Accessory Dwelling Unit (ADU) Permit in Helena, Montana
VerifiedRequired for construction of an Accessory Dwelling Unit on a residential parcel within Helena city limits. Helena City Code Title 11 (Zoning) formally defines and permits ADUs by right in nearly all residential and mixed-use zoning districts; construction itself follows the standard City of Helena residential building permit process under the 2021 IRC/IBC.
Verified 2026-07-02 · Source
When you need this permit
- ADU defined at Helena City Code 11-2-4 as 'a self-contained living unit on the same parcel as a single-dwelling unit of greater square footage that includes its own cooking, sleeping, and sanitation facilities and complies with or is otherwise exempt from any applicable building code, fire code, and public health and safety regulations'
- Per the Title 11 Land Use Table (City Code 11-2-3), 'Residence, accessory dwelling unit (ADU)' is listed as Permitted (P) by right in the R-R, R-1, R-2, R-3, R-4, R-O, B-1, B-2, B-3, DT, and TR zoning districts, subject to the standards of City Code Section 11-2-5J (Not Permitted in CLM, M-I, and Airport districts)
- Construction must comply with the same 2021 IRC/IBC standards, climatic design criteria (Table R301.2), and permit application process as other residential building permits
- Setback (City Code 11-4-2) and lot coverage (City Code 11-4-1) requirements apply to the ADU structure
Required documents
- Required
Permit Application (City of Helena Building Division)
Universal application form; project scope identified as new ADU construction
- Required
Residential Plan Submittal Requirements
Same plan submittal checklist used for new one- and two-family dwelling construction
- Required
Site Plan
Shows the primary dwelling, proposed ADU location, and compliance with City Code 11-4-2 setbacks and 11-4-1 lot coverage limits
Fee schedule
| Fee type | Amount | Notes |
|---|---|---|
| Building Permit Fee — valuation-based (same Ordinance 3134 table as new construction) | Per Ordinance 3134 Appendix A valuation table, based on the ADU's construction valuation | No separate ADU-specific fee schedule is published by the City of Helena; an ADU is billed as new residential construction under the standard valuation-based table |
| Plan Review (Plan Check) Fee | 65% of the Building Permit Fee | Per the City's standard building permit fee structure |
Review timeline
~10–15 business days
Typical estimate — confirm current times with the Helena building department
Inspection process
- 1
Foundation
Before concrete pour
- 2
Framing
After framing complete, before insulation or wall cover
- 3
MEP Rough-In
Electrical, plumbing, mechanical rough-in before walls closed (separate trade permits required)
- 4
Final
Approved final inspection required before occupancy
Tips
- Helena's zoning code (Title 11) explicitly defines and permits ADUs by right in nearly every residential and mixed-use zoning district — confirm your specific parcel's zone using the City of Helena Zoning Map before assuming by-right status.
- There is no separate ADU building-permit fee schedule; budget using the same Ordinance 3134 valuation-based table as a standalone new home.
- Setback and lot coverage compliance (City Code 11-4-1, 11-4-2) is checked independently of the building code review — confirm with the Planning Division early in design.
Frequently asked questions
- Are ADUs allowed in Helena?
- Yes. Helena City Code 11-2-4 defines an Accessory Dwelling Unit, and the Title 11 Land Use Table lists ADUs as Permitted (P) by right in nearly all residential and mixed-use zoning districts (R-R, R-1 through R-4, R-O, B-1 through B-3, DT, and TR), subject to City Code Section 11-2-5J standards.
Sources & verification
Verified against official sources. Last reviewed 2026-07-02.
- City of Helena — Community Development Department, Building Division — official building department
- Helena City Code 11-2-4 — Land Use Definitions for Zoning Districts (ADU definition)
- Helena City Code 11-2-3 — Land Use Table for Zoning Districts (ADU permitted-use table)
- City of Helena — Building Permit Types
Fees, timelines, and adopted codes are researched from each jurisdiction's published records — see how we verify. Requirements change and vary by project, so always confirm the current details with the Helena building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.
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