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All GuidesADU & In-Law Suite · Clay County

ADU Cost and Permits in Clay County, FL (2026)

An accessory dwelling unit (ADU) in Clay County, FL runs $40,000–$95,000 for a garage conversion, $80,000–$220,000 for an attached in-law suite addition, and $150,000–$450,000+ for a detached new-build ADU. Clay County requires a Conditional Use Permit through the Planning and Zoning Division on top of standard building permits — and Florida's 2026 ADU statute (HB 1239) preempts some local restrictions but doesn't eliminate the planning review. Most HOAs in Fleming Island and Eagle Harbor still restrict ADUs in their covenants.

Cost ranges

What you'll typically pay.

Garage Conversion ADU

$40,000 – $95,000

Existing 2-car garage converted to a one-bed, one-bath unit with kitchenette. Existing slab and walls; new insulation, HVAC, plumbing, electrical, flooring. Typical 8–14 weeks.

Attached In-Law Suite Addition

$80,000 – $220,000

New 400–700 sqft addition attached to the main house with separate entrance, full kitchen or kitchenette, full bath, bedroom, possibly small living area. Tied into existing HVAC or with mini-split. Typical 14–22 weeks.

Detached New-Build ADU

$150,000 – $450,000+

Fully separate dwelling, 500–1,000+ sqft, own foundation, own utilities or sub-metered, own HVAC. Functions as a rental, in-law residence, or guest house. Typical 20–32 weeks.

Ranges reflect typical Northeast Florida market pricing as of May 2026. Not Tivey-specific quotes — get a real range in 90 seconds via the form below.

Clay County permit walkthrough

The permit, step by step.

  1. 1

    Pre-application — Conditional Use Permit determination

    Clay County requires a Conditional Use Permit for an Accessory Dwelling Unit through the Planning and Zoning Division. The CUP goes to the Planning Commission for review and may require a public hearing. Process runs 8–16 weeks separate from the building permit.

  2. 2

    Florida 2026 ADU statute review

    Florida HB 1239 (effective 2026) preempts some local zoning restrictions on ADUs in single-family residential zones, but Clay County still requires the Conditional Use Permit. Owner-occupancy and short-term rental restrictions vary; Tivey navigates both.

  3. 3

    HOA covenant review

    Many Clay County HOAs (Fleming Island Plantation, Eagle Harbor, Pace Island) restrict ADUs in their covenants regardless of state preemption. The HB 1239 preemption applies to government zoning, not to private HOA covenants. Verify before scope.

  4. 4

    Application via Tyler Technologies EPL (after CUP approval)

    Building, mechanical, electrical, and plumbing permits all required. Detached ADUs may require separate utility service or sub-metering arrangements with JEA or Clay County Utility Authority.

  5. 5

    Notice of Commencement (over $5,000)

    Required. Filed at the Clay County Courthouse before first inspection.

  6. 6

    Permit fees and impact fees

    Building permit fee is $1 per $1,000 of construction value plus $50 application. ADUs adding habitable square footage incur Clay County impact fees (school, transportation, parks) — typically $4,000–$10,000 for a typical attached or detached ADU.

  7. 7

    Inspections (full residential schedule)

    A detached ADU sees the full residential inspection schedule — footing, foundation, slab, framing, rough plumbing, rough electrical, rough mechanical, insulation, drywall, exterior, final framing, final occupancy. Attached ADUs follow the addition inspection schedule.

  8. 8

    Certificate of Occupancy

    A habitable ADU requires a Certificate of Occupancy at the final inspection. The CoC is what makes the unit legally rentable or occupiable as a separate dwelling.

What's not in the cost ranges

Three items commonly add to a Clay County ADU budget:

  • Impact fees. Clay County impact fees on the new conditioned square footage: $4,000–$10,000 for a typical ADU.
  • Utility connection fees. Sub-metering or new service from JEA / CCUA: $2,000–$8,000.
  • Public hearing legal coordination (if required). Some Clay County ADU CUPs require a public hearing; legal coordination adds $1,500–$5,000.

Why this is worth doing

ADUs in Clay County have multiple use cases worth thinking through before scope:

  • Aging-in-place for parents. The most common driver. A ground-floor in-law suite or detached cottage lets aging parents live independently next door without the move into senior housing.
  • Adult children launching. Especially in Fleming Island where housing prices have climbed past first-time-buyer reach.
  • Rental income. Subject to HOA restrictions, ADU rental can offset a meaningful portion of mortgage. Florida HB 1239 changed some short-term rental restrictions; long-term tenancy is generally permitted.
  • Resale value. A permitted ADU adds substantial appraised value — typically more than its cost — because it functions as a separate-income unit.
FAQ

Frequently asked.

  • Does Florida's 2026 ADU law mean I can just build one?

    No. HB 1239 preempts certain local zoning restrictions in single-family residential zones, but Clay County still requires a Conditional Use Permit through Planning and Zoning. The state law removes some barriers (minimum lot size restrictions, owner-occupancy mandates in some cases) but doesn't eliminate the planning review or the building permit process.

  • Can my HOA still prohibit an ADU even with the state law?

    Yes. HB 1239 preempts government zoning restrictions, not private HOA covenants. If your Clay County HOA's recorded covenants prohibit ADUs, that prohibition stands regardless of state preemption. Mark verifies HOA covenants on the Day-1 walkthrough.

  • How long does the Clay County ADU permit process take?

    Plan on 8–16 weeks for the Conditional Use Permit (with possible public hearing), then 6–10 weeks for building permit issuance after CUP approval. Total elapsed time before construction can start is typically 14–26 weeks. Construction adds 8–32 weeks depending on type.

  • Do I need separate utilities for a detached ADU?

    Sometimes. Clay County allows shared utilities with the main house in many cases, but if the ADU will be rented separately or have a different occupant, sub-metering or separate service is often required. JEA and CCUA each have their own connection process.

  • What's the cheapest ADU option in Clay County?

    Garage conversion. Existing slab, existing walls, existing roof — all of which substantially reduce cost. A 2-car garage conversion to a one-bed, one-bath ADU runs $40,000–$95,000 depending on finish level and how much HVAC, plumbing, and electrical needs to be added. Caveat — you lose the garage as parking, and many HOAs require covered parking, which could mean adding a carport.

More cost & permit reads

Related guides.

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