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Commercial Building Permit (New Construction / Tenant Improvement) in Unincorporated Twin Falls County, Idaho

Required for new commercial buildings, tenant improvements, and change-of-use projects in unincorporated Twin Falls County. Governed by the 2018 International Building Code (IBC) with Idaho Amendments. A separate Commercial Plan Review Fee applies (65% of the building permit fee, or $200, whichever is greater). Applications submitted by email/upload or through the Citizens Connect permit portal.

Verified 2026-07-08 · Source

When you need this permit

  • Building permit required for new commercial construction, tenant improvements, additions, and change-of-occupancy projects
  • Commercial Building Permit Application (2025 fillable form)
  • Plans Analysis required for all commercial building plans
  • Plans stamped by an Idaho-licensed architect or engineer where required
  • Site plan, floor plans with dimensions, elevation views, footing/foundation dimensions with reinforcing, typical construction detail, cross-section and stair detail, truss/floor joist details
  • South Central Public Health District approval/permit and approved stamped site plan
  • Highway District, Canal Company, and Fire District approval/comment letters
  • Deed showing ownership; Authorization Form if applicant is not the property owner
  • Commercial Plan Review Fee (65% of building permit fee or $200, whichever is greater) due at time of plan submittal

Required documents

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Fee schedule

Building permit fee — Commercial occupancy groups (A, B, E, F, H, I, M, S, U), valuation basisTwin Falls County Community Development Services Fee Schedule, effective September 1, 2025 (TFCO-BLD-FEES-2025-base-FINAL.pdf)
Per-square-foot rate varies by occupancy group and construction type (Type IA through VB); e.g. Business (B): $90.88–$132.95/sq ft; Mercantile (M): $63.76–$95.14/sq ft — see full 2025 fee schedule for all groups/types
Commercial Plan Review FeeTwin Falls County 2025 Fee Schedule; unchanged from the prior 2021 schedule
65% of the building permit fee, or $200.00, whichever is greater
Commercial DemolitionTwin Falls County 2025 Fee Schedule
Based on valuation

Review timeline

Plan review
Not published — contact the department

How long did your Commercial Building Permit (New Construction / Tenant Improvement) permit actually take in Unincorporated Twin Falls County?

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

Inspection process

  1. 1

    Footing / Foundation

    Request by phone 24/7 at 208-734-9490 ext. 1 — requests received by 9:00 AM generally completed same day

  2. 2

    Framing / Structural

    Requires plumbing, electrical, gas, mechanical, fireplace, and firewall/sprinkler rough-in inspections signed off by the State of Idaho first

  3. 3

    Final

    Requires all trade final inspections signed off by the State of Idaho first; Certificate of Occupancy issued after all required inspections pass

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

Tips

  • Commercial Plan Review Fee is 65% of the building permit fee (or $200 minimum) — notably higher than the 35%/$100 minimum residential plan review fee.
  • A 'Plans Analysis' is required for all commercial building plans per the Building Applications Submittal Checklist.
  • Electrical and plumbing trade permits are issued by the Idaho Division of Building Safety (state), not the county; mechanical/HVAC permits are issued by Twin Falls County directly.
  • No published commercial-specific review-timeline figure exists; the county's only published plan-review estimate (seven business days) is explicitly scoped to residential projects.

Frequently asked questions

Unincorporated Twin Falls County requires a commercial building permit (new construction / tenant improvement) for: Building permit required for new commercial construction, tenant improvements, additions, and change-of-occupancy projects; Commercial Building Permit Application (2025 fillable form); Plans Analysis required for all commercial building plans; Plans stamped by an Idaho-licensed architect or engineer where required; Site plan, floor plans with dimensions, elevation views, footing/foundation dimensions with reinforcing, typical construction detail, cross-section and stair detail, truss/floor joist details; South Central Public Health District approval/permit and approved stamped site plan; Highway District, Canal Company, and Fire District approval/comment letters; Deed showing ownership; Authorization Form if applicant is not the property owner; Commercial Plan Review Fee (65% of building permit fee or $200, whichever is greater) due at time of plan submittal. If your project isn't listed, confirm with Twin Falls County Community Development Services — Building Department at 208-734-9490 before starting work.

Effective September 1, 2025, the Commercial Plan Review Fee is 65% of the building permit fee, or $200, whichever is greater — unchanged from the prior 2021 fee schedule. This is separate from and higher than the residential plan review fee (35% or $100 minimum). Source: Twin Falls County Community Development Services Fee Schedule, effective 9/1/2025.

Unincorporated Twin Falls County does not publish a plan-review timeline for this permit. Contact Twin Falls County Community Development Services — Building Department at 208-734-9490 for current turnaround.

You'll need: Commercial Building Permit Application (2025-09 fillable form); Building Applications Submittal Checklist (5/2024); South Central Public Health District Approval. Depending on your project, Unincorporated Twin Falls County may also ask for: Commercial BP Information Handout (Rev. 1/2014). See the required-documents checklist on this page for details on each.

Unincorporated Twin Falls County requires 3 inspection(s) for a commercial building permit (new construction / tenant improvement), in order: Footing / Foundation, Framing / Structural, Final. Schedule each through Twin Falls County Community Development Services — Building Department (208-734-9490).

Apply through Twin Falls County Community Development Services — Building Department at 630 Addison Avenue West, Suite 1100, Twin Falls, ID 83301. Phone: 208-734-9490. Office hours: Mon–Fri 8:00 AM – 5:00 PM (Building Department closed for lunch 12:30 PM – 1:30 PM). Official information: https://twinfallscounty.org/community-development-services/.

Unincorporated Twin Falls County, Idaho has adopted: 2018 International Building Code (IBC) with Idaho Amendments; 2018 International Residential Code (IRC) with Idaho Amendments; 2018 International Energy Conservation Code (IECC) with Idaho Amendments; 2018 International Mechanical Code (IMC) with Idaho Amendments; 2018 International Fuel Gas Code (IFGC) with Idaho Amendments; 2018 International Existing Building Code (IEBC) with Idaho Amendments; 2018 International Fire Code (IFC) with Idaho Amendments; 2018 Idaho Manufactured Home Installation Standards. Local amendments apply — see the Unincorporated Twin Falls County overview page for the full list.

Sources & verification

Verified against official sources. Last reviewed 2026-07-08.

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

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Commercial Building Permit (New Construction / Tenant Improvement) in other cities

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