Kearns ADU Builders: Rules, Costs, and Whether Your Lot Is a Fit
If you own a single-family home in Kearns, you most likely have a path to add an ADU — but the smart first move is a feasibility check, not a builder call. An accessory dwelling unit (ADU) is a second, self-contained home on your lot — a basement apartment, a garage conversion, an attached addition, or a detached backyard cottage. Kearns allows all of these on qualifying single-family lots (5,000 sq ft or larger), with one ADU per lot, owner-occupancy, and a building permit required. The type your lot can support depends on zone, parking, setbacks, and utilities — which is why builder quotes come after feasibility, not before.
Last verified: June 2026. Kearns's ordinances, Utah state ADU law, fees, and market costs change. Confirm the current rules for your specific parcel before you commit.
Utah ADU Builders is a Utah-focused ADU planning, feasibility, and builder-matching resource — not a city office, Salt Lake County, the Municipal Services District, a contractor, architect, engineer, lender, or permit authority. We may receive compensation when homeowners request estimates or are connected with local professionals. That compensation does not change how we explain Kearns's ADU rules, costs, feasibility factors, or permitting risks. This page is informational only; verify all rules against the current City of Kearns code before you commit to any plan.
✅ What we verified for this page
- City of Kearns Zoning Code, Title 19, §19.42.030 (Accessory Dwelling Units) and §19.42.310 (Short-Term Rentals), as amended in 2025.
- Utah state ADU law — internal ADUs (Utah Code §10-21-303, originating in HB 82, 2021) and the new detached-ADU statute (Utah Code §10-21-304, effective October 1, 2026).
- Utah Office of Property Rights guidance on impact fees, HOAs, and tiny homes.
- How to check a contractor's license — Utah Division of Professional Licensing (DOPL) license lookup.
- Cost and timeline figures are typical Salt Lake Valley planning ranges (estimates), explained in the cost section below — not a site-specific quote.
What we can't verify from a webpage is your individual lot — its exact setbacks, utility capacity, and zoning fit. That's what a feasibility review is for.
Can you build an ADU in Kearns?
Usually, yes — if your property and the ADU type fit local rules. Kearns permits internal, attached, and detached ADUs, plus garage and basement conversions, on qualifying single-family lots of 5,000 sq ft or more. But "allowed in Kearns" is not the same as "feasible on your lot": parking, setbacks, utilities, and owner-occupancy can all change the answer.
Kearns ADU quick answers
| Your question | The practical answer | Why it matters |
|---|---|---|
| Can I build an ADU in Kearns? | Likely, on a qualifying single-family lot (5,000 sq ft+) that can meet parking, setback, lot-coverage, utility, and owner-occupancy rules. | A builder quote is only useful after feasibility is screened. |
| Does Kearns allow detached backyard units? | Yes — Kearns's own code allows detached ADUs, which not every Utah city does. Height, setback, and foundation rules still apply. | Detached units carry the most site risk and cost. |
| Should I call builders first? | Usually no. First confirm which ADU type your lot can actually support. | Different ADU types create very different cost and permit paths. |
| Can I rent it out? | Yes, as a long-term rental (30+ days), and you'll need a business license. Short-term/Airbnb use is prohibited in Kearns. | Rental use is a legal question, not just a construction one. |
| Can I sell the ADU separately later? | No. An ADU can't be sold or subdivided into its own lot. | This affects your exit strategy. |
| Best next step? | Check your lot's feasibility, then compare realistic build paths. | It prevents bad quotes and wasted design money. |
Who regulates an ADU in Kearns
Kearns is a small city with an unusual recent history, and it trips up a lot of homeowners. Kearns was a metro township from 2015 until 2024, and on May 1, 2024 it became the City of Kearns. It still contracts its planning and development services through Salt Lake County's Municipal Services District (MSD). What that means for you: your ADU follows the City of Kearns's own zoning code, plus a building permit and inspections under the adopted building and fire codes — administered by the MSD on Kearns's behalf.
This matters in one very practical way: if a builder, a blog, or an AI summary quotes you Salt Lake City ADU rules — or treats Kearns as unincorporated county land — those rules may not match Kearns's code. Kearns's ADU standards live in its city code at §19.42.030, and that's what governs your lot. Always verify against the current Kearns provisions.
What kind of ADU should a Kearns homeowner consider first?
Compare ADU types before you compare builders. The right conversation with a builder is completely different depending on whether you're finishing a basement, converting a garage, adding on, or building a standalone cottage — and each path has its own cost and permitting friction.
