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Residential New Construction Building Permit – LA County (ADU/JADU)

The LA County ADU Building Permit, Explained for Homeowners If you own a home in unincorporated Los Angeles County and you want to build an accessory dwelli...

Written by 1-800-ADU-Pros

•7 min read

Residential New Construction Building Permit – LA County (ADU/JADU)

The LA County ADU Building Permit, Explained for Homeowners

If you own a home in unincorporated Los Angeles County and you want to build an accessory dwelling unit (ADU) or junior ADU (JADU), there's one document that actually lets you start construction: the Residential New Construction Building Permit from LA County Public Works, Building & Safety Division (BSD). Here's exactly what it is, how to get it, and the mistakes that trip people up.

What this permit actually is

Think of the County process as two departments, two sign-offs. First, Regional Planning (DRP) approves your project from a zoning and land-use standpoint — is an ADU allowed here, at this size, with these setbacks? Second, Building & Safety issues the building permit that says your plans are safe and code-compliant, and that you may break ground.

This building permit is that second sign-off. It's the County's version of a City of LA "LADBS" permit, and you file it online through the EPIC-LA portal. Without it, you can't legally build, can't get inspections, and can't get a final Certificate of Occupancy.

Do you actually need it?

Yes — if your property sits in unincorporated LA County (not inside a city like Los Angeles, Pasadena, or Long Beach, which run their own building departments). And there's no skipping it: garage conversions, new detached units, and even the County's free pre-approved standard plans all still require this permit.

What you'll need to file

Have these ready before you start:

  • Architectural plans — site/plot plan, floor plan, roof plan, and elevations
  • Structural plans — foundation and framing details, with calculations where required
  • Title 24 energy calculations — the state energy-compliance sheets
  • Regional Planning (DRP) approval — required before the permit can be issued
  • Any other approvals on your Agency Referral Sheet (Fire, Public Health/septic, sewer, grading)

A shortcut worth knowing

LA County offers three free Pre-Approved Standard ADU Plans (Plan A: 1,200 sf / 3BR; Plan B: 1,200 sf / 2BR; Plan C: 800 sf / 1BR). Because they're already vetted by Planning and Building & Safety, they skip much of the design review and shorten your timeline. You still pull the permit and pay fees — but the plan check is far faster.

How to file, step by step

  1. Secure Regional Planning approval first — file the land-use application with a site-specific plot plan (or use a pre-approved plan).
  2. Open an EPIC-LA account at epicla.lacounty.gov and start a Residential New Construction permit for your ADU/JADU.
  3. Upload your full plan set — architectural, structural, and Title 24.
  4. Pass completeness screening. BSD confirms your package is complete and hands you an Agency Referral Sheet.
  5. Pay plan check fees and let a plans examiner review. Expect a correction list — that's normal.
  6. Correct and resubmit until plans are approved.
  7. Submit all agency approvals, including the DRP sign-off.
  8. Pay the remaining fees, pull the permit, build, and schedule inspections.

Fees and timeline

There's no flat fee — building permit and plan check costs are valuation-based and calculated automatically in EPIC-LA. For LA-area ADUs in 2026, plan check commonly runs about $1,300–$5,000, with combined permit + plan check often $5,000–$14,000. Budget separately for sewer/water connection (up to $2,500) and impact fees ($3–$4 per finished square foot).

One win for 2026: under SB 543, ADUs and JADUs under 500 square feet of assessable space are now exempt from school impact fees — a $3,000–$5,000 savings in many districts.

On timing, state law gives you teeth. The County must send a completeness/missing-items list within 15 business days, and must approve or deny a complete application within 60 days. Realistically, plan for a permit decision within about three months of a complete submission; plan check alone is roughly 4–10 weeks.

Common pitfalls

  • Filing before DRP approval. Building & Safety can review but cannot issue until Regional Planning signs off.
  • City vs. County mix-up. This permit is only for unincorporated County; in a city, you file with that city's department.
  • Incomplete packages. A missing Title 24 set fails the completeness screen and never starts your 60-day clock.
  • Underestimating extra reviews. Unincorporated parcels often route through Fire and Public Health — more fees, more time.
  • Treating connection and impact fees as part of the permit fee. They're separate, and they add up.

Bottom line

The ADU building permit is the green light to build — but it's the second gate, not the first. Line up Regional Planning, assemble a complete plan set (or grab a free standard plan), and file through EPIC-LA. Do that, and California's 60-day clock works in your favor.

Sources: LA County Public Works Building & Safety ADU pages, EPIC-LA portal, LA County Planning, and 2026 California ADU law summaries (SB 543). Always confirm current fees and requirements with your local district office.

