Building permits, zoning and land rules in Hardin, Montana

At a glance

Building permits

City application portal; confirm project requirements with Building and Code¹

Zoning

City zoning applies inside Hardin²

Septic permits

County sanitarian approval before installation⁴

Manufactured homes

Allowed subject to district and siting requirements³

RV living and tiny homes

Private-lot occupancy rules unconfirmed; ask the city²

Accessory dwellings

State law requires an ADU by right on a qualifying single-family lot⁵

Wells

State water-right process applies; city well restrictions unconfirmed⁶

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 Hardin, MT?

Start with Hardin’s Building and Code Department: the city provides an online portal for building applications and permit searches.¹ We could not confirm the complete city building-permit requirement, exemptions, inspection schedule or current fee schedule; ask the department to identify those requirements for your proposed work.¹ Do not use the rural county answer for a city address: Montana’s single-family building-permit exemption is conditional on there being no applicable local ordinance, and the state roster identifies Hardin as a residential building-code jurisdiction within city limits.⁷ For land outside Hardin, read the Big Horn County guide and confirm jurisdiction before applying.⁷

Does Hardin have zoning, lot limits and setbacks?

Hardin has zoning inside city limits, and manufactured-home permissions vary by district.²³ AO permits Class A and Class B manufactured homes; SR permits single-family dwellings and those manufactured-home classes at a maximum density of 1 dwelling per net acre, with the homes on a continuous concrete-block wall or footing.³ In R3 manufactured-home parks, maximum density is 9 manufactured homes per net acre and site ground coverage is limited to 50%, including the ordinance’s parking calculation.³⁸ R3 manufactured-home side setbacks are at least 7.5 feet, and the public-right-of-way setback is at least 15 feet; these are not citywide setbacks for every house.⁹ Ask the city to identify your district and its complete dimensional requirements.¹⁰

Can you live in an RV, tiny home or ADU in Hardin?

We could not confirm whether Hardin allows living in an RV on a private lot, temporary camping during construction, or a tiny home as a primary residence; ask the city about your proposed use before buying the unit.¹ Manufactured-home permissions are district-specific and do not establish permission for an RV or every type of tiny home.³ Montana law requires a zoning municipality to allow at least one accessory dwelling unit by right on a lot containing a single-family dwelling, subject to applicable building, fire and health requirements.⁵ A detached or attached ADU may not exceed 75% of the primary dwelling’s gross floor area or 1,000 square feet, whichever is less; municipal water and sewer will-serve letters may be required.⁵

How do septic permits work inside Hardin?

For a Hardin property proposing septic rather than public sewer, contact the Big Horn County Environmental Health Department’s sanitarian about the septic application and site review.⁴ Submit a written request with the address, property description and current owner, and send the application and fee two weeks before the desired site visit.⁴ Septic installation cannot begin until the sanitarian issues a permit to construct, and a final inspection is required before burial.¹¹ A Montana Certificate of Subdivision Approval does not replace the local drainfield permit.¹² We could not confirm Hardin’s sewer-connection trigger; ask the city about sewer service before commissioning a septic design, and ask the sanitarian for the current fee.¹¹¹

Building a home in Hardin: what are the steps?

1. Ask the city to confirm the parcel’s zoning district and whether your proposed dwelling type fits that district.²³
2. Contact Hardin’s Building and Code Department for the building-permit requirements, application documents, fees and inspection schedule for your project; applications and permit searches are available through its citizen portal.¹
3. Ask the city about water and sewer availability and connection requirements; if proposing a drainfield, obtain the county sanitarian’s construction approval before installation.¹⁴
4. Ask the city to identify the local floodplain administrator and check for a designated Special Flood Hazard Area before site work; Montana’s floodplain review covers more than just the house, including fill and manufactured-home placement.¹³

What should you check before buying land in Hardin?

A private well in Hardin needs a water-right review as well as confirmation of any city restrictions: Montana’s small-groundwater exception may apply at no more than 35 gallons per minute and 10 acre-feet per year.⁶ Beginning in 2026, the state requires a Notice of Intent before drilling or developing a new exempt well or using its water, with a $400 filing fee; we could not confirm Hardin’s separate private-well rules.⁶ If access intersects a Montana state highway, state approach approval applies to new or modified approaches and certain changes in use.¹⁴ Owner-builder status also needs care: Montana’s contractor-license exemption does not waive applicable building, trade or inspection requirements.¹⁵

Watch-outs

• Hardin’s R3 manufactured-home setbacks apply to that district’s sites, not every residential lot in Hardin.⁹
• We could not confirm private-lot RV occupancy or minimum dwelling size in Hardin; ask the city before committing to a dwelling or temporary living arrangement.¹
• Obtain septic construction approval before installation and arrange the final inspection before burying the system.¹¹

Sources

1. Hardin Building and Code Department (hardinmontana.gov)
2. Chapter 1 Zoning (Hardin), quoted and re-checked
3. 11-1-2-3: District Uses Permitted (Hardin), quoted and re-checked
4. Septic Permitting, quoted and re-checked
5. 76-2-345. Accessory dwelling units -- regulations -- restrictions, MCA (Montana statewide rule), quoted and re-checked
6. Exempt Well Updates and Information (Montana statewide rule), quoted and re-checked
7. bsd.dli.mt.gov, quoted and re-checked
8. 11-1-2-3: District Uses Permitted (Hardin), quoted and re-checked
9. 11-1-2-3: District Uses Permitted (Hardin), quoted and re-checked
10. Hardin City-County Planning Board (hardinmontana.gov)
11. Big Horn County Environmental Health Department (bighorncountypublichealth.com)
12. Engineering Infrastructure & Subdivisions (Montana statewide rule), quoted and re-checked
13. Stream Permitting (Montana statewide rule), quoted and re-checked
14. Approach Manual for Landowners and Developers (Montana statewide rule), quoted and re-checked
15. Montana Code Annotated, Title 37, Chapter 45, Construction Contractors (Montana statewide rule), 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.