Kearns ADU build-path comparison
| ADU type | What it is | Best for | Watch-outs in Kearns |
|---|---|---|---|
| Internal / basement ADU | A unit created inside your existing home | Parent suite, lower-cost long-term rental, least exterior change | Egress windows, ceiling height, fire separation, 1 parking space, owner-occupancy |
| Garage conversion | Turning an existing garage into a living unit | Reusing space you already have | You must replace any parking the conversion removes |
| Attached ADU | A new unit built as an addition sharing a wall | More space without a separate backyard building | Setbacks, addition design and engineering, utility routing |
| Detached ADU | A standalone backyard cottage | Privacy, family separation, stronger rental appeal | Lot size, 5 ft setbacks, height limits, slab foundation, 2 parking spaces |
| Prefab / tiny-home-style ADU | A compact, often factory-built detached unit | A faster, more predictable detached option | Still must meet Kearns's ADU rules, building code, and a permanent foundation |
Internal or basement ADU
For many Kearns homes — which often have full basements — this is the first path to screen because it reuses existing space. It can still require egress windows (an emergency exit window large enough to climb through), a side or rear entrance, fire separation, and code upgrades, so price the full scope, not just finishes.
Garage conversion
A garage conversion looks cheap because the shell exists, but parking is usually the deciding factor. Kearns requires you to replace, on-site, any parking the conversion removes from the main home — so confirm you can do that before you design.
Detached ADU
A detached cottage is the most popular option for privacy and rental separation, and Kearns's code allows it — but it carries the most site rules. Before you request a detached quote, screen for lot size, the 5-foot side and rear setbacks, the 6-foot separation from the house, height limits, foundation, drainage, and two on-site parking spaces.
Prefab or tiny-home-style ADU
A prefab unit isn't a shortcut around the rules. Utah lets cities set a minimum square footage for dwellings (but cities can't require a minimum over 1,000 square feet), and a tiny home used as an ADU still has to meet Kearns's ADU standards, building code, and sit on a permanent foundation. Utah ADU Builders may have referral or partner relationships, including with Nest Tiny Homes (which serves Salt Lake County), for some compact or prefab-style ADU inquiries — if so, that relationship will be disclosed at the time of any referral, and it doesn't mean a particular unit is pre-approved or code-compliant for your specific lot.
Kearns ADU rules at a glance
These are the rules that most often change a project's scope. They come from the City of Kearns Zoning Code (§19.42.030, as amended in 2025) and Utah state law. Treat them as current requirements to confirm for your parcel, not guarantees.
| Rule | What Kearns requires | Why it matters |
|---|---|---|
| ADU types | Internal, attached, and detached ADUs plus conversions are allowed on qualifying single-family lots | More options than the statewide minimum |
| Lot size | Single-family lot of 5,000 sq ft or greater (internal, attached, and detached) | Below this, or on a townhome/multifamily lot, an ADU isn't permitted |
| Number of ADUs | One ADU per lot | You can't add a second unit |
| Owner occupancy | Owner must live in the main home or the ADU; a signed affidavit is recorded. Limited exceptions (medical, military service, or religious reasons) allow up to a two-year absence with an on-site manager | You (or a future buyer) must live on-site |
| Parking | 1 on-site space for an internal or attached ADU; 2 on-site spaces for a detached ADU — in addition to the home's existing parking. A garage conversion must replace any parking it removes | Parking is one of the most common reasons a project stalls |
| Setbacks (detached) | 5 ft side, 5 ft rear, and 6 ft from the main house (or the public-utility-easement line if greater); offset 10 ft from the home's front façade; not in the front or corner-side yard | Determines whether a detached unit physically fits |
| Height (detached) | 20 ft for a detached ADU; 28 ft above a garage; and no detached ADU may be taller than the existing home | Limits a tall two-story cottage |
| Foundation | A detached ADU must sit on a permanent concrete slab (unless above a garage) — not on a basement, piers, or a temporary/wheeled base | Affects design and cost |
| Utilities | Must connect to water and sewer, with capacity confirmed by your water provider before a permit. An ADU may not be separately metered from the main home | A utility hookup — tying the ADU into water, sewer, and power — is a real cost and approval step |
| Rental type | Long-term only (30+ days). Kearns prohibits short-term rentals citywide, and a business license is required to rent | No Airbnb-style income |
| Separate sale | An ADU can't be sold or subdivided into its own lot | Affects resale and exit plans |
| Appearance | The home must keep the look of a single-family residence; a detached ADU matches the home's roof pitch and general color, with a separate entrance to the side or rear | Design constraint |
| Permit | A building permit is required before you build or convert; the unit must meet building, fire, and health codes | Unpermitted units are a liability when you rent or sell |
Sources: City of Kearns Zoning Code §19.42.030 and §19.42.310 (kearns.municipalcodeonline.com); Utah Code §10-21-303. Last verified June 2026 — confirm the current Kearns code for your parcel.
