Utah ADU Rules by City (2026): Internal, Detached, Owner Occupancy & Permits
Utah does not have one yes-or-no answer for ADUs — it has two layers. State law makes an internal ADU (a unit built inside your existing home, like a basement apartment) a permitted use in most residential zones, and effective October 1, 2026, many cities must also allow a detached ADU (a backyard cottage or garage apartment) on lots of at least 11,000 square feet. But your city still controls parking, owner occupancy, setbacks, rental rules, and fees. This guide is best for Utah homeowners deciding whether an ADU is realistic before they pay for plans; it's not a permit approval, and every project still depends on your lot.
Utah ADU Builders is a Utah-focused ADU planning, feasibility, and builder-matching resource — not a city, government office, law firm, lender, architect, engineer, or licensed contractor. We may earn compensation when homeowners request estimates or are connected with local professionals; that never changes how we explain Utah ADU rules, cost ranges, feasibility factors, or permitting risks. A feasibility review is a planning starting point — not permit approval, legal or engineering advice, financing approval, or a construction quote.
State law checked: October 3, 2026. City rows retain their own verification dates; July rows are historical unless updated separately.
Which layer applies to you? (Start here)
| Your situation | The likely rule | What it means |
|---|---|---|
| Basement or in-home unit (internal ADU) | Allowed statewide as a permitted use in most residential zones — the protection applies to an owner-occupied single-family home, and cities can still require permits, parking, and a rental license | Usually the most straightforward path to check first |
| Backyard cottage or garage apartment (detached ADU) | Required since Oct. 1, 2026 in specified municipalities: first-, second-, third-, or fourth-class cities, plus fifth-class cities of at least 5,000 residents in first-, second-, or third-class counties. Qualifying lots must be at least 11,000 sq ft and contain a single-family dwelling where that dwelling is a permitted use; allowed local development and owner-occupancy rules still apply. | More lot- and city-sensitive; "allowed" is not the same as "unconditional" |
| Not sure your city or lot qualifies | Depends on your exact parcel | A property-level feasibility check answers it before you spend money |
What we verified for this page
- Utah state ADU law — Utah's Office of Property Rights Ombudsman summary, the Utah State Legislature, and Utah Code Title 10, Chapter 21 (municipalities) and Title 17, Chapter 80 (counties), including SB 284 (2026) on detached ADUs.
- Impact-fee treatment for internal ADUs (Utah Code § 11-36a-202).
- City and county ordinances from official sources for Salt Lake City, unincorporated Salt Lake County, Provo, Ogden, Draper, Millcreek, Murray, Lehi, West Jordan, Cottonwood Heights, North Salt Lake, Holladay, and South Salt Lake.
- Cost inputs from 2026 industry cost estimates (shown as planning ranges, not quotes).
- What we did not do: we did not confirm your specific parcel's zoning, utility capacity, or HOA rules. Those require a property-level review. Some city-source rows may predate the October 1, 2026 effective date of S.B. 284 and do not establish current implementation; use them as dated snapshots and confirm the current adopted rule.
Are ADUs legal in Utah? The two-layer rule
Yes — but "legal" depends on the type of ADU and your city. An ADU (accessory dwelling unit) is a smaller, self-contained second home on the same lot as a main house. Utah law guarantees one kind of ADU statewide and, as of 2026, sets a new baseline for another kind — while leaving many practical rules to your city or county.
Layer 1: What state law guarantees
An internal ADU is a unit created inside your existing single-family home — most often a basement apartment or a converted lower level — intended for a long-term rental of 30 or more consecutive days. Under Utah law, an internal ADU is a permitted use in areas zoned primarily for residential use, which means the city can't force it through a discretionary hearing or special approval if it meets the standards. Two things to know: the state protection applies specifically to a detached single-family home the owner occupies as their primary residence, and internal ADU construction is not subject to impact fees — the one-time fees cities charge new construction to fund roads, sewer, parks, and similar infrastructure. (Source: Utah Office of Property Rights Ombudsman; Utah Code § 10-21-303 and § 11-36a-202.)
