Franklin County, Idaho Building Permit Guide

Franklin County’s Building Department is a one-inspector office at 561 West Oneida in Preston. Every structure over 200 square feet needs a permit, the building permit fee is 1% of the value the Building Inspector assesses, and a septic permit from Southeastern Idaho Public Health has to come first. The county also issues mechanical (HVAC) permits; electrical and plumbing permits come from the State.

When does Franklin County require a permit?

A building permit must be in hand before construction begins, and the county’s packet sets the line at 200 square feet: all structures larger than that need a permit. Building without one brings a fine of double the permit fee.

Check the lot first. The county’s packet explains that all land in the county is zoned agriculture and has to be changed to become a building lot. It tells applicants to trace the parcel’s history back to June 1993 to see whether it has been split, and to contact the county before designing a house. In an approved subdivision a copy of the deed is enough.

Who issues building permits in Franklin County?

The county Building Department, in the Extension & Road Department building in Preston, permits the unincorporated county. Randy Henrie is the Building Inspector, and permits are sent to him directly. The six incorporated cities differ:

• Preston: the City’s own Building Department, with applications filed online through Cloudpermit. The City says to expect at least 30 days between application and permit.
• Franklin: the City has its own Building Permit Application, filed at City Hall, 128 East Main (208-646-2300), and approved by a city official.
• Clifton: applications are picked up from and returned to Clifton City (City Clerk, 208-339-8500). The county’s Building Inspector reviews the plans, sets the fee and inspects. Clifton requires a permit for anything over 120 sq ft.
• Weston: the City publishes no permit information at present; City Hall is at 18 South Center, and its clerk can be reached at 208-339-7369.
• Dayton: the City publishes no permit information. Dayton City Hall is at 999 North Westside Highway, 208-747-3589; ask there or the county Building Inspector whether an address inside the city files with the county.
• Oxford: the published sources do not say who permits inside the city; the county Building Inspector can tell you whether an Oxford address files with the county.

Franklin County permit forms

There is no portal. The forms are PDFs on the Building Department page, and everything can be handed in at the office or emailed.

• Building Permit packet — the process sheet, a signature checklist, the plan submittal list, the inspection process and the one-page Building Permit Application. The application asks for the owner, the construction address, the contractor and licence number, the type of construction, the estimated cost and lender, and a plot plan.
• Agricultural Building Permit — a rules sheet, the Ag Permit Agreement and the application.
• Mechanical Permit — a one-page form priced per dwelling unit or per appliance.
• Address Verification form — issued by the Building Inspector, by appointment, before you collect the checklist signatures.

The department also posts a Residential Builders Handbook, its climatic design criteria and a roof snow load map.

Franklin County permit fees

Franklin County does not use a valuation table. The Building Inspector reviews the plans, assesses a value for the building and charges 1% of it. The application has a grid for the area and value of the main floor, upper floor, basement, crawl space, garage and patio.

On that basis a house the inspector values at $350,000 carries a $3,500 building permit fee, and its mechanical permit is $110. The county notifies you when the permit is ready.

Mechanical, electrical and plumbing permits

Franklin County splits the trades. The county’s own Mechanical Permit covers HVAC and gas work, and the state’s permit map sends HVAC applicants in the unincorporated county, Clifton, Preston and Weston to the Franklin County building inspector. Electrical and plumbing permits are state permits from the Idaho Division of Occupational and Professional Licenses. In Dayton the state map lists all three trades, HVAC included, as state-issued.

The county inspects rough mechanical work (ducts, flues and appliances) at its framing inspection, and checks that the state’s rough electrical and plumbing inspections are done at that stage and the trade finals before its own final.

