Garage With Loft Cost Calculator, Bozeman, MT
Price the garage and the loft on separate bands, with the deeper footings a second storey needs and the stair shown as their own lines.
No obligation. Every estimate starts with a walkthrough of the lot, the access and where the building can actually sit.
Gallatin County, MTCalculator
Price a garage with a loft
Loft area is set as a percentage of the footprint, because an attic truss rarely gives you the whole floor plate at usable height.
These are planning estimates, not quotes. Every figure comes from published cost bands for the Gallatin Valley in 2026. A calculator cannot see your ground, your access, your utilities or your drawings, and it does not know what a geotechnical report will find. Treat the range as a way to decide whether a project is worth pursuing, not as a price.
Why these numbers
What a loft actually adds to the cost
Space above a garage is good value per square foot, because you are building it under a roof you were paying for anyway. Three things stop it being free, and the calculator shows all three.
The first is the foundation. A loft makes the building a two-storey structure, and inside Bozeman that moves the footing requirement from 36 inches to 48 across the entire footprint. More excavation, more concrete, deeper frost wall.
The second is the structure above. Attic trusses create a room inside their own depth and are the cheaper route, with a room shape fixed by the truss geometry. A full framed second floor gives you the whole footprint at full height and costs more. The calculator prices them differently and keeps both inside the published loft band of $45 to $82 per square foot.
The third is the stair, which is the item people forget entirely. A code-compliant stair takes real floor area out of the garage below and where it lands decides how the loft gets used.
One thing this calculator deliberately does not price is a dwelling. Add sleeping, cooking and bathing and the loft becomes an accessory dwelling unit, regulated as housing at $190 to $330 per square foot. That is on the ADU page.
Ranges reflect what a detached garage costs to build in the Gallatin Valley in 2026, including footings to 36 inches, framing, roofing, siding, overhead doors and normal permit costs. They exclude long utility runs, difficult access, septic work and site grading beyond the building pad. For national context, HomeGuide, 2026 national cost guide for a two-car detached garage puts a two-car detached garage at $20,000 to $57,600 with an average near $38,800. Bozeman sits at the upper half of that range, and a heated shop finish goes past the top of it.
Cost factors
What moves the number most
Truss or framed floor
Attic trusses are efficient and fix the room shape. A framed second floor gives you the full footprint at full height and reads as a taller building from the street, which matters where there is a height limit.
48 inches, not 36
Two storeys means deeper footings across the whole footprint inside Bozeman. It is the cost people most often leave out when they estimate a loft themselves.
Real floor area
A compliant stair takes space out of the garage below. Position it at the same time as the door layout, or you end up with a two-car garage that fits one car.
Next step
Decide the loft before the foundation goes in
Designing for a loft and not building it is inexpensive. Adding one later means a new foundation, so this is the decision to make early.
Questions
About these costs
How much does a loft add?
$45 to $82 per square foot of usable loft area, plus the deeper footings and the stair. On a 24 by 36 garage with a 65 percent loft, insulated and wired but not finished, the whole building runs roughly $96,000 to $133,000 inside Bozeman city limits.
Fully finish the loft and the same building goes to about $145,000 to $195,000.
Why are the footings deeper?
Because a loft makes it a two-storey structure. The City of Bozeman publishes 36 inches for one storey and 48 for two, and that applies to the whole footprint rather than just the loaded walls.
Outside city limits the frost line is the same even though the enforcing authority is not.
Attic trusses or a framed second floor?
It depends what the space is for. Seasonal storage and a workbench are well served by attic trusses, which are efficient and arrive as a single engineered package. A studio or office usually wants the framed floor, because you get the full footprint at full height.
A framed floor also reads as a taller building, which matters where a height limit or design review applies.
Can I finish the loft later?
Yes, and it is a sensible way to phase the cost. Build the structure, stair, windows and insulation now and leave the interior finish. Pick the "insulated, wired, not finished" option to see that number.
What you cannot phase is the foundation depth, the floor structure or the roof geometry. Rough in the electrical while the walls are open.
Is a loft the same as an apartment?
No. A loft used for storage or work is part of an accessory structure. Add sleeping, cooking and bathing and it is a dwelling unit, regulated as housing with different code requirements and a different permit path.
The dwelling portion runs $190 to $330 per square foot, which is why it is not in this calculator. See the garage apartment page.
Related
Other calculators and pages
Garage with loft
Attic truss against framed floor, and where loft projects go wrong.
Service page →Garage apartment (ADU)
When the loft becomes a dwelling, and what Montana law settled in 2023.
Service page →Detached garage calculator
The same building without the second storey, for comparison.
Open calculator →Get it real
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