Do I Need a Permit to Build a Deck in Montana?
Deck permit requirements. When you need a permit, footing depth, guard rail rules, and inspection stages.
Yes — unless it's a small ground-level platform under 200 sq ft.
When a Permit Is Required
Most jurisdictions require a deck permit for: decks over 200 square feet, decks more than 30 inches above grade, any deck attached to the house via a ledger board, and decks with structural modifications. A small freestanding platform under 200 sq ft and under 30 inches high may be exempt — but check with your city.
Footings and Frost Line
Deck footings must extend below the local frost line — the required depth varies by climate and elevation, so confirm the depth your city requires. This is one of the most common inspection points. Footings that are too shallow will fail inspection.
Guards and Railings
Guards are required when the deck surface is 30 inches or more above grade. Minimum guard height is 36 inches for residential decks (42 inches for commercial) under the IRC. Baluster spacing must be less than 4 inches — the classic 'sphere test' (a 4-inch sphere should not pass through).
Ledger Board Attachment
The ledger board (where the deck attaches to the house) is the #1 failure point for decks. Inspectors check that ledger boards are attached with lag screws or through-bolts — nails are never acceptable. Proper flashing above the ledger is also required to prevent water damage.
Most useful decks need a permit. Plan for three inspections (footings, framing, final) and confirm your local frost-line footing depth.
Permit fees by city in Montana
Verified from each city’s published fee schedule. Where a city has no separate fee listed for this project, open the city page for the current requirements and amount.
| City | Permit fee | Source |
|---|---|---|
| Anaconda-Deer Lodge | $12.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Belgrade | Valuation x 0.0024Verifiedvia Residential Building Permit (New Construction, ADU, Addition, Remodel) | Residential Building Permit (New Construction, ADU, Addition, Remodel) → |
| Billings | $30.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Bozeman | (Administrative Charges/Employee/Hour + Inspector's Hourly Pay Rate) x Table A factor (amount of inspection time per sq ft, by construction type and fire rating) x Building Square FootageVerifiedvia Residential New Construction Permit | Residential New Construction Permit → |
| Butte-Silver Bow | $75.00 per hour, one-hour minimumVerifiedvia New Residential Construction Permit | New Residential Construction Permit → |
| Choteau | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| City of Deer Lodge | $20Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Colstrip | See city page for the current Residential Building Permit (New Construction / Addition / Alteration / Repair / Move) fee | Residential Building Permit (New Construction / Addition / Alteration / Repair / Move) → |
| Columbia Falls | Calculated at time of submission based on project valuation; the City's own application form does not print a standalone valuation-fee table (field left blank for Building Department completion). No dedicated Columbia Falls fee-schedule document was found published separately from the application form after exhaustive search of the City's DocumentCenter, site search, and Resolutions listings.Verifiedvia Residential Building Permit (New Construction / Addition / Remodel / Repair) | Residential Building Permit (New Construction / Addition / Remodel / Repair) → |
| Conrad | See city page for the current Zoning and Building Permit (New Construction / Addition / Alteration / Repair) fee | Zoning and Building Permit (New Construction / Addition / Alteration / Repair) → |
| Cut Bank | $23.50 (subject to the $100.00 minimum permit fee)Verifiedvia Residential Building Permit (New Construction / Addition / Alteration) | Residential Building Permit (New Construction / Addition / Alteration) → |
| Darby | $29.38Verifiedvia Building Permit (New Construction, Addition, Alteration, Repair) | Building Permit (New Construction, Addition, Alteration, Repair) → |
| East Helena | See city page for the current Construction Permit — Residential Building (New Construction / Addition / Remodel) fee | Construction Permit — Residential Building (New Construction / Addition / Remodel) → |
| Forsyth | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| Glasgow | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| Great Falls | Ranges from $62.61 (value $1-$1,000) up to $710.45 (value $49,001-$50,000), per the $1,000-increment table in Exhibit AVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Hamilton | See city page for the current Residential Building Permit (New Construction / Addition / Remodel) fee | Residential Building Permit (New Construction / Addition / Remodel) → |
| Hardin | See city page for the current Residential Building Permit (New Construction / Addition / Alteration / Re-Roof) fee | Residential Building Permit (New Construction / Addition / Alteration / Re-Roof) → |
| Havre | $23.50Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Helena | Per Ordinance 3134 Appendix A valuation table, based on deck construction valuationVerified | Deck Permit → |
| Kalispell | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Laurel | See city page for the current Residential Building Permit (New Construction) fee | Residential Building Permit (New Construction) → |
| Lewistown | See city page for the current Residential Building Permit (New Construction / Additions) fee | Residential Building Permit (New Construction / Additions) → |
| Libby | $24Verifiedvia Residential Building Permit (New Construction / Addition / Alteration / Repair) | Residential Building Permit (New Construction / Addition / Alteration / Repair) → |
| Livingston | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Manhattan | See city page for the current Residential Building Permit (New Construction, Addition, Remodel) fee | Residential Building Permit (New Construction, Addition, Remodel) → |
| Miles City | Set by a City of Miles City fee schedule adopted by council resolution under City Code § 5-4; the specific dollar-valuation table was not independently locatable as a standalone published document as of this review (see note)Verifiedvia Building Permit (New Construction / Addition / Remodel / Repair) | Building Permit (New Construction / Addition / Remodel / Repair) → |
| Missoula | $36 permit fee + $11.00 plan review feeVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Missoula County (Unincorporated) | $26.00Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Polson | 35% of the Building Permit FeeVerifiedvia Zoning Conformance & Building Permit (New Construction / Addition / Remodel) | Zoning Conformance & Building Permit (New Construction / Addition / Remodel) → |
| Red Lodge | See city page for the current Residential Building Permit (New Construction / Addition / Alteration) fee | Residential Building Permit (New Construction / Addition / Alteration) → |
| Ronan | $35.00 for up to $1,999Verifiedvia Building Permit (New Construction / Addition / Alteration / Repair) | Building Permit (New Construction / Addition / Alteration / Repair) → |
| Shelby | $23.50Verifiedvia Building Permit (New Construction / Addition / Structural Alteration) | Building Permit (New Construction / Addition / Structural Alteration) → |
| Sidney | $23.50Verifiedvia Residential Building Permit | Residential Building Permit → |
| Stevensville | $35 (minimum fee)Verifiedvia Building Permit (New Construction / Addition / Remodel) | Building Permit (New Construction / Addition / Remodel) → |
| Townsend | See city page for the current Building Permit — Residential Building (New Construction / Addition / Remodel) fee | Building Permit — Residential Building (New Construction / Addition / Remodel) → |
| Troy | $24Verifiedvia Residential Building Permit (New Construction / Addition / Alteration / Repair) | Residential Building Permit (New Construction / Addition / Alteration / Repair) → |
| Unincorporated Yellowstone County | Calculated based on project valuation (fee schedule not published inline on the application; contact Building Codes Bureau at (406) 841-2056 for the current valuation-based fee table)Verifiedvia Residential Building Permit | Residential Building Permit → |
| West Yellowstone | See city page for the current Residential Building Permit (New Construction / Addition / Alteration / Repair) fee | Residential Building Permit (New Construction / Addition / Alteration / Repair) → |
| Whitefish | Based on a percentage of the estimated project cost (valuation-based); a deposit is required at time of permit submittalVerifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |