Law · Tracker · Reference
Utah SB284 Detached ADU Tracker
By the Utah ADU Builders Research Team
Page updated: . State law checked: . City records: Provo and West Jordan sources checked ; Lehi published code checked . City adoption status is not comprehensively recertified.
Editorial note: This research page carries no lead form, affiliate link, paid placement, or builder referral. It exists to state the law accurately.
State law status — October 3, 2026
Utah Code §10-21-304 took effect on October 1, 2026. Its detached-ADU requirement applies to specified municipalities and to lots or parcels of at least 11,000 square feet that contain a single-family dwelling where that dwelling is a permitted use. Cities may allow detached ADUs on smaller lots. The state requirement does not approve an individual property or establish that a city’s published application guidance is current.
We built this page by reading the enrolled bill against the codified statute and checking official city sources one by one. Every figure, date, and rule below is tied to a primary source you can open yourself.
What Utah SB284 requires: the bottom line
Since October 1, 2026, covered Utah cities have been subject to §10-21-304’s requirement to permit detached ADUs on qualifying single-family lots of at least 11,000 square feet and its prohibition on requiring a conditional-use permit for a detached ADU in a primarily residential zone.
Governor Spencer Cox signed S.B. 284 on March 18, 2026. Most of its provisions took effect May 6, 2026; the detached-ADU section took effect October 1, 2026.
This land-use standard does not predict the value an ADU adds to a property. For the separate appraisal comparisons, see ADU property value evidence.
Here is the law at a glance.
| Item | What the law says | Primary source |
|---|---|---|
| Statute | Utah Code § 10-21-304, “Detached accessory dwelling units” | Enrolled S.B. 284 (2026) |
| Bill | S.B. 284, “Local Land and Water Modifications,” 2026 General Session | Utah Legislature |
| Sponsors | Sen. Lincoln Fillmore (chief); Rep. Jill Koford (House) | Enrolled S.B. 284 |
| Signed into law | March 18, 2026, by Gov. Spencer Cox | Governor’s Office |
| Detached-ADU section effective date | October 1, 2026 | § 10-21-304 (Effective 10/01/26) |
| Statewide lot floor | 11,000 sq ft or larger, with a single-family dwelling, where that dwelling is a permitted use | § 10-21-304(1)(a) |
| Smaller lots | Cities — may — permit detached ADUs on lots under 11,000 sq ft | § 10-21-304(1)(b) |
| Unit type covered | Detached (external) ADUs only — not internal/basement ADUs | § 10-21-101(9); internal ADUs at § 10-21-303 |
| Who is bound | “Specified municipalities” (cities), not counties | § 10-21-304(1)(a); definition at § 10-21-101(25) |
Sources: Enrolled S.B. 284 (2026); Utah Code §\u00a010-21-101 and §\u00a010-21-304; Utah Governor’s Office. Verified October 3, 2026.
What every covered city must do, may not do, and may still do
This is the part most summaries skip. Utah Code § 10-21-304 is built as a three-part deal: a short list of things a covered city must allow, a short list of things it may not require, and a longer list of local controls it may keep. Understanding those three buckets is the difference between “detached ADUs are legal everywhere now” (wrong) and knowing exactly what a city can and cannot do to your project.
We read § 10-21-304 in full and sorted every operative clause into the three buckets. The subsection citations are exact.
| Requirement | Subsection |
|---|---|
| Adopt a land-use regulation permitting a detached ADU on any lot or parcel that is 11,000 sq ft or larger and contains a single-family dwelling, if the single-family dwelling is a permitted use there | § 10-21-304(1)(a) |
| Require detached ADUs to comply with all applicable building, health, and fire codes | § 10-21-304(2)(a) |
| Provide a process for the owner of a legally constructed accessory structure to convert it into a detached ADU (subject to setback rules and building/health/fire codes) | § 10-21-304(2)(b) |
Source: Utah Code §\u00a010-21-304. Verified October 3, 2026.
