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

At a glance

Building permit

Required for regulated construction and changes; listed minor work is exempt¹

Building codes

The county adopted the 2018 building and residential codes, with local amendments⁶⁷

Zoning

Yes, administered by the county in unincorporated areas³

Septic permits

Eastern Idaho Public Health evaluates sites and issues permits⁵⁸

RV or tiny-home living

Longer-term RV living requires a permit and at least a 1-acre legal parcel⁹

Owner-builder

Owners may be exempt from contractor registration, but not from applicable permits or inspections¹⁰¹¹

Residential lot size

Varies by zoning district from 1 to 40 acres, subject to stated exceptions¹²

Private well

An IDWR drilling permit is required before drilling¹³

Who to call

Contact details are copied from each office’s official page and were checked against it on October 12, 2026.

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

Unincorporated Jefferson County requires a building permit for regulated construction, alteration, repair, moving, demolition, occupancy changes and regulated system work.¹ Listed minor residential work and structures are exempt, but an exempt structure under 200 square feet still needs a zoning certificate.¹ A manufactured home also requires a county building permit before placement.¹⁴

Unincorporated Jefferson County uses the 2018 International Building Code and International Residential Code, adopted in 2022 with county amendments.⁶⁷ Idaho separately requires permits for electrical, plumbing and HVAC work subject to its state-administered program.¹⁵ Give Planning, Zoning & Building the parcel number and project scope before ordering plans.² An accessory dwelling unit may be allowed where the zone permits it, with a maximum of 1,200 square feet of living area and 2 bedrooms, plus building, septic, access and inspection requirements.¹⁶

Who handles Jefferson County building permits and inspections?

Jefferson County Planning, Zoning & Building is the first stop for a project in unincorporated Jefferson County; the office is at 210 Courthouse Way, Suite 170, Rigby, and the phone number is (208) 745-9220.² The department manages land use and development exclusively in unincorporated Jefferson County, while its building-permit service also covers Lewisville, Menan and Rigby.²

Start through the county's online permit portal by creating and validating an account and uploading the required documents.²¹⁷ Plan-review, GIS and technology fees come before further review, followed by zoning, floodplain and plan review; after approval and final payment, the county issues the permit and the permit sign must be posted.¹⁷ Jefferson County publishes a fee schedule, but charges vary by permit type and are set by the Board of County Commissioners.¹⁸ Typical processing is approximately 15 business days for noncommercial applications and 20 business days for commercial applications.¹⁷

Does Jefferson County, Idaho have zoning?

Jefferson County zoning applies to unincorporated land; Rigby has its own zoning districts inside city limits.³⁴ Eastern Idaho Public Health remains the septic authority throughout Jefferson County.⁵ County districts include AG-40, AG-20, AG-10, R-10, R-5, R-1, SN, RR/C, R/O, C-2, C-1, L-I and H-I; uses and dimensional standards vary by district.¹⁹ Ask Planning, Zoning & Building to confirm the parcel's mapped district before purchase.²

In agricultural and residential districts, property-line setbacks start at 10 feet for buildings up to 14 feet high and increase with height; measurements extend to projecting roof overhangs, porches or decks.²⁰ Standard street setbacks are 80 feet from the road centerline, and private-road setbacks are 25 feet from the easement edge; qualifying nonconforming parcels have exceptions.²⁰ In commercial and industrial districts, the property-line minimum is 0 feet, increasing to 25 feet beside residential districts; street setbacks generally start at 80 feet, with 90 feet required along major roads.²¹ Commercial and industrial building heights depend on the specific use and/or fire district approval.²²

How do septic permits work in Jefferson County?

Eastern Idaho Public Health regulates and permits on-site sewage disposal in Jefferson County; its local office is at 380 Community Lane in Rigby and its phone number is (208) 745-7297.⁵²³ A new, expanded, repaired, replacement, tank-only, central or large-soil-absorption installation requires a septic permit, a scaled or dimensional plot plan, a building plan and a site evaluation by an Environmental Health Specialist.⁸ The septic permit is required before obtaining the county building permit.⁸

The permit remains valid for 2 years and may be renewed for $50.⁸ A permitted system cannot receive wastewater until the final installation inspection.²⁴ Only 13.3% of Jefferson County soils rate as lacking severe limitations for a conventional drain field, so complete the site evaluation early.²⁵ A septic permit may be denied where public or central wastewater treatment is reasonably accessible.²⁶

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

In unincorporated Jefferson County, using an RV as primary living quarters outside a legal RV or manufactured-home park for more than 30 days in a one-year period requires an RV residency permit and a legal parcel of at least 1 acre.⁹ Authorization lasts up to 1 year, with a possible 1-year extension for appropriate screening and a compliance inspection after 6 months.⁹ An RV used with an open building permit does not need the additional residency permit.⁹ The RV needs acceptable wastewater disposal, setbacks and approved skirting; rental use and another occupied RV on the property are prohibited.⁹

Jefferson County includes tiny houses in its RV living-quarters definition under these conditions.²⁷ We could not confirm a general minimum dwelling size; ask Planning, Zoning & Building to classify the proposed home.² Cottage housing developments require a conditional use permit, with cottages containing 400 to 1,600 square feet.²⁸²⁹ Within those developments, cottages and ADUs over garages have a 25-foot height cap, accessory structures have an 18-foot cap, and roof portions above 18 feet need at least a 6:12 pitch.²⁸

Building a home in Jefferson County: what are the steps?

