Bolthole Index

Custer County, Idaho

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

62Index Score / 100
#20 of 44 in Idaho

Unincorporated Custer County, Idaho uses zoning compliance and building notification tied to septic approval rather than a full code-inspected building-permit program1. County zoning still controls land use, lot size and building dimensions, while Eastern Idaho Public Health issues septic permits23. Electrical, plumbing and HVAC work requires the applicable trade permits4.

At a glance

Building permit
Limited: zoning compliance and building notification tied to septic approval, not a full code-inspected county permit program1
Zoning
Yes, in unincorporated Custer County25
Septic permit
Required through Eastern Idaho Public Health for construction, modification or most repairs36
RV living
Temporary or intermittent use only, except an owner may occupy one while building a dwelling on the same property7
Tiny home
No specific occupancy rule confirmed; ask Planning and Zoning how the proposed dwelling and parcel are classified2
Owner-builder
No explicit county exemption confirmed; ask Planning and Zoning and the applicable state trade-permit office84
Minimum lot size
Varies by zoning district and utility conditions9
Private well
Obtain an IDWR drilling permit before drilling10

Who to call

Planning & zoning

Custer County Planning and Zoning

County zoning certificates, land-use questions and rural addressing

(208) 879-6894

801 E. Main Ave. #385 (FedEx or UPS), PO Box 385 (USPS), Challis, Idaho 83226-0385

Septic permits

Eastern Idaho Public Health, Custer County

Septic applications, site evaluations, permits and final inspections

(208) 522-8064

610 Clinic Road, Suite A, Challis, ID 83226

Contact details are copied from each office’s official page and were checked against it on September 27, 2026.

Do you need a building permit in Custer County, Idaho?

Custer County does not present its rural process as a full code-inspected building-permit program; the county uses a zoning compliance certificate and building notification tied to septic approval1. That limited answer does not mean a project is permit-free. Unincorporated land is zoned, with district and overlay rules governing uses, dimensions and other site standards511. Electrical, plumbing and HVAC work requires permits under Idaho's trade programs4. New manufactured homes also require a state installation permit before work starts where no approved local building program operates, followed by approval before occupancy1213. Custer County's materials do not confirm general county building inspections or a certificate-of-occupancy requirement, so ask Planning and Zoning how the office will classify the exact project before ordering materials114.

Who handles Custer County building and zoning questions?

Custer County Planning and Zoning is the first county office for zoning certificates, parcel-use questions and rural addressing14. The office is at 801 E. Main Ave. in Challis and can be reached at (208) 879-689414. Because the county process is limited rather than a full code-inspected permit program, ask the office to identify the required zoning paperwork for the proposed structure and zoning district111. Separate state permits apply when the work includes electrical, plumbing or HVAC systems4. Eastern Idaho Public Health is the separate contact for septic review, and Idaho's water-resources agency handles well-drilling permits310. County materials reviewed do not settle owner-builder exemptions, general inspections or occupancy certificates, so put those questions directly to Planning and Zoning before construction814.

Does Custer County have zoning?

Yes. The zoning ordinance applies in unincorporated Custer County and establishes districts, overlays, permitted uses, height and area regulations, zoning permits and enforcement provisions25. The ordinance establishes six zoning districts and overlays that add requirements where mapped11. Minimum lot size therefore depends on the parcel's district and utility conditions: the cited schedule sets different standards for agricultural, transitional agricultural, residential, industrial and commercial land9. Dwellings may not exceed 35 feet in any zone unless the stated special-permit or other exceptions apply15. A buyer should have Planning and Zoning identify the parcel's district and overlays before treating an advertised use as allowed1411. Custer County's reviewed rules do not confirm a countywide minimum dwelling floor area, so ask the office about a proposed tiny home rather than assuming that a small structure is automatically occupiable2.

How do septic permits work in Custer County?

