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Mechanical / HVAC Permit in Unincorporated Ada County, Idaho

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.

Verified 2026-06-29 · Source

When you need this permit

  • All installation, replacement, or repair of heating, cooling, ventilation, or fuel gas systems
  • Residential: submit Residential Mechanical Permit application by email to mechanical@adacounty.id.gov
  • Commercial: submit Commercial Mechanical Permit application by email to mechanical@adacounty.id.gov
  • Idaho contractor registration number required for commercial applicants Contractor

Required documents

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Fee schedule

Residential Mechanical Permit — Base feeAda County Residential Mechanical Permit Application (2025)
$35.00
Residential — Furnace, air conditioner, heat pump, condenser, boiler (not supplying potable water), pool heater, or any other permanent space conditioning applianceAda County Residential Mechanical Permit Application (2025)
$25.00 for each
Residential — Exhaust duct or ventilation duct, head unit (mini-split), fireplace, hydronic system (closed loop only), residential energy storage systemAda County Residential Mechanical Permit Application (2025)
$15.00 for each
Residential — Fuel gas pipingAda County Residential Mechanical Permit Application (2025)
$5.00 per outlet
Commercial Mechanical Permit — Base fee plus percentageAda County Commercial Mechanical Permit Application (2025)
$35.00 base + 2% of total bid amount

Review timeline

Plan reviewTypical estimate — confirm current times with the Unincorporated Ada County building department
~1–5 business days

How long did your Mechanical / HVAC Permit permit actually take in Unincorporated Ada County?

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

Inspection process

  1. 1

    Gas Piping Pressure Test

    Required before concealing gas piping — verify no leaks under test pressure per 2018 IFGC

  2. 2

    Rough-In / Ductwork

    Mechanical equipment and ductwork installed before walls closed — verify clearances and support per 2018 IMC. Request by 4:30 PM by phone or before midnight by email for next-day scheduling.

  3. 3

    Final

    Equipment operational, combustion air verified, venting correct per 2018 IMC/IFGC

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

Tips

  • Residential mechanical permits use a per-item fee schedule: $25 per furnace/AC/heat pump/pool heater, $15 per mini-split/fireplace/exhaust duct/hydronic system, $5 per gas outlet.
  • Commercial mechanical permits use $35 base + 2% of total bid amount.
  • HVAC design (Manual J, D, and S) is required to accompany the building permit application for new dwellings — not a separate submittal under the mechanical permit.
  • Submit the residential or commercial mechanical permit application by email to mechanical@adacounty.id.gov as a PDF.

Frequently asked questions

Yes. Replacing a furnace requires a Residential Mechanical Permit from Ada County Development Services — Building Division. Fee: $35 base + $25 for the furnace appliance = $60 minimum for a furnace-only replacement. Submit the Residential Mechanical Permit application by email to mechanical@adacounty.id.gov. Source: Ada County Residential Mechanical Permit Application (2025).

Residential: $35 base, plus $25 per furnace/AC/heat pump/pool heater, $15 per mini-split/fireplace/exhaust duct/closed-loop hydronic, $5 per gas outlet. Commercial: $35 base + 2% of total bid amount. Source: Ada County Mechanical Permit Applications (2025), adacounty.id.gov/developmentservices/permitting-division/applications-forms-templates/

Plan review for a mechanical / hvac permit in Unincorporated Ada County typically runs 1–5 business days. This is an estimate, not a published figure — confirm current review times with Ada County Development Services — Building Division at 208-287-7900.

You'll need: Residential Mechanical Permit Application (2025). Depending on your project, Unincorporated Ada County may also ask for: Commercial Mechanical Permit Application (2025). See the required-documents checklist on this page for details on each.

Unincorporated Ada County requires 3 inspection(s) for a mechanical / hvac permit, in order: Gas Piping Pressure Test, Rough-In / Ductwork, Final. Schedule each through Ada County Development Services — Building Division (208-287-7900).

Apply through Ada County Development Services — Building Division at 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. Official information: https://adacounty.id.gov/developmentservices/building-division/.

Unincorporated Ada County, Idaho has adopted: 2018 International Building Code (IBC) — adopted via Ordinance #919, Ada County Code; 2018 International Residential Code (IRC) — adopted via Ordinance #919; 2018 International Existing Building Code (IEBC) — adopted via Ordinance #919; 2018 International Energy Conservation Code (IECC) — Commercial Provisions; Residential as modified by Idaho Statute Title 39 Chapter 41; adopted via Ordinance #919; 2018 International Mechanical Code (IMC) — adopted via Ordinance #919; 2018 International Fuel Gas Code (IFGC) — adopted via Ordinance #919; 2018 International Urban-Wildland Interface Code (IUWIC) — adopted via Ordinance #919; 2018 International Swimming Pool and Spa Code (ISPSC) — adopted via Ordinance #919. Local amendments apply — see the Unincorporated Ada County overview page for the full list.

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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