One more piece of good news on cost: under Utah law, construction of an internal ADU is not subject to impact fees — the one-time fees a city or district charges a new unit to offset its effect on roads, sewer, and parks. A detached new build may still involve impact fees, utility connection costs, or other charges depending on how the work is classified, so it's worth confirming.
What Utah's 2026 ADU law changes (and what it doesn't)
Kearns is already ahead of the state on this. Utah's 2026 Legislature passed SB 284, which adds a new statute (Utah Code §10-21-304) requiring certain cities to allow a detached ADU as a permitted use in some zones. That statute takes effect October 1, 2026 — so it is not yet in force as of this writing.
Before it, state law only protected internal ADUs statewide; detached units were left entirely to each city. Because Kearns already permits detached ADUs under its own code, the new statute mostly reinforces what Kearns already allows — but you should confirm how the specifics apply to your lot once the law takes effect, especially if your zone has conditions the statute may affect.
How much does an ADU cost in Kearns?
Don't price a Kearns ADU off a single statewide average. Cost depends on the ADU type, existing conditions, utilities, parking, design and engineering, finishes, and permit requirements. The ranges below are estimates for the Salt Lake Valley, not quotes.
| ADU type | Typical all-in estimate | What moves the number |
|---|---|---|
| Basement / internal conversion | ~$50,000–$120,000 | Egress, ceiling height, fire separation, finishes |
| Garage conversion | ~$80,000–$150,000 | Replacement parking, slab/structure condition, utilities |
| Attached addition | ~$150,000–$250,000 | Foundation, design/engineering, utility extension |
| Detached new build | ~$200,000–$400,000+ | New foundation, separate utilities, full structure, finishes |
How we estimate: these are typical Salt Lake Valley planning ranges compiled from recent Utah ADU builder pricing and our own cost guide (updated 2026). They're planning ranges to orient your budget — not a quote for your project. Plan on permit and plan-review fees in the range of roughly $1,000–$8,000+ depending on scope, and a typical timeline of about 6–10 months from design through construction. Your actual numbers depend on your site.
Why a cheap quote can get expensive:
A low bid often assumes the wrong ADU type, skips parking replacement, ignores utility upgrades, or prices finishes before zoning and site feasibility are confirmed. The better question isn't "which builder is cheapest?" — it's "which build path is legally and physically realistic on my lot?"
For a full breakdown by type, size, and finish level, see our Utah ADU cost guide.
What could disqualify or delay your Kearns ADU
An ADU is not automatically a smart project just because Utah has become more ADU-friendly. The right project depends on your lot, the rules, your utilities, your budget, and your use case — and being honest about the dealbreakers up front saves real money. The most common early stoppers in Kearns aren't "bad builders." They're site constraints:
- ✗The property is a townhome, condo, or attached/multifamily unit — Kearns's ADU rules don't apply to those.
- ✗The lot is under 5,000 sq ft, or can't meet parking, setback, or lot-coverage requirements.
- ✗There's no room to add the required off-street parking — one space for an internal/attached ADU, two for a detached one — or a garage conversion removes parking the main home needs.
- ✗A detached unit can't fit within the 5-foot setbacks, the 6-foot separation from the house, or the height limits once the site plan is drawn.
- ✗An HOA restricts detached units. Under Utah law, where an internal ADU wouldn't violate local land-use, building, health, or fire code, an HOA or CC&Rs can't prohibit renting it — but a detached ADU is a separate matter and may still be restricted, so check your CC&Rs.
- ✗Water, sewer, or electrical capacity is limited, which can add significant cost.
- ✗The plan depends on short-term rental income, which Kearns prohibits.
- ✗The budget doesn't match the ADU type you want.
If several of these apply to you, the honest answer may be "not yet" — and the right next step is a feasibility review to find the path that does work, not a contractor sales call.
Kearns ADU feasibility checklist
Before you spend money on plans or collect multiple bids, run through these questions. If several answers are "I don't know," your next step is a feasibility review, not a builder quote.