Reference card

  • Official number: No standalone form number — applied for as a "Residential New Construction Building Permit" application inside the EPIC-LA portal (permit type: Building / New Construction, ADU/JADU project).
  • Issuing body: Los Angeles County Public Works, Building & Safety Division (BSD), filed through the EPIC-LA online portal. Applies to properties in unincorporated LA County only.
  • What it is: The County's construction building permit for an ADU/JADU in unincorporated LA County — the document that authorizes you to build and get inspections, issued by Building & Safety after Regional Planning's land-use approval.
  • Who needs it: You need it if your property is in unincorporated LA County (not inside an incorporated city like LA, Pasadena, or Long Beach — those have their own building departments) and you are building, converting, or substantially altering an ADU or JADU. You cannot skip it: even a garage-conversion ADU or a pre-approved standard-plan ADU still requires this building permit before construction and to get a final/Certificate of Occupancy. The only thing it does NOT cover is the upstream zoning approval (Regional Planning) — that is a separate sign-off you bring into this process.
  • Fees: No single flat fee — building permit + plan check fees are valuation-based and calculated automatically when you apply in EPIC-LA. Typical 2026 ranges seen for LA-area ADUs: plan check roughly $1,300–$5,000, with combined permit + plan check commonly $5,000–$14,000. Add likely sewer/water connection fees (often up to $2,500) and impact/development fees ($3–$4 per finished square foot). School impact fees may apply — but as of Jan 1, 2026 (SB 543) ADUs/JADUs under 500 sf of assessable space are exempt. Unincorporated parcels routed through extra departments (Fire, Public Health/septic) incur additional review fees. Confirm exact figures for your parcel in EPIC-LA or with your local district office.
  • Timeline: State ADU law sets the pace: the County must give a written completeness/missing-items list within 15 business days, and must approve or deny a COMPLETE application within 60 days. In practice, plan an permit decision roughly within ~3 months of submitting a complete package. Plan check itself typically runs about 4–10 weeks for standard review (around 2–4 weeks under express/standard-plan paths). Correction cycles and missing agency approvals are the usual reasons it slips past 60 days.

Requirements

  • Complete architectural plans — site/plot plan, floor plan, roof plan, and elevations
  • Structural plans — foundation and framing details, plus structural calculations where required
  • Title 24 energy compliance sheets/calculations
  • Regional Planning (DRP) approval — must be obtained and submitted before the building permit can be issued
  • Any other agency approvals listed on your Agency Referral Sheet (e.g., County Fire, Public Health/septic, Public Works sewer or grading)
  • Property/parcel information and project valuation (used to calculate fees)
  • Optional shortcut: one of the County's three free Pre-Approved Standard ADU Plans (A: 1,200 sf 3BR/1BA, B: 1,200 sf 2BR/1BA, C: 800 sf 1BR/1BA), which skips much of the architectural/structural review

How to file

  1. Get Regional Planning (DRP) approval first — file the land-use/zoning application with a site-specific plot plan and obtain DRP's sign-off (or use a pre-approved standard plan to streamline it)
  2. Create an account at the EPIC-LA portal (epicla.lacounty.gov) and start a Building / Residential New Construction permit application for your ADU or JADU
  3. Upload your full plan set — architectural, structural, and Title 24 energy documents
  4. Pass the completeness screening — BSD checks your package is complete and issues an Agency Referral Sheet listing every approval you still need
  5. Pay plan check fees and let a plans examiner review for code compliance; expect a correction list
  6. Make corrections and resubmit; repeat the recheck cycle until plans are approved
  7. Submit all agency approvals, including the Regional Planning sign-off
  8. Pay remaining permit fees and pull the issued permit, then begin construction and schedule inspections (rough, then final) toward your Certificate of Occupancy

Common pitfalls

  • Filing the building permit before Regional Planning (DRP) approval is in hand — BSD can review but cannot ISSUE until DRP signs off, stalling you at step 6/7
  • Confusing County with City — this permit only covers unincorporated LA County; inside an incorporated city you file with that city's building department (e.g., LADBS), not EPIC-LA
  • Forgetting the Title 24 energy calcs — an incomplete package fails the completeness screen and never starts the 60-day clock
  • Underestimating unincorporated-area referrals — Fire, Public Health/septic, and Public Works reviews each add fees and time and appear on your Agency Referral Sheet
  • Assuming a pre-approved standard plan is permit-free — the free standard plans speed REVIEW but you still pull this building permit and pay fees
  • Treating sewer/water connection and impact fees as part of the permit fee — they are separate and can add several thousand dollars
  • Missing the under-500-sf school-fee exemption (SB 543, effective 1/1/2026) and overpaying

Sources

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