1. Ask Jefferson County Planning, Zoning & Building to confirm the parcel's mapped district, allowed use, setbacks and dimensional standards.³⁰
2. Document the water source and sewer provider, or obtain the applicable Eastern Idaho Public Health authorization and septic permit before applying for the county building permit.³¹⁸
3. Obtain an Idaho Department of Water Resources drilling permit before drilling a private well.¹³
4. Create the county portal account, upload the plans and documents, and pay the initial review fees.¹⁷
5. Complete zoning, floodplain and plan review, pay the remaining fees, receive the permit and post its sign.¹⁷
6. Obtain the required electrical, plumbing and HVAC permits for regulated trade work.¹⁵
7. Pass required final inspections; Jefferson County does not issue the applicable certificate of occupancy or completion until failed items are corrected and reinspected.³²

What should you check before buying land in Jefferson County?

Jefferson County's residential minimum lot sizes vary by zoning district from 1 to 40 acres, with exceptions including smaller clustered lots and qualifying Suburban Neighborhood lots served by community sewer and water.¹² Development in regulated unincorporated Jefferson County floodplain areas requires a floodplain development permit; the county ADU application also calls for an elevation certificate for floodplain construction.³³³⁴

For a private well, Idaho requires a drilling permit and a licensed well driller before construction.¹³ If access connects to an Idaho state highway, an Idaho Transportation Department encroachment permit is required for the driveway or street approach.³⁵ Jefferson County's effective property-tax rate is about 0.5%, with a median annual bill of about $1,775.³⁶³⁷ Confirm that the parcel and any proposed division comply with county subdivision rules before relying on a seller's description.³⁸ A short-term rental of fewer than 30 consecutive days is a residential zoning use and must occupy a structure designed for a single-family household.³⁹

Watch-outs

• A manufactured home without a HUD certificate label is not allowed unless it qualifies under the stated Idaho-law exception.⁴⁰
• We could not confirm Jefferson County agricultural building-exemption terms; ask Planning, Zoning & Building before treating a barn or other farm structure as exempt.²
• An Idaho owner doing work on the owner's own land may be exempt from contractor registration when the owner does not intend to sell within 12 months, but applicable permit and inspection duties still remain.¹⁰¹¹
• An exempt structure under 200 square feet still requires a Jefferson County zoning certificate.¹
• A non-habitable structure may encroach within the standard 60-foot canal setback only with written permission from the canal company.²⁰

Sources

1. Structures Requiring Building Permits, quoted and re-checked
2. Jefferson County Planning, Zoning & Building Department (jcgov.us)
3. Part III Land Development Ordinances, quoted and re-checked
4. Rigby: Chapter 4 Establishment of Zones (Jefferson County), quoted and re-checked
5. Septic Rules & Forms, quoted and re-checked
6. jcgov.us, quoted and re-checked
7. Part III Land Development Ordinances, quoted and re-checked
8. Septic Permit Application Packet, quoted and re-checked
9. jcgov.us, quoted and re-checked
10. Frequently Asked Questions (FAQ) - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
11. How To Purchase a Trade Permit (Idaho statewide rule), quoted and re-checked
12. Part III Land Development Ordinances, quoted and re-checked
13. Wells Overview (Idaho statewide rule), quoted and re-checked
14. jcgov.us, quoted and re-checked
15. Frequently Asked Questions (FAQs) - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
16. Accessory Dwelling Unit Building Permit Application - Help Guide, quoted and re-checked
17. Plan Submittal to CO Issuance - Building Permit Process, quoted and re-checked
18. Fees, Planning, Zoning & Building Department, quoted and re-checked
19. Part III Land Development Ordinances, quoted and re-checked
20. Part III Land Development Ordinances, quoted and re-checked
21. Part III Land Development Ordinances, quoted and re-checked
22. Part III Land Development Ordinances, quoted and re-checked
23. Eastern Idaho Public Health - Jefferson County Office (eiph.id.gov)
24. IDAPA 58.01.03 Individual/Subsurface Sewage Disposal Rules (Idaho statewide rule), quoted and re-checked
25. Share of soils USDA rates "not limited" for a conventional septic drain field (SSURGO). A strict rating: the median county is about 6% and a tenth of counties are 0%, so a low figure means most lots need a site evaluation or an engineered system, not that septic is impossible. Cite it only with that caveat: Bolthole Index county data
26. IDAPA 58.01.03 Individual/Subsurface Sewage Disposal Rules (Idaho statewide rule), quoted and re-checked
27. jcgov.us, quoted and re-checked
28. Part III Land Development Ordinances, quoted and re-checked
29. Part III Land Development Ordinances, quoted and re-checked
30. Part III Land Development Ordinances, quoted and re-checked
31. Accessory Dwelling Unit Building Permit Application - Help Guide, quoted and re-checked
32. Building Permit Process: Plan Submittal to CO Issuance, quoted and re-checked
33. Floodplain Development Permit Application, quoted and re-checked
34. Accessory Dwelling Unit Building Permit Application - Help Guide, quoted and re-checked
35. Types of Right-of-Way Encroachment Permits (Idaho statewide rule), quoted and re-checked
36. Effective property tax rate: Bolthole Index county data
37. Median property tax bill: Bolthole Index county data
38. Part III Land Development Ordinances, quoted and re-checked
39. Part III Land Development Ordinances, quoted and re-checked
40. Part III Land Development Ordinances, quoted and re-checked

Written October 12, 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.