Eastern Idaho Public Health issues wastewater permits for Custer County and performs application review, onsite evaluation and inspection1617. A valid installation permit is required before constructing or modifying an individual or subsurface sewage system, and most repairs also require one6. Submit the application with a plot plan and building plan, then arrange the onsite evaluation before permit issuance17. The system must pass final inspection before it is covered or receives wastewater1718. Site feasibility deserves early attention because only 4.1% of county soils are rated without severe limitations for a conventional septic drain field19. Public or central wastewater availability can also affect approval because the director may deny an onsite permit when those facilities are reasonably accessible20. Contact the district at its Challis office before fixing a house location, driveway or well location on the site plan17.

Can you live in an RV or tiny home in Custer County?

Custer County permits temporary or intermittent RV use under conditions, but an RV generally may not serve as a dwelling7. A property owner may live in an RV while constructing a dwelling on the same property; after the residence zoning certificate is completed or expires, the RV must return to temporary or intermittent use7. The RV must remain registered and serviceable, cannot acquire decks, additions or skirting, and must use an approved sewage system or be self-contained and taken to an approved dumping location7. Floodplain use must also comply with the county flood-damage ordinance7. No specific tiny-home occupancy rule or minimum dwelling floor area was confirmed, while zoning districts and dimensional rules still apply2. Ask Planning and Zoning how a tiny home would be classified and what zoning certificate is required for the parcel14.

Building a home in Custer County: the steps in order

  1. Ask Custer County Planning and Zoning to confirm the parcel's district, overlays, allowed residential use and required zoning certificate1411.
  1. Have Eastern Idaho Public Health review the septic application, plot plan and building plan, then complete its onsite evaluation before permit issuance17.
  1. Obtain the septic installation permit before construction, modification or covered repairs, and preserve access for the final inspection618.
  1. Obtain Idaho permits for electrical, plumbing and HVAC work, and obtain the state installation approval that applies to a new manufactured home where there is no approved local building program412.
  1. Obtain an IDWR drilling permit before drilling a private well10.
  1. If access connects to a state highway, obtain the Idaho Transportation Department encroachment permit before work in the highway right-of-way21.

What should you check before buying land in Custer County?

Start with zoning and septic feasibility: Custer County has mapped districts and overlays, while only 4.1% of its soils avoid a severe conventional-drain-field limitation1119. Terrain narrows the easy building envelope because 21.8% of county land is at a slope of 15% or less22. Confirm legal access and identify who owns the road; a driveway connecting to an Idaho state highway requires a state encroachment permit, while the county-road approach rule was not confirmed in the reviewed materials21. Budget for water separately because drilling a well requires an IDWR permit10. Floodplain development requirements remain unconfirmed, although the RV rule expressly makes floodplain RV use subject to the county flood-damage ordinance7. For carrying costs, the effective property-tax rate is about 0.3%, and the median annual property-tax bill is about $9032324.

Watch-outs

  • An RV is not a general-purpose permanent dwelling in unincorporated Custer County; owner occupancy while constructing a dwelling is a conditional exception7.
  • Only 4.1% of county soils are rated without severe limits for a conventional septic drain field, so obtain the site evaluation before committing to a house site1917.
  • County floodplain-development requirements were not confirmed; ask Planning and Zoning before disturbing land in a mapped floodplain714.