Layer 2: What your city still controls
State law permits specific local conditions for internal ADUs. A municipality may exclude lots of 6,000 sq ft or less, preserve the home’s single-family appearance, require one extra on-site parking space except where the ordinance already requires four off-street spaces, require garage or carport replacement parking, require a rental permit or license, and prohibit rentals of fewer than 30 consecutive days. A mapped exclusion may cover up to 25% of primarily residential land, subject to the statutory new-construction and final-plat exception. The separate 67% provision applies only where the main campus of a state or private university with at least 10,000 students is located in the city.
A note for county residents
If your home is in an unincorporated area rather than inside city limits, county rules apply instead of a city's. The statewide internal-ADU protections carry over to counties (Utah Code § 17-80-303), but the specific standards — like Salt Lake County's lot-size minimums — differ by county.
What changed in 2026: detached ADUs and the 11,000-square-foot rule
The biggest recent change is for detached ADUs — standalone backyard cottages, garage apartments, or guest houses separate from the main home. For years these were almost entirely up to each city, and many cities made them difficult or impossible. Utah's SB 284 (2026) changed that.
The requirement took effect October 1, 2026. Under §10-21-304, specified municipalities must adopt regulations permitting a detached ADU on a lot of at least 11,000 sq ft that contains a single-family dwelling, where that dwelling is a permitted use. Covered municipalities are first-, second-, third-, or fourth-class cities, plus fifth-class cities of at least 5,000 residents in first-, second-, or third-class counties. Cities may permit detached ADUs on smaller lots as well. (Sources: Utah Code §§10-21-101(25), 10-21-304.)
What SB 284 does not do — and this is where people get tripped up:
- It does not make detached ADUs unconditional. Cities keep control over size, height, setbacks (the minimum distance a structure must sit from your property lines), lot coverage, design compatibility, utilities, and rental duration, and they can cap parking within limits.
- It does not remove owner-occupancy authority. Many cities require the owner to live on the property for a detached ADU too.
- It does not extend the internal-ADU impact-fee exemption to detached ADUs, so a detached unit may be subject to local impact fees, utility-connection fees, or capacity charges.
- It does not erase your HOA. State law limits an HOA's ability to prohibit the rental of a compliant internal ADU, but HOA covenants (the "CC&Rs" recorded against homes in many subdivisions) can still complicate a detached unit — check yours.
The October 1, 2026 effective date has passed. Older city materials may have been superseded or may describe a rule the statute now limits. Compare the current adopted ordinance with §10-21-304; a city’s website-update schedule does not postpone the state requirement. Check development-agreement exceptions and parcel-specific standards before proceeding.
Utah ADU rules by city
Use this table to find your city's rule pattern before you spend on drawings or quotes. It compares whether internal and detached ADUs are allowed, whether owner occupancy is required, whether short-term rentals are allowed in an ADU, and the local rules that most often decide feasibility. Every row was checked against the city's official ADU page or code, and all rows were verified in July 2026; because cities are updating for SB 284 through 2026, confirm your exact parcel before designing.
Launch coverage: high-demand Wasatch Front and selected Utah cities. We add city rows as official sources are verified.
Legend: Internal ADU = unit inside the home. Detached ADU = separate backyard/garage structure. Short-term rental (STR) = nightly/vacation rental (e.g., Airbnb), which is a separate city licensing question. "Not found in source reviewed" = the official page we checked didn't resolve that cell as of July 2026 — verify during a feasibility review.
