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Residential Building Permit (New Construction / Addition) in Unincorporated Ada County, Idaho

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.

Verified 2026-06-29 · Source

When you need this permit

  • Building permit required for all new residential construction, additions, and structural alterations in unincorporated Ada County
  • Submit complete digital PDF application package (application form + all plan sheets as individual files, not a single zip) by email
  • Site plan showing proposed and existing structures in relation to all property lines, easements, wells, and septic tanks/drainfields
  • Foundation plan with layout, venting, and section details showing sizes, depths, and grade
  • Floor framing plan with member specifications, sizes, spans, support, and subfloor details
  • Floor plan detailing conditioned, unconditioned, and covered areas with windows and door openings labeled
  • Braced wall line plan with methods noted and panel lengths dimensioned
  • Wall/building sections with insulation R-values, U-factors, and framing specifications
  • Roof framing plan with venting, spacing, framing, and connection details
  • HVAC design and layout required for new dwellings — Manual J, D, and S (or Wrightsoft) submittal required
  • Elevations for all sides of the structure
  • Electrical layout showing switches, receptacles, lights, vents, and smoke/CO detectors
  • Post-frame/pole buildings: stamped engineering required; steel buildings: stamped engineering including foundation design required
  • Central District Health approval required if property is on septic
  • ACHD impact fees for residential dwellings accepted at the Building Division (receipt copy required if paid directly to ACHD)

Required documents

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Fee schedule

Building permit feeCredit card payments assessed 2.4% convenience fee (minimum $2); e-checks flat $3.00. Fee schedule updated November 2025 in conjunction with new Ada County Zoning Code.
Valuation-based per Ada County 2025 Fee Schedule (Resolution 3149, effective November 2025); see Building-Fees.pdf at adacounty.id.gov/developmentservices/permitting-division/fees/

Review timeline

Plan reviewTypical estimate — confirm current times with the Unincorporated Ada County building department
~5–21 business days

How long did your Residential Building Permit (New Construction / Addition) 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

    Footing

    Always required — request by 4:30 PM by phone or before midnight by email for next-day scheduling. Rebar not required unless part of an engineered design or subdivision-wide geotechnical report; footing inspection still required even without rebar.

  2. 2

    Foundation (if applicable)

    Not required where rebar is placed above code minimum unless required by engineer or on approved plans; inspector confirms per Building Division FAQ.

  3. 3

    Framing

    After framing, sheathing, and rough-in trades complete — before insulation or wall cover

  4. 4

    Final

    All work complete per approved plans; Certificate of Occupancy or final approval issued

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

Tips

  • Submit all plan documents as individual PDF files — not combined into a single file and not in a zip archive. Each plan sheet should be a separate attachment.
  • HVAC design (Manual J, D, and S) is required for all new dwellings — submit as an individual file. Ada County uses 2018 IMC.
  • Post-frame/pole buildings and steel buildings always require stamped engineering. Stick-framed buildings with any wall height over 12 feet require engineering for tall walls and shearwall design.
  • Electrical permits (including electric water heaters) are NOT issued by Ada County — contact the Idaho Division of Building Safety (DBS) at 1-800-839-9239.
  • Central District Health (CDH) approval is required for any addition/expansion on a property served by a septic system, regardless of whether plumbing work is involved.
  • Inspection requests must be made the day before via phone (before 4:30 PM) or email (before midnight). AM/PM scheduling is accommodated when possible but not guaranteed.
  • Cold weather concrete: protect from freezing; if average daily temp below 20°F, heat continuously for 72 hours; third-party special inspection and reports required.
  • Ada County does not require a building permit for fences — but fencing standards in ACC 8-5-3-44 still apply, including the clear vision triangle on corner lots (ACC 8-1A-2).
  • Projects within a Planned Community require HOA Design Approval before Ada County issues a building permit.

Frequently asked questions

Ada County does not require a building permit for installing a fence. However, fencing standards do apply — see Ada County Code 8-5-3-44 for standards and ACC 8-1A-2 (Figure 3) for clear vision triangle requirements on corner lots. Source: adacounty.id.gov/developmentservices/permitting-division/

In Unincorporated Ada County, the published Building permit fee is: Valuation-based per Ada County 2025 Fee Schedule (Resolution 3149, effective November 2025); see Building-Fees.pdf at adacounty.id.gov/developmentservices/permitting-division/fees/. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Plan review for a residential building permit (new construction / addition) in Unincorporated Ada County typically runs 5–21 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: Building Permit Application (Rev. 02.06.2026); Building Permit Application Checklist — Single Family Dwellings; Full Plan Set (Site Plan, Foundation, Floor Framing, Floor Plan, Braced Wall, Wall Sections, Roof Framing, Elevations, Electrical Layout, Details); Manual J, D, and S (or Wrightsoft). Depending on your project, Unincorporated Ada County may also ask for: Simple Dwelling Additions Checklist; Central District Health Approval. See the required-documents checklist on this page for details on each.

Unincorporated Ada County requires 4 inspection(s) for a residential building permit (new construction / addition), in order: Footing, Foundation (if applicable), Framing, 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/.

Submit your application by email to mechanical@adacounty.id.gov with the building permit application form and all plan documents as individual PDF files — not in a single merged PDF and not in a zip file. Once the Permitting Team confirms completeness, they will contact you for payment. Only e-checks ($3 flat) and credit cards (2.4% fee, minimum $2) are accepted. Source: adacounty.id.gov/developmentservices/permitting-division/applications-forms-templates/

No, rebar in footings is not required unless it is part of an engineered design or a subdivision-wide geotechnical report. However, a footing inspection is always required. A foundation inspection is not required where rebar is placed above code minimum unless the engineer or the approved plans require one. Source: adacounty.id.gov/developmentservices/building-division/

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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