Who approves a deck around Big Sky

"Does a deck in Big Sky need a permit?" has no one-word answer. The state does not issue a building permit for a single-family home here, but a deck can still need a county Land Use Permit, committee approval under the covenants, a floodplain permit, and a state electrical permit. Which ones apply depends on the lot.

Step 1: Is the lot inside a local code jurisdiction?

Montana lets cities, towns, and counties run their own building code programs. The Montana Building Codes Bureau keeps the list. Its version dated October 7, 2026 includes Bozeman (building, plumbing, electrical, mechanical, and more, within city limits) and West Yellowstone (residential building permits within town limits). Big Sky, Gallatin Gateway, Ennis, Gallatin County, and Madison County are not on it.

The list's header puts everything else under the state: "All other areas are under the jurisdiction of the State Building Codes Bureau." The Bureau's permit FAQ then says a building permit is not required for a single-family residence unless you live inside a local government's jurisdiction.

So if your lot is in Big Sky, Gallatin Gateway, or Ennis, no building permit applies to a deck on a single-family home. In Bozeman or West Yellowstone, ask the city or town building office. Bozeman's own deck permit threshold was not confirmed for this guide, so this page gives no size cutoff.

Montana adopted the 2024 International Residential Code effective September 26, 2026. The state building code does not apply to a single-family home's deck outside a local program (MCA 50-60-102). The 2024 IRC is still a sound design reference, and lenders, insurers, and buyers may ask how the deck was built.

Step 2: Which county?

Big Sky spans Gallatin and Madison counties. Local reporting places Meadow Village, Town Center, and the canyon in Gallatin County, and the resort base at Mountain Village, Moonlight Basin, and the upper mountain communities in Madison County. Your property tax bill or a parcel map settles it for your lot.

Gallatin County side: the Land Use Permit

The Gallatin Canyon/Big Sky Zoning Regulation covers the Gallatin County side. It was adopted in 1996 and last updated November 13, 2025, by Resolution 2025-095.

Gallatin County's Land Use Permit instructions say approval "is required prior to construction of most structures in County zoning districts." The site plan has to label outdoor amenities, and the county's own examples are "decks, porches, hot tubs, fire pits." Applications go through the county's MyGov portal, and the county asks applicants to account for a minimum of four weeks for staff processing. Treat that as planning guidance, not a promise.

The regulation exempts minor structures of 300 square feet of floor area or less from the Land Use Permit requirement, though they still have to meet the rest of the regulation. Whether an attached deck counts as its own structure or as part of the house is not spelled out, so ask the Planning Department before assuming a small deck is exempt.

The Big Sky Fire Department has its own Land Use Permit form, linked from the county's zoning permits page. Gallatin County has other zoning districts in the area too, including the Hebgen Lake district along the north shore of Hebgen Lake, northwest of West Yellowstone. The county's zoning map shows which district, if any, covers a parcel.

Madison County side

Madison County's planning regulations page lists subdivision regulations, a growth policy the county describes as non-regulatory, road standards, and sensitive-lands mapping. It lists no zoning district. So the Gallatin County Land Use Permit has no counterpart here, and private covenants carry most of the rules.

Step 3: Covenants and design review

In areas covered by the Big Sky Owners Association, the Big Sky Architectural Committee reviews exterior changes. Its approved minutes for January 8, 2026 record a minor alteration approval for two deck replacements where the design and footprint stayed the same. Even a replacement that kept the same design and footprint, with new materials and railing, went to the committee.

If your lot is in a private community, ask its owners association whether it has design review and what it requires: what drawings it wants, how often the committee meets, and whether it requires an architect. Put that schedule ahead of the contractor's.

Step 4: Water

A deck near the Gallatin River or another watercourse raises two separate questions. Zoning setbacks under the Big Sky regulation keep structures 100 feet from the river's main branch and 50 feet from other watercourses. Gallatin County's floodplain regulations, Ordinance 2023-004, require a permit for construction or placement of structures in the regulatory floodplain. Madison County's rules are in Ordinance 1-2024. Decks near the Gallatin River covers both.

Step 5: Electrical

State electrical permits are required on electrical work in Montana outside the local jurisdictions that run their own electrical program. A homeowner can wire their own home under a homeowner's electrical permit. Anything else needs a permit pulled by a Montana-licensed electrical contractor, with the work done by a licensed electrician. Lighting on the stairs, an infrared heater, and a hot tub circuit all fall under this rule.

A checklist for your lot

1. Is the lot inside Bozeman or West Yellowstone? If yes, call the city or town building office.
2. Is it on the Gallatin side or the Madison side? On the Gallatin side, check the zoning district and whether a Land Use Permit applies.
3. Do covenants apply? Get the design review requirements and meeting calendar.
4. Is there water within 150 feet, or a mapped floodplain? Check setbacks and floodplain maps.
5. Will the deck have power? Plan for a state electrical permit.

For the structural side, read snow load and footing depth. When you know which approvals apply, send a deck request and note them in the message.