Building a Shed in Montana? Permit Rules to Know

Montana's Split Enforcement System

Montana has one of the most unusual building permit structures in the country. The state adopts a uniform building code — currently the 2021 IBC and 2021 IRC with Montana amendments — but enforcement is split between the state Building Codes Program and certified local governments.

Cities, counties, and towns in Montana can choose to enforce building codes locally by getting certified through the state Building Codes Program. Billings, Missoula, Bozeman, Great Falls, Helena, and several other municipalities have done this. In these jurisdictions, local building officials issue permits, review plans, and perform inspections according to the state-adopted codes (with any local amendments).

Areas that have not established local enforcement fall under the state Building Codes Program's jurisdiction. Here's where it gets interesting for shed builders: state law specifically exempts private garages and private storage buildings used for the owner's own use from state building permits. This exemption, found in the state building permit statutes, means that in unincorporated areas and smaller communities without certified local programs, a homeowner building a personal storage shed may not need a building permit at all.

But even where the building permit exemption applies, local zoning permits or land use permits are nearly always required. Montana counties and cities have their own zoning ordinances that regulate setbacks, lot coverage, and permitted uses. For a broader look at how shed permits work nationally, see our national guide to shed permits.

The 200-Square-Foot Threshold in Local Jurisdictions

In cities and counties with certified local building code enforcement, the standard shed permit threshold is 200 square feet, consistent with the IRC's exemption in Section R105.2. Sheds that meet all of the following criteria are typically exempt from a building permit:

• One story with no loft or upper level
• Detached from the primary dwelling
• Used for storage, tools, or playhouse purposes — not habitable, not for business, not for vehicle storage
• Under 200 square feet of floor area
• Generally under 12 feet in height
• Meeting all setback requirements for the zoning district

Missoula County's building permit guide makes an important clarification: the 200-square-foot exemption cannot be cumulative. You can't build two 199-square-foot sheds and claim both are exempt. The exemption covers one shed for storage or play purposes.

Even when a building permit isn't required, a zoning compliance permit or land use permit almost always is. This permit verifies that the shed meets setback requirements, doesn't exceed lot coverage limits, and complies with the zoning district's rules for accessory structures.

How Five Montana Cities Handle Shed Permits

Billings: Valuation-Based Fees with Joint City-County Planning

Billings is Montana's largest city, and its Building Division handles permits from the 5th floor of City Hall. The city follows the 200-square-foot exemption for building permits and requires zoning compliance for all new structures. Billings and Yellowstone County share a joint City-County Planning Department, but building permits are only required within the city limits — Yellowstone County itself does not issue building permits for structures outside Billings city limits.

Permit fees in Billings are valuation-based, meaning they're calculated as a percentage of the estimated construction cost. For a typical residential shed, expect fees in the range of $50 to $150 depending on size and complexity. The city's plan review process takes two to three weeks on average, with residential projects given priority alongside more complex plans.

Missoula: Strict Exemption Rules and Agricultural Exceptions

Missoula has one of the more detailed building permit programs in the state. The city enforces the 2021 IRC and IBC with state amendments, and the 200-square-foot shed exemption comes with clear conditions: the shed must be used only for storage or as a children's playhouse, cannot be used for habitable purposes or vehicle parking, and the 200-square-foot limit is not cumulative across multiple structures.

Missoula County has a well-organized building projects guide that walks through the permit process step by step. The county charges a $150 fee for processing agricultural exemption applications for farm buildings. Non-agricultural shed permits are valuation-based, and the review process typically takes two to four weeks.

The county also notes that decks under 30 inches in height are exempt from building permits, regardless of size — a useful distinction if you're combining a shed with an adjacent platform or small deck.

Bozeman: Each Structure Gets Its Own Permit

Bozeman is one of Montana's fastest-growing cities, and its Building Division enforces a clear rule: one structure equals one permit. Detached structures like garages and sheds on the same lot as a house each require their own separate permit. The city provides a list of work exempt from permits based on the IRC, and sheds under 200 square feet fall within that exemption.

