Building permits, zoning and septic rules in Madison County, Idaho

At a glance

Building permit

Required through the county for county-administered projects; ask the city inside municipal limits¹³

Zoning

County zoning applies in unincorporated areas; cities may use their own zoning²⁶

Septic permit

Issued by Eastern Idaho Public Health⁴

RV or tiny home

Private-land occupancy rules are unconfirmed; ask Planning and Zoning⁷

Owner-builder

Owners working on their own land may be exempt from contractor registration, but not automatically from permits or inspections⁸

Agricultural buildings

Qualifying agricultural buildings are exempt from state building codes; county setback and easement permits may still apply⁹

Private well

Obtain an IDWR drilling permit and use an IDWR-licensed driller¹⁰

Who to call

Contact details are copied from each office’s official page and were checked against it on October 9, 2026.

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

Yes. For projects under Madison County jurisdiction, the county requires building permits for new homes, additions, remodels, accessory structures, manufactured homes, solar work, demolition, and fire or flood repairs¹. The Building Department reviews plans and performs construction inspections¹¹. Incorporated cities may administer their own building permits and zoning, so confirm the correct building office for property inside city limits; Eastern Idaho Public Health still administers septic permits across Madison County³⁴. County-administered construction must comply with adopted building codes and ordinances⁵. Qualifying agricultural buildings are exempt from state building codes, but Madison County may issue an agricultural-exempt permit to enforce road setbacks and utility easements⁹.

Who issues Madison County building permits, and how do you reach them?

For county-administered building permits, plan review and construction inspections, contact the Madison County Building Department at 208-359-6305 or visit 134 E Main, Rexburg, ID 83440¹¹. Building-permit applications may be started in the county portal by project type, with plans and supporting documents uploaded as PDFs¹². Building-permit fees vary by project and permit type and may use project valuation, so request a current estimate from the Building Department¹³. For county zoning approval and land-use questions, contact Madison County Planning and Zoning at 208-359-6207⁷. Mechanical, electrical and plumbing permits and inspections are handled through the City of Rexburg building department⁵. Inside an incorporated city, confirm that city's building-permit and zoning process; septic permits remain with Eastern Idaho Public Health³⁴.

Does Madison County have zoning?

Madison County administers zoning in unincorporated areas, while incorporated municipalities such as Rexburg may administer their own zoning ordinances²³. Uses and dimensional standards depend on the parcel's jurisdiction and zoning district⁶. In the county Agricultural Zone, minimum lot width is 250 feet; the front setback is 50 feet, or 60 feet along a major or minor arterial; side and rear setbacks are 10 feet and 25 feet, with a 50-foot street-side setback for corner lots¹⁴. These Agricultural Zone figures do not answer the setback question in another district. Ask Madison County Planning and Zoning for an unincorporated parcel's district and approvals, or the applicable city for property inside municipal limits⁷¹⁵. We could not confirm current county rules for minimum dwelling size, lot coverage, building height, accessory dwellings, or private-land RV and tiny-home occupancy.

How do septic permits work in Madison County?

Eastern Idaho Public Health administers septic permits throughout Madison County, including addresses inside incorporated cities⁴¹⁶. It issues septic permits for new, replacement, expanded, remodeled and repaired systems¹⁷. The application requires a plot plan, floor plans, a signed information page and payment, followed by a site evaluation; obtain the septic permit before the building permit¹⁷. Individual-system septic permits cost $900, central or large soil-absorption-system permits cost $3,000, and tank-only or vault-privy permits cost $450¹⁷. The tank and drainfield must remain uncovered for final inspection, and Eastern Idaho Public Health requires 48 hours' notice¹⁸. About 42% of county soils avoid severe limitations for a conventional drain field, so keep septic feasibility as a purchase contingency¹⁹.