| Prohibition on the city | Subsection |
|---|---|
| Require a conditional use permit for a detached ADU that sits in a primarily residential zone | § 10-21-304(3)(a) |
| Require more than two on-site parking spaces for a detached ADU that is 650 sq ft or larger | § 10-21-304(3)(b) |
| Require more than one on-site parking space for a detached ADU smaller than 650 sq ft | § 10-21-304(3)(c) |
| Impose design standards that conflict with Utah Code § 10-20-618 (limits on regulating building design elements) | § 10-21-304(3)(d) |
Source: Utah Code §\u00a010-21-304. Verified October 3, 2026.
| Local control the city keeps | Subsection |
|---|---|
| Apply rules on structure size, dimension, height, and maximum lot coverage | § 10-21-304(4)(a)(i) |
| Apply setback rules (which may weigh proximity to property lines and other structures, easements, window orientation, and massing) | § 10-21-304(4)(a)(ii) |
| Require the detached ADU to be designed consistent with the single-family dwelling | § 10-21-304(4)(a)(iii) |
| Prohibit a detached ADU that is larger than the single-family dwelling on the same lot | § 10-21-304(4)(b)(i) |
| Prohibit a detached ADU inside a public utility easement or other recorded easement | § 10-21-304(4)(b)(ii) |
| Prohibit a detached ADU in the front-yard area of a lot | § 10-21-304(4)(b)(iii) |
| Prohibit renting a detached ADU for fewer than 90 consecutive days (i.e., restrict short-term rentals) | § 10-21-304(4)(b)(iv) |
| Require the owner to live in either the detached single-family dwelling or the detached ADU on the lot | § 10-21-304(4)(c) |
| Require replacement on-site parking when a detached garage is converted into a detached ADU | § 10-21-304(4)(d) |
| Prohibit more than one ADU on a lot or parcel | § 10-21-304(4)(e) |
| Prohibit a detached ADU where a required utility service (sewer, culinary water, electrical, storm water) is not adequately available or lacks sufficient capacity | § 10-21-304(4)(f) |
Sources: Enrolled S.B. 284 (2026), Utah Code §\u00a010-21-304. Verified October 3, 2026.
Two more limits round out the section. Section 10-21-304(5) says the statute does not override (a) local rules for detached accessory buildings that are not dwelling units, (b) restrictions on detached ADUs written into a development agreement a city signed on or before May 6, 2026, or (c) any other detached-ADU regulation or administrative action that is not otherwise prohibited by law. So a pre-existing development agreement can still control.
Read together, the three tables tell the real story. A covered city cannot make you get a conditional use permit in a residential zone, cannot pile on parking beyond the caps, and cannot simply say no on a qualifying 11,000-square-foot lot. But it can still shape height, setbacks, size, design, short-term-rental use, owner occupancy, and utility adequacy. “Allowed” is not the same as “unregulated.” official local frost-depth criteria
Is the SB284 detached ADU minimum lot size 10,000 or 11,000 square feet?
The enacted statewide floor is 11,000 square feet. You will also see 10,000 — and there is a legitimate reason, because 10,000 is a real number in Utah ADU practice. It is just not the number the state floor is set at. If you are citing the statewide threshold, cite 11,000 and cite § 10-21-304(1)(a).
Here is where each number actually comes from.
| The figure | Where it appears | What it actually is |
|---|---|---|
| 11,000 sq ft | Utah Code § 10-21-304(1)(a); enrolled S.B. 284 | The enacted statewide floor every covered city must honor |
| 10,000 sq ft (a local rule) | West Jordan’s adopted external-ADU rules and its 2026 ADU application | A lawful local floor set below the state floor — expressly allowed by § 10-21-304(1)(b), which lets a city permit detached ADUs on lots under 11,000 sq ft |
| 10,000 sq ft (in write-ups) | Some industry and early-summary write-ups of the bill | Not the enacted statewide floor; a figure that circulated around the bill and around local ordinances |
Sources: Utah Code §\u00a010-21-304(1)(a)–(b); enrolled S.B. 284; West Jordan City ADU application and City Code §\u00a013-5B-8. West Jordan city-source snapshot: July 1, 2026; state-law check: October 3, 2026.