Sources

  1. Custer County, Idaho - Planning and Zoning (2026 county census)
  2. Ordinance No. 2007-09 Zoning Ordinance (2026 county census)
  3. Eastern Idaho Public Health - Septic (2026 county census)
  4. Frequently Asked Questions (FAQs) - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
  5. Ordinance No. 2007-09 Zoning Ordinance, quoted and re-checked
  6. Septic | Eastern Idaho Public Health, quoted and re-checked
  7. Ordinance No. 2007-09 Zoning Ordinance, quoted and re-checked
  8. (2026 county census)
  9. Ordinance No. 2007-09 Zoning Ordinance, quoted and re-checked
  10. Wells Overview (Idaho statewide rule), quoted and re-checked
  11. Ordinance No. 2007-09 Zoning Ordinance, quoted and re-checked
  12. Building Archives - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
  13. Building Archives - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
  14. Custer County Planning and Zoning (custercountyidaho.org)
  15. Ordinance No. 2007-09 Zoning Ordinance, quoted and re-checked
  16. Septic Rules & Forms, quoted and re-checked
  17. Eastern Idaho Public Health, Custer County (eiph.id.gov)
  18. IDAPA 58.01.03 Individual/Subsurface Sewage Disposal Rules (Idaho statewide rule), quoted and re-checked
  19. Share of soils without severe limits for a conventional septic drain field (USDA SSURGO): Bolthole Index county data
  20. IDAPA 58.01.03 Individual/Subsurface Sewage Disposal Rules (Idaho statewide rule), quoted and re-checked
  21. Types of Right-of-Way Encroachment Permits (Idaho statewide rule), quoted and re-checked
  22. Share of land at 15% slope or less: Bolthole Index county data
  23. Effective property tax rate: Bolthole Index county data
  24. Median property tax bill: Bolthole Index county data

Written September 27, 2026 from the rules quoted below, each taken from an official source and re-checked by an independent reviewer. This is research, not legal advice: rules change, so confirm with the office before you buy or build.

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County locator

Custer County in Idaho

62
County map
Custer County highlighted among the Idaho counties · colored by Index score

How Custer County scores

Seclusion89100% ev.
Self-Sufficiency36100% ev.
Admin Boringness5190% ev.
Durability37100% ev.
Property Autonomy90100% ev.
Carry Cost78100% ev.

Evidence strength: 98%. This reports direct-source completeness and fallback use; it is separate from the score and is not a confidence interval. How it works →

$406kTypical home
0.3%Property tax
$3,588Land / acre
21.9"Annual rain
12.5% of yrsSevere drought
0.1 / yr (+0.1)Mid-century 100°F days
24.1 daysMid-century dry spell
1.35" (+5.2%)Mid-century 1-day rain
1.21×Wildfire change factor
100%Forward climate coverage
$1,396Home insurance / yr
2.1% / yrInsurance growth
2.01%Nonrenewal rate
county median (2+ published ZIPs)Insurance basis
1,511Radius comparison (15 mi)
0.9People / sq mi
94.1%Federal land
21.8%Land at 15% slope or less
4.1%Septic soil without severe limits
119,776 acWorkable land screen
35.9%Wooded land
22.6 tonsBiomass / forest ac
38.6°FAvg temp

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Answers from the rulebook for Custer County

What the ordinances and state agencies actually say — one answer per question, each quoted from the official source and independently re-checked.

Custer County rules

  • County-wide zoningPresent

    Zoning regulation in the unincorporated territory of Custer County.

    • The ordinance establishes zoning districts, overlays, permitted uses, height and area regulations, building-zoning permits, and enforcement provisions.
    “The following zoning districts are hereby established. For the interpretation of this Ordinance, six zoning districts and overlays have been formulated to realize the general purposes as set forth in this Ordinance.”
  • Zoning districtsPublished

    Custer County zoning districts and overlays.

    • The ordinance establishes six zoning districts and overlays.
    • The county also publishes a Custer County Zoning Map.
    “The following zoning districts are hereby established. For the interpretation of this Ordinance, six zoning districts and overlays have been formulated to realize the general purposes as set forth in this Ordinance. The overlays provide for additional requirements in those areas of the districts that they cover.”
  • Minimum lot sizeSpecified

    Lots in Custer County zoning districts.

    • Agricultural Zone A: 20 acres, subject to stated lot-split rules and exceptions.
    • Transitional Agricultural: 2.5 acres.
    • Residential: 9,000 square feet if proper septic is provided.
    • Industrial: 1 acre.
    • Commercial: 9,000 square feet if central water and sewer are provided and approved by District 7 Health District.

    Agricultural minimum lot size: 20 acres (Certain pre-November 10, 2003 parcels may qualify for lot splits; specified splits may range from 2.5 to 7 acres; special conditional-use circumstances may allow a post-division parcel of at least 5 acres.) · Transitional Agricultural minimum lot size: 2.5 acres · Residential minimum lot size: 9000 square feet (If proper septic system; footnote also states central water and sewer must be provided and approved by District 7 Health District where applicable.) · Industrial minimum lot size: 1 acre · Commercial minimum lot size: 9000 square feet (If central water and sewer are provided and approved by District 7 Health District.)

