What you need to know now about accessory dwelling unit contractors:
- An ADU contractor manages design, permitting, and construction of a self-contained secondary unit on your property. Scope clarity before signing is non-negotiable.
- ADU costs in Salt Lake City run from $80,000 for a garage conversion to $300,000+ for a detached new build. The contractor you hire determines whether that number holds.
- Utah state law and Salt Lake County’s 2024 ordinance have made ADU building more accessible, but local zoning still varies by city, lot size, and unit type.
- The Ironwood Precision Build Method locks in your project scope and budget before construction starts, preventing surprise costs or timeline shifts.
The right contractor makes an ADU build feel manageable. The wrong one turns a six-month project into a 15-month ordeal with surprise invoices at the end. Here is what to know before you hire.
What Does an Accessory Dwelling Unit Contractor Actually Do?
An accessory dwelling unit contractor is a licensed builder who manages the construction of a secondary living unit on your existing residential property. In a full-service arrangement, that includes design, engineering, permit filing, construction, and final inspections, all under one contract.
An ADU is a fully independent dwelling, its own entrance, kitchen, bathroom, and living area, built on the same lot as your primary residence. It carries the same code requirements as any home. That level of complexity is why the contractor you choose matters as much as the plans you draw.
In Salt Lake City, the contractor also needs to understand how Utah state ADU law, Salt Lake County’s updated 2024 ordinance, and your specific city’s zoning code all layer together. Those three frameworks frequently say different things, and the contractor has to resolve the conflict before construction begins.
Which Type of ADU Contractor Is Right for Your Project?
Not every firm that calls itself an ADU contractor offers the same scope. Understanding the distinction saves time and prevents the most common source of project frustration: discovering mid-build that your contractor does not handle something you assumed they did.
Is a Design-Build Firm the Best Choice?
A design-build firm handles both architectural plans and physical construction under one contract. You have a single point of contact from concept through completion.
That streamlines decision-making and eliminates the communication gap between designer and builder. Most ADU projects go sideways precisely in that gap.
The tradeoff is that you are not getting competitive bids on design separately. For homeowners who want price transparency and one entity accountable for everything, design-build is the stronger choice.
When Does a General Contractor Make Sense?
Some homeowners choose to hire an architect or draftsman separately, then bring in a general contractor to execute the build. This gives more control over the design phase but adds coordination complexity.
If you go this route, confirm the GC has pulled ADU permits in your specific city. Permit familiarity matters because it directly affects timelines. A contractor who has built ADUs in Salt Lake City moves through the city’s process faster than one doing it for the first time.
What Do Specialized ADU Builders Offer?
A subset of contractors focus exclusively on accessory dwelling units. They tend to have strong permit relationships and established processes for common ADU types like garage conversions, detached cottages, and basement conversions.
Useful if your project is fairly standard. For more complex builds or sites with unusual conditions, a design-build firm with broader experience handles complications more readily.
What ADU Types Can You Build in Salt Lake City?
Detached ADU
A freestanding structure separate from the main home. Maximum privacy for occupants, highest rental income potential, and the biggest impact on property value. Also the most expensive to build, since you are starting from a foundation.
In Salt Lake County, detached ADUs can be up to 20 feet tall or match the height of the main home, depending on setbacks. Most homeowners in the Salt Lake Valley targeting rental income choose this type when the lot allows.
Attached ADU
An attached ADU connects to the primary residence, typically via a shared wall. It shares some utility infrastructure with the main home, which reduces cost.
Floor plans tend to be more constrained than a detached unit, but the reduction in foundation and utility work makes it meaningfully cheaper. A good option when the lot does not support a fully separate structure.
Garage Converted Into an ADU
Converting an existing garage into livable space is often the most cost-effective path. The structure is already there. Walls, roof, foundation. You are finishing and upgrading it to residential standards.