| City / jurisdiction | Internal ADU | Detached ADU | Owner occupancy required? | Short-term rental in ADU? | Notable local rules |
|---|---|---|---|---|---|
| Salt Lake City | Yes — no size cap | Yes — no conditional-use hurdle | Yes (owner or family member; limited exceptions) | No — city code requires the ADU covenant to state that the ADU and the main home can't be used for short-term rental | One ADU per lot; detached ≤ 1,000 sq ft; 17 ft base height with code-listed taller options; recorded covenant; pre-approved standard plans available (site review still required) |
| Salt Lake County (unincorporated) | Yes — lot ≥ 6,000 sq ft | Yes — lot ≥ 7,000 sq ft (6,000 in PC zone) | Yes — recorded affidavit | Long-term focus; verify STR during feasibility review | Detached ≥ 10 ft from rear line and 6 ft from house; may be separately metered (owner billed); business license required |
| Provo | Yes | Yes — SB 284 expands eligibility beyond the prior ADU overlay (≥ 11,000 sq ft); city notes its rules may change under SB 284 | Yes — owner in main home or ADU | No | High parking requirement (up to ~4 spaces, some tandem allowed); detached needs its own meter; deed restriction recorded; rental license |
| Ogden | Yes | Yes — 300–800 sq ft, ≤ 25% of rear yard | Yes — rent one unit, not both | No | Non-owner unit limited to 2 adults; single-family appearance required; land-use permit then building permit |
| Draper | Yes — lots > 6,000 sq ft (see city's prohibited-area map) | July 2026 city-source snapshot: lots ≥ 12,000 sq ft. The 11,000 sq ft state floor took effect Oct. 1, 2026 for covered municipalities; verify current local standards | Yes | 30+ day rentals only | One ADU only; no internal ADU if a detached ADU exists; extra parking space required; no separate meters |
| Millcreek | Yes — no lot minimum | Yes — lot ≥ 8,000 sq ft, ≤ 1,000 sq ft, rear yard | Yes — year-round | Detached: no. Internal/attached: allowed with a license | Max 2 adults; no separate meters; no ADUs on slopes over 30%; garage conversions must replace covered parking |
| Murray | Yes | Yes — separate attached/detached standards | Yes | No (nothing under 30 days) | One ADU per lot; licensed contractor/building permit; business license for long-term rental |
| Lehi | Yes — no size cap | Yes — minimum 11,000 sq ft; Development Code §26.040 amended July 14, 2026 | Yes — recorded declaration | No (under 30 days not allowed) | One ADU per lot; finished dwelling area smaller than the primary home; at least 6 ft from the home; verify parking and height against the current code |
| West Jordan | Yes | Yes — external units in specified zones; in PC/LSFR/VLSFR zones only on platted lots 10,000 sq ft+ | Yes-conditional: if the owner occupies the home or the ADU, the other unit may be rented; if the owner occupies neither, they may rent the home and ADU as one unit or rent only one — not both separately | No (30+ day rentals required) | One ADU only (not both internal and external); detached footprint smaller than the house; recorded covenant; business license to rent |
| Cottonwood Heights | Yes | Historically a conditional use — updating for SB 284 | Yes | No | License/permit required; confirm current detached rule during the 2026 transition |
| North Salt Lake | Yes | Yes — including above-garage and detached | Yes | Possible only with a separate short-term-rental land-use permit + business license (plus the ADU land-use permit); primary must be owner-occupied; 30-day maximum stays | Rules updated April 2025; no fee for the land-use permit; extra parking for 2+ bedroom ADUs |
| Holladay | Yes | July 2026 city-source snapshot: minimum is a half-acre (21,780 sq ft) or twice the zone minimum. The 11,000 sq ft state floor took effect Oct. 1, 2026 for covered municipalities; verify current local standards | Yes — owner must live onsite | No — ADUs must be rented for a minimum of 30 consecutive days | No separate meters; not allowed on a property with a failing septic tank; dark-sky lighting and larger setbacks for external units |
| South Salt Lake | Yes — no size cap | Yes (external) — up to two ADUs total (one internal + one external), in R1/RM zones | Yes — owner or an immediate family member | No — not permitted in single-family zones | Lot ≥ 6,000 sq ft; external unit ≤ 2 bedrooms; ADU ≤ 50% of rear yard; at least one on-site space; no separate meters |
Don’t see your city, or see “not found in source reviewed”? The detached-ADU requirement has applied in specified municipalities since October 1, 2026. Your zone, lot, existing dwelling, setbacks, occupancy, utilities, parking, permits, and private restrictions still require an address-specific check.
Official sources for each row (for your own verification):
Salt Lake City ADU handbook and City Code 21A.40.200; Salt Lake County Office of Regional Development; Provo City Code 14.30 and Provo's SB 284 page; Ogden City Code 15-13-39; Draper City ADU page; Millcreek City ADU page; Murray City ADU page; Lehi City Code Ch. 26 and the Engage Lehi detached-ADU amendment page; West Jordan City Code 13-5B-8 and the West Jordan ADU application; Cottonwood Heights ADU page; North Salt Lake City Code 10-19-17 and its short-term-rental page; Holladay ADU/short-term-rental page; South Salt Lake ADU page and Ordinance 2024-01. Full links are at the end of this page.
Internal vs. detached: which path is realistic for you?