Two things are true at once. First, 11,000 is the floor the state imposes. Second, a city may go lower. Section 10-21-304(1)(b) says nothing stops a municipality from permitting detached ADUs on lots smaller than 11,000 square feet — so a city with a 10,000-square-foot local threshold (West Jordan is a real, adopted example) is fully consistent with the law. The city example is dated to the source review shown below; check current local rules.
There is also a legislative-origin footnote worth getting right. The detached-ADU section did not start inside SB284. It began as a Land Use Task Force provision in a separate 2026 bill, H.B. 477, “Land Use Regulation Revisions,” whose introduced text proposed enacting the very same Utah Code § 10-21-304. According to the Utah Land Use Institute, H.B. 477’s provisions were amended into SB284 late in the session because SB284 was further along procedurally. The enacted floor is 11,000 square feet in either bill’s lineage.
Which Utah cities does SB284’s detached ADU rule apply to?
SB284’s detached-ADU mandate applies to “specified municipalities” — a defined term — and it applies to cities, not to counties or unincorporated land. If you own land in an unincorporated county area, § 10-21-304 is not your rule.
Utah Code § 10-21-101(25) defines a specified municipality as:
- a city of the first, second, third, or fourth class; or
- a city of the fifth class with a population of 5,000 or more, if that city is located within a county of the first, second, or third class.
In plain terms this reaches essentially every Utah city of roughly 10,000 residents or more (first through fourth class), plus smaller fifth-class cities of 5,000 or more that sit in the state’s larger counties. Which specific cities land inside the definition turns on each city’s legal class and population and on its county’s class — not on any single population number.
How many cities is that? Utah has not published an official SB284 coverage roster. The closest practical list is the state’s Moderate Income Housing (MIH) reporting roster, maintained by the Utah Housing and Community Development office under the same Title 10, Chapter 21. Its 2025 roster names 86 cities (and 9 counties). Treat that roster as a sense of scale and a starting point, not as a § 10-21-304 coverage list: the statutory definition in § 10-21-101(25) is what actually decides which cities are bound.
Counties are not covered by § 10-21-304. The detached-ADU mandate lives in the municipal chapter of the code. SB284’s parallel county provisions address other topics, not a county detached-ADU requirement.
Towns and the smallest cities may fall outside the definition. A fifth-class city under 5,000 residents, or one outside a first-, second-, or third-class county, is not a “specified municipality” for this section.
What SB284 does not change
SB284 did not make every Utah lot buildable, and it did not touch internal or basement apartments. It also did not suspend building, health, fire, setback, or utility rules.
- It does not cover internal or basement ADUs. Section 10-21-304 is about detached units. Internal accessory dwelling units are governed separately under Utah Code § 10-21-303.
- It does not make every lot eligible. The mandate applies to qualifying lots of 11,000 square feet or more that already contain a single-family dwelling, where single-family use is permitted.
- It does not waive codes or permits. Detached ADUs must still meet building, health, and fire codes (§ 10-21-304(2)(a)), and a project still runs through normal permitting, setback, and utility-capacity checks.
- It does not erase pre-existing agreements. Restrictions on detached ADUs in a development agreement a city signed on or before May 6, 2026 still stand (§ 10-21-304(5)(b)).
| Common claim | What the primary source says | Source |
|---|---|---|
| “SB284 legalizes basement/internal ADUs statewide” | It covers detached (external) ADUs only; internal ADUs are a separate section | § 10-21-304; § 10-21-303 |
| “The statewide lot floor is 10,000 sq ft” | The enacted floor is 11,000 sq ft; a city may allow smaller lots but is not required to | § 10-21-304(1)(a)–(b) |
| “Every Utah city — or every city over 5,000 — must comply” | Only “specified municipalities” (a city-class and county-class test) are bound; counties are not | § 10-21-101(25); § 10-21-304(1)(a) |
| “Cities can no longer require owner occupancy” | A city may require the owner to live in either the home or the ADU | § 10-21-304(4)(c) |
| “Cities can no longer restrict short-term rentals of ADUs” | A city may bar renting a detached ADU for fewer than 90 consecutive days | § 10-21-304(4)(b)(iv) |
| “Detached ADUs are now allowed on any lot” | Only qualifying lots (11,000+ sq ft with a single-family dwelling, where single-family use is permitted); codes, permits, and utility capacity still apply | § 10-21-304(1)(a), (2) |
Source: Enrolled S.B. 284 (2026), Utah Code §\u00a010-21-304, §\u00a010-21-101, §\u00a010-21-303. Verified October 3, 2026.