One important note: a garage conversion may affect your parking compliance. Salt Lake County requires at least one on-site parking space for the ADU, in addition to parking for the main home. Confirm this before you start drawing plans.
Internal ADU
An internal ADU carves a separate, self-contained unit out of your existing home’s footprint. Common in Salt Lake Valley, where finished basements are standard.
The city code has no maximum size restriction for internal ADUs, which gives more design flexibility than detached units. Internal ADUs cannot have separate utility meters in Salt Lake County. The property owner receives utility bills for both units.
How Much Does an ADU Cost in Salt Lake City in 2026?
ADU costs in Utah track closely with national averages but run higher than some markets due to land costs and labor demand in the Salt Lake Valley. Nationally, the average ADU runs around $180,000, with most projects landing between $40,000 and $360,000, according to ADU cost data published by Angi in 2026.
| ADU Type | Typical Cost Range | Cost Per Sq Ft | Build Timeline |
|---|---|---|---|
| Garage Conversion | $80,000 to $150,000 | $100 to $200/sq ft | 3 to 6 months |
| Internal / Basement ADU | $90,000 to $175,000 | $120 to $220/sq ft | 4 to 7 months |
| Attached ADU | $150,000 to $280,000 | $150 to $250/sq ft | 5 to 9 months |
| Detached New Build | $175,000 to $350,000+ | $200 to $350/sq ft | 6 to 12 months |
These ranges reflect Salt Lake City market conditions as of 2026. Lot access, finish quality, and utility connection complexity all move the number.
Costs shown are general estimates based on national averages, not a quote. Pricing varies widely by project scope, materials, labor rates, and site conditions. Use to frame budget thinking, then get a real number from a contractor.
Wondering where your specific ADU project might land? Ironwood walks every homeowner through a detailed scope-and-cost conversation before any commitment. Explore our ADU services →
What Do ADU Permits Look Like in Utah?
Permitting is where most ADU timelines either stay on track or fall apart. Understanding the process before you hire helps you ask the right questions.
How Does Utah State Law Interact With Local Zoning?
Utah has passed state-level ADU legislation that sets baseline rules around lot minimums, setbacks, and permissible unit types. Local city codes must remain consistent with those standards.
Where city rules are stricter than state minimums, city rules apply. This interplay has generally expanded ADU access across the Salt Lake Valley over the past several years. But it means your contractor must know both layers, state law and city code together.
What Did Salt Lake County’s 2024 Ordinance Change?
On June 4, 2024, Salt Lake County adopted a new ordinance designed to reduce barriers to ADU construction. Key provisions under the updated rules:
- Internal ADUs: Lot must be at least 6,000 sq ft
- Detached ADUs: Lot must be at least 7,000 sq ft
- Occupancy: Property owner must reside on-site, with limited exceptions for military, medical, or religious service
- One ADU per lot: Internal or detached, not both
- No separate sale: ADUs cannot be subdivided or sold independently from the main property
What Do Permits Cost for an ADU in Utah?
Permit fees for ADU projects typically run $5,000 to $10,000 depending on unit type and municipality. That covers plan review, building permit fees, and environmental assessments.
Impact fees, water and sewer connection fees, and fire safety fees may apply to larger units. Architectural plans run an additional $8,000 to $15,000 or more depending on complexity.
What Slows ADU Permits Down?
The NAHB has identified three recurring hurdles to ADU construction: discretionary permit review processes, owner-occupancy requirements, and minimum lot size restrictions.
In some jurisdictions, conditional use permits require public hearings and non-refundable fees before approval is granted. An experienced local contractor navigates these before they become delays, not after.
Why Does the Precision Build Method Produce Different ADU Outcomes?
Most ADU problems share a common root: something was not defined upfront.
The contractor’s scope was vague. The contract did not specify which fixtures were included. Change orders started appearing. The budget grew. The timeline slipped. At the end, the homeowner had a completed unit but a sour experience.