    “Transitional Agricultural 35 ft. 2.5 acres (fn. 1) Residential 35 ft. 9,000 sq. ft. – if proper septic system (fn. 2) Industrial No limitation 1 acre Commercial No limitation 9,000 sq. ft. (fn. 2)”
  • Building heightSpecified

    Building height in Custer County zoning districts.

    • Agricultural and Industrial districts have no limitation in the table, but dwellings may not exceed 35 feet in any zone.
    • Transitional Agricultural, Residential, Commercial, and Industrial rules and special conditional-use exceptions apply.
    • Height exceptions include certain roof appurtenances and residential cross-slope modification.

    dwelling maximum height: 35 feet (A special conditional-use permit may authorize greater height subject to fire, aviation, view, neighborhood, light/air, and environmental findings; certain non-occupiable roof appurtenances are exempt.)

    “*Dwellings shall not exceed 35 feet in ANY zone. (Ordinance 2016-01) [...] No building or other structure erected in any land use district shall have a height greater than that specified in Official Height and Area Regulations, Article VII, except that the Board, by Special Conditional Use Permit may authorize a greater height”
  • Living in an RVLimited

    Temporary or intermittent recreational-vehicle use in county-regulated territory.

    • The RV must be currently registered and serviceable.
    • It may not be set on blocks with tires or running gear removed.
    • No decks, additions, or skirting are allowed.
    • It may not be used as a dwelling, except by property owners during construction of a dwelling on the same property; after completion or expiration of the residence zoning certificate, use reverts to temporary or intermittent use.
    • There must be no mail service.
    • The RV must connect to an approved sewage system or be self-contained and removed to empty holding tanks at an approved location.
    • The RV may not be used as a rental property.
    • RV use in floodplains must comply with the Flood Damage Prevention Ordinance.
    “The RV shall not be used as a dwelling. The owners must have a primary residence other than the RV. There shall be no mail service to this type of use. An RV may be used as a dwelling for the owners of the property during construction of a dwelling on the same property as the RV site.”
  • Who permits septicLocal

    Individual and subsurface sewage systems serving Custer County within Eastern Idaho Public Health's district.

    • Eastern Idaho Public Health serves Custer County as part of its multi-county health district.
    “Serving Bonneville, Clark, Custer, Fremont, Jefferson, Lemhi, Madison, and Teton Counties [...] To achieve the Health District’s objectives in this program we: Review applications for disposing of waste water, Perform onsite evaluations, Issue waste water permits, Conduct inspections, Provide technical assistance and education to the public and those that install septic systems.”

Idaho rules that apply here

  • Building permitLimited

    New manufactured-home installations in Idaho locations without an approved local building program.

    • The installation permit and tag are required only for new homes.
    • The requirement applies in areas where there is not an approved local building program.
    • The permit must be obtained before starting installation.
    “An installation permit and installation tag (required only for new homes) is required by Idaho Division of Occupational and Professional Licenses prior to starting the installation in areas where there is not an approved local building program.”
    One more reviewed finding on this topic
  • Building code adoptedAdopted (with conditions)

    Building construction in Idaho subject to the Idaho Building Code Act and the Idaho Division of Occupational and Professional Licenses building-code program.

    • The adopted codes include amendments identified by Idaho; local-government application is subject to the Idaho Building Code Act.
    • The reference to the 2020 Edition is an identifier to the legislative session in which amendments were adopted.
    • Amendments can be made in any legislative cycle regardless of code cycle.
    • The cited DOPL page states that existing rules remain in effect for 2026–2027.

