Missoula ADU Permits & Requirements
Application fee capped at $250 · 4–10 weeks timeline · No impact fees or owner-occupancy
Quick Answer
Missoula ADUs: $160K–$260K
Permits: $250–$4,500 · Updated April 2026
Permit Fees Breakdown
| Fee Type | Cost |
|---|---|
| Land-Use Application Review | $0–$250 |
| Building Permit | $1,500–$4,500 |
| Plan Review | $500–$1,500 |
| Water / Sewer Connection | $2,000–$8,000 |
| Impact Fees | $0 |
Fees are estimates and change — verify all current amounts with the City of Missoula Development Services before you budget.
Permit Process Timeline
Project Review Team (PRT) Meeting
1–2 weeksVirtual feasibility meeting with Missoula planning, engineering & building staff
Plan Preparation
3–6 weeksPlans meeting Title 20, snow-load, frost-depth & any WUI standards
Building Permit Review
4–8 weeksDevelopment Services review for zoning & building code compliance
Construction
3–6 monthsBuild phase with required inspections; WUI materials on interface lots
Final Inspection & CO
1–2 weeksFinal inspections and Certificate of Occupancy
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Zoning & Requirements
Max ADU Size
~600 sq ft*
Height Limit
Per zone*
Setbacks
Per Title 20*
Parking
None required
*Missoula has historically capped ADUs near 600 sq ft; state law (SB 528) allows up to the lesser of 1,000 sq ft or the primary home's floor area, and the ordinance is being updated. Verify current size, height & setback limits for your parcel with City of Missoula Development Services.
Key Regulations
- Montana SB 528 (2023) requires Missoula to allow at least one ADU per single-family lot — upheld by the Montana Supreme Court
- No impact fees on ADUs; land-use application review fee capped at $250
- No owner-occupancy requirement — you may rent both the primary home and the ADU to separate tenants
- No additional off-street parking mandated for an ADU
- Snow-load (~40 psf) and frost-depth (~3–4 ft) engineering is required — factor into structure cost
- Foothill / wildland-urban interface lots need ignition-resistant materials and defensible space
Climate & Construction Notes
Missoula's mountain-valley setting brings a roughly 40 psf ground snow load, about 3–4 feet of frost depth, and wildfire exposure in foothill neighborhoods like the Rattlesnake, Grant Creek, Pattee Canyon, and the Miller Creek benches. Expect frost-protected foundations, snow-rated roof framing, and — on interface lots — Class A roofing, ember-resistant vents, and zoned defensible space. Verify requirements with the City of Missoula and Missoula County.
Frequently Asked Questions
How long does it take to get an ADU permit in Missoula?
Building-permit review is typically 4–10 weeks for a complete submittal. Total project time including design and construction is usually 6–11 months. A Project Review Team meeting up front helps avoid resubmittals.
What types of ADUs are allowed in Missoula?
Missoula allows detached, attached, and garage or basement conversion ADUs in its Title 20 residential and mixed zones. The local size cap has historically been around 600 sq ft — confirm the current maximum for your lot with Development Services.
Do I need to live on the property to build an ADU in Missoula?
No. Montana SB 528 bans owner-occupancy requirements, so you can rent both the primary home and the ADU to separate tenants. Always confirm current rules with Missoula's Development Services department.
More Missoula ADU Resources
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