Utah SB 284: What the New Detached ADU Law Means for Your Property
Utah SB 284 is the 2026 state law that requires larger Utah cities to allow a detached ADU — a standalone backyard cottage, casita, or converted detached garage — on qualifying lots of 11,000 square feet or larger that already have a single-family home. The detached-ADU rule takes effect October 1, 2026. It's most useful for owners of larger lots in covered cities. It won't help every property, and your city and your HOA can still attach real conditions.
An ADU (accessory dwelling unit) is a second, smaller home on the same lot as a main house — a basement apartment, a room above a garage, or a separate cottage in the backyard.
Bottom line: SB 284 opens the door for detached ADUs — it does not hand you approval
Starting October 1, 2026, "specified municipalities" (a defined group of larger Utah cities) must allow a detached ADU on any lot that is 11,000 sq ft or larger, already contains a single-family dwelling, and is in a zone where single-family homes are already allowed. On those lots, a city cannot force you through a discretionary "conditional use" hearing just to have a detached ADU, and it cannot pile on excessive parking requirements.
But this is a floor, not a green light. Your city can still enforce setbacks, height and size limits, design rules, owner-occupancy, a 90-day minimum rental term, a one-ADU-per-lot cap, and a hard "no" if your utilities can't handle the extra unit. And if you're in an HOA, the HOA can still prohibit a detached ADU outright.
SB 284 at a glance
| Question | Short answer |
|---|---|
| What does SB 284 actually change for homeowners? | It mainly legalizes detached ADUs on qualifying lots in covered cities. |
| Does it cover basement apartments? | No — internal/basement ADUs are governed by a separate, older rule (see below). |
| Key lot-size number? | 11,000 sq ft is the statewide floor in covered cities. |
| Can cities allow smaller lots? | Yes. Cities may choose to permit detached ADUs below 11,000 sq ft. |
| When does it take effect? | The detached-ADU section takes effect October 1, 2026. |
| Does it remove permits? | No. You still need building permits and full code compliance. |
| Can cities still require owner-occupancy? | Yes — they may require you to live in the main home or the ADU. |
| Can cities ban Airbnb-style rentals? | They may require rentals of 90+ consecutive days, which effectively blocks short-term rental. |
| Can my HOA still say no? | Yes, for a detached ADU. |
| Smartest first step | Check whether your specific lot, city, and utilities can support it — before buying plans or requesting bids. |
What we verified for this page
We wrote this from primary and official sources, not headlines:
- Utah Code § 10-21-304 — the detached-ADU section created by SB 284 (effective October 1, 2026).
- Utah Code § 10-21-101 — statutory definitions of ADU, detached ADU, internal ADU, and "specified municipality."
- Utah Code § 10-21-303 and Utah's Property Rights Ombudsman / Department of Commerce guidance — for the internal-ADU baseline and HOA rules.
- City sources — Salt Lake City's ADU handbook and code, Provo's ADU and SB 284 pages, and West Jordan's and Lehi's ADU ordinances/materials, used as examples only, not a full statewide table.
Full links are in the "Sources we checked" section at the bottom.
What is Utah SB 284?
SB 284 is a broad 2026 Utah land-use bill ("Local Land and Water Modifications") enacted during Utah's 2026 General Session. Most of it took effect May 6, 2026, but the part most homeowners care about — the detached-ADU requirement now in Utah Code § 10-21-304 — takes effect October 1, 2026.
Before SB 284, cities had wide latitude to restrict or even prohibit detached backyard units outright. SB 284 removes that blanket power on qualifying lots in covered cities, while leaving cities plenty of room to regulate the details.
Why SB 284 looks confusing online
If you search the bill, you'll find the Legislature's raw PDF, bill trackers, advocacy summaries, and builder posts — and some of them cite different numbers because the bill changed several times before it passed. A common example: some summaries say the lot threshold is 10,000 sq ft. The final law says 11,000 sq ft for the statewide requirement. When numbers conflict, the current Utah Code wins, and that's what this page follows.
Does SB 284 mean I can build a detached ADU on my lot?
Maybe. SB 284 helps if your property is in a covered city, your lot is at least 11,000 sq ft, it already has a single-family home, and your setbacks, utilities, parking, and intended use can be satisfied. It is not a blanket "yes" for every Utah lot — especially small-town, rural, or HOA-restricted properties.
Here's a quick feasibility scorecard to gut-check your situation before you spend anything:
| Check | If yes | If no |
|---|---|---|
| Is your property in a "specified municipality"? | Keep going — the state floor likely applies | The statewide requirement may not reach you; verify locally |
| Is the lot 11,000 sq ft or larger? | Strong fit under the state rule | Your city may still allow a smaller lot — don't assume either way |
| Does it already have a single-family home? | Keep going | Likely not eligible under this specific rule |
| Are single-family homes allowed in that zone? | Keep going | A zoning problem — verify locally |
| Will setbacks, height, and lot coverage work? | Keep going | Your design may need to change |
| Do your utilities have capacity? | Keep going | This is a common, expensive dealbreaker |
| Is your rental plan legal locally (30+ or 90+ days)? | Keep going | A short-term rental limit may apply |
| Any HOA or recorded restriction? | Keep going | Treat this as a separate, real hurdle |
If you answered "yes" down the left column, your lot likely fits the state baseline and is worth a closer look. Any "no" isn't automatically a dead end — several of these are city-specific — but each one is a reason to verify before you pay for plans.
