The cheapest new ADU there is, because the shell already exists. Three things decide whether it stays cheap: the slab, the ceiling height, and the parking you have just removed.
A planning estimate, not a contractor quote. Nothing you enter is sent anywhere.
This is a planning estimate, not a contractor quote. It is built from Utah’s own accessory dwelling unit statute, from Bountiful’s published ADU requirements, and from current Wasatch Front ADU cost data. It cannot see your ceiling height, what your lot does at the back, what the panel can carry, or what is behind the basement wall — and those are the things a real price turns on. Impact fee figures are allowances: Bountiful publishes its own schedule, and it is worth confirming the current numbers with Planning on 801-298-6190 before you budget.
A garage conversion is the cheapest way to add a dwelling to a property, and the reason is simple: the slab, the walls and the roof are already there. You are buying insulation, services and finishes rather than a building, which is why it runs roughly $125 to $275 per square foot against $250 to $450 for a detached unit.
Three things decide whether it stays that cheap. A garage slab is poured to take a car — sloped to the door, rarely insulated, often thinner at the edges than a habitable floor wants. Ceiling height gets eaten from both ends once you build the floor up and drop a ceiling. And the conversion deletes covered parking on a property that, with an ADU on it, now needs more parking rather than less.
There is also a legal distinction worth knowing, and it is not cosmetic. A conversion inside an attached garage is generally an internal accessory dwelling unit — staff review in Bountiful, and exempt from impact fees under Utah Code 10-21-303. A detached garage is a separate building, so neither applies.
Not a style question. A conversion within the primary dwelling is generally an internal ADU: staff review and no impact fees. A separate building in the back garden is neither, and it needs a trench for power, water and waste as well.
Poured for a car, not for a bedroom. It slopes to the door, it usually has no insulation and often no moisture barrier. Levelling it is a real line; replacing it is the most expensive item on this page and occasionally the right answer.
A habitable room needs a genuine finished height, and a conversion loses height at both ends — an insulated build-up over the slab and a ceiling under the joists. A garage that measured fine can stop measuring fine. It is the one dimension that can end the project.
Bountiful requires an additional off-street space for the ADU, on top of what the house already needs — and you have just deleted two covered spaces. On a narrow lot with one driveway that can mean widening, re-grading and paving.
A garage almost never has any. The bathroom and the kitchen have to reach a waste line, and the distance is trenched through a slab that is already there. If the unit sits below the line, the waste has to be pumped.
Usually filled in as a wall with a window, which needs a new header and a finish that matches the house. Glazed doors cost more and are where the light comes from, which on a converted garage matters more than it sounds.
Send a description of the property, roughly what you are picturing, and who the space is for. Every plan starts with your lot — the ceiling height, the fall of the ground and what the services can carry decide more than the floor plan does.
Roughly $60,000 to $170,000 in Utah, or about $125 to $275 per square foot. A standard two-car garage of around 440 sq ft with a sound slab and decent ceiling height sits near the lower half of that; a cracked slab or a tight ceiling moves it up quickly.
If the garage is attached to the house, generally yes — it is a unit created within the primary dwelling, which is what Utah's internal ADU statute covers, and that means staff review in Bountiful and no impact fees. A detached garage is a separate structure, so it is not. It is worth confirming which side of that line your garage falls on before budgeting.
Bountiful requires an additional off-street space for the ADU, and the conversion removes the covered parking the house had. On a wide driveway that is straightforward. On a narrow bench lot with one drive it can mean widening and paving, and occasionally it is the constraint that stops the project rather than the budget.
A habitable room needs a genuine finished height, and you lose some at the floor to insulation and some at the ceiling. Measure from the slab to the underside of the joists before assuming it works — under 8 ft means raising the roof, lowering the slab, or accepting a thinner floor system that performs worse.
Usually nothing structural, but it was poured for a car: sloped to the door so water runs out, generally uninsulated and often without a moisture barrier beneath it. Living on it without addressing that is how you get a cold, damp floor. Levelling and building up over a sound slab is normal; replacing it is occasionally necessary.
It can be kept and insulated as a feature, but it rarely seals or insulates as well as a wall and the room tends to read as a garage. Most conversions fill the opening with a wall and a window, or with glazed doors where the light and the outlook justify it.
Roughly three to five months on site, plus permit review of about four to eight weeks for an attached garage handled as an internal unit. It is the fastest new ADU on this site as well as the cheapest.
No. It is a planning estimate. The two things most likely to move it are the slab and the ceiling height, and both are worth measuring before you budget.