    International Building Code: 2018 edition, with amendments · International Residential Code: 2018 edition, parts I, II, III and IX, with Idaho amendments; collectively named Idaho Residential Code (2020 Edition) · International Energy Conservation Code: 2018 edition, with amendments; collectively named Idaho Energy Conservation Code (2020 Edition) · International Existing Building Code: 2018 edition

    “Building Codes: 2018 International Building Code, with amendments 2018 International Residential Code (parts I, II, III and IX), with Idaho amendments collectively named the Idaho Residential Code (2020 Edition) 2018 International Energy Conservation Code, with amendments collectively named the Idaho Energy Conservation Code (2020 Edition) 2018 International Existing Building Code”
  • InspectionsRequired

    All manufactured-home installations in Idaho before the manufactured home is occupied.

    • The inspection and approval are performed by DOPL or the authority having jurisdiction.
    • Inspection and approval must occur before occupancy.
    “All installations must be inspected and approved by the Idaho Division of Occupational and Professional Licenses or the authority having jurisdiction before the manufactured home is occupied.”
  • Camping on your landLimited

    Camping or parking a vehicle or trailer on Idaho Fish and Game Wildlife Management Areas and access sites separate from a WMA.

    • The restriction applies in areas posted against camping or parking.
    • Leaving an unattended camp, vehicle, or trailer for more than 48 hours is prohibited without authorization.
    • Camping or parking for more than 10 days during any 30-day period on one WMA or one separate access site is prohibited without authorization.
    • The rule permits authorization by the Commission, Director, Regional Supervisor, or designee.

    unattended duration: > 48 hours (Unless specifically authorized by the Commission, Director, Regional Supervisor, or designee.) · camping or parking duration: > 10 days during any 30-day period per WMA or separate access site (Unless specifically authorized by the Commission, Director, Regional Supervisor, or designee.)

    “camp or park a vehicle or trailer for more than ten (10) days during any thirty (30) day period”
  • Accessory dwellingsLimited

    Accessory dwelling units for Idaho DEQ wastewater-flow and septic-system sizing purposes; this claim does not establish statewide zoning permission.

    • An ADU is sized as a single-family dwelling for the cited wastewater-flow guidance.
    • An ADU may combine flows with another structure into one system.
    • Any common septic tank must be large enough to hold the required capacity from both structures.
    • Local land-use, building, and septic authorities may impose additional requirements.

    wastewater flow basis: single-family dwelling

    “Size as a single family dwelling. Can combine with another structure's flows into one system”
  • Septic permitRequired

    Modification, repair, or construction of an individual or subsurface sewage disposal system in Custer County.

    • Portable non-discharging systems may be used temporarily.
    • Individual subsurface sewage systems may be repaired for broken or clogged solid piping or electrical/mechanical malfunctions; such repair may not expand the system unless authorized.
    “It shall be unlawful for any person to cause or to perform the modifications, repair or construction of any individual or subsurface sewage disposal system within the State of Idaho unless there is a valid installation permit authorizing that activity.”
  • Septic inspectionRequired

    Individual and subsurface sewage disposal systems constructed or installed under Idaho’s onsite wastewater rules.

    • The Director requires one or more inspections necessary to determine compliance.
    • The permittee must uncover or make available for inspection any portion covered or concealed in violation of the rules.
    • If preparation is required, the applicant or permittee must provide at least 48 hours’ advance notice, excluding weekends and holidays.
    • For individual systems, the public health district inspects the installation.
    • Large soil absorption systems are inspected by the public health district and DEQ.

    advance inspection notice: >= 48 hours (Excludes weekends and holidays.)

    “No system may receive wastewater until the Director conducts a final installation inspection”
  • Well permitRequired

    Construction or drilling of wells in Idaho, including domestic wells.

    • Before drilling, the well owner or driller must obtain a drilling permit from IDWR.
    • All wells must be constructed by a well driller with a valid IDWR license.
    • The separate water-right permit exemption for domestic purposes does not eliminate the drilling-permit requirement.
    • For new diversions in qualifying subdivisions filed on or after July 1, 2025, a water-right permit is required in a moratorium area, critical groundwater area, or groundwater management area, except for in-home uses and watering livestock.
    • Well construction rules apply to wells and other artificial openings more than 18 vertical feet below land surface.

    well depth threshold: > 18 vertical feet below land surface (The cited well-construction rules describe covered wells and artificial openings.) · subdivision application date: >= 2025-07-01 (Applies to qualifying new diversions described in Idaho Code § 42-227(4).)