Ironwood’s Precision Build Method addresses this at the source. Every scope item is defined, priced, and agreed upon before construction begins. Hardware, fixtures, utility connections, finish selections. Nothing is left to be “figured out later.” That upfront alignment is what allows us to hold to the agreed cost and schedule.
We carry nearly 80 years of combined construction experience across our team. That depth means we have seen the conditions that derail projects, and we design our process to prevent them.
Our clients do not need a 15% to 20% contingency fund because the estimate we give is the estimate we build to.
What Does the Precision Build Method Cover?
- Detailed pre-construction scope review with every trade involved
- Fixed-price agreements tied to a specific, documented scope
- Permit management from application through final inspection
- Design and engineering coordination in-house
- Single project manager contact from kickoff through final walkthrough
Not sure whether to add on to your home or build an ADU? Our home additions guide breaks down when each approach makes more financial sense. Read: Home Additions in Utah →
Why Are ADUs Worth Building in Salt Lake City Right Now?
Properties with ADUs see average value increases of 20 to 30%. That gain comes from added square footage, rental income potential, and appeal to an expanding buyer pool looking for multigenerational living options.
That last factor is significant. Multigenerational home purchases hit an all-time high in 2024, with 17% of all homes bought that year going to multigenerational households, the highest proportion since NAR began tracking the figure in 2013.
Aging parents, adult children, and multi-income households are all driving demand for properties that can house two households on one lot.
Salt Lake Valley’s housing market reinforces this trend. The Harvard Joint Center for Housing Studies’ 2025 State of the Nation’s Housing report found that housing affordability is at record lows, pushing more families toward creative living arrangements. An ADU on an existing lot is exactly that kind of arrangement.
What Are the Most Common Uses for an ADU in Salt Lake City?
- Rental income: Long-term tenants, furnished rentals, or month-to-month arrangements. A 600 to 800 sq ft detached ADU in the Salt Lake Valley typically generates meaningful monthly income that offsets carrying costs.
- Aging parents: Private space on the same lot, close proximity without sharing a primary residence.
- Adult children: Independence without the full cost of a separate property.
- Home office or studio: Dedicated, separated workspace without a commute.
- Guest suite: Full privacy for extended visits, with none of the disruption of integrating guests into the main home.
What Should You Look for When Hiring an ADU Contractor?
Hiring an ADU contractor is different from hiring a general remodeler. The permitting complexity, zoning knowledge, and design coordination requirements are higher. Here is what separates a capable ADU contractor from one who is figuring it out on your project.
Does the Contractor Have Current Licensing and Insurance?
Every contractor who pulls permits in Utah must be licensed through the Utah Division of Occupational and Professional Licensing. Verify the license is current before you sign anything.
Ask for a certificate of general liability insurance and verify the policy is active, not a document from a previous year.
Has the Contractor Pulled ADU Permits in Your Specific City?
Ask for examples of ADUs the contractor has successfully permitted in your specific city. A contractor who has pulled ADU permits in Salt Lake City, Draper, Herriman, and West Jordan understands how each jurisdiction’s building department operates.
One who has not done it in your city will spend your project time learning the process.
How Does the Contractor Define Scope Before Signing?
This is the question most homeowners do not know to ask. How the contractor defines and documents scope upfront tells you more about how the project will go than any reference call.
Ask: “What does your contract specify regarding fixtures and finishes? What falls outside your scope?” If the answer is vague, the invoice will not be.
How Do They Manage Trades and Communicate Through the Build?
ADU projects involve multiple trades working in a specific sequence. Framing before electrical, electrical before insulation, insulation before drywall. When a trade finishes late, the next one cannot start.
Ask how the contractor manages trade sequencing and what their communication protocol is when something shifts.
What Warranty Does the Contractor Offer?
Ask what the contractor warranties and for how long. Workmanship warranties typically run one year. Structural warranties often extend longer. Get the terms in writing.
