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Accessory Dwelling Unit (ADU) Permit in Missoula, Montana

Required for construction of a new accessory dwelling unit (detached, internal, or internal addition) on a residential parcel within Missoula city limits. Governed by Missoula Municipal Code Title 20 (Zoning), Section 20.45.060, as amended by Ordinance 3669 (October 2020), which removed the prior owner-occupancy and additional-parking requirements. A building permit is required in addition to zoning compliance review.

Verified 2026-07-02 · Source

When you need this permit

  • ADUs allowed by right in all Residential, Business (B), Commercial (C), and Limited Industrial-Residential (M1-R) zoning districts
  • One ADU permitted per parcel occupied by a single detached house; not allowed in special districts or PUDs unless the district/PUD expressly permits them
  • Detached ADU floor area capped at 600 sq ft (per MMC 20.45.060.B.8.a, as amended by Ordinance 3669)
  • Internal ADU floor area capped at the lesser of 40% of the primary dwelling's gross floor area (excluding attached garage) or 600 sq ft
  • Maximum detached ADU height: 25 feet (MMC 20.45.060.C.3, as amended by Ordinance 3669)
  • No owner-occupancy requirement (removed by Ordinance 3669, effective ~November 2020)
  • No additional off-street parking required for the ADU itself, though existing required parking for the primary dwelling must be maintained
  • Building permit required for all new ADU construction or conversion of existing structures to include an ADU — apply through Accela Citizen Access

Required documents

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Fee schedule

Building Permit Fee — valuation-based (same table as new residential construction)City of Missoula FY26 Building Permit and Plan Review Fee Schedule (Resolution 8887, effective Jan 1–Dec 31, 2026)
$36 minimum (valuation $1–$500) up to $1,582 for the first $100,000 plus $9.94 per additional $1,000; see full valuation table

Review timeline

Plan reviewTypical estimate — confirm current times with the Missoula building department
~56–84 business days

How long did your Accessory Dwelling Unit (ADU) Permit permit actually take in Missoula?

Anonymous — one question, no email. Answers are combined and only shown once at least 5 people have reported.

Inspection process

  1. 1

    Footing and Foundation

    Before concrete pour (detached ADU)

  2. 2

    Framing/Structural

    Structural framing, egress, fire separation

  3. 3

    MEP Rough-In

    Mechanical, electrical, plumbing rough-ins before wall cover

  4. 4

    Final

    All work complete, ready for occupancy

See the full Missoula inspection guide — scheduling & re-inspection fees →

Tips

  • As of Ordinance 3669 (October 2020), Missoula ADUs no longer require owner-occupancy or a deed restriction, and no longer require an additional off-street parking space — verify current status with Development Services since ADU policy has been an active area of city housing-policy revision.
  • Detached and internal ADUs are capped at 600 sq ft; internal ADUs also cannot exceed 40% of the primary dwelling's gross floor area.
  • Confirm zoning eligibility before applying — ADUs are not allowed in special districts or PUDs unless the district/PUD explicitly permits them.
  • Contact Development Services' zoning information line at (406) 552-6625 or the general Building Division line at (406) 552-6630 to confirm current ADU rules for your parcel.

Frequently asked questions

Missoula requires an accessory dwelling unit (adu) permit for: ADUs allowed by right in all Residential, Business (B), Commercial (C), and Limited Industrial-Residential (M1-R) zoning districts; One ADU permitted per parcel occupied by a single detached house; not allowed in special districts or PUDs unless the district/PUD expressly permits them; Detached ADU floor area capped at 600 sq ft (per MMC 20.45.060.B.8.a, as amended by Ordinance 3669); Internal ADU floor area capped at the lesser of 40% of the primary dwelling's gross floor area (excluding attached garage) or 600 sq ft; Maximum detached ADU height: 25 feet (MMC 20.45.060.C.3, as amended by Ordinance 3669); No owner-occupancy requirement (removed by Ordinance 3669, effective ~November 2020); No additional off-street parking required for the ADU itself, though existing required parking for the primary dwelling must be maintained; Building permit required for all new ADU construction or conversion of existing structures to include an ADU — apply through Accela Citizen Access. If your project isn't listed, confirm with City of Missoula Development Services — Building Division (Community Planning, Development & Innovation) at (406) 552-6630 before starting work.

In Missoula, the published Building Permit Fee — valuation-based (same table as new residential construction) is: $36 minimum (valuation $1–$500) up to $1,582 for the first $100,000 plus $9.94 per additional $1,000; see full valuation table. These are the jurisdiction's own published figures — see the fee schedule table and source citations on this page.

Plan review for an accessory dwelling unit (adu) permit in Missoula typically runs 56–84 business days. This is an estimate, not a published figure — confirm current review times with City of Missoula Development Services — Building Division (Community Planning, Development & Innovation) at (406) 552-6630.

You'll need: Building Permit Application (Accela Citizen Access); Construction Drawings. See the required-documents checklist on this page for details on each.

Missoula requires 4 inspection(s) for an accessory dwelling unit (adu) permit, in order: Footing and Foundation, Framing/Structural, MEP Rough-In, Final. Schedule each through City of Missoula Development Services — Building Division (Community Planning, Development & Innovation) ((406) 552-6630).

Apply through City of Missoula Development Services — Building Division (Community Planning, Development & Innovation) at 435 Ryman St., Missoula, MT 59802. Phone: (406) 552-6630, email: BLDG@ci.missoula.mt.us. Office hours: Permit/application questions: Mon–Fri 9:00 AM–4:00 PM, (406) 552-6060, coordinators@ci.missoula.mt.us. Building code questions: Mon–Fri 8:00 AM–5:00 PM, (406) 552-6630, BLDG@ci.missoula.mt.us. Inspection scheduling: (406) 552-6040 or text (888) 413-4439.. Official information: https://www.ci.missoula.mt.us/3202/Building-Division.

No. Ordinance 3669, adopted by the Missoula City Council on October 19, 2020, removed both the owner-occupancy requirement and the additional off-street parking requirement for ADUs, though any parking required for the primary dwelling must still be maintained.

Detached ADUs are capped at 600 sq ft. Internal ADUs are capped at the lesser of 40% of the primary dwelling's gross floor area (excluding an attached garage) or 600 sq ft. Maximum detached ADU height is 25 feet. Source: Missoula Municipal Code 20.45.060, as amended by Ordinance 3669.

Sources & verification

Verified against official sources. Last reviewed 2026-07-02.

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 Missoula building department before you submit. PermitBase is an independent reference and is not affiliated with any government agency.

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Accessory Dwelling Unit (ADU) Permit in other cities

Bozeman, MontanaGreat Falls, MontanaHelena, MontanaKalispell, MontanaUnincorporated Yellowstone County, MontanaAlbuquerque, New MexicoArvada, ColoradoAurora, Colorado

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