Why Montana Driveway Permits Matter
Building or upgrading a driveway in Big Sky Country isn’t as simple as pouring concrete or laying gravel. Montana’s wide-open spaces still fall under city, county, and state rules that protect roads, drainage, and utilities. Skipping the permit can trigger stop-work orders, fines, or even a bill from the highway department to tear out brand-new work. Understanding the permit maze up-front saves money, time, and headaches.
Who Actually Requires a Driveway Permit in Montana?
State Highways (MDT Right-of-Way)
If your curb cuts onto U.S. or state routes—like U.S. 93, MT 200, or I-115 in Bozeman—you need an Access Permit from the Montana Department of Transportation (MDT). The state owns the first 30–50 ft (and sometimes more) from the centerline of most numbered highways.
County Roads
Counties such as Yellowstone, Gallatin, Missoula, and Flathead each have their own “Approach/Entrance Permits.” The standard review window is 10–15 business days, and most counties require a sketch showing:
- Property lines
- Prodriveway location
- Distance to nearest intersection
- Drainage direction
City or Town Streets
Cities like Billings, Helena, Great Falls, and Missoula treat driveways as “minor street cuts.” A city public-works permit is mandatory, and you’ll pay for both the permit and a pavement cut restoration fee if you disturb the street.
Step-by-Step: How to Apply for a Driveway Permit in Montana
Gather Site Info Before You Call
- Measure setbacks: Record the distance from property lines, fire hydrants, and utility poles.
- Mark utilities: Call 811 (Digline) at least two business days before you sketch anything.
- Take photos: Shoot the existing curb, ditch, culvert, and any vegetation that may affect drainage.
Choose the Correct Form
MDT’s form is “Access Permit Application & Highway Approach Specification” (MDT-ADM-004). Counties and cities have their own one-page or online versions. Download the latest PDF—older editions are rejected.
Submit Plans & Pay Fees
- Two copies of a site plan drawn to scale (1″=20′ is typical)
- Cross-section showing driveway slope, culvert size, and materials
- Check or credit-card payment (MDT: $160 for a standard residential approach; counties range $25–$100)
Wait for Field Review
An MDT area supervisor will visit to verify sight-distance (minimum 300 ft on 55 mph roads). Cities inspect for ADA sidewalk clearance and gutter flow. Expect one “revision letter” asking for tweaks—90% of first-time applications need one.
Receive the Written Permit
You have 180 days to start work under an MDT permit; cities give 6–12 months. Extensions are possible but require another fee.
Montana Driveway Design Rules You Must Follow
Width Limits
- Single-family: 12–18 ft (measure at the property line)
- Shared or multi-family: up to 24 ft with written justification
- Commercial: 28 ft max for two-way, 35 ft for truck docks
Radius & Slope
MDT requires a 25-ft minimum outside radius for cars, 40 ft for RVs. Grade cannot exceed 8% for the first 20 ft from the road edge; after that 12% is allowed if the surface is concrete or asphalt.
Culvert & Drainage
Any ditch crossing needs a galvanized or HDPE culvert sized by county engineers—usually 15″ dia. for up to 1-acre drainage, 18–24″ for larger. You must provide 6″ of compacted gravel bedding and 12″ of cover over the pipe.
Materials Allowed
- Urban streets: Concrete or asphalt to the back of sidewalk
- Rural state highway: Bituminous surface treatment (chip-seal) is fine if it meets 4″ compacted thickness
- Gravel driveways: Permitted on county roads but must be treated with dust suppressant May–September in many counties
Typical Driveway Permit Costs Across Montana
| Jurisdiction | Application Fee | Inspection/Cut Restoration | Total Range (single-family) |
|---|---|---|---|
| MDT State Highway | $160 | $0* | $160 |
| Yellowstone County | $50 | $0 | $50 |
| City of Billings | $60 | $130 | $190 |
| Missoula County | $75 | $0 | $75 |
| City of Missoula | $85 | $160 | $245 |
*MDT does not charge a separate inspection fee unless you damage state property.
Hidden Costs to Budget For
- Traffic control: $150/day for flaggers on busy state roads
- Culvert pipe: $12–$20 per foot plus delivery
- Sidewalk replacement: $8–$12 per sq ft if city crews do it
Timeline: How Long Does the Permit Process Take?
Best-Case (No Revisions)
- Day 0: Submit application online or in person
- Day 10: Field inspection scheduled
- Day 15: Permit issued; you start construction
Realistic Timeline (With One Revision)
- Week 1: Submit plans
- Week 3: Inspector asks for wider culvert
- Week 4: You resubmit culvert detail
- Week 5: Permit approved
Peak Season Rush
Between May and August, MDT offices can add 5–10 days. Submit in March or September for faster turnaround.
Top 5 Homeowner Mistakes (and How to Avoid Them)
- Guessing the Right-of-Way Width
Montana highways can own up to 150 ft. Check the MDT right-of-way map before you design; otherwise you may place the garage on land you don’t own. - Forgetting Utility Clearances
Power lines require 10 ft horizontal, gas lines 5 ft. Mark utilities early so you don’t pay to move a 30-ft approach. - Using the Wrong Culvert Material
Some counties ban plastic pipe under driveways that carry irrigation flow. Ask the road foreman what’s accepted. - Pouring Concrete Before Final Inspection
MDT must measure culvert invert elevation while it’s still visible. If you bury it early, they can make you expose it again. - Skipping Dust Control on Gravel
Flathead County issues $250 fines for untreated dusty driveways June–August. A $75 magnesium-chloride treatment keeps neighbors and officials happy.
Do You Need a Contractor or Engineer?
When an Engineer Is Mandatory
- Driveway serves 20+ car trips per day (MDT threshold)
- Slope over 15%
- Shared commercial access with adjacent parcels
When a Licensed Contractor Is Enough
Standard single-family asphalt or concrete approaches under 150 ft long can be permitted with a contractor’s stamp. Drivewayz USA and similar companies already carry the $100,000 liability bond MDT requires, speeding up approval.
DIY Possibilities
Gravel driveways on county roads are homeowner-friendly if you rent a mini-excavator and follow the culvert spec sheet. Remember: you still need the permit first.
Environmental & Winter Considerations
Stream & Wetland Setbacks
Montana’s Stream Protection Act requires 25 ft from ordinary high-water marks. If your approach crosses an intermittent channel, you’ll need a 310 permit from the local conservation district—add 30 days.
Frost Heave & Base Depth
Place 6″ of crushed base (¾-inch minus) in western Montana, 8–10″ east of the divide where frost depth hits 30″. A geo-textile fabric layer prevents spring “potato-chipping” of asphalt edges.
Snow-Plow Safety
Keep the driveway mouth flush with the road; a 2″ lip will catch plow blades and earn you a repair bill. Install reflective markers 6 ft off the shoulder so county plows see your culvert ends.
Frequently Asked Questions
If the widening stays inside the originally approved width and within the same right-of-way limits, most counties allow it under the original permit. Check with the road department; anything beyond the original footprint or culvert size needs an amendment.
MDT and most counties will issue a cease-and-desist order and may require complete removal of the unauthorized work. Fines start at $250 plus restoration costs. Insurance claims can also be denied if unpermitted work damages utilities.
Yes. Each curb cut—whether it’s a single entrance or dual openings—requires its own permit. Circular drives often need two permits and must show how trucks will turn without backing onto the roadway.
Montana doesn’t have a statewide setback, but most cities require 3–5 ft from the side lot line for the approach flare. Counties are flexible unless the driveway blocks a neighbor’s future access. Always verify with local zoning; HOA rules can add stricter buffers.