The single most useful question isn't "does Utah allow ADUs?" — it's "which type of ADU fits my home, my city, and my budget?" Here's the honest comparison.
| Internal ADU (basement / in-home) | Detached ADU (backyard cottage / garage apartment) | |
|---|---|---|
| Statewide protection | Strong — permitted use in most residential zones for an owner-occupied home | New floor under SB 284 (specified municipalities, lots 11,000 sq ft+), effective Oct. 1, 2026 |
| Impact fees | Internal-ADU construction within an existing primary dwelling is exempt under §11-36a-202(2)(a)(vi) | Not covered by that specific exemption — may apply |
| HOA reach | HOA can't prohibit renting a compliant internal ADU | HOA covenants may still restrict a detached unit |
| Typical cost | Lower — uses existing structure | Higher — new foundation, walls, roof, utilities |
| Most common blockers | Owner occupancy, parking, egress/ceiling height, garage-parking replacement | Lot size, setbacks, utility capacity, HOA, owner occupancy |
| Best when | You have usable interior space and want the cheaper path | You have a larger lot and want more privacy or a purpose-built unit |
A necessary reality check: an ADU is not automatically a smart project just because Utah has become more ADU-friendly. The right project depends on your lot, your city, your utilities, your budget, and how you plan to use it. A feasibility review exists to catch the dealbreakers — parking, setbacks, utilities, HOA, owner occupancy — before you pay for design work, not after.
If your goal is…
- Housing for a parent or adult child: an internal ADU or a modest detached unit is often the fastest, lowest-risk path. Family use may change whether a rental license is required, but many cities still require an ADU permit or land-use approval for a separate dwelling unit even when rent isn't the goal — so confirm your city's process.
- Long-term rental income: check owner occupancy first. Many Utah cities require the owner to live on the property, which rules out buying a home purely to rent both units.
- The cheapest way in: an internal conversion of existing space is usually the lowest cost — but only if parking, egress, and utility capacity work.
- A separate, purpose-built unit: detached is your path, and SB 284 likely helps if your lot is 11,000 sq ft or larger — but budget for possible impact fees, utilities, and stricter design rules.
The rules that most often decide whether your ADU works
A legal "yes" is only the first filter. In practice, a handful of local rules decide whether a real Utah property can move forward. These are the factors worth checking before anything else.
| Rule | Why it matters | What to check |
|---|---|---|
| ADU type | Internal, attached, detached, and garage conversions trigger different rules | Decide the type first, then the city |
| Zoning & lot size | The detached state mandate covers qualifying 11,000 sq ft+ lots in specified municipalities; cities may allow smaller lots. Cities may bar internal ADUs on lots of 6,000 sq ft or less. | Confirm your zone and lot area at the parcel level |
| Parking | Parking can kill an otherwise-legal ADU | Count required stalls, tandem rules, and garage-replacement rules |
| Owner occupancy | Many cities require the owner to live on-site | Rental-only investment plans may fail |
| Short-term rental | Airbnb-style use is often prohibited or limited to 30+ days | Separate long-term feasibility from STR assumptions |
| Setbacks, height, lot coverage | Especially decisive for detached units | A big lot can still fail on buildable area |
| Utilities & septic | Capacity and connection rules add cost or block approval | Verify sewer/water/electrical capacity early; properties on septic may be excluded |
| HOA / CC&Rs | Private covenants can restrict detached units even where the city allows them | Read your CC&Rs before designing |
| Permits & licenses | ADUs are never 'build without permits' projects | Expect a building permit and, for rentals, a business/rental license |
How do city rules change what an ADU costs?
City rules don't just decide whether you can build — they move the price. Detached units can carry impact and utility-connection fees that internal units don't, parking and setback rules can force a smaller or more complex design, and owner-occupancy rules can affect how you finance the project. Treat any dollar figure as a planning estimate, not a quote.
As a rough 2026 planning range across Utah, design fees commonly run about $5,000–$15,000, permit fees about $1,000–$5,000, and construction roughly $80,000–$250,000 — with basement and garage conversions on the low end and new detached units on the high end. What pushes cost up: difficult site conditions (rocky soil, steep grade, limited access), custom design, high-end finishes, and separate utility meters or capacity upgrades. What keeps cost down: using an existing footprint like a basement or garage, staying within your lot's utility capacity, and prefab or modular construction where local codes allow. (Estimates reflect 2026 Utah industry figures; confirm against local bids.)