Bozeman updated its fee schedule in September 2023 via Resolution 5517. Fees are valuation-based and tend to be slightly higher than some other Montana cities, reflecting Bozeman's rapid growth and high construction costs. Plan review runs two to four weeks. The city uses ProjectDox, an electronic plan review system, for permit submissions.

Great Falls and Helena: Straightforward Approaches

Great Falls adopted the 2021 building codes including the IRC, IBC, and associated mechanical and plumbing codes in June 2022. The city follows the standard 200-square-foot exemption and processes shed permits through its Building Division. Fees are valuation-based, and review times are typically one to three weeks for straightforward accessory structures.

Helena, the state capital, follows a similar approach. As the home of the state Building Codes Program, Helena's local building division enforces the same codes that the state program oversees. The 200-square-foot exemption applies, and the permitting process is relatively straightforward for small residential structures.

Snow Loads: Montana's Defining Design Factor

No discussion of shed construction in Montana is complete without addressing snow loads. The state's varied terrain and mountain climate produce some of the most extreme snow load variations in the country, and the building code takes this seriously.

The state building code requires snow loads to be determined by the local building official. In areas under state jurisdiction (outside certified local governments), the design snow load must be based on the Montana State University study "Snow Loads for Structural Design in Montana" (2004 revised edition). This study maps ground snow loads across the state with granular detail.

General snow load ranges by region:

• Eastern Montana plains (Miles City, Glendive): 25–40 pounds per square foot
• Central Montana valleys (Great Falls, Helena): 40–60 pounds per square foot
• Western Montana valleys (Missoula, Kalispell): 50–70 pounds per square foot
• Mountain areas and higher elevations: 80–150+ pounds per square foot
• Near Glacier National Park: Can exceed 200 pounds per square foot at higher elevations

Even a shed that's exempt from a building permit must be structurally capable of handling the snow load for its location. A collapsed shed during a heavy snowfall can damage adjacent vehicles, equipment, or neighboring structures. Pre-built shed manufacturers selling in Montana should design their roofs for applicable snow loads, but verify this before purchasing.

The building code also allows the building official to require monolithic slabs for single-story storage buildings to be designed and stamped by a Montana-registered engineer at the official's discretion. This is more common in areas with severe snow loads or challenging soil conditions.

The Agricultural Exemption

Montana's strong agricultural tradition is reflected in its building code. Agricultural buildings not intended for human habitation or commercial use on properties classified as agricultural may be exempt from building permits. The key requirements:

• The property must have an approved Agricultural Land Classification through the Montana Department of Revenue under Montana Code Annotated Section 15-7-202
• The building must be directly related to farming or ranching activities
• The building cannot be used for human habitation or commercial purposes like selling goods

The definition of agriculture includes raising crops, feeding and breeding livestock, poultry, and bees, as well as producing food, feed, fruits, vegetables, sod, nursery stock, and fiber commodities for commercial purposes.

This exemption does not apply to a suburban homeowner building a storage shed for lawn equipment. If your property isn't classified as agricultural, the standard permit rules apply. If you believe your property qualifies, contact your local building division to begin the exemption process.

Foundation Choices in Montana's Climate

Montana's climate presents unique challenges for shed foundations. The state's frost depth varies from about 36 inches in lower-elevation western valleys to 48 inches or more in colder areas. Any permanent foundation needs footings below the frost line to prevent heaving.

Gravel pads are popular for small to mid-size sheds. A well-compacted gravel base provides drainage and a level surface without requiring below-grade footings. In Montana's arid climate, gravel pads also reduce moisture problems compared to placing a shed directly on soil.

Concrete piers or sono-tube footings extending below the frost line provide the most stable support for larger sheds. The building code requires footings at least 3 feet below grade for single-story buildings, and the building official may require deeper footings in areas with severe frost conditions.

