industry observation. Always get a parcel-specific quote from a licensed OWTS Professional before budgeting. Start the OWTS layout during design — not after plans are submitted.

Wildland-Urban Interface (WUI) and fire safety

Most unincorporated areas of San Diego County sit within Cal Fire–designated Fire Hazard Severity Zones, often classified as High or Very High. The County’s Building Code amendments require, for WUI projects:

• 100 ft of fuel modification around the structure (or to the property line, whichever is nearer), with the inner 50 ft cleared, irrigated, and planted with fire-resistant species
• Ignition-resistant construction including exterior walls, eaves, vents (ember-resistant), roof assemblies, and decking
• Defensible space maintained year-round
• Access for fire apparatus — driveway width, slope, turnaround, and gate clearances meeting your fire district’s standard
• Water supply — sometimes including dedicated tanks (Rancho Santa Fe FPD is particularly strict)

To check your parcel, enter your address at the Cal Fire FHSZ viewer. If you’re in a High or Very High zone, WUI-rated construction adds a meaningful premium to the build budget (Dwelling Index editorial estimate — varies by design and district).

Fire sprinklers — when they’re required (and when they’re not)

California Residential Code Section R313.2 requires automatic residential sprinkler systems in newly constructed one- and two-family dwellings, with one important ADU exception: fire sprinklers are not required in an ADU when sprinklers were not required by the building code applicable to the existing primary residence at the time it was built. A 1970s ranch home that was never required to have sprinklers can usually add an ADU without retrofitting sprinklers — unless that home was substantially altered in a way that triggered sprinkler retrofit. Always confirm with your specific fire district; some districts have local amendments that go beyond state code.

The County’s roughly 20 local fire districts

Unincorporated San Diego County is served by a patchwork of fire authorities, each with its own development-review process. Knowing your district matters because some (Rancho Santa Fe Fire Protection District is the textbook example) impose stricter standards than the County baseline. Key districts include:

• San Diego County Fire (Cal Fire)
• Alpine Fire Protection District
• Bonita-Sunnyside Fire Protection District
• Borrego Springs Fire Protection District
• Deer Springs Fire Protection District
• East County Fire Protection District
• Julian-Cuyamaca Fire Protection District
• Lakeside Fire Protection District
• North County Fire Protection District (Fallbrook/Bonsall)
• Pine Valley Fire Protection District
• Rancho Santa Fe Fire Protection District
• San Miguel Fire Protection District
• Valley Center Fire Protection District
• Vista Fire Department (limited unincorporated)

PDS publishes a current Fire District Contact List. Verify your district during Step 4 of the process.

Grading on slopes and earthwork

Per PDS-658 and the County Grading Ordinance, a grading plan and permit are typically triggered when earthwork reaches 200 cubic yards or cut/fill reaches 8 ft in vertical dimension. Steep lots (over 10% slope) increase costs significantly; the County notes that grading on slopes exceeding 25% may require additional engineering or be infeasible. If your lot has any meaningful grade, talk to the County Land Development counter at (858) 694-2055 or ldpermitcounter@sdcounty.ca.gov before paying for design.

Solar PV — Title 24 Part 6

California’s Title 24 Part 6 Building Energy Efficiency Standards require solar photovoltaic systems on newly constructed, non-manufactured, detached ADUs. Important distinctions:

• Attached ADUs are treated as additions and do not require PV.
• Conversion ADUs generally do not require PV.
• JADUs are exempt.
• Manufactured homes are not subject to the Energy Code at all.
• Factory-built housing must comply with Title 24. “Prefab” and “modular” terminology can describe either category — confirm your product’s regulatory classification before assuming exemption.

Can you use County Dwelling Unit Plans A–F?

Yes. The County of San Diego publishes a free library of six standard dwelling-unit plans (Plans A–F) usable as ADUs or single-family dwellings in unincorporated areas. They are approximately 85% complete and require you to fill in project-specific information before submittal. Used on the right lot, these plans can speed plan review and save on design costs — but they’re not a guarantee of approval and they don’t fit every site. For a deeper breakdown, see our companion piece: San Diego County Pre-Approved ADU Plans.

The Plans A–F catalog

Source: County of San Diego Dwelling Unit Building Plans page. Each plan is published at approximately 85% completion.