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

We could not confirm a Madison County rule that generally allows or forbids living in an RV or tiny home on private land. In an unincorporated area, ask Madison County Planning and Zoning whether the unit is an allowed dwelling, whether temporary occupancy during construction is allowed, and which zoning approval and setbacks apply²⁷. Inside a city, ask that municipality because local zoning varies across Madison County³. Septic permits do not shift to the city: constructing, repairing or modifying an onsite sewage system generally requires an Eastern Idaho Public Health installation permit, while portable non-discharging systems are only temporary²⁰⁴. Every manufactured-home installation must be inspected and approved by the state or authority having jurisdiction before occupancy²¹.

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

1. Identify whether the parcel is unincorporated or inside a city; obtain county zoning approval from Madison County Planning and Zoning or city zoning approval from the applicable municipality³⁷.

1. For a private well, obtain an Idaho Department of Water Resources drilling permit and use an IDWR-licensed driller¹⁰.

1. Submit the septic-permit application, plot plan, floor plans, signed information page and fee to Eastern Idaho Public Health; its site evaluation and septic permit come before the building permit¹⁷.

1. Apply for the building permit through the county portal when Madison County has jurisdiction, or confirm the city process inside municipal limits¹²³.

1. Obtain mechanical, electrical and plumbing permits and inspections through the City of Rexburg building department⁵.

1. Leave the septic tank and drainfield uncovered and arrange the final inspection with Eastern Idaho Public Health²².

What should you check before buying land in Madison County?

First identify the zoning authority: Madison County handles zoning in unincorporated areas, while incorporated cities may apply different zoning rules²⁶. Request the parcel's zoning district, allowed use, zoning approval, setbacks and lot standards from Madison County Planning and Zoning or the applicable city before choosing a homesite⁷¹⁵. A private well requires an Idaho Department of Water Resources drilling permit and a licensed driller¹⁰. Only about 42% of county soils avoid a severe conventional-drain-field limitation, and Eastern Idaho Public Health reviews new subdivisions for wastewater suitability¹⁹²³. The county's Fire & Flood Permit covers repairs after fire or flood damage, not the broader rules for new floodplain development²⁴. A state-highway driveway requires an Idaho Transportation Department encroachment permit²⁵.

Watch-outs

• Madison County's private-land RV, tiny-home and minimum-size rules could not be confirmed; ask county Planning and Zoning for unincorporated land or the applicable city inside municipal limits³⁷.
• An agricultural-exempt permit does not establish that a structure may be used as a dwelling or bypass road setbacks and utility easements²⁶⁹.
• A driveway connecting to an Idaho state highway requires an Idaho Transportation Department encroachment permit²⁵.

Sources

1. Building Department, quoted and re-checked
2. Madison County Ordinance 469 and Planning and Zoning Code Change Packet, quoted and re-checked
3. Public Hearing Application – Zone Change, quoted and re-checked
4. Septic, quoted and re-checked
5. Building Department, quoted and re-checked
6. Madison County Ordinance 469 and Planning and Zoning Code Change Packet, quoted and re-checked
7. Madison County Planning and Zoning (madisoncountyid.gov)
8. Frequently Asked Questions (Contractors), quoted and re-checked
9. Title 39, Chapter 41, Idaho Building Code Act, quoted and re-checked
10. Wells Overview, quoted and re-checked
11. Madison County Building Department (madisoncountyid.gov)
12. Building Department, quoted and re-checked
13. Building Department, quoted and re-checked
14. Madison County Planning and Zoning Commission Packet, March 11, 2026, quoted and re-checked
15. Madison County Planning and Zoning Commission Packet, March 11, 2026, quoted and re-checked
16. Septic and Septage, quoted and re-checked
17. Septic Permit Application Packet, quoted and re-checked
18. Septic Permit Information Sheet, quoted and re-checked
19. 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
20. eiph.id.gov, quoted and re-checked
21. Building Archives - Division of Occupational and Professional Licenses (Idaho statewide rule), quoted and re-checked
22. Septic Permit Application Packet, quoted and re-checked
23. Land Development, quoted and re-checked
24. Building Department, quoted and re-checked
25. Types of Right-of-Way Encroachment Permits (Idaho statewide rule), quoted and re-checked
26. Building Department, quoted and re-checked

Written October 9, 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.