Building permits for unincorporated Twin Falls County, including the cities’ areas of impact, are issued by the Twin Falls County Building Department, part of Community Development Services, at 630 Addison Ave. West, Suite 1101, Twin Falls, (208) 933-9279; the office closes for lunch from 12:30 to 1:30 pm. The county issues building and mechanical permits. Electrical and plumbing permits come from the state Division of Occupational and Professional Licenses (DOPL). Twin Falls County had 97,539 people in the Census Bureau’s 2025 estimate, the fifth-largest county population in Idaho.
This guide covers the department and how to reach it, the local conditions that shape a filing here, what permits cost and who may pull them, and how inspections are booked. Rules that apply everywhere in Idaho are summarized in each section, with a link to the full statewide explanation.
This guide covers unincorporated Twin Falls County, including the areas of impact around its eight cities. The City of Twin Falls, Buhl and Kimberly run their own building departments inside their limits; for a parcel inside Castleford, Filer, Hansen, Hollister or Murtaugh, ask the city which office issues the permit.
Other agencies may need to approve the plans. The county asks applicants to contact the local fire department, health department, highway district and canal company, which may need to issue permits or approve the plans, and on canyon rim land the county’s rim setback applies. Settle these for the parcel before design.
What requires a building permit in Twin Falls County?
Where a city or county enforces building codes, a permit is required under its ordinance before construction, alteration or repair (Idaho Code 39-4111).
Permit required
- New residential and commercial construction, additions, remodels and tenant improvements
- Structural and load-bearing work, foundations, decks, porches, stairs, garages and accessory buildings
- Electrical service changes, panel work, generators, solar, EV chargers and most wiring
- Plumbing, water heaters, sewer and water connections, gas piping, backflow and fixture relocations
- HVAC installation and replacement, ductwork, ventilation, combustion air and fuel-gas appliances
- Roofing, siding, windows, signs, pools, demolition, grading, erosion control and right-of-way work where regulated
Typically exempt
- Painting, wallpaper, flooring, trim, cabinets and countertops
- Minor repairs replacing existing materials in kind with no structural or system change
- Small detached accessory structures below the local threshold, without utilities, where zoning allows
- Portable equipment or temporary work the adopted code specifically exempts
Which work is exempt is set by the adopted codes (IBC and IRC Section 105.2) and the local ordinance, and an exemption from a building permit is not an exemption from zoning, setbacks, floodplain rules, utility approval or a fire authority review. Confirm scope with the department before work starts rather than after.
Short on time to read all of this?
Get a free quote →Which code edition applies
Twin Falls County has adopted the 2018 editions, with Idaho amendments, of the International Building, Residential, Energy Conservation, Mechanical, Fuel Gas, Existing Building and Fire Codes, and the 2018 Idaho Manufactured Home Installation Standards. Local ordinances, the fee schedule, the submittal process and the site conditions are the variables.
Idaho’s building codes are set statewide and enforced by the cities and counties that run a building program: the 2018 International Building Code and the Idaho Residential Code (based on the 2018 IRC), the 2018 Idaho Energy Conservation Code, the 2023 National Electrical Code, and a state plumbing code based on the 2015 Uniform Plumbing Code rather than the International Plumbing Code. Idaho’s adopted codes
Who handles permitting in Twin Falls County?
The county permits unincorporated territory, including the area of impact around each city. The county has adopted an area of impact map for each of its eight cities — Buhl, Castleford, Filer, Hansen, Hollister, Kimberly, Murtaugh and Twin Falls — all on December 19, 2025 (county code 8-22-3). For each area, the county code makes that city’s comprehensive plan and zoning and subdivision code the governing plan and ordinance, as Idaho Code 67-6526 allows a county to do for a specific area of impact, and the county’s Community Development Services and Planning and Zoning Commission administer and enforce them; the city gets notice and may comment. The City of Twin Falls confirms that in its area of impact building and mechanical inspections are done by the county and electrical and plumbing inspections by the state.
| Detail | Information |
|---|---|
| Authority | Twin Falls County Building Department (building and mechanical permits); state DOPL for electrical and plumbing |
| Jurisdiction | Unincorporated Twin Falls County, including the cities’ areas of impact |
| Cities inside | Buhl, Castleford, Filer, Hansen, Hollister, Kimberly, Murtaugh and Twin Falls |
| Site conditions | Canyon rim overlay, floodplain, septic, canal company and highway district approvals |
| Permit applications | Residential, remodel, commercial, manufactured home (block set or permanent foundation), mechanical, demolition, and the agricultural building exemption |
| Boundary to check | City limits; in an area of impact the county issues the permit and applies the city’s zoning code |
| Code | Idaho adopted codes — 2018 I-Codes with Idaho amendments, 2023 NEC |
| Common outside reviews | Fire department, South Central Public Health District, highway district (Buhl, Filer, Murtaugh or Twin Falls) for driveways, canal company; county floodplain development permit |
Not sure this scope needs a permit?
