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Accessory Structure Permit (Sheds, Detached Garages, ADUs) in Ammon, Idaho

Required for detached accessory structures over 200 square feet, garages, and Accessory Dwelling Units (ADUs) in Ammon. Reviewed against the 2018 IRC, City of Ammon Accessory Building Checklist standards, and (for ADUs) Ammon Municipal Code Title 10, Chapter 7, Section 4.

Verified 2026-07-04 · Source

When you need this permit

  • One-story detached accessory structures over 200 square feet require a building permit
  • Structures 12+ feet behind the main house: minimum 3-foot property-line setback (may vary with height/roofing)
  • Structures less than 12 feet behind the main house: must meet zone-specific side-yard setbacks (RE: 20 ft; RP/RP-A: 10 ft; R1/R1-A: 8 ft) and minimum 3-foot setback from any other structure unless firewalls are installed
  • Covered structures (combined) may cover up to 30% of the backyard
  • Walls 10 feet or taller require professional engineering; irregular or post-and-beam structures require a licensed engineer/architect stamp
  • Structures must be designed for 115 mph wind load and 50 psf ground snow load
  • All utilities must connect through the main house
  • For ADUs specifically: maximum size is 75% of the main house's above-grade living space OR 1,000 square feet, whichever is more restrictive; same ownership as main house (cannot be subdivided); only one ADU per lot; no separate address; ADU must use the same driveway as the main house; permitted under Ammon Municipal Code Title 10, Chapter 7, Section 4

Required documents

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Fee schedule

Residential Valuation — Shed (no foundation/slab)City Fee Resolution 2026-008, Section 1-A
$15.00 per square foot
Residential Valuation — Garage/Shed (with foundation)City Fee Resolution 2026-008, Section 1-A
$21.00 per square foot
Building Permit FeeCity Fee Resolution 2026-008, Section 1-A
Per the same valuation-based Building Permit Fee table as new residential construction, applied to the accessory structure's calculated valuation
Building Code Plan Review Fee — Residential ProjectsCity Fee Resolution 2026-008, Section 1-B
10% of the Building Permit Fee

Review timeline

Plan review
Not published — contact the department

How long did your Accessory Structure Permit (Sheds, Detached Garages, ADUs) permit actually take in Ammon?

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

Inspection process

  1. 1

    Footing/Foundation

    Required before concrete pour where a foundation is used

  2. 2

    Framing

    Structural framing and connections

  3. 3

    Final

    Final inspection of completed structure

See the full Ammon inspection guide — scheduling & re-inspection fees →

Tips

  • The 200-square-foot threshold for accessory structures is a bright-line rule stated directly by the City — smaller detached structures do not require a permit.
  • ADUs cannot be given a separate address, must share the main house's driveway, and must connect to the main house's utilities with no additional service lines — this is stricter than some neighboring jurisdictions' ADU ordinances.
  • Structures with walls 10 feet or taller, or with irregular/post-and-beam framing, need a stamped engineer or architect design, not just prescriptive plans.

Frequently asked questions

Only if the one-story detached accessory structure exceeds 200 square feet. Source: City of Ammon Accessory Building Checklist page.

In Ammon, the published Residential Valuation — Shed (no foundation/slab) is: $15.00 per square foot. Additional published fees: Residential Valuation — Garage/Shed (with foundation) — $21.00 per square foot; Building Permit Fee — Per the same valuation-based Building Permit Fee table as new residential construction, applied to the accessory structure's calculated valuation; Building Code Plan Review Fee — Residential Projects — 10% of the Building Permit Fee. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Ammon does not publish a plan-review timeline for this permit. Contact City of Ammon Building Department at 208-612-4000 for current turnaround.

You'll need: BluePrince Accessory Structure / Minor Permit Application; Footing and Foundation Plans. Depending on your project, Ammon may also ask for: Electrical, Mechanical, and Plumbing Plans; Engineering Stamp. See the required-documents checklist on this page for details on each.

Ammon requires 3 inspection(s) for an accessory structure permit (sheds, detached garages, adus), in order: Footing/Foundation, Framing, Final. Schedule each through City of Ammon Building Department (208-612-4000).

Apply through City of Ammon Building Department at 2135 South Ammon Road, Ammon, ID 83406. Phone: 208-612-4000, email: building@cityofammon.us. Office hours: Monday-Friday 7:30 AM-12:00 PM & 1:00 PM-4:30 PM (permits not accepted after 4:00 PM); Inspection hours Mon-Thu 9:00 AM-3:00 PM, Fri 9:00 AM-12:00 PM. Official information: https://www.cityofammon.us/departments/building/.

Ammon, Idaho has adopted: City of Ammon Building Department adopts codes independently by ordinance under Ammon Municipal Code Title 07 (Building Regulations); the City self-administers building, electrical, plumbing, and mechanical permitting rather than relying on the Idaho Division of Building Safety for direct administration. Source: City of Ammon Building Department page, https://www.cityofammon.us/departments/building/; 2018 International Building Code (IBC), published by the International Code Council. Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/IBC2018P6; 2018 International Residential Code (IRC) for One- and Two-Family Dwellings. Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/IRC2018P6; 2018 International Existing Building Code (IEBC). Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/IEBC2018P5; 2018 International Fire Code (IFC). Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/IFC2018P6; 2018 International Fuel Gas Code (IFGC). Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/IFGC2018/index; 2018 International Mechanical Code (IMC). Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/IMC2018P4; 2018 International Energy Conservation Code (IECC). Source: City of Ammon Building Department page, code link to https://codes.iccsafe.org/content/iecc2018; 2017 Idaho State Plumbing Code (based on the Uniform Plumbing Code, adopted statewide pursuant to Idaho Code Title 54, Chapter 26). Source: City of Ammon Building Department page; National Electrical Code (NEC) — City of Ammon Building Department page identifies the currently adopted edition as the 2023 NEC (NFPA 70), consistent with the edition adopted statewide by Idaho pursuant to Idaho Code Section 54-1001. Electrical permits within Ammon city limits are issued and inspected by the City's own Building Department. Source: City of Ammon Building Department page, code link to https://www.nfpa.org/codes-and-standards/nfpa-70-standard-development/70; Ammon Municipal Code Title 10, Chapter 7 (Planning and Zoning — Accessory Dwelling Units, Section 4) governs ADU standards enforced in conjunction with Building Department permitting. Source: City of Ammon ADU Regulations page, https://www.cityofammon.us/services/building-permits/adu-regulations/; Ammon Municipal Code Section 15.04.030 establishes stop-work-order and violation-fee authority for work commenced without a required building permit. Source: City Fee Resolution 2026-008 (Resolution Number 2026-008, adopted April 16, 2026, effective April 16, 2026), Section 1-B. Local amendments apply — see the Ammon overview page for the full list.

The maximum is whichever is more restrictive: 75% of the main house's above-grade living space, or 1,000 square feet. Source: City of Ammon ADU Regulations page, citing Ammon Municipal Code Title 10, Chapter 7, Section 4.

Sources & verification

Verified against official sources. Last reviewed 2026-07-04.

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 Ammon building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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