When pre-approved plans are the wrong choice

• Sloped or constrained lot — Plans A–F assume a relatively flat, regular building pad.
• Unique site constraints — easements, view corridors, mature trees, HOA restrictions.
• Strong design preferences — these are functional plans, not premium architecture.
• Fee threshold targeting — sometimes a custom 749 sq ft design is more livable than Plan E (800 sq ft) and avoids the 750 sq ft local impact-fee cliff entirely.

What if your ADU was already built without permits?

California’s Assembly Bill 2533 (2024) gives owners of ADUs and JADUs built before January 1, 2020 a streamlined permit path through County PDS, provided the structure can be brought up to applicable health, safety, and building standards. Under County § 6156’s AB 2533 language, the permits needed to correct the violation must be approved without penalty, and the applicant shall not be required to pay impact fees or connection/capacity charges — except when utility infrastructure is required to comply with health and safety standards. Owners may obtain a confidential third-party code inspection from a licensed contractor before submitting an application.

AB 2533 in plain English

AB 2533 doesn’t say your unpermitted ADU is automatically legal. It says you can apply for an after-the-fact permit using a less punitive process, with the requirement that the structure meet specific safety standards (electrical, plumbing, fire egress, ventilation, structural soundness).

Email PDS.ADUQuestions@sdcounty.ca.gov to start the conversation. County staff can discuss options without obligation.

Can you sell a County ADU separately under AB 1033?

Yes, as of April 4, 2026. On March 4, 2026, the San Diego County Board of Supervisors voted unanimously to adopt an Assembly Bill 1033 program allowing the separate sale of ADUs in unincorporated communities through a condominium conversion process. The ordinance took effect April 4, 2026. The County is collecting feedback May 1–31, 2026 on draft optional local implementation criteria — verify the latest program details on the County’s ADU Zoning Ordinance Amendment page before filing.

This is one of the most consequential ADU policy shifts in San Diego County in a decade. Before April 2026, owners in unincorporated communities could rent an ADU but couldn’t sell it separately from the primary house. With the AB 1033 program live, the financial calculus of building an ADU shifts: you now have an exit strategy that doesn’t require selling the main house too.

What AB 1033 lets unincorporated owners do

• Build an ADU on a lot with an existing primary dwelling per the standard County process described above
• After the ADU is built and final-inspected with a Certificate of Occupancy — or, for a pre-existing ADU, after meeting the County’s required housing-quality or code-inspection standards — apply for condominium conversion under the Davis-Stirling Common Interest Development Act
• Provide written lienholder consent from any party holding a mortgage or security interest
• Notify utility providers of the condominium creation and separate conveyance
• Comply with County review of OWTS and well items where applicable, and any fire-safety conditions
• Once converted, the ADU becomes a separately deeded condominium unit that can be sold, financed, or transferred independently

What the program does not do

• Does not bypass mapping requirements — a Tentative Parcel Map or Tentative Map is still required
• Does not waive lender consent
• Does not apply to JADUs
• Does not automatically resolve HOA restrictions or covenants — those are private agreements addressed separately

Practical implications

• Financing flexibility — an ADU you can someday sell is a different financial asset than one you can only rent
• Family transfers — adult children can purchase the ADU from parents
• Investor pathways — small-scale developers can build and sell ADUs as starter housing without the lot
• Exit liquidity — owners who want to scale back can sell the ADU and stay in the main house, or vice versa

How to finance the permit and build phase

Most homeowners fund the design, permit, and build phases through one of four lanes: a home equity line of credit (HELOC) for predictable phased draws, a cash-out refinance to convert equity into liquid construction capital, a construction-to-permanent loan that funds the build and rolls into a final mortgage, or a renovation loan that uses after-renovation value to qualify. We discuss financing as lanes, not lender rankings. We never claim a specific rate, APR, or monthly payment as a guarantee. Compare offers from licensed lenders, read every disclosure, and don’t sign anything you don’t understand.

