Do I Need a Permit to Replace Windows in Montana?
Quick Answer
Usually no — but yes if you change the size of the opening.
When You Don't Need a Permit
Like-for-like window replacements — where the new window fits the exact same rough opening — typically do not require a building permit. This covers most standard window replacements where you are upgrading the glass, frame material, or energy efficiency without altering the wall structure.
When You Do Need a Permit
A permit is required when you change the size of a window opening (larger or smaller), add a new window where one didn't exist, convert a window to a door or vice versa, or install egress windows for basement bedrooms. These changes involve structural modifications (headers, jack studs) that must be inspected.
Energy Code Requirements
Replacement windows generally must meet the locally adopted energy code — most jurisdictions follow the IECC. Check the NFRC label on any window before purchasing and confirm your local edition's window U-factor requirement. This applies even when no permit is required — it's a code requirement.
Egress Windows
If you're adding a bedroom in a basement, most jurisdictions require an egress window with a minimum 5.7 sq ft net clear opening and a sill no higher than 44 inches above the floor (the IRC standard). Window wells deeper than 44 inches need a permanently attached ladder or steps. This always requires a permit.
Bottom Line
Swapping windows in the same opening? No permit needed. Changing the opening size or adding egress windows? Get a permit.
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) → |
| 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 → |
| 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) → |
| Havre | $23.50Verifiedvia Residential Building Permit (New Construction / Addition / Remodel) | Residential Building Permit (New Construction / Addition / Remodel) → |
| Helena | $22.00Verifiedvia Residential Building Permit (One- and Two-Family Dwelling — New Construction) | Residential Building Permit (One- and Two-Family Dwelling — New Construction) → |
| Kalispell | $23.50Verifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| Missoula | $36 permit fee + $11.00 plan review feeVerifiedvia Residential Building Permit (New Construction) | Residential Building Permit (New Construction) → |
| 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 → |