Pole barn-style construction is common for larger sheds and agricultural buildings in Montana. Pressure-treated posts set in concrete below the frost line support the roof and walls. Pole barns that don't meet the building permit exemption criteria need a building permit, and Missoula County requires engineered plans stamped by a Montana-licensed professional engineer for pole barns.

For pre-built sheds on temporary foundations (skids or surface blocks), the main concern is anchoring. Montana can experience high winds, particularly on the eastern plains and through mountain passes. An unsecured shed can slide off its foundation or become airborne in severe windstorms.

Setbacks, Lot Coverage, and Zoning

Zoning rules in Montana cities and counties regulate where you can place a shed on your property. Common requirements include:

Setbacks — the minimum distance from property lines. Typical residential setbacks for accessory structures in Montana cities range from 3 to 5 feet for side and rear property lines, with larger front yard setbacks. Exact requirements vary by zoning district.

Lot coverage — the maximum percentage of the lot that can be covered by structures, including the house, garage, and all accessory buildings. Adding a large shed could push a property over its lot coverage limit.

Height limits — most zoning districts limit accessory structure height to 12 to 15 feet. Taller structures may require a variance.

Number of accessory structures — some zoning districts limit how many outbuildings you can have per lot.

In Billings, contact the joint City-County Planning Department at (406) 657-8247 for zoning questions. In Missoula, the Planning, Development & Sustainability department handles zoning compliance. Each city has its own zoning map and dimensional requirements table.

Montana's Short Construction Season

Montana's construction season is short, particularly in the northern and mountainous parts of the state. Ground freezing, heavy snowfall, and limited daylight compress the window for outdoor construction into roughly May through October in many areas.

The state Building Codes Program acknowledges this reality and has a notable accommodation: while the building code technically prohibits starting construction without a permit, special arrangements can sometimes be made to begin foundation work before the permit is formally issued. The state notes this is particularly relevant for pouring footings or foundations, which need to happen before the ground freezes.

If you're planning a shed project, submit your permit application early in the season. The state Building Codes Program averages three weeks for plan review. Certified local jurisdictions vary, with most cities processing simple residential permits in one to four weeks. Starting the permit process in March or April gives you the best chance of building during the warmer months.

Wildland-Urban Interface Considerations

Montana adopted the 2021 International Wildland-Urban Interface Code (IWUIC) effective June 2022. This code applies to construction in areas where development meets or intermixes with wildland vegetation — a common situation across much of western and central Montana.

In wildland-urban interface (WUI) zones, additional requirements may apply to shed construction:

• Fire-resistant roofing materials may be required
• Defensible space around the structure may need to be maintained
• Siding and exterior materials may need to meet specific fire ratings

If your property is in or near a WUI zone, check with your local fire district or building department for any additional requirements that apply to accessory structures.

Consequences of Skipping the Permit

Building without a required permit in Montana can result in:

• A Notice of Violation and Order to Comply (NOV) from the building official, requiring you to bring the structure into compliance
• After-the-fact permit fees that are higher than the original permit would have cost
• Requirements to expose covered work for inspection, which can mean removing interior finishes, siding, or roofing so an inspector can verify code compliance
• Fines and penalties that accumulate until the violation is resolved
• Problems at sale when the unpermitted structure is discovered during a home inspection or appraisal

The state permit fee for a shed is modest — typically 1% to 2% of the building's assessed value, with a minimum of $23.50 for structures valued at $500 or less. For a $2,000 shed, the fee is approximately $70. The cost of retroactive compliance is always higher.

If you're also planning a garage or carport alongside your shed, each structure typically needs its own permit and zoning approval. Plan your accessory buildings together so you can verify total lot coverage compliance before starting construction.

For an overview of all building permit requirements in Montana — including decks, fences, pools, and more — see our complete Montana building permit guide.