A setback is the minimum distance a building must sit from your property lines or other structures. A specified municipality is a defined class of larger Utah cities — more on that in the FAQ below.
What SB 284 guarantees you (what your city can't do)
On a qualifying lot in a covered city, SB 284 sets a baseline your city cannot undercut. This is the "teeth" of the law — the reason it's a genuine change and not just a headline.
| Your city cannot | What it means for you |
|---|---|
| Require a conditional use permit for a detached ADU in a primarily residential zone | No discretionary, case-by-case hearing just to have the unit — though a standard building permit still applies |
| Require more than 2 on-site parking spaces for a detached ADU 650 sq ft or larger | Predictable parking demands |
| Require more than 1 on-site parking space for a detached ADU under 650 sq ft | Lighter parking for smaller units |
| Impose design standards that conflict with Utah's building-design-elements law | Limits how far a city can dictate the look of your unit |
A conditional use permit is a discretionary approval a city grants case-by-case, often after a public hearing — historically a major roadblock for backyard units.
What your city can still require
SB 284 is a floor, not a free-for-all. Cities keep meaningful control over the details, and those details decide whether a project is realistic on your lot.
| Your city may still | Why it matters |
|---|---|
| Require setbacks, size, height, and lot-coverage limits | Can shrink or reshape what you're allowed to build |
| Require the ADU be designed to match the main home | May raise design cost |
| Prohibit an ADU larger than the main home | Caps your square footage |
| Prohibit placing the unit in a front yard or in a utility easement | Limits where it can go on the lot |
| Require owner-occupancy (you live in the main home or the ADU) | Can rule out pure investor use |
| Require rentals of 90+ consecutive days | Effectively blocks short-term rental |
| Require replacement parking when a detached garage is converted | Adds cost if the garage held required parking |
| Cap the lot at one ADU | You generally can't stack an internal and a detached unit |
| Prohibit the ADU if utilities can't support it | One of the biggest practical dealbreakers |
"Owner-occupancy" means a rule requiring the property owner to actually live on the property. A "short-term rental" generally means renting for less than about 30 days, like Airbnb or Vrbo.
Owner-occupancy and rentals: don't assume investor use
SB 284 explicitly lets cities require the owner to live in either the main home or the detached ADU, and lets cities require a 90-day minimum rental term. If your plan depends on nightly rental income or on never living on-site, confirm your city's rules first — those two levers can change the entire financial picture.
Utilities can still be a dealbreaker
Even a perfect-size lot can fail on utilities. A city may deny a detached ADU if the unit can't get adequate utility hookup — the connections to water, sewer, and power — or if the system it must connect to lacks capacity. In older Utah neighborhoods, sewer capacity and electrical service are common friction points, and upgrades can add real cost. This is why a paper "yes" isn't the same as a buildable "yes."
A "utility hookup" is the physical connection of a unit to water, sewer, and power. Cities may also charge an impact fee — a one-time charge on new development to help pay for public infrastructure.
Internal ADU vs. detached ADU — which one does SB 284 change?
SB 284 changes the rules for detached ADUs. It does not change the separate, older rule for internal ADUs (basement apartments and similar). Confusing the two is one of the most common mistakes homeowners make with this law.
| Internal ADU | Detached ADU | |
|---|---|---|
| What it is | A unit inside your existing home's footprint — most often a basement apartment | A separate structure in the yard: a cottage, casita, or converted detached garage |
| Statewide protection | Treated as a permitted use in areas zoned primarily for residential use (since 2021), subject to Utah Code § 10-21-303 exceptions and local requirements | Newly required on qualifying lots ≥ 11,000 sq ft in specified municipalities, starting October 1, 2026 (SB 284) |
| Common city conditions | May bar units on lots under 6,000 sq ft; one extra parking space; a rental permit; a short-term rental ban; a rule that the unit not change the home's appearance | Setbacks, size/height/coverage, design match, owner-occupancy option, 90-day rental option, one-ADU-per-lot cap, utility capacity |
| HOA power | An HOA generally cannot block the rental of a compliant internal ADU | An HOA can prohibit a detached ADU entirely |
Can your HOA still stop you? This is the part the headlines skip
Yes — and this is the biggest catch in the whole law.
Utah's guidance is explicit: an HOA can prohibit a detached ADU even when state law and your city would otherwise allow it. (By contrast, an HOA generally cannot block the rental of a compliant internal ADU.) If your property is in an HOA, read your CC&Rs before you spend a dollar on plans.
Here's the honest version most builder ads won't give you: 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 — and for a detached unit, whether an HOA sits between you and the backyard you're picturing. That's exactly what a feasibility check is for: it's cheaper to find out on paper than after you've paid an architect.
