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Accessory Dwelling Unit (ADU) in Unincorporated Washington County, Utah

Required for construction of a secondary dwelling unit on a residential property in unincorporated Washington County, including basement apartments, detached cottages, and garage conversions. All ADUs require a 25-foot minimum setback on all sides per the Washington County FAQ page. Fees are valuation-based.

Verified 2026-07-01 · Source

When you need this permit

  • Property must be in a zone that allows ADUs — see Washington County zoning code at codelibrary.amlegal.com/codes/washingtoncout/
  • 25-foot minimum setback on all sides for all accessory dwelling units (per Washington County FAQ)
  • Adequate parking, separate entrance, fire separation from primary unit

Required documents

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Fee schedule

Building PermitGrounded/verified: ADUs are new residential construction and are assessed on the same valuation-based building permit table as the Residential Building Permit — Washington County Community Development Fees page (washco.utah.gov/departments/community-development/fees/, re-fetched 2026-07-01) publishes no separate ADU-specific fee tier. This is a fully grounded valuation-based fee, not an estimate. The 25-ft minimum setback requirement is independently confirmed live on the Washington County Community Development FAQ page (washco.utah.gov/departments/community-development/frequently-asked-questions-faq/, fetched 2026-07-01: 'Note: All accessory dwelling units have a 25' minimum setback on all sides'). lastVerified 2026-07-01.
Valuation-based per the Washington County building permit fee schedule (see residential building permit fees above)
State SurchargeWashington County Community Development Fees page, verified 2026-07-01.
1% of the permit fee

Review timeline

Plan reviewTypical estimate — confirm current times with the Unincorporated Washington County building department
~14–30 business days

How long did your Accessory Dwelling Unit (ADU) permit actually take in Unincorporated Washington County?

Anonymous — one question, no email. Answers are combined and only shown once at least 5 people have reported.

Inspection process

  1. 1

    Foundation

    Footings, forms, rebar — before concrete pour

  2. 2

    Framing

    Structure, fire separation, egress windows

  3. 3

    MEP Rough-In

    Mechanical, electrical, plumbing rough-ins before walls closed

  4. 4

    Insulation

    Insulation and vapor barrier before drywall

  5. 5

    Final

    All work complete, smoke/CO detectors, address posted, ready for occupancy

See the full Unincorporated Washington County inspection guide — scheduling & re-inspection fees →

Tips

  • All ADUs in unincorporated Washington County require a 25-foot minimum setback on all sides per the Washington County FAQ page — not the standard 5-foot accessory structure setback.
  • Check the Washington County zoning code at codelibrary.amlegal.com to confirm your property and zone permit an ADU.
  • Utah HB 82 (2021) requires most Utah jurisdictions to allow at least internal ADUs — Washington County complies.
  • A short-term rental license from the Washington County Clerk's office is required before renting an ADU short-term.

Frequently asked questions

Unincorporated Washington County requires an accessory dwelling unit (adu) permit for: Property must be in a zone that allows ADUs — see Washington County zoning code at codelibrary.amlegal.com/codes/washingtoncout/; 25-foot minimum setback on all sides for all accessory dwelling units (per Washington County FAQ); Adequate parking, separate entrance, fire separation from primary unit. If your project isn't listed, confirm with Washington County Community Development Department (Building Division) at (435) 301-7250 before starting work.

In Unincorporated Washington County, the published Building Permit is: Valuation-based per the Washington County building permit fee schedule (see residential building permit fees above). Additional published fees: State Surcharge — 1% of the permit fee. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Plan review for an accessory dwelling unit (adu) permit in Unincorporated Washington County typically runs 14–30 business days. This is an estimate, not a published figure — confirm current review times with Washington County Community Development Department (Building Division) at (435) 301-7250.

You'll need: Online Permit Application; Building Plans; Site Plan; Geotechnical Report; REScheck Energy Compliance. See the required-documents checklist on this page for details on each.

Unincorporated Washington County requires 5 inspection(s) for an accessory dwelling unit (adu) permit, in order: Foundation, Framing, MEP Rough-In, Insulation, Final. Schedule each through Washington County Community Development Department (Building Division) ((435) 301-7250).

Apply through Washington County Community Development Department (Building Division) at 111 East Tabernacle St., St. George, UT 84770. Phone: (435) 301-7250. Office hours: Mon–Fri, normal business hours (24-hour advance notice required for inspections). Official information: https://www.washco.utah.gov/departments/community-development/.

Unincorporated Washington County, Utah has adopted: 2024 International Building Code (IBC), including Appendices C and J — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(a); supersedes the 2021 edition previously listed here; 2021 International Residential Code (IRC) — Utah Code § 15A-2-103(1)(b); REMAINS CURRENT, UNCHANGED by the 7/1/2026 amendment; Appendix AQ of the 2021 IRC — statewide per Utah Code § 15A-2-103(1)(c); not itemized on any Washington County page found, added here per statute; 2024 International Plumbing Code (IPC) — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(d); supersedes the 2021 edition previously listed here; 2024 International Mechanical Code (IMC) — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(e); supersedes the 2021 edition previously listed here; 2024 International Fuel Gas Code (IFGC) — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(f); supersedes the 2021 edition previously listed here; 2023 National Electrical Code (NEC) — Utah Code § 15A-2-103(1)(g); UNCHANGED by the 7/1/2026 amendment (NOTE: Washington County's own website has been observed referencing 2020 NEC on older pages; the legally in-force statewide edition is 2023 NEC — no county page is known to have been updated to reflect this); 2024 International Energy Conservation Code (IECC), single unsplit statewide edition — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(h); supersedes the 2021 edition previously listed here; 2024 International Existing Building Code (IEBC) — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(i); supersedes the 2021 edition previously listed here; Residential provisions of the 2024 International Swimming Pool and Spa Code (ISPSC) — CURRENT statewide as of 7/1/2026 per Utah Code § 15A-2-103(1)(n); supersedes the 2021 edition previously listed here; MBI 1200 and MBI 1205 (manufactured/modular construction standards) — statewide per Utah Code § 15A-2-103(1)(o); not itemized on any Washington County page found, added here per statute; NOTE (2026-07-16 re-verification): The Utah Code § 15A-2-103 version effective 7/1/2026 (superseded 1/1/2027) took effect 15 days before this re-verification. This entry previously described the 2024-cycle codes in future tense ('effective through June 30, 2026' / 'takes effect July 1, 2026'); that date has now passed, so IBC/IPC/IMC/IFGC/IECC/IEBC/residential ISPSC are now stated as CURRENT (2024 editions), while IRC (2021) and NEC (2023) remain unchanged as already correctly stated. No Washington County page listing IBC/IRC/IPC/IMC/IECC editions specifically was found on live re-check of the Community Development FAQ and Building Permit Documents pages (2026-07-16), so there is no city-page lag to record for those codes beyond the pre-existing NEC observation above..

Most likely yes, depending on your zoning. Washington County regulates ADUs at codelibrary.amlegal.com/codes/washingtoncout/latest/washingtonco_ut/0-0-0-4763. All ADUs require a 25-foot minimum setback on all sides. Contact Community Development at (435) 301-7250 to confirm your property qualifies.

Sources & verification

Verified against official sources. Last reviewed 2026-07-01.

Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Unincorporated Washington County building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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Accessory Dwelling Unit (ADU) in other cities

Bountiful, UtahDraper, UtahEagle Mountain, UtahKaysville, UtahLayton, UtahLehi, UtahLogan, UtahNorth Salt Lake, Utah

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