A separate building in the back garden, priced properly: the foundation the slope actually needs, the trench, the fees — and a check against Bountiful's lot size and accessory-footprint limits before any of it matters.
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 detached ADU is a small house. It has its own foundation, its own roof, its own envelope and its own connections, and that is why it costs what it costs — roughly $250 to $450 per square foot all in across the Wasatch Front, against $100 to $250 for the same floor area inside an existing house.
Two things decide where inside that range you land, and neither is the kitchen. The first is what the ground does: Bountiful climbs the bench, and a lot that falls away changes the foundation, the retaining and the drainage before it changes anything you can see. The second is how a machine reaches the back of the lot, because on a narrow side yard every yard of concrete and every truss is a separate problem.
Before either matters, though, there are two feasibility questions worth answering for free. Bountiful publishes a buildable-lot minimum of around 8,000 sq ft for a detached unit, and limits the combined footprint of all accessory structures to roughly 10 per cent of the lot as a permitted use or 15 per cent as a conditional use. An existing garage counts toward that. This calculator checks both as you go.
Bountiful's published bar for a detached unit is a buildable lot of around 8,000 sq ft. Utah's statute uses a different figure — 6,000 sq ft — but that one is about internal units. Two thresholds, two different questions, and they get conflated constantly.
Roughly 10 per cent of the lot as a permitted use, 15 per cent as a conditional use, counting every accessory structure including the garage you already have. It is the rule that quietly decides how big the new unit can be, and it is far cheaper to discover now than after a design.
Slope decides the foundation type, the retaining and the drainage. On a real bench lot the foundation and site work can be a fifth of the job before a single wall goes up, which is why the survey line on this estimate is not optional.
A wide side yard and a tight one build the same unit for very different money. Where a machine will not fit the trench gets hand-dug and the material gets barrowed, and the labour on identical work rises sharply.
Power, water and sewer all have to reach the unit, and anything the trench crosses — a driveway, a patio, mature roots — gets cut and put back. Siting the unit closer to the house is the cheapest saving available on this page.
A detached ADU in Bountiful is decided by the Administrative Committee, not by staff. That means an application package as well as a drawing set, and a calendar that runs longer than an internal unit's.
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.
Yes, as a conditional use. The city publishes that internal ADUs are reviewed and approved by city staff, while detached ADUs are a conditional use requiring Bountiful City Administrative Committee approval. That is a real difference in both time and certainty, and it is worth understanding before a designer starts.
Bountiful's published range for a detached unit is roughly 350 to 1,250 sq ft, subject to the accessory-structure footprint limit — around 10 per cent of the lot as a permitted use, or 15 per cent as a conditional use, counting everything already on the lot. Confirm the current figures with Planning on 801-298-6190.
Bountiful's published bar for a detached unit is a buildable lot of around 8,000 sq ft. Buildable area is measured rather than assumed, so a lot that looks marginal is worth a conversation rather than a guess. Note that Utah's 6,000 sq ft figure is a different rule about internal units.
Yes. Bountiful requires that the owner occupy one of the two units, and records a deed restriction to that effect. You also cannot rent both units — renting both would make the property a duplex rather than a house with an ADU.
Bountiful's published requirements do not permit separate meters for an ADU. That surprises people who assumed they would bill a tenant directly for utilities, and it is worth knowing before you plan around it.
On a flat lot, not much. On a real bench slope the foundation, retaining and drainage together can reach a fifth of the project. That is the single biggest reason two quotes for the same size unit come out far apart, and it is why the order of operations matters: look at the ground, then draw the unit.
Roughly seven to twelve months on site, plus permit review of about six to twelve weeks — longer than an internal unit because the conditional use decision sits in front of the building permit. If a date matters, start the application conversation early.
No. It is a planning estimate. On a detached unit the two lines most likely to move are the foundation and the access, and neither can be settled from a web page.