County-specific financing friction to plan for

• Septic reserve — if your ADU triggers septic upgrades, demonstrate funds for those upgrades inside your project budget at underwriting.
• WUI / fire reserve — WUI construction premiums need to be priced in upfront.
• Outside-agency fees before issuance — school, fire, water, sewer, and DEHQ fees are typically due before the County will issue your permit.
• Longer rural construction timelines — fire-district inspections and septic milestones can extend the schedule, which matters for construction-loan draw schedules.
• AB 1033 lienholder consent — if you plan to convert the ADU to a separately saleable condominium later, your current lender’s consent is required. Get that conversation started early.

What should you do next?

If you’re in unincorporated San Diego County and you’re serious about an ADU, the first move is verification: confirm jurisdiction, confirm zone, confirm parcel status, identify your fire district and septic situation — and only then choose between County Plans A–F, a custom architect, or a design-build firm. A clean two hours spent at the start saves four to twelve weeks downstream.

Frequently asked questions

What we verified

We compiled this guide by working from primary sources. Last verified May 15, 2026. Where a handout and the codified ordinance differ, this guide uses the current codified County ordinance or state code.

• County of San Diego ADU page — scope, eligibility, permit requirement, AB 2533 path, AB 1033 condo-conversion program, fee-waiver expiration date
• County of San Diego ADU Handbook (April 2024) — 14-step process, size matrix, ADU types, setback, height, parking, septic, WUI, solar
• County Zoning Ordinance § 6156 — codified County ADU regulations including ADU count, 31-day rental minimum, parking exemptions, AB 1033, AB 2533
• PDS-613 FY 2025–26 fee schedule (effective July 1, 2025) — plan-review and permit formulas
• PDS-441A — How to Obtain a Building Permit Summary
• PDS-658 — Minimum Essential Plan Submittal Items
• County ADU Zoning Ordinance Amendment page — AB 1033 program effective date, May 2026 feedback window
• County Dwelling Unit Building Plans page — Plans A–F catalog and ~85% complete status
• County Building Permit Expiration page — two-year expiration, 180-day inspection cadence, three-year max
• California Government Code § 66317 — 15-business-day and 60-day permit clocks
• California Government Code § 66311.5 — local impact-fee exemption for ADUs ≤ 750 sq ft
• California Education Code § 17620 — school developer fee authority and 500 sq ft threshold
• Assembly Bill 2533 (2024) — pre-2020 unpermitted ADU streamlining
• Assembly Bill 1033 (2023) — separate sale via condominium conversion
• California Residential Code R313.2 — fire sprinkler requirement and ADU exception
• California Title 24 Part 6 (CEC ADU FAQs, 2025) — solar PV requirement scope
• San Diego Unified School District developer-fee schedule — $5.38/sq ft residential, effective May 11, 2026
• San Dieguito Union High School District developer-fee schedule — $2.72/sq ft residential, with 500 sq ft exemption confirmed

Any figure, rule, or process step that materially changes between verification dates will be reflected on the next quarterly refresh. We track fee-schedule updates around July 1 (start of County FY), state-law changes around January 1, school-district fee updates throughout the spring, and the active County feedback window on AB 1033 optional criteria (May 1–31, 2026). To submit a correction, email our editorial team via the Corrections page.

Methodology

The Dwelling Index is an independent research resource covering ADU financing, costs, and regulations. We are not a lender, broker, or builder. We do not accept payment in exchange for editorial position. Our affiliate links — when present — fund this site and never alter our editorial recommendations; see our Partner Vetting Policy and Editorial Standards.

For this guide, we read every primary County PDS document published as of the verification date, pulled fee math directly from PDS-613, confirmed statute citations against the California Legislature’s LegInfo system, verified school-district fee rates against each district’s published developer-fee schedule, and confirmed the AB 1033 program adoption against the County Board of Supervisors record. Where a County handout and the codified County ordinance differed, we used the current codified ordinance. Where a number could not be verified to a primary source, we labeled it as a Dwelling Index editorial estimate based on industry observation. See our full Methodology and Corrections policies.

This page is informational and does not constitute legal, financial, tax, construction, or lending advice. Verify all fees, timelines, and code requirements with County PDS, your fire district, DEHQ, your school district, and qualified local professionals before making decisions. We do not guarantee permit approval, qualification for any financing product, or specific rates. State ADU law preempts local zoning where they conflict — but local code, building, fire, health, and water-agency requirements still apply.