Utah SB284 detached ADU tracker: dated city-source records
The state detached-ADU requirement took effect on October 1, 2026. The city table below is a partial source snapshot: Provo and West Jordan sources were checked July 1, 2026, and Lehi’s published code was checked October 3, 2026. It has not been recertified as a current adoption roster. The table does not establish present city compliance or eligibility for a particular property.
| City | Official source | Detached-ADU lot threshold in cited source | Relationship to 11,000 sq ft state floor | Last verified |
|---|---|---|---|---|
| Provo | Provo SB284 public notice + interactive eligibility map; city ADU program page | Applies SB284’s criteria and maps eligible parcels (single-family home required; detached/external only) | Implementing the state rule; eligibility shown parcel-by-parcel on the city map | July 1, 2026 |
| West Jordan | West Jordan ADU application (2026) + City Code §\u00a013-5B-8 (Ord. 21-18, amended Ord. 22-21); Feb. 24, 2026 Committee-of-the-Whole ADU review | External ADUs on platted lots 10,000 sq ft and larger, in R-1, RR, RE, PC, LSFR, and VLSFR zones | Below state floor — more permissive Allowed by §\u00a010-21-304(1)(b); rules are zone-limited and predate SB284, so conforming updates may still follow | July 1, 2026 |
| Lehi | Current published Development Code Chapter 26, §26.040; amendment history includes July 14, 2026 | 11,000 sq ft minimum for a detached ADU | Matches the state’s lot-size floor; this threshold check does not certify that every local provision conforms to state law or that a particular parcel qualifies | October 3, 2026 |
Sources: Provo City SB284 notice/map and Provo ADU program page; West Jordan ADU application and City Code §\u00a013-5B-8; Lehi Development Code Chapter 26 and Engage Lehi — Detached ADU Development Code Amendment. State law checked October 3, 2026; Provo and West Jordan retain July 1 city snapshots; Lehi code checked October 3, 2026.
Machine-readable versions: latest CSV (stable URL); October 3, 2026 edition
How to read this table. Provo and West Jordan reflect sources checked July 1, 2026; Lehi’s published code was checked October 3, 2026. These dated records may have been superseded. A city’s absence from this table does not establish that it failed to act. For current rules, check the adopted code and any uncodified ordinance with that city. A threshold check does not certify every provision’s conformity with §10-21-304 or approve a particular parcel.
Provo, in detail
Provo is the clearest verified example. Its public notice explains that SB284 requires cities of 5,000 or more to allow detached ADUs, states that eligibility requires an existing single-family home on the lot, and is explicit that the law reaches detached/external units only — not internal or basement units. Provo published an interactive map that shades the parcels meeting SB284’s detached-ADU criteria alongside its older ADU overlay, and its ADU program page notes that some details may still change as it finalizes implementation.
The broader rollout
Future city-record updates will identify the adopted ordinance or other official source, its effective date, the date it was checked, and whether it supersedes an earlier snapshot. A proposal, hearing notice or eligibility map will remain labeled as such; it will not be treated as proof of final adoption.
How we built and verified this tracker
We wanted a page a reporter, planner, attorney, or homeowner could rely on without re-reading the statute themselves — so we worked from primary sources and dated everything. Here is exactly what we did.
- We worked from two primary legal sources. The enrolled copy of S.B. 284 (the version that passed both chambers and was signed) and Utah Code § 10-21-304 as enacted by it. We used the enrolled bill to confirm the enactment language and effective dates, matched every claim in the tables above to a specific subsection of § 10-21-304, and took the definitions from § 10-21-101.
- We confirmed the effective dates from the bill itself. The bill’s “Utah Code Sections Affected” list shows § 10-21-304 enacted with an effective date of October 1, 2026, while most other sections (including the § 10-21-101 definitions) took effect May 6, 2026.
