An addition that shares a wall with the house. This tool prices the part most quotes gloss over — where new framing meets old, and what a house of a given age tends to be hiding when the wall comes off.
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.
An attached ADU sits between the basement and the back garden, and it sits closer to the back garden than most people expect. Sharing a wall saves you a short utility run and one elevation of framing. It does not save you a foundation, a roof, the impact fee, or the fire separation two dwellings sharing a wall are required to have.
What it adds instead is the tie-in. Joining new framing to an existing roof is the fiddliest part of the job and the part that leaks if it is rushed, and joining a new footing to an old one means finding out how deep the old one actually goes. Across the Wasatch Front an attached unit runs roughly $225 to $375 per square foot all in.
This calculator therefore asks two questions a generic tool does not: what happens where the rooflines meet, and roughly when the house was built. Both are about the same thing — how much of what you find will differ from what the drawings say.
A ground-level addition off the side is the straightforward version. Over an existing garage the footprint is already there but the structure usually has to be checked and often reinforced. A second storey over the house is the most disruptive version there is.
The line nobody prices and everybody pays for. A cross gable into an existing slope means new valleys, new flashing and a junction that has to shed Utah snowmelt for thirty years. Where the pitch changes, it is more again.
Not a location index. It is what gets found when the wall comes off: footings shallower than expected, no sheathing behind the siding, wiring that has to be brought up, and walls that are not quite where the plan says.
Usually a new footing dug alongside and tied in. Occasionally the existing structure can carry it, which is the largest single saving available here — and entirely contingent on an engineer saying so.
Where two dwellings share a wall, fire separation is a code item rather than a comfort one. Sound separation is the comfort one, it is not required, and it is the thing people most often wish they had done at the same time.
An addition that does not match reads as an addition forever. Matching weathered brick, stucco or siding costs more than the original did, and it is worth deciding early whether to match or to deliberately differentiate.
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, but by less than people assume — roughly $225 to $375 per square foot against $250 to $450. You save a separate roof plane, a long trench and one elevation of framing. You do not save the foundation, the impact fee, or the work of tying new framing into an existing roof, which is fiddlier than building clear of the house.
Generally not. Utah's internal ADU statute is about a unit created within the primary dwelling. A new addition is new floor area, so it does not attract the statutory protections or the impact-fee exemption an internal unit does. A conversion inside an attached garage is usually a different matter, which is worth asking about specifically.
Where the two rooflines meet. It is a small area of a drawing and a disproportionate share of the risk, because a valley or a change of pitch has to be detailed properly and flashed properly or it will find its way into the wall below. It deserves more of a designer's attention than its share of the budget suggests.
Often yes, and it is a sensible use of a footprint that already exists. Whether the existing structure can carry a floor, walls and a roof it was never designed for is an engineer's question, and it is the one to answer before the design goes far — because it changes the shape of the project, not just the price.
Where two dwellings share a wall or a floor, a rated separation is a code requirement rather than an option. Sound separation is separate, is not required, and is the thing most people wish they had specified once someone is living on the other side of the wall.
Only if it is designed and budgeted to. Matching a weathered exterior costs more than the finish did new, and on some houses a deliberate contrast is both cheaper and better looking. It is a decision worth making on purpose rather than discovering at the end.
Roughly six to nine months on site, plus permit review. It is less disruptive than a second storey and more disruptive than a basement conversion, because the house is opened up at the point where the two structures meet.
No. It is a planning estimate. On an attached unit the line most likely to move is the tie-in, because nobody knows exactly what is behind the wall until it is open.