    “Prior to drilling a well, the well owner or well driller must first obtain a drilling permit from IDWR.”
  • Mandatory utility hookupConditional

    Proposed individual or subsurface sewage disposal systems where public or central wastewater treatment facilities may be available.

    • The Director may deny a septic permit when public or central wastewater treatment facilities are reasonably accessible.
    • The cited rule does not establish a universal statewide requirement to connect every property to public sewer.
    • Subsurface septic discharge remains an identified onsite disposal method.
    “Public or central wastewater treatment facilities are reasonably accessible.”
  • Driveway accessRequired

    Private and public driveways or streets connecting to Idaho state highway right-of-way.

    • An ITD encroachment permit is required for private and public approaches, including driveways and streets.
    • No activity may occur on state highway rights-of-way until the Department or a delegated local highway agency issues an approved permit, except emergency approval affecting highway operations and motorist safety may precede processing.
    • A Traffic Impact Study may be required for new or expanded development seeking direct access to a state highway when the stated thresholds are met, unless waived by the District Engineer.

    peak-hour trips for possible TIS requirement: >= 100 new trips (unless waived by the District Engineer) · daily traffic for possible TIS requirement: >= 1000 vehicles per day (unless waived by the District Engineer)

    “Encroachment permits approved by the Department are required for private and public approaches (driveways and streets), utilities and other miscellaneous encroachments.”

Still unanswered

We looked and could not find an official answer yet. Silence is not permission — ask the county directly.

  • Owner-builder exemption — Owner-builder exemptions in Custer County.
  • Certificate of occupancy — Certificates of occupancy in Custer County.
  • Minimum dwelling size — Minimum dwelling size in county zoning districts.
  • Lot coverage — Lot coverage limits in Custer County zoning districts.
  • Tiny homes — Tiny-home occupancy in unincorporated Custer County.
5 more unanswered
  • Manufactured homes
  • Off-grid sanitation
  • Agricultural exemption
  • Building in a floodplain
  • Short-term rentals

Each answer was extracted from an official source and independently re-checked against that source by a second reviewer. That is an evidence check, not legal advice. Rules change; confirm with the authority before you buy or build.

Living off-grid in Custer County, Idaho

Is Custer County a good place to live off-grid or homestead?

Custer County scores 62/100 on the Bolthole Index, a solid county profile. Its strengths: a stronger property-autonomy legal backdrop and deep seclusion — about 1,511 people within 15 miles. Watch-outs: thin water margin (21.9″/yr rainfall) and elevated current hazard exposure.

Do you need a building permit in Custer County, Idaho?

Custer County requires a building permit only in limited cases (such as floodplains or specific zones), and it enforces county zoning. Onsite septic is permitted by Eastern Idaho Public Health. These answers are quoted from official sources and independently re-checked. Rules change and cities within the county differ — always confirm with the county before you buy or build.

Can you live in an RV or tiny home on your land in Custer County?

Living in an RV on your own land in Custer County is limited to specific cases: Temporary or intermittent recreational-vehicle use in county-regulated territory. The RV must be currently registered and serviceable. It may not be set on blocks with tires or running gear removed. Confirm with the county before relying on it.

How much does land cost in Custer County, Idaho?

Land in Custer County runs about $3,588 per acre, based on the latest county data.

What is the water situation in Custer County?

Custer County gets about 21.9" of rain a year, with severe drought in roughly 12.5% of years.

How remote is Custer County?

A typical private-land location has about 1,511 people within 15 miles and 378,055 within 100 miles. These radius catchments are the published fallback where road routing is unavailable.

Off-grid gear

Going off-grid in Custer County means bringing your own water and power. The kit we’d start with:

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How Custer compares in Idaho

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