Get a free quote →Canyon rim parcels have a county setback. In the canyon rim overlay district no dwelling may be built within 100 feet of the rim (county code 8-6G-4). A smaller setback needs an application to the director prepared by an Idaho licensed professional engineer, with a parcel map showing the setback, the building location, the disposal facilities and any drainageways, and then a conditional use permit; it can never be less than 50 feet. The zoning administrator decides where the rim is, and structures in the overlay are limited to 35 feet in height.
Where public sewer does not reach, a septic system needs an installation permit from South Central Public Health District, 1020 Washington St N, Twin Falls, (208) 737-5900. Driveway permits come from the Buhl, Filer, Murtaugh or Twin Falls Highway District, or from the Idaho Transportation Department on a state highway.
In 2025, building permits issued in unincorporated Twin Falls County authorized 132 new privately owned housing units, 130 of them single-family homes, according to the U.S. Census Bureau Building Permits Survey.
Electrical, plumbing and HVAC permits come from the state’s Division of Occupational and Professional Licenses unless the city or county runs its own program by ordinance. Septic systems need a health district installation permit, a highway district controls the roads in its system, and since 2024 the county’s zoning applies in a city’s area of impact. Who issues permits in Idaho
Permit types
Residential permits
Residential applications are filed with the county, which has separate forms for new homes, residential remodels, manufactured homes and mechanical work. Foundation walls over 9 feet tall need an engineered design, and buildings over two storeys or of unusual design may also need one.
Snow, seismic and wildland exposure
The county publishes one set of design criteria. Design to a ground snow load of 30 psf; a wind speed of 115 mph (IRC, 3-second gust) or 105 mph for IBC risk category II buildings, exposure C; seismic design category C; a frost depth of 24 inches; and a soil bearing pressure of 1,500 psf unless a soils investigation is provided.
The seismic design category is also set by the site under the adopted codes, and wildland-urban interface rules apply where the city, county or fire district has adopted them. Confirm the design criteria for the parcel with the Twin Falls County Building Department at the start of design.
Rather talk it over?
Call 1-855-478-4290 →Commercial permits
Commercial work follows the International Building Code: any building not covered by the International Residential Code is permitted and inspected under the IBC, and the plans must be stamped and signed by an Idaho licensed architect or engineer. Commercial plan review is 65% of the building permit fee or $200, whichever is greater.
A local government must say within 10 business days (residential) or 20 (commercial) whether an application is complete, and if an inspection is not made within 48 business hours the permit holder may hire a third-party inspector and is refunded the fee (Idaho Code 39-4117, 39-4118). Deadlines on Idaho permits
Twin Falls County permit costs and fees
Twin Falls County building permit fees are based on a per-square-foot valuation table by occupancy and construction type, with a plan review fee on top; mechanical permit fees are based on the living space. Electrical and plumbing permits are bought from the state. The minimum penalty for work started without a permit is an amount equal to the building permit fee.
| Fee component | How it works |
|---|---|
| Residential building permit | Set by the adopted county fee schedule |
| Commercial building permit | Set by the adopted fee schedule |
| Plan review | Per the adopted schedule |
| Trade permits | Charged separately by whoever issues them: the city or county, or the state where it issues trade permits |
| Outside agency reviews | Charged by the agency: the health district for a septic permit, the highway district for a driveway; the county charges for a floodplain development permit |
| Re-inspections and revisions | Charged where the local schedule provides for them |
Need a real number for a specific Twin Falls County project? Send us the scope, address and valuation and we will identify the filing path, the reviews it will trigger and the fee categories that will apply.
Fee schedules are revised on each jurisdiction’s own cycle, so ask the issuing department for the schedule in force on your filing date, and ask separately about plan review, trade, re-inspection and revision charges. How Idaho permit fees work
Rather not deal with the Twin Falls County building department?
Get a free quote →Trade permits and who may pull them
Permit required
- Service upgrades, panels, new circuits, solar PV, EV chargers and generators
- New plumbing, fixture relocations, water heaters, sewer and water connections and gas piping
- Furnaces, boilers, heat pumps, ductwork, ventilation and commercial kitchen exhaust
- Fire alarm, sprinkler and suppression systems on commercial work
Typically exempt
- Replacing a fixture, switch, receptacle or light with no alteration to wiring or piping
- Clearing a stoppage without replacing or rearranging concealed piping
- Filter, thermostat and routine component service
- Appliance repair that does not alter the gas, electrical or venting connection
Contractors must register with the state, and electrical, plumbing and HVAC contractors are licensed by the state; a city or county may not require an extra licence or fee for HVAC work. Contractor registration in Idaho
How to apply for a Twin Falls County building permit
The county permits all unincorporated land, including the areas of impact, where the city’s zoning code applies.
Septic needs a health district permit; driveways need a highway district permit.
Manufactured homes have their own applications; agricultural buildings are exempt from the codes (Idaho Code 39-4116(5)).
Dwellings must be 100 feet from the rim; a smaller setback needs an engineer’s application and a conditional use permit.
