Unincorporated Ada County building permit requirements

Ada County Development Services — Building Division

Verified 2026-06-29 · Source

6 permit types208-287-7900Mon–Fri 8:00 AM – 5:00 PM

Department information

Address: 200 W. Front Street (Ada County Courthouse, 2nd Floor), Boise, ID 83702-7300
Phone: 208-287-7900
Email: mechanical@adacounty.id.gov
Office hours: Mon–Fri 8:00 AM – 5:00 PM
Website: Official site

Codes adopted

Idaho adopts a statewide baseline building code set under the Idaho Building Code Act (Idaho Code Title 39, Chapter 41) and IDAPA rules administered by the Idaho Division of Occupational and Professional Licenses (DOPL). Effective January 1, 2021, the statewide baseline includes the 2018 International Building Code (IBC), 2020 Idaho Residential Code (based on the 2018 IRC Parts I–III and IX with Idaho amendments), 2020 Idaho Energy Conservation Code (based on the 2018 IECC with Idaho amendments), 2018 International Existing Building Code (IEBC), 2018 International Mechanical Code (IMC), 2018 International Fuel Gas Code (IFGC), and 2018 International Fire Code (IFC). The National Electrical Code is adopted separately by the Idaho Electrical Board (IDAPA 24.39.10), not bundled with the building code: Idaho enforces the 2023 NEC, effective July 1, 2024 (the state used the 2017 NEC with amendments before that and skipped the 2020 edition). Local jurisdictions must enforce the state baseline and may adopt amendments only where those amendments are at least as stringent as the state-adopted editions; local amendments may not be less restrictive. Enforcement is local — each city or county issues permits and performs inspections. Always confirm the current adopted edition and any local amendments with your specific jurisdiction before submitting plans.

2018 International Building Code (IBC) — adopted via Ordinance #919, Ada County Code2018 International Residential Code (IRC) — adopted via Ordinance #9192018 International Existing Building Code (IEBC) — adopted via Ordinance #9192018 International Energy Conservation Code (IECC) — Commercial Provisions; Residential as modified by Idaho Statute Title 39 Chapter 41; adopted via Ordinance #9192018 International Mechanical Code (IMC) — adopted via Ordinance #9192018 International Fuel Gas Code (IFGC) — adopted via Ordinance #9192018 International Urban-Wildland Interface Code (IUWIC) — adopted via Ordinance #9192018 International Swimming Pool and Spa Code (ISPSC) — adopted via Ordinance #919

Permit types

Residential Building Permit (New Construction / Addition)

Required for new single-family dwellings, additions, detached garages, shops, carports, patio covers, elevated decks, and accessory structures in unincorporated Ada County. Ada County Building Division has issued permits since 1975 under the Ada County Building Code. Plans Examiners review construction drawings and Building Inspectors perform on-site inspections. Applications are submitted digitally as PDF files by email to the Building Division.

Commercial Building Permit (New Construction / Tenant Improvement)

Required for all new commercial, industrial, and multi-family buildings (three or more units), tenant improvements, remodels, and change-of-use projects in unincorporated Ada County. Governed by the 2018 International Building Code (IBC) as adopted by Ada County Ordinance #919. Applications submitted digitally by email.

Mechanical / HVAC Permit

Required for heating, ventilation, air conditioning, fuel gas piping, and related mechanical installations in unincorporated Ada County. Residential and commercial mechanical permits are both issued by Ada County Development Services — Building Division. Governed by the 2018 International Mechanical Code (IMC) and 2018 International Fuel Gas Code (IFGC) as adopted via Ordinance #919. Applications submitted digitally by email.

Grading & Drainage Permit

Required for grading and drainage work in unincorporated Ada County. Three tiers apply based on the area of disturbance and project type: Tier 1 for residential grading under one acre, Tier 2 for disturbance of one acre or more, and Tier 3 for commercial projects and new subdivisions. Governed by the 2018 International Building Code and Ada County Code (ACC 8-6). Applications submitted digitally by email.

Swimming Pool / Spa Permit

Required for in-ground swimming pools, above-ground pools, and spas in unincorporated Ada County. Governed by the 2018 International Swimming Pool and Spa Code (ISPSC) as adopted via Ordinance #919. A special barrier acknowledgment letter signed by the contractor and property owner is required BEFORE Ada County will issue the pool building permit. Unfinished pool permits (no final inspection within one year) trigger a property alert preventing new building permits.

Agricultural Structure Permit (Zoning Certificate)

An agricultural structure in unincorporated Ada County requires the issuance of a Zoning Certificate before construction begins. Qualifies only for structures on a 'farm' (5 acres or more in agricultural use with agricultural exemption) that are used exclusively for agricultural purposes — not for dwellings or personal item storage. Application fee is $100. Governed by Ada County Code ACC 8-2-23-2.

Tips & gotchas

All applications are submitted digitally by email to mechanical@adacounty.id.gov. Submit each document as a separate PDF file — not merged into a single PDF and not compressed in a zip archive. Zips take longer to process.
Payment is required before processing begins. Only e-checks ($3.00 flat) and credit cards (2.4% convenience fee, minimum $2) are accepted.
Electrical permits (wiring, panels, electric water heaters) are issued by the Idaho Division of Building Safety (DBS), NOT Ada County. Contact DBS at 1-800-839-9239.
Inspection requests must be made the day before the inspection is needed — by phone before 4:30 PM, or by email before midnight. AM/PM scheduling is accommodated when possible but not guaranteed.
Ada County does NOT require a building permit for installing a fence. Fencing standards still apply under ACC 8-5-3-44, and corner lot clear vision triangles under ACC 8-1A-2.
Swimming pool permits have a one-year final inspection requirement. If a final is not requested within one year, a property alert is placed preventing new building permits on the parcel.
Central District Health (CDH, 208-327-7499) approval is required for any addition, expansion, or significant alteration on a property served by a septic system — regardless of whether plumbing work is involved.
Projects in a Planned Community require HOA Design Approval before Ada County issues a building permit.
Post-frame/pole buildings require stamped engineering. Steel buildings require stamped engineering including foundation design. Stick-framed walls exceeding 12 feet require engineering for tall walls and shearwall design.
HVAC design (Manual J, D, and S) must accompany the building permit application for new dwellings — not a separate permit submittal.
Fee schedule updated November 2025 in conjunction with the new Ada County Zoning Code (effective November 2025). New ACHD impact fees effective March 1, 2026.
Ada County Development Services is located on the 2nd floor of the Ada County Courthouse, 200 W. Front Street, Boise. Hours: Mon–Fri 8:00 AM – 5:00 PM.

Sources & verification

Verified against official sources. Last reviewed 2026-06-29.

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

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