What to submit for a Franklin County building permit

How to apply for a Franklin County permit: 6 steps

Franklin County inspections

The permit holder calls the Building Inspector at 208-221-6149 between 9:00 a.m. and 5:00 p.m., Monday to Friday, and gives 24 hours’ notice. Five inspections are required:

• Footing and setback: excavation 30 inches below final grade and at least 80 feet from the center of the county road or 50 feet from the fence, whichever is further; rebar tied and lifted about 3 inches; the concrete-encased (Ufer) electrical ground in place; no frost in the ground.
• Foundation: forms and rebar in place at 24 inches on center, block-outs in, cold joints doweled.
• Framing and mechanical: sheathing before house-wrap; then framing, fire blocking and bracing after the roof and windows are on and before insulation, with rough electrical, plumbing and mechanical in place.
• Sheetrock: after it is hung and before taping.
• Final: before moving in, with finish grade done and the trade finals complete.

Local Franklin County filing considerations

Codes: Ordinance 2003-1, last amended on June 8, 2026, adopts whichever editions of the building, residential, energy, mechanical, fuel gas and fire codes and the Idaho Plumbing Code the state has approved, so the county moves to new editions when the state does.

City areas of impact: the county has adopted area of impact ordinances for Clifton, Dayton, Franklin, Preston and Weston. Land in those fringes is outside the city limits and applies to the county. The Preston ordinance (2024-12-23-C) and the Dayton one (2025-12-22) each draw the area half a mile out from the city limits, have the County send any project that needs a building permit to the City for comment at least 15 days before its first decision, and bar permanent buildings within 25 feet of the City’s water transmission line.

Shed sizes differ by place: the county’s threshold is 200 sq ft, Clifton’s is 120 sq ft, and Preston exempts buildings of 120 sq ft and under that are less than 10 feet tall.

Snow in the canyons: roof snow load rises from 40 lb in the valleys to 50 to 70 lb in the canyons; the county posts a roof snow load map.

Idaho building code

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

Official Franklin County permitting resources

These are the primary sources behind this guide. Codes, fee schedules and procedures change — confirm the position for your filing date.

• Idaho DOPL HVAC permit questions
• Idaho DOPL building program
• Franklin County Planning and Zoning: Development Code and area of impact ordinances
• Franklin County Building Department and permit forms
• Idaho DOPL building questions
• Franklin County building permit packet and application
• Franklin County Agricultural Building Permit
• Franklin County Mechanical Permit
• Franklin County climatic and geographic design criteria
• Franklin County Ordinance 2003-1, amended June 8, 2026 (adopted codes)
• Southeastern Idaho Public Health: septic permits
• City of Preston Building Department
• Clifton City permits
• Franklin County list of cities, with city hall addresses and phones
• Franklin County Ordinance 2024-12-23-C: City of Preston area of impact
• Idaho DOPL permit map for electrical, plumbing and HVAC permits

Franklin County building permit FAQs

How much is a building permit in Franklin County?

1% of the value the Building Inspector assesses for the building, so $3,500 on a $350,000 house. An agricultural building permit is a flat $100.

What size building needs a permit?

Any structure over 200 sq ft in the unincorporated county. Clifton and Preston use 120 sq ft.

Does a barn or shop need a permit?

Yes, if it is 200 sq ft or larger. A building that is not residential or commercial qualifies for the $100 Agricultural Permit, with an 80-foot setback from the center of a county road.

Who issues HVAC permits in Franklin County?

The county, on its Mechanical Permit: $110 per unit for a new dwelling, or $45 plus $10 per appliance in an existing one. Electrical and plumbing permits come from the State.

Who issues septic permits?

Southeastern Idaho Public Health, at 42 West 1st South in Preston. The county will not issue the building permit until the septic permit is complete.

How do I schedule an inspection?

Call the Building Inspector at 208-221-6149 between 9:00 a.m. and 5:00 p.m. on a weekday, with 24 hours’ notice.

Does the county permit work inside Preston?

No. Preston has its own Building Department and takes applications through Cloudpermit. Franklin City also has its own application.

How long is a Franklin County permit good for?

Work must start within 180 days and the permit expires after one year.

Simplify Franklin County permitting with Alliance Permitting

Alliance Permitting is a permit documentation and submission company in Idaho. We prepare your paperwork, file it correctly and coordinate with the permitting authority 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.

This guide is provided by Alliance Permitting for general information about Franklin County permitting. Requirements, fees, and procedures change; confirm details with the permitting authority before relying on them.