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

Required for construction of an internal or detached ADU in unincorporated Cache County. The fee schedule lists separate fee items for Internal ADU and Detached ADU (which uses the same fee tiers as new SFD construction). Contact Planning & Zoning for zoning eligibility.

Verified 2026-07-17 · Source

When you need this permit

  • Property must be zoned to allow ADU use — contact Cache County Planning & Zoning at (435) 755-1640
  • Internal ADUs (basement apartments, garage conversions) require a separate building permit
  • Detached ADUs are valued and permitted under the standard new-construction fee schedule
  • Separate entrance required from primary dwelling

Required documents

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Fee schedule

Internal ADU PermitCache County Building Division Fee Schedule, Ord. 2024-18 (adopted 11/6/2024) — flat fee, re-confirmed live 2026-07-01; re-confirmed again live 2026-07-17, unchanged
$300
Internal ADU Plan ReviewCache County Building Division Fee Schedule, Ord. 2024-18
$50
Detached ADU — valuation $0–$300,000Cache County Building Division Fee Schedule, Ord. 2024-18 — Detached ADU has its own valuation-tier table (distinct from the actual SFD table); re-verified live 2026-07-17 against the PDF's 'Detached Accessory Dwelling Unit (ADU)' table, confirmed matching
$2,500
Detached ADU — valuation $300,000–$500,000Cache County Building Division Fee Schedule, Ord. 2024-18
$3,000
Detached ADU — valuation $500,000–$750,000Cache County Building Division Fee Schedule, Ord. 2024-18
$3,800
Detached ADU — valuation $750,000–$1,000,000Cache County Building Division Fee Schedule, Ord. 2024-18
$4,800
Detached ADU — valuation over $1,000,000Cache County Building Division Fee Schedule, Ord. 2024-18
Consult building department
Plan Review Fee (Detached ADU)Cache County Building Division Fee Schedule, Ord. 2024-18
15% of base permit fee
State SurchargeCache County Building Division Fee Schedule, Ord. 2024-18
1% of permit fee
Re-Inspection FeeCache County Building Division Fee Schedule, Ord. 2024-18
$75

Review timeline

Plan reviewTypical estimate — confirm current times with the Unincorporated Cache County building department
~3–30 business days

How long did your Accessory Dwelling Unit (ADU) permit actually take in Unincorporated Cache 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

    Final

    All work complete, smoke/CO detectors, address posted

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

Tips

  • Utah HB 82 (2021) requires most jurisdictions to allow internal ADUs. Contact Cache County Planning & Zoning at (435) 755-1640 to confirm your property's eligibility for an ADU.
  • Internal ADUs use a flat $300 permit fee plus $50 plan review. Detached ADUs are valued and priced under the standard SFD fee tiers.
  • Every ADU bedroom requires an egress window with a minimum 5.7 sq ft net clear opening, sill no higher than 44 inches above the floor.
  • Impact fees may be reduced or waived for ADUs under Utah state law — confirm with Cache County.

Frequently asked questions

Unincorporated Cache County requires an accessory dwelling unit (adu) permit for: Property must be zoned to allow ADU use — contact Cache County Planning & Zoning at (435) 755-1640; Internal ADUs (basement apartments, garage conversions) require a separate building permit; Detached ADUs are valued and permitted under the standard new-construction fee schedule; Separate entrance required from primary dwelling. If your project isn't listed, confirm with Cache County Building Division at (435) 755-1650 before starting work.

Internal ADUs: $300 permit fee plus $50 plan review per Ord. 2024-18 (adopted 11/6/2024). Detached ADUs are priced under the new SFD fee tiers based on valuation ($2,500 up to $300,000; $3,000 for $300k–$500k, etc.) plus 15% plan review and 1% state surcharge.

Plan review for an accessory dwelling unit (adu) permit in Unincorporated Cache County typically runs 3–30 business days. This is an estimate, not a published figure — confirm current review times with Cache County Building Division at (435) 755-1650.

You'll need: Building Permit Application; Approved Zoning Clearance and Site Plan; Full Construction Plans (PDF). See the required-documents checklist on this page for details on each.

Unincorporated Cache County requires 4 inspection(s) for an accessory dwelling unit (adu) permit, in order: Foundation, Framing, MEP Rough-In, Final. Schedule each through Cache County Building Division ((435) 755-1650).

Apply through Cache County Building Division at 179 N Main St, Suite 305, Logan, UT 84321. Phone: (435) 755-1650, email: cachecountyplanreview@gmail.com. Office hours: Mon–Fri 8:00 AM – 5:00 PM (permit pickup/payment ends at 4:45 PM). Official information: https://www.cachecounty.gov/building/.

Unincorporated Cache County, Utah has adopted: 2024 International Building Code (IBC), including Appendices C and J — Utah Code § 15A-2-103(1)(a); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); 2021 International Residential Code (IRC), plus Appendix AQ of the 2021 IRC — Utah Code § 15A-2-103(1)(b)/(c); unchanged by the July 1, 2026 revision — still the current edition; 2024 International Plumbing Code (IPC) — Utah Code § 15A-2-103(1)(d); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); 2024 International Mechanical Code (IMC) — Utah Code § 15A-2-103(1)(e); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); 2024 International Fuel Gas Code (IFGC) — Utah Code § 15A-2-103(1)(f); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); 2024 International Energy Conservation Code (IECC) — Utah Code § 15A-2-103(1)(h); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); statute has no residential/commercial split — one edition applies to both. NOTE (county page live-checked 2026-07-16): the Cache County Building Code Information page lists 2024 IECC in its main statewide-codes list but separately carries a 'Residential Code: 2021 IRC and the 2021 IECC' line for dwellings up to a duplex — that residential IECC carve-out lags the statute, which adopts a single 2024 IECC edition with no residential/commercial split; the statewide 2024 IECC governs.; 2024 International Existing Building Code (IEBC) — Utah Code § 15A-2-103(1)(i); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); 2024 International Swimming Pool and Spa Code (ISPSC), residential provisions — Utah Code § 15A-2-103(1)(n); current edition as of July 1, 2026 (2021 edition governed through June 30, 2026); 2023 National Electrical Code (NEC) — Utah Code § 15A-2-103(1)(g); statewide in force, unchanged by the July 1, 2026 revision. NOTE: The Cache County Building Code Information page (last seen 2026-06-30) still lists '2020 NEC' — that page is not updated; the statewide 2023 NEC is the legally in-force edition.; NOTE (verified 2026-07-16 against the live Utah Code § 15A-2-103 text, version headed 'Effective 7/1/2026 / Superseded 1/1/2027'): the 2024 editions of IBC, IPC, IMC, IFGC, IECC, IEBC, and ISPSC listed above took effect July 1, 2026, replacing the 2021 editions; IRC (2021) and NEC (2023) did not change. The 1/1/2027 version of the statute carries identical editions, so no further flip is expected then. This file previously forecast this change but still led with the 2021 editions as current — corrected on this date..

Sources & verification

Verified against official sources. Last reviewed 2026-07-17.

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 Cache 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

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