How Utah cities are handling detached ADUs (real examples)
SB 284 sets a statewide floor, but each city still writes and enforces its own rules — which is why two neighbors in different cities can get very different answers. These four cities are examples that show the range; this is not a complete statewide table.
| City | Detached ADU lot rule | Notable local conditions |
|---|---|---|
| Salt Lake City | Relatively permissive for a large city; allows ADUs in residential zones | One ADU per lot; detached side/rear setbacks of 3 ft where applicable; detached height limited to 17 ft, with exceptions up to 24 ft for a pitched roof or 20 ft for a flat roof when larger setbacks are provided |
| Provo | Allows detached ADUs with detailed standards; publishes a parcel eligibility map | Detached unit set back at least 10 ft from a property line (or the home's existing setback, whichever is less); at least 200 sq ft; must be architecturally compatible; requires its own address and a separate utility meter; Provo notes SB 284 applies to detached/external units, not internal/basement units |
| West Jordan | Allows detached ("external") ADUs on platted lots 10,000 sq ft and larger in listed zones — more permissive than the state floor | Unit's footprint must be smaller than the house; not allowed in the front yard; design review required; long-term rental only (no rentals under 30 days); one ADU per lot (you can't have both an internal and an external unit) |
| Lehi | Already allowed detached ADUs, but only on much larger lots than the new state floor | Lehi's code required a minimum lot size of about 14,520 sq ft (roughly a third of an acre); to comply with SB 284, Lehi is updating its code to allow detached ADUs on parcels 11,000 sq ft or larger. Confirm Lehi's current adopted code. |
The takeaway isn't the specific numbers — it's that your city's setbacks, design rules, utility requirements, and rental terms are what you actually build against. Verify your city's current adopted code before you commit. For a broader breakdown, see our Utah ADU rules by city guide.
What SB 284 means for cost, timeline, and talking to a builder
SB 284 can improve your legal odds. It does nothing to make construction cheap, fast, or guaranteed. A detached ADU is still new construction: design, site work, utilities, city review, engineering, financing, and builder availability all drive the number and the calendar.
The biggest swing factor for detached units is almost always utilities — whether your lot can connect to water, sewer, and power, and whether the system has capacity. A garage or existing-structure conversion usually costs less than a brand-new detached cottage, but even conversions can get expensive when meters, service upgrades, or grading are involved. We don't publish cost figures on this law page because they change and depend heavily on your site; for current ranges and what moves them, see our Utah ADU cost guide.
What to do before October 1, 2026
Use the runway before the detached-ADU rule takes effect to pressure-test your property. Don't rely on a social post, a neighbor, or a builder ad as proof that your lot qualifies.
- 1Confirm your city and whether it's a specified municipality.
- 2Confirm your lot or parcel size.
- 3Confirm the property already has a single-family home.
- 4Confirm single-family use is allowed in your zone.
- 5Look at your buildable rear-yard area, setbacks, and lot coverage.
- 6Check for recorded easements.
- 7Identify sewer, water, and electrical access — and ask about capacity.
- 8Decide your use: family housing, long-term rental, or something else.
- 9Check owner-occupancy and minimum-rental rules for your city.
- 10Read your HOA's CC&Rs if you have an HOA.
- 11Run a feasibility and cost screen before buying plans.
Related Utah ADU guides
Utah ADU Laws Overview
The full state-law framework, history, and what changed in 2026.
Utah ADU Rules by City
City-by-city breakdown of lot sizes, setbacks, and local conditions.
Utah ADU Setback Requirements
How far your ADU must sit from the property line, by city.
Utah ADU Parking Requirements
State parking caps and the 2026 detached-ADU parking rule.
Utah ADU Cost Guide
What drives cost for detached and internal ADUs in Utah.
Detached ADU Builders Utah
Backyard cottage options, costs, and how to vet builders.
Frequently asked questions about Utah SB 284
Sources we checked
State law
- Utah SB 284 — enrolled (enacted) bill text — source of the enacted detached-ADU section (§ 10-21-304, effective October 1, 2026), the definitions (§ 10-21-101), and the effective-date structure.
- SB 284 — bill status and history — Utah Legislature.
- Utah Property Rights Ombudsman / Dept. of Commerce — ADUs — internal-ADU baseline (§ 10-21-303) and impact-fee treatment.
- Utah Dept. of Commerce — HOAs and ADUs — HOA rules for internal vs. detached ADUs.
City examples
- Salt Lake City — ADU Handbook (see also Salt Lake City Code § 21A.40.200)
- Provo — ADU standards (City Code 14.30.030)
- Provo — SB 284 ADU eligibility notice
- West Jordan — ADU application (external ADUs on 10,000+ sq ft lots)
- West Jordan — adopted ordinances
- Lehi — Detached ADU code amendment (state requirements)
Thinking about a detached ADU under the new law? The single most valuable next step isn't plans or quotes — it's a property-specific feasibility read on your lot, city, and utilities.