For a full breakdown by ADU type and city, see our Utah ADU cost guide.
How to tell if your property is likely a fit
A city table tells you the rule pattern; feasibility depends on your address. Before you pay for plans, run this quick scorecard. If you're landing in the "yellow" or "red" columns on the factors that matter to you, that's a signal to get a property-level review — not to give up.
| Factor | 🟢 Green flag | 🟡 Yellow flag | 🔴 Red flag |
|---|---|---|---|
| ADU type | Internal unit in existing footprint | Garage conversion or addition | Detached unit with tight setbacks/utilities |
| Lot size | Clearly above your city's threshold | Near the threshold | Below the threshold |
| Zoning | Clearly in an ADU-permitted zone | Overlay/restricted area unclear | Zone appears excluded |
| Parking | Existing off-street capacity | Needs reconfiguration | Can't meet the city requirement |
| Owner occupancy | Owner will live on-site | Trust/LLC or temporary-absence questions | Investor rental where the city requires owner occupancy |
| Rental plan | 30+ day rental or family use | Medium-term rental | Short-term/nightly rental assumption |
| Utilities | Existing capacity likely | Upgrades possible | Septic or capacity/easement problem |
| HOA | No HOA, or ADU-friendly | Unclear CC&Rs | Likely HOA conflict |
| Budget | Matches the ADU type | Needs financing | No realistic path yet |
Most common dealbreaker by type: Internal — owner occupancy, parking, and egress/ceiling height. Detached — lot size, setbacks, utility capacity, and HOA covenants. Garage conversion — replacing the parking you remove, plus bringing the space up to building code.
What to do after you find your city
Don't start with drawings. Start with feasibility, then a rough cost path, then a build decision. A sensible order looks like this:
- 1Find your city's row above and note the rule pattern.
- 2Pick your likely ADU type — internal, garage conversion, attached, or detached.
- 3Check the deciders — lot size, zoning, parking, owner occupancy, rental plan, utilities, and HOA. See our Utah ADU permits guide for the permit process.
- 4Run a feasibility and cost check for your exact parcel.
- 5Only then request detailed estimates or design work.
For homeowners whose city and lot appear to support a detached or prefab-style unit, some pre-approved and modular plan paths can save time — for example, Salt Lake City's building department maintains a library of pre-approved ADU standard plans, which currently includes plans from several firms, among them our partner Nest Tiny Homes. A partnership doesn't mean city endorsement, plan approval for your parcel, guaranteed cost, or guaranteed builder availability — and even with a pre-approved plan, a site review, permits, and fees still apply. Utah ADU Builders can help you compare site-built, modular, and prefab ADU paths once a feasibility check confirms your parcel.
Related guides
Frequently asked questions
Sources & how we verified this
State law and definitions:
- Utah Office of Property Rights Ombudsman — Accessory Dwelling Units: commerce.utah.gov
- Utah State Legislature — SB 284 (2026), Local Land Use Modifications: le.utah.gov
- Utah Code (Title 10, Ch. 21; Title 17, Ch. 80; § 11-36a-202): le.utah.gov
City and county ADU pages:
- Salt Lake City ADU standard plans & handbook: slc.gov
- Salt Lake City Code 21A.40.200: amlegal.com
- Salt Lake County (Office of Regional Development): saltlakecounty.gov
- Provo City Code 14.30 and SB 284 page: provo.municipal.codes and provo.gov
- Ogden City Code 15-13-39: amlegal.com
- Draper City ADU page: draperutah.gov
- Millcreek ADU page: millcreekut.gov
- Murray City ADU page: murray.utah.gov
- Lehi City Code Ch. 26 and Engage Lehi (detached ADU update): engagelehi.org
- West Jordan City Code 13-5B-8 and ADU application: amlegal.com
- Cottonwood Heights ADU page: cottonwoodheights.utah.gov
- North Salt Lake ADU page and short-term rental page: nslcity.org
- Holladay ADU / short-term rental page: holladayut.gov
- South Salt Lake ADU page: sslc.gov
Rules change, especially through 2026 as cities implement SB 284. We re-check these sources on a regular schedule, but a page you read here should never replace a property-specific review before you pay for plans or sign a construction agreement.