What Are the Biggest ADU Contractor Red Flags?
Some patterns signal problems before they become expensive lessons.
| Red Flag | What It Usually Means |
|---|---|
| No written scope before contract signing | Change orders are the business model |
| Lowest bid by a wide margin | Scope is incomplete; costs will appear later |
| Cannot name recent ADU permit history in your city | Learning your permit process on your timeline |
| Vague about which fixtures and finishes are included | Expect “owner to supply” surprises at finish stage |
| No single point of contact after contract is signed | Coordination gaps between trades, slower issue resolution |
| Contingency language of 15% to 20% built into the contract | Budget not based on actual scope |
Frequently Asked Questions About ADU Contractors in Utah
What is the difference between an architect and a contractor?
An architect creates the design and engineering drawings for your ADU. A contractor builds it. For a full-service ADU project, a design-build firm combines both under one contract. You get design and construction from a single team. If you hire them separately, make sure both parties communicate directly throughout the project; gaps between design intent and field execution are where expensive misunderstandings occur.
What is the best definition of an accessory dwelling unit?
The legal definition matters more than the common one. An ADU is a permanently habitable, code-compliant secondary dwelling on the same lot as a primary residence. “Permanently habitable” is the key phrase. It means the unit must meet the same life-safety, structural, and mechanical standards as the main home. That separates an ADU from a she-shed, a finished garage, or a bonus room. If it does not have a permitted kitchen, a permitted bathroom, and a legal egress, it is not an ADU.
What is another name for an ADU?
ADUs go by many names depending on region and type: in-law suite, granny flat, carriage house, backyard cottage, casita, secondary dwelling unit, garage apartment, and guest house. The terminology sometimes signals the specific form. A casita typically refers to a detached structure, while an in-law suite is usually attached or internal. In Utah, all of these fall under the legal definition of an accessory dwelling unit and are subject to the same permit and zoning requirements.
What is the smallest size for an ADU?
In most Utah jurisdictions, the minimum livable area for an ADU is 150 to 300 square feet, though practical construction floors tend to run higher. A fully functional space needs room for sleeping, cooking, a bathroom, and circulation, which pushes realistic minimums toward 400 square feet for comfortable occupancy. Check your specific city’s code, as minimum sizes vary across Salt Lake County municipalities.
What are the most common mistakes when building an ADU?
The five most common: hiring a contractor without confirmed ADU permit history in your city; signing a contract without a fully documented scope; underestimating permitting timelines; failing to confirm parking compliance before finalizing the ADU type; and assuming the project will run on the same schedule as a simpler renovation. ADUs are full residential builds. They involve the same trade sequencing, inspection milestones, and code compliance as building a home. Treating them like a standard remodel is where most projects go wrong.
How long does it take to build an ADU in Salt Lake City?
Timeline depends on ADU type, permit complexity, and contractor process. Garage conversions run 3 to 6 months from permit approval. Attached units run 5 to 9 months. Detached new builds run 6 to 12 months. Permit approval itself typically takes 4 to 12 weeks in the Salt Lake Valley, depending on the city and whether the application is complete at submission. A contractor who regularly files ADU permits in your city moves through this step faster than one who does not.
How Do You Start an ADU Project With Ironwood?
The first conversation is not a sales call. It is a discovery session. What you want to build, what your lot allows, and what a realistic budget looks like for your specific conditions.
Ironwood Custom Builders serves the full Salt Lake Valley, including Salt Lake City, Sugar House, Draper, Sandy, South Jordan, West Jordan, Herriman, Holladay, Murray, Taylorsville, Cottonwood Heights, Millcreek, and Park City.
With nearly 80 years of combined experience and a process built to prevent the delays and surprises that define most ADU projects, we know what a well-run ADU build looks like. We build that way every time.
Ready to talk through your ADU? No commitment, no pressure. Just a real conversation about what is possible on your property. Contact Ironwood →
