Building permits, zoning and land rules in Lemhi County, Idaho

Yes. Lemhi County requires a building permit application, complete building plans and a plot plan for building construction, and a septic permit is required when building in the county¹⁰. Work cannot begin and inspections will not be performed until the building permit has been issued⁵.

The county enforces adopted building regulations, including the Idaho Residential Code 2020 Edition, which consists of specified parts of the 2018 International Residential Code with Idaho amendments^2,11. Electrical, plumbing and HVAC permits are obtained through the Idaho Division of Occupational and Professional Licenses¹⁰.

A qualifying agricultural building may receive a permit exemption only when it is used solely for eligible agricultural purposes and the Assessor determines the land is actively devoted to agriculture¹². That exemption does not cover human habitation, public use, repair shops or personal-vehicle garages and storage, and the building must still satisfy county placement plus applicable snow and wind standards¹².

The Lemhi County and City Building Department handles county building permits from its office at 200 Fulton Street, Suite 204 in Salmon; call 208-742-1703². The department assists with land-use questions, checks compliance with existing regulations, enforces adopted building codes and provides emergency addressing².

Start with the department before ordering plans because the required documents can depend on the project. Lemhi County’s published process calls for a permit application, complete building plans, a plot plan showing the proposed building location and a septic permit for county construction¹⁰. The plot plan should be resolved before site preparation because county setbacks vary with road frontage, lot position, wall height and special locations such as stream corridors⁵.

Inspections must be requested 24 hours in advance, and no work may be covered or go beyond the inspection point until it is inspected¹³. Required stages include footings, stemwalls, concrete slab, framing, insulation, interior wall finishing and the final inspection; a re-inspection costs $47¹³. Ask the Building Department for the permit fee schedule, which we could not confirm².

Yes. Lemhi County has an official zoning map, zoning districts and district-specific standards and uses³. Within the Salmon Area of City Impact, both the Salmon Development Code and Lemhi County Development Code apply, with the more restrictive provision controlling when they conflict⁶.

Lot size is not one countywide figure. Minimums vary with zoning, site characteristics, central water or sewer availability, groundwater vulnerability and named planning areas⁶. Newly created lots require at least 110 feet of frontage; the code identifies a basic one-acre minimum but provides different minimums for serviced land and groundwater-vulnerability areas⁶.

County permit materials also specify setbacks and tell applicants to verify the applicable distance before preparing the site⁵. A parcel review should therefore identify the zoning district, any overlay, legal lot status, access, utilities and the precise setbacks rather than assuming that rural acreage is unrestricted.

Eastern Idaho Public Health administers septic permitting in Lemhi County from its Salmon office at 801 Monroe; call (208) 756-2123⁷. The district reviews wastewater applications, performs onsite evaluations, issues permits and conducts inspections⁴.

A valid installation permit is required before constructing, modifying or repairing an individual or subsurface sewage system, subject to limited exceptions for certain piping or mechanical repairs⁴. An Environmental Health Specialist must inspect the installed system before it is covered, and a system covered prematurely must be uncovered⁷.

Soils deserve early attention: only about 4.4% of county soils are rated without severe limitations for a conventional septic drain field¹⁴. Treat that as a screening signal, not a parcel verdict; the district’s site evaluation determines what can be permitted. Where public or central wastewater treatment is reasonably accessible, Idaho’s rules allow the permitting authority to deny an onsite septic permit¹⁵.

The county's guidance says temporary recreational lodging is the only legal use of an RV, and RV placement and occupancy are regulated by local planning and zoning rules¹⁶. We could not confirm a rule that allows living in an RV on private land during construction, so before relying on one, ask the Building Department how the parcel’s zoning district treats occupancy, whether a permit is needed and what approved sanitation must be in place. Requirements for RV parks do not answer that private-parcel question; RV parks must have ready access to water, sewerage and electricity services⁶.

A tiny home is not automatically outside the permit system: the county says every dwelling, including a tiny house, must fit one of its classifications, and a tiny house classified as an RV may face planning and zoning approval challenges¹⁶. Site-built and modular buildings must meet the building code's minimum area, described as about 150 square feet¹⁶. Building permits and district zoning standards apply^3,5. We could not confirm a separate countywide minimum dwelling floor area, so ask the Building Department to review the proposed structure, foundation, use and zoning district.

Manufactured or mobile homes used as permanent single-family dwellings are allowed only under stated conditions: qualifying construction standards, removal of the hitch, wheels, chassis and running gear, attachment to a permanent foundation, and permanent utility connections⁶. Every manufactured-home installation must also be inspected and approved by the state or authority having jurisdiction before occupancy¹⁷.

1. Ask the Building Department to identify the zoning district, overlays, setbacks and required submittals for the parcel. County zoning and development standards vary by district and planning area³.

1. Confirm that Eastern Idaho Public Health can approve an onsite wastewater system before fixing the house site. The district performs site evaluations and issues septic permits⁴.

1. Resolve water and access. Idaho requires an IDWR drilling permit before a well is drilled⁹. Work on a driveway or other access within a county road right-of-way requires the county access permit; a state-highway connection requires an ITD encroachment permit^18,19.

1. Submit the building application, complete plans, plot plan and septic permit required by the county process¹⁰.

1. Obtain electrical, plumbing and HVAC permits through the Idaho Division of Occupational and Professional Licenses¹⁰.

1. Receive the building permit before starting work, then request each inspection 24 hours ahead, from footings through the final^5,13.

1. Keep the septic installation uncovered until the required health-district inspection is complete⁷.

Start with buildability, not the listing description. Confirm the zoning district, overlays, legal access, applicable setbacks and whether the lot can support the intended use. Lemhi County regulates subdivisions, and each subdivision lot must accommodate a permitted use²⁰.

Make septic feasibility an early contingency because only about 4.4% of county soils rate without severe limitations for a conventional drain field¹⁴. The county is also steep overall, with about 28.4% of its land at a slope of 15% or less, so a parcel-specific house site, driveway and drain-field layout matter¹⁴.

Check flood status before designing because development in a Special Flood Hazard Area requires a floodplain development permit before work begins⁶. Such projects also need a final as-built elevation certificate before the county issues a Certificate of Compliance or Occupancy⁶. Confirm whether access meets the county-road or state-highway permit path^18,19. Finally, budget around the countywide effective property-tax rate of about 0.4%, while verifying the actual parcel assessment and exemptions with the county¹⁴.