- Is the property a qualifying single-family home (not a townhome or multifamily unit), on a lot of at least 5,000 sq ft?
- Are you in an HOA? If so, are you considering an internal or a detached unit?
- Which ADU type fits your goal: internal, garage conversion, attached, or detached?
- Is the use family housing, long-term rental, a home office, or guest space?
- Can you provide the required off-street parking (one space for internal/attached, two for detached) — and would a garage conversion remove parking the home needs?
- For a detached unit: can it meet the 5-foot side/rear setbacks, the 6-foot separation from the house, and the height limits, on a slab foundation?
- For an internal unit: do egress, ceiling height, fire separation, and a side/rear entrance need work?
- Are you fine living in the home or the ADU (owner-occupancy is required)?
- Are you assuming short-term rental income? Kearns prohibits it, so that plan won't work.
- Is your budget realistic for the ADU type you want?
How the Kearns ADU process actually works
The realistic order is feasibility first, design second, permit third, builder pricing fourth, and construction after approvals. No one can promise approval or a fixed timeline — but here's what usually has to happen.
| Step | What happens | What can slow it down |
|---|---|---|
| 1. Feasibility screen | Confirm property type, ADU type, parking, setbacks, HOA, utility capacity | Wrong ADU type, no parking room, HOA limits |
| 2. Choose the path | Decide internal, garage, attached, detached, or prefab | Budget mismatch |
| 3. Design & site review | Site plan, floor plan, egress, utilities, drainage, foundation | Needing engineering or a redesign |
| 4. Permit package | Submit required plans and documents; secure approvals and water-provider confirmation | Missing drawings, utility confirmation, code conflicts |
| 5. Builder estimates | Compare bids against the same scope | Quotes that aren't apples-to-apples |
| 6. Build & inspections | Construct under permit and pass inspections | Change orders, utility surprises, inspection corrections |
You don't need a full plan set to start. Knowing your property type, the ADU type you want, your parking situation, your HOA status, and a rough budget is enough to begin a useful feasibility review.
How to compare Kearns ADU builders before you request estimates
Compare builders after you know your likely ADU path — because a detached-cottage builder, a basement remodeler, a garage-conversion contractor, and a prefab supplier are solving different problems, and their quotes aren't interchangeable. When you do compare, hold every bid to the same standard:
- A current Utah contractor license you can confirm through the Utah DOPL license lookup.
- A clear, written scope of work.
- The same ADU type and square footage across bids.
- Utility and site-work assumptions spelled out.
- Permit and design responsibility clearly assigned.
- A written change-order policy and warranty terms.
- Proof of insurance.
- A timeline framed as an estimate, not a guarantee.
Is a Kearns ADU a smart project for you?
It depends on your goal. An ADU can be an excellent move for family housing or long-term rental income — or the wrong move on a lot that can't support it affordably. Match the project to the goal:
Housing a parent or family member
Prioritize accessibility, privacy, safety, and the layout that fits the need. The "best" ADU here may not be the highest-rent one.
Long-term rental income
Use conservative numbers and remember Kearns requires long-term rentals (30+ days) and a business license. We don't promise rent, cash flow, appreciation, or financing approval — those depend on the market and your situation.
Selling later
Owner-occupancy and the no-separate-sale rule shape how the property can be used and sold. An ADU adds living space and flexibility, but it isn't a separately sellable second house.
Frequently asked questions
Your next step
The fastest way to stop guessing is to confirm what your specific Kearns lot can support — the ADU type, the local friction points, and a realistic cost range — before you commission design or collect quotes. Our feasibility check starts there, moves to a cost estimate, and can connect you with local builder or estimate options when you're ready.
Concept image: a realistic single-story detached ADU behind a Salt Lake Valley home. Actual design, cost, and approval depend on your site and current Kearns rules.
Sources
- City of Kearns Zoning Code, Title 19 — §19.42.030 (Accessory Dwelling Units) and §19.42.310 (Short-Term Rentals), as amended 2025
- Utah Code §10-21-303 (internal ADUs; from HB 82, 2021) and §10-21-304 (detached ADUs; SB 284, 2026, effective October 1, 2026)
- Utah Office of Property Rights (Utah Department of Commerce) — ADU guidance on impact fees, HOAs, and tiny homes
- Greater Salt Lake Municipal Services District — City of Kearns community page (incorporation and 2024 city status)
- Utah Division of Professional Licensing (DOPL) — contractor license lookup