- We confirmed the signing. The Utah Governor’s Office and the Legislature’s own bill record show Gov. Cox signed S.B. 284 on March 18, 2026.
- We traced the legislative origin. We confirmed from its introduced text that H.B. 477, “Land Use Regulation Revisions,” proposed the same § 10-21-304, and relied on the Utah Land Use Institute for the account that those provisions were amended into SB284.
- We checked city sources against the statute. For the implementation table, we used official city materials only — a city notice, an adopted ordinance or code section, a staff report, an official map, or a city public-engagement page.
- We labeled what we could not fully verify. Where a widely repeated detail was not confirmable against a primary record, we left it out rather than state it as fact.
What counts as a source here: the Utah Code, the Utah Legislature’s bill versions and status page, the Governor’s Office, and official city or county publications. What does not: builder blogs, real-estate marketing pages, forum posts, or third-party summaries. Those are useful for spotting questions, not for stating the law.
Limitations — what this tracker does and does not show
This page is strongest on the statewide law and its dates, and still growing on city-by-city detail. We would rather say that plainly than overstate our coverage.
- Checks have separate dates. State-law content was checked October 3, 2026. Each city row has its own check date; a July 2026 row is historical and should not be treated as a current October 2026 ordinance review.
- City coverage is partial. This release verifies official sources for Provo, West Jordan, and Lehi. It does not yet claim a complete statewide, city-by-city implementation count.
- Older rows need current local confirmation. Historical July 2026 city materials may have been superseded. The state requirement is already in effect; compare the current adopted code with §10-21-304 before making a property decision.
- It is educational, not legal advice. Land-use outcomes turn on your specific lot, zone, city ordinance, utilities, and site conditions. For a decision on a particular property, confirm current local code with the city and, where stakes are high, a qualified Utah land-use attorney or your city planning department.
- “Covered” is defined by statute, not by our list. Whether a given city is a “specified municipality” depends on its current class and its county’s class under Utah law, not on whether it appears in our snapshot.
Change log
- October 3, 2026 — source review. Rechecked §§10-21-304 and 10-21-101, confirmed that the detached-ADU section is operative, replaced pre-effective-date wording, and labeled the July city table as a historical snapshot. No individual city ordinance or parcel eligibility was recertified in this update.
- July 1, 2026 — first release. Verified Utah Code § 10-21-304 and the § 10-21-101(25) “specified municipality” definition against the enrolled S.B. 284; confirmed the October 1, 2026 effective date and the March 18, 2026 signing; captured and verified official ADU sources for Provo, West Jordan, and Lehi; documented the § 10-21-304 legislative origin (H.B. 477 → S.B. 284) and the 10,000-vs-11,000 distinction.
State-law and city-source check dates are shown separately above. Each city record retains its own source-check date.
How to cite this page
Suggested citation:
Utah ADU Builders Research Team. “Utah SB284 Detached ADU Tracker.” Utah ADU Builders, state law checked October 3, 2026; city records dated individually. https://utahadubuilders.com/research/utah-sb284-detached-adu-tracker
The underlying legal facts come from the primary sources listed below; where you can, cite Utah Code § 10-21-304 and the enrolled bill directly.
Frequently asked questions
Is Utah SB284 in effect?
Yes. Utah Code §10-21-304, the detached-ADU section enacted by SB284, took effect on October 1, 2026. The bill's general effective date was May 6, 2026. The detached-ADU section applies to specified municipalities and qualifying lots; permits, applicable codes and lawful local development standards still apply.
Is the SB284 detached ADU lot threshold 10,000 or 11,000 square feet?
The enacted statewide floor is 11,000 square feet (Utah Code § 10-21-304(1)(a)). A 10,000-square-foot figure appears in some summaries and is also a legitimate local threshold — West Jordan, for example, permits external ADUs on lots of 10,000 square feet and larger — because § 10-21-304(1)(b) lets a city permit detached ADUs on lots smaller than 11,000 square feet. For the statewide requirement, use 11,000.
Where did Utah Code § 10-21-304 come from?
