Can You Build an ADU in Missoula?
Yes — Missoula is governed by Montana's statewide ADU law, which limits what the city can restrict. A 700 sq ft detached ADU here runs about $151,000–$247,000.
Construction costs in Missoula track close to the Montana state average.
Detached ADU (700 sq ft)
$151,000–$247,000
Garage conversion (400 sq ft)
$47,000–$86,000
Statewide protection
Yes
What applies in Missoula
Montana's SB 528 (2023) requires cities over 5,000 residents to allow at least one ADU per single-family lot by right, with limited parking and design standards.
Because Montana has a statewide ADU law (Montana SB 528 (2023)), Missoula must follow these minimums even where its older zoning code is stricter. Confirm fees and design standards with the Missoula planning department.
Estimate your Missoula ADU cost
Your property
ADU typeEstimated cost in Montana
$151,000 – $247,000
≈ $216–$353/sq ft turnkey · midpoint $199,000
- $135,300
- Construction
- $35,800
- Design & permits
- $27,900
- Site work
- iSize set locally. This state leaves ADU size limits to your city — typical caps run 600–1,200 sq ft. Check your local code.
- ✓No extra parking likely required. Set by local ordinance — commonly 1 space per ADU unless near transit.
- iOwner-occupancy varies. Owner-occupancy rules are set locally in this state.
- ✓Lot has room. A 700 sq ft ADU uses about 12% of your 6,000 sq ft lot — comfortably within typical coverage limits.
Rule basis: Montana SB 528 (2023)
If you rent it out
$1,050–$1,700
est. rent/mo
8.3%
gross yield
13 yrs
payback
~$15,345/yr after a 7% vacancy allowance, before financing & maintenance.
Financed over 20 yrs at 7.5%, the build is about $1,603/mo — vs ~$1,375/mo in estimated rent.
Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.
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Other Montana cities
Estimates are for planning only and are based on regional construction-cost indices and published statewide ADU statutes. Local ordinances, lot conditions and contractor pricing vary — always confirm with your city planning department and a licensed contractor.