What's the frost depth for my address in Great Falls?

Great Falls frost depth ranges from 42 to 60 inches depending on location and soil type. The city's online permit portal or building department can confirm your address. Western Great Falls (toward the foothills) tends toward 60 inches; city-center and riverside lots are closer to 42-48 inches. Deck posts, shed footings, and fence posts must bottom out below the frost line. Don't guess — call or check the portal before you dig.

Can I pull a permit myself if I'm the owner and going to do the work?

Yes, Montana law allows owner-builders on owner-occupied residential property to pull permits and do the work themselves. You cannot hire licensed contractors to do the labor; you do it yourself or have unlicensed family help. The City of Great Falls recognizes this and will issue owner-builder permits for decks, fences, sheds, additions, and other residential work. Inspections are strict because the city wants to make sure it's actually the owner working, not a contractor posing as an owner-builder.

How much does a permit cost in Great Falls?

Permit fees vary by project type and valuation. Fences and small sheds are typically $75-$200 flat-fee permits. Decks run $100-$250 depending on size. Additions and new construction are usually 1-2% of project valuation, ranging $200-$1,000+. Electrical subpermits are $50-$150. Fees can change; confirm with the building department. There are no surprise plan-review or reinspection fees bundled in — you only pay if you make a correction.

What happens if I skip the permit?

Unpermitted work is a civil violation in Montana. The city can issue a stop-work order, demand that you obtain the permit retroactively, and require a costly inspection to verify the work was done to code. If the work is substandard, you may have to tear it out and redo it. Unpermitted additions and structural work can also cloud your title, making the house harder to sell or refinance. Insurance may not cover damage from unpermitted work. The permit fee is cheap insurance against this headache.

How long does plan review take in Great Falls?

Plan review averages 2 to 4 weeks for additions and new construction, 1 to 2 weeks for simpler projects like decks and sheds. Over-the-counter permits (small fences, sheds under 200 square feet with no utilities) can issue same-day if you submit before 3 PM and meet all requirements. The city processes most permits through the online portal; you can check status from your phone. If the department has questions or wants revisions, they'll email you through the portal.

Do I need a soil test for my addition or foundation?

Maybe. Great Falls has glacial soil with pockets of expansive clay, especially in the lower parts of town near the Missouri River. The city may require a geotechnical report if your excavation reveals clay or if you're on a slope. Most deck posts and fence footings don't trigger this. New building foundations and additions typically do if soil is uncertain. Ask the building department when you submit your permit application — they'll tell you based on your property and what you're building.

Is there a high-wind zone designation for Great Falls?

Yes. Northern Cascade County, including Great Falls, is designated 100+ mph wind zone under the 2015 IBC. This affects roof framing, garage doors, and some structural details for new construction and additions. Wind-load calculations are required in plan review. This is not a barrier to most residential projects, but it means your design and framing details need to account for high wind loads. It's more common for additions and roof replacements to trigger wind-design review.

Can I file for a permit online?

Yes. Great Falls has an online permit portal where you can submit applications, pay fees, upload documents, and check status. The portal is the fastest way to file. Some small, simple projects (over-the-counter permits) are faster if you walk in with paper and complete the form on site, but the online portal is open 24/7 and gives you a record. Check the city's website for the portal link and current hours.

Building Permits in Great Falls, MT (2026)

Do I need a permit in Great Falls, MT?

Great Falls sits in Montana's 6B climate zone — long, hard winters with frost depths reaching 42 to 60 inches depending on your part of town. That matters for decks, sheds, and anything with footings. The City of Great Falls Building Department enforces the 2015 International Building Code with Montana amendments, which means you're working with familiar code sections but with state-level tweaks around owner-builder work and high wind zones. Most residential projects — decks, fences, sheds, additions, roofing, electrical work — require a permit. The good news: Great Falls allows owner-builders on owner-occupied property, so you can pull permits yourself and do the work yourself; you just can't hire out the labor on an owner-builder permit. The city has an online permit portal for filing and status checks, though some smaller projects still move faster over the counter at City Hall. Plan on 2 to 4 weeks for typical plan review. Frost depth is the single biggest variable in Great Falls permitting — get your footing depth wrong and you'll get a rejection in the middle of winter when digging is hardest.

What's specific to Great Falls permits

Great Falls sits on glacial soil with pockets of expansive clay, especially in the lower parts of town near the Missouri River. This means soils testing is sometimes required for new construction and additions — if your excavation reveals clay or you're near a slope, the building department may ask for a geotechnical report before issuing a footing permit. It's rare for a fence or small deck, but common for additions and pole structures. The city's online permit portal can tell you if your property has a known soil flag.

Frost depth is more variable here than in flat prairie. Western Great Falls (near Belt and Neihart foothills) can hit 60 inches; city-center lots near the river bottom out around 42 to 48 inches. Always ask the building department which frost depth applies to your address — don't guess. Deck posts, shed footings, and fence posts all bottom-out below the frost line. A rejected footing inspection at 36 inches in January is expensive and delays work.

The 2015 IBC with Montana amendments is the working code. Montana has adopted state amendments around owner-builder liability and wind design — listen for 'wind speed 100+ mph zone' in the northern county, which affects roof framing and garage door design. The code edition doesn't change fast, so if you've done work in Great Falls before, you're on solid ground.

Great Falls does allow owner-builders to pull permits and do work themselves on owner-occupied residential property (single-family, duplex, triplex). You cannot hire licensed contractors to do the work; you do it yourself or have unlicensed help. This is a real advantage for decks, fences, and small additions — no general contractor markup. But inspections are strict because the city is watching for owner-builder permits that are really fronts for contractor work. Inspection calls should be made by you or a family member living in the house, not a contractor's employee.

Plan review times are typical for a city this size: 2 to 4 weeks for new construction, 1 to 2 weeks for straightforward additions and decks. Over-the-counter permits (fences under 6 feet, shed under 200 square feet with no electrical, etc.) can issue the same day if you show up before 3 PM. The city processes most permits through the online portal, but you can still walk in with paper. Mobile-friendly site; check status from your phone.

Most common Great Falls permit projects

These five projects account for most residential permits filed in Great Falls. Each has Montana-specific twists — mainly around frost depth, owner-builder status, and soil conditions. Click any project to see local thresholds, cost ranges, and what inspections you'll need.

Decks

Decks over 30 inches high or over 200 square feet require a permit. Posts must bottom out below your frost depth (42-60 inches). Owner-builders can pull these. Expect $100–$250 permit fee and a footing inspection plus a final inspection.

Fences

Fences over 6 feet require a permit; corner-lot sight triangles are restricted. Posts also need frost-depth bottoming. Most wood and chain-link fences under 6 feet are exempt. $75–$150 permit, one inspection at footing stage.

Roof replacement

Roof replacements require a permit if you're changing framing, structure, or going above 4:12 pitch in high-wind zones. Wind speed matters — northern county is high-wind. Inspection on completion. $100–$300 permit; mostly paperwork if framing doesn't change.

Electrical work

Circuits, outlets, sub-panels, all require an electrical permit. New service upgrades always need one. $50–$150 electrical permit (subpermit under main building permit or standalone). Rough-in and final inspection. Licensed electrician usually files; homeowner can on owner-builder permit.

Room additions

Any room addition requires a permit. Plan on soil testing if you're near a slope or in expansive-clay zone. Footings, framing, and final inspection. Owner-builders can file. Expect $200–$800 permit fee and 3-4 weeks plan review.

Do I need a building permit in Great Falls, MT?