How building permits work in Idaho
These rules apply across Idaho. Each local guide above covers what is specific to that jurisdiction: its building department and contacts, local conditions, fees and inspections.
The codes Idaho has adopted
Idaho’s building codes are set statewide under the Idaho Building Code Act (Idaho Code Title 39, Chapter 41) and enforced by the cities and counties that choose to run a building program. The Idaho Building Code Board adopts and amends the International Building Code and the Idaho Residential Code through negotiated rulemaking, and a new edition takes effect on January 1 of the year after the board adopts it (Idaho Code 39-4109).
The codes in force
- 2018 International Building Code with Idaho amendments, plus the 2021 IBC provisions for mass timber construction (IDAPA 24.39.30; Idaho Code 39-4109A).
- Idaho Residential Code: Parts I, II, III and IX of the 2018 International Residential Code with Idaho amendments, for one- and two-family dwellings.
- 2018 Idaho Energy Conservation Code for houses, approved by the Legislature, and the 2018 IECC commercial provisions with amendments.
- 2018 International Existing Building Code.
- Idaho electrical code: the 2023 National Electrical Code with amendments, adopted by the Legislature (Idaho Code 54-1001).
- Idaho State Plumbing Code: the 2015 Uniform Plumbing Code with appendices and Idaho amendments (IDAPA 24.39.20), not the International Plumbing Code.
- 2018 International Mechanical Code and Fuel Gas Code for HVAC work.
- The International Fire Code, adopted by the State Fire Marshal (IDAPA 18.08.01).
What local governments may change
A city or county that enforces building codes must adopt the IBC, the Idaho Residential Code and the energy code by ordinance. It may amend the codes to reflect local concerns at an equivalent level of protection, but it may not adopt residential provisions the board has not adopted. For houses it may amend only the administrative part, definitions, the design criteria of Section R301 (such as snow load) and the appendices, plus other parts of Part III where it finds good cause (Idaho Code 39-4116).
Single-family homes and duplexes do not have to be sprinklered, and agricultural buildings such as barns, livestock shelters and equipment storage are exempt from the codes, though a county may issue a permit for road setbacks and utility easements (Idaho Code 39-4116). A permit application is governed by the law in effect when it is received.
Who issues permits, and who else approves
Local building code enforcement in Idaho is optional: a city or county that has not run a program may start one by ordinance, and may contract it out (Idaho Code 39-4116). Where a local government enforces building codes, a permit is required under its ordinance before construction, alteration or repair (Idaho Code 39-4111). Buildings owned by state agencies are reviewed, permitted and inspected by DOPL and the State Fire Marshal instead (Idaho Code 39-4103).
Trade permits may come from the state
Electrical, plumbing and HVAC permits follow their own rules. The state’s electrical inspection does not apply where a city or county inspects electrical work by ordinance (Idaho Code 54-1001B); a plumbing permit comes from DOPL unless the county or city regulates plumbing by an equivalent ordinance (Idaho Code 54-2620); and an HVAC permit comes from the authority having jurisdiction, with none needed to repair or maintain an existing system (Idaho Code 54-5016). So on one project the building permit can come from the city and a trade permit from the state.
Other approvals
- Septic systems: installing, modifying, repairing or expanding an individual or subsurface sewage disposal system needs an installation permit, which the public health district finalizes (IDAPA 58.01.03).
- Roads: where a highway district exists, its commissioners have exclusive jurisdiction over the highways and public rights-of-way in its system (Idaho Code 40-1310), so driveway and right-of-way approvals come from the district.
- Fire: the International Fire Code is adopted by the State Fire Marshal and enforced by local fire authorities.
Areas of city impact
Each county adopts, by ordinance, a map of the area of impact around each city in the unincorporated county. Since a 2024 amendment, the county’s comprehensive plan and its zoning and subdivision ordinances apply in the area of impact; the city gets notice of county hearings and may comment. An area of impact generally extends no more than two miles from city limits, must exist before the city annexes adjacent land, and is reviewed at least every five years (Idaho Code 67-6526).
Deadlines on local permits and inspections
Two recent sections of the Building Code Act set deadlines for local governments that issue building permits:
- The local government must publish a document describing its permit requirements, and tell an applicant within 10 business days (residential) or 20 business days (commercial) whether an application is complete, listing anything missing (Idaho Code 39-4117).
- If a requested inspection is not performed within 48 business hours, the permit holder may hire a qualified third-party inspector and is refunded the inspection fee. If an inspector fails work but does not give the reason within three business days, 10 percent of the inspection fee is refunded (Idaho Code 39-4118).
An alteration permit may not require upgrading unaffected existing parts of a building that complied with the code in force when they were built, unless the department identifies a specific substantial safety hazard (Idaho Code 39-4111).
Energy and existing buildings
Houses follow the 2018 Idaho Energy Conservation Code, and commercial buildings the 2018 IECC commercial provisions with Idaho amendments (IDAPA 24.39.30). Work on existing buildings can use the 2018 International Existing Building Code.
How permit fees work
Each city or county that issues permits sets its own fees. Where DOPL issues the permit, its fees are set by rule (IDAPA 24.39.30). Trade permits issued by DOPL carry the state’s trade permit fees.
Contractor registration and trade licences
It is unlawful to work as a contractor in Idaho without registering with the state, and a contractor may not engage another contractor who must be registered unless that contractor shows proof of registration (Idaho Code 54-5204). Electricians, plumbers and HVAC contractors licensed under their own chapters do not also need contractor registration for that work (Idaho Code 54-5205).
The state licenses electrical contractors and journeymen, plumbing contractors and journeymen, and HVAC contractors and journeymen through DOPL. A city or county may not require any extra licence or fee for HVAC work (Idaho Code 54-5015), and one with qualified plumbing inspectors is the only kind that may charge plumbers an occupational licence fee (Idaho Code 54-2619).
How long permits last
How long a permit stays valid is set by the adopted code and the local ordinance: under Section 105.5 of the IBC and the IRC a permit becomes invalid if work does not start within 180 days or is suspended for 180 days, and local governments may amend the IRC’s administrative part (Idaho Code 39-4116). Willfully violating the Building Code Act is a misdemeanor, with each day a separate offense (Idaho Code 39-4126).