It originated as a Land Use Task Force provision. H.B. 477, “Land Use Regulation Revisions,” proposed enacting § 10-21-304 in the 2026 session; per the Utah Land Use Institute, those provisions were amended into S.B. 284, which was further along procedurally and became the vehicle that passed. The enacted floor is 11,000 square feet.
Does SB284 apply to basement or internal ADUs?
No. SB284’s § 10-21-304 covers detached (external) ADUs only. Internal accessory dwelling units are addressed separately in Utah Code § 10-21-303. Provo’s official SB284 notice makes the same distinction.
Does SB284 mean every Utah homeowner can now build a detached ADU?
No. The rule applies to “specified municipalities” and to qualifying lots — generally 11,000 square feet or larger with a single-family dwelling, where single-family use is permitted. Projects still depend on zoning, local development standards, utility capacity, building permits, and health and fire codes.
Can a Utah city still require owner occupancy for a detached ADU?
Yes. Under § 10-21-304(4)(c), a city may require the owner to live in either the detached single-family dwelling or the detached ADU on the same lot.
Can a city require parking for a detached ADU?
Yes, but it is capped. A city may require no more than two on-site parking spaces for a detached ADU of 650 square feet or larger, and no more than one for a unit under 650 square feet (§ 10-21-304(3)(b)–(c)).
Can a detached ADU be used as a short-term rental?
A city may prohibit it. Section 10-21-304(4)(b)(iv) lets a municipality bar a detached ADU from being rented for fewer than 90 consecutive days. Whether that restriction applies depends on local code, so check your city.
Do counties have to allow detached ADUs under SB284?
No. The § 10-21-304 mandate applies to cities (“specified municipalities”), not counties. Unincorporated county land follows separate county land-use rules.
Which cities count as a “specified municipality”?
Cities of the first through fourth class, plus fifth-class cities of 5,000 or more residents located in a first-, second-, or third-class county (Utah Code § 10-21-101(25)). In practice that reaches most Utah cities of roughly 10,000 residents or more, plus some smaller ones in larger counties.
Primary sources
- Enrolled S.B. 284 (2026 General Session), “Local Land and Water Modifications” — the final signed text, including Utah Code §§ 10-21-101 and 10-21-304: le.utah.gov/Session/2026/bills/enrolled/SB0284.pdf
- S.B. 284 bill page and version history (Utah Legislature): le.utah.gov/~2026/bills/static/SB0284.html
- Utah Code § 10-21-304, “Detached accessory dwelling units”: le.utah.gov/xcode/Title10/Chapter21/10-21-S304.html
- Utah Code § 10-21-101, definitions (including “specified municipality” and “detached accessory dwelling unit”): le.utah.gov/xcode/Title10/Chapter21/10-21-S101.html
- Utah Code § 10-21-303, internal accessory dwelling units: le.utah.gov/xcode/Title10/Chapter21/10-21-S303.html
- H.B. 477 (2026), “Land Use Regulation Revisions” — bill page and introduced text proposing § 10-21-304: le.utah.gov/~2026/bills/static/HB0477.html
- Utah Land Use Institute — land-use legislative commentary noting H.B. 477’s provisions were amended into S.B. 284: utahlanduse.org/blog/
- Governor’s Office, bills signed March 18, 2026: governor.utah.gov/uncategorized/gov-cox-signs-72-bills-in-the-2026-general-legislative-session/
- Utah Housing & Community Development — Moderate Income Housing reporting roster and criteria: jobs.utah.gov/housing/affordable/moderate/reporting/
- Provo City — Accessory Dwelling Unit (ADU) Eligibility Expansion (SB284 notice + map): provo.gov/CivicAlerts.aspx?AID=303
- Provo City — Accessory Dwelling Units program page: provo.gov/1367/Accessory-Dwelling-Units
- West Jordan City — Accessory Dwelling Unit application (2026): westjordan.utah.gov — ADU Application PDF
- West Jordan City Code § 13-5B-8, Accessory Dwelling Units: codelibrary.amlegal.com — West Jordan §\u00a013-5B-8
- Lehi City — Detached ADU Development Code Amendment (Engage Lehi): engagelehi.org — Detached ADU Development Code Amendment
This resource is educational and is not legal advice. Verify current statute and local ordinances before making property decisions.