30 psf ground snow load; 115 mph wind (IRC), exposure C.
Contractors register with the state; electricians, plumbers and HVAC contractors hold state licences.
Under Section 105.5 of the adopted codes a permit becomes invalid if work does not start within 180 days or stops for 180 days; check whether the local ordinance amends that. How long Idaho permits last
Inspections in Twin Falls County
The county sets the order: the plumbing, electrical, gas, mechanical, fireplace and firewall or sprinkler rough-in inspections must be signed off on the construction card before the framing inspection is requested, and their finals before the final building inspection.
Want this handled start to finish?
Get a free quote →Call the building inspection line, (208) 735-4429, or the mechanical line, (208) 735-4432, with the permit number, property address, contact and type of inspection. Requests called in after 7:00 am are scheduled for the next working day, and inspections run Monday to Friday, typically 9:30 am to 4 pm, except holidays.
Do not cover work before the required inspection has been approved. The approved construction documents must be kept at the site (IBC 107.3.1, IRC R106.3.1).
Twin Falls County permit search and official resources
Permit records sit with the authority that issued them, which in Idaho means the record may be split. A property can have records with several bodies: the building department, the state where it issued trade permits, a highway district for access and the health district for a septic system. If you are buying, refinancing or renovating, ask the Twin Falls County Building Department what it holds for the parcel, and ask separately about the septic and access records where those apply.
Where a property has been annexed, permits issued before annexation may still be held by the county.
Confirm the code edition against Idaho’s adopted list. Idaho enforces the 2018 International Building Code and the Idaho Residential Code (based on the 2018 IRC), the 2023 National Electrical Code and a plumbing code based on the 2015 Uniform Plumbing Code. A new edition takes effect on January 1 after the Idaho Building Code Board adopts it (Idaho Code 39-4109), so check the codes and local amendments in force on your filing date.
These are the primary sources behind this guide. Codes, fee schedules and portal procedures change. Confirm the position for your filing date.
- Twin Falls County Community Development Services — Building Department
- Idaho DOPL — adopted building codes
- Idaho DOPL — plan review and permits
- Idaho Contractors Board — contractor registration
Frequently asked questions
Does the county permit inside the City of Twin Falls?
No. Inside the City of Twin Falls, the city’s Building Safety Department does all inspections, including electrical, plumbing and mechanical. In the city’s area of impact the county issues building and mechanical permits, applying the city’s zoning code, and the state handles electrical and plumbing.
Inspections are where schedules slip.
Get a free quote →What applies to a manufactured home?
The county has separate applications for a manufactured home on a block set and on a permanent foundation. The plans must show that the installation meets the State of Idaho installation standards, and any remodel, modification or attachment to the home must be drawn and wet-stamped by an Idaho licensed engineer.
Does my accessory building need a permit?
Agricultural buildings are exempt from the building codes; a county may issue permits for them only to check road setbacks and utility easements (Idaho Code 39-4116(5)), and Twin Falls County handles them with an Agricultural Building Exemption and an Ag Exempt Siting Permit. For other accessory buildings, the exempt work is set by the adopted codes, so confirm with the department before building.
What does the health district do?
Installing, modifying, repairing or expanding a septic system needs an installation permit, which the public health district finalizes (IDAPA 58.01.03).
Which code edition applies in Idaho?
Idaho enforces the 2018 International Building Code with Idaho amendments and the 2021 IBC mass timber provisions, the Idaho Residential Code based on the 2018 IRC, the 2018 Idaho Energy Conservation Code and the 2023 National Electrical Code (IDAPA 24.39.30; Idaho Code 54-1001).
Does the International Plumbing Code apply?
No. Idaho has adopted the Idaho State Plumbing Code, based on the 2015 Uniform Plumbing Code with Idaho amendments (IDAPA 24.39.20).
Simplify Twin Falls County permitting with Alliance Permitting
In Twin Falls County we settle where the parcel sits first — inside a city, in a city’s area of impact or in the rest of the county — and whether the canyon rim overlay applies.
Trusted by leading builders, developers, and national contractors — 21+ years of filing in the jurisdictions we write about.
Contractors and builders choose Alliance for Twin Falls County because the work is done by people who have stood at the counter:
- We check septic, highway district and canal company requirements before design on rural parcels.
- We confirm manufactured housing and accessory building rules up front.
- We check the canyon rim setback before a dwelling is sited.
- We confirm county versus city and impact-area jurisdiction.
- We confirm the county’s published snow, wind and seismic criteria with your designer before design.
Alliance Permitting is a permit documentation and submission company in Idaho. We prepare your paperwork, file it correctly and coordinate with the building department through issuance. We are not a contractor and we do not perform licensed plan review or inspections; that work stays with your licensed team and the jurisdiction.
Ready to break ground in Twin Falls County sooner?
Let Alliance prepare, file, and track your Twin Falls County permits while your crew stays on the job.
More Idaho permitting guides
This guide is provided by Alliance Permitting for general information about Twin Falls County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.