Two Utah ADU Statutes, and 11,000 Square Feet Decides Which One
Utah Service Area
Utah's detached ADU mandate lands on October 1, 2026. On that date, Utah Code section 10-21-304 requires municipalities of 5,000 or more residents to permit a detached accessory dwelling unit on any lot of 11,000 square feet or larger. No conditional-use permit. No maximum size beyond the size of the primary home.
Apex Drafting produces custom house plans, ADU sets, addition and remodel drawings, and permit-ready documents for Utah homeowners, builders and contractors as a remote service. This page covers what the two governing statutes say and what the October date means if you are deciding right now.
Two statutes govern Utah ADUs, and they cover different units
Most writing on Utah ADUs collapses two separate laws into one blur. They are not the same, they passed five years apart, and which one applies depends on whether the unit is inside your house or behind it.
HB 82 (2021): internal ADUs by right, statewide
HB 82, codified at Utah Code 10-9a-530 and effective October 1, 2021, made internal accessory dwelling units a permitted use by right in most residential zones across Utah. A conforming internal unit does not go through a conditional-use process or a discretionary hearing. The statute removed the statewide owner-occupancy mandate while leaving cities free to keep their own, and defined internal ADUs as rentals of 30 days or more, which excludes nightly rentals. That has been the law for five years, and it is still the path that applies to most Utah lots, because most Utah lots are smaller than 11,000 square feet.
SB 284 (2026): detached ADUs, effective October 1, 2026
SB 284 (2026 General Session, "Local Land and Water Modifications") created Utah Code section 10-21-304, effective October 1, 2026. It requires municipalities of 5,000 or more residents to permit a detached accessory dwelling unit on any lot of 11,000 square feet or larger that contains a single-family dwelling where single-family is a permitted use.
- Cities cannot require a conditional-use permit for a qualifying detached ADU.
- Cities cannot impose a maximum size other than capping the unit at the size of the primary home.
- Setbacks, height, parking, owner-occupancy and design standards stay local.
- Cities without a conforming ADU policy must adopt one by October 2026.
Read together, the shape of the law is clear. The state took away the discretionary veto and the size cap. It did not take away the city's dimensional and occupancy rules. Anyone telling you SB 284 means you can build whatever you like in the backyard is misreading it, and anyone telling you nothing changed has not read it.
What the October 1 date means if you are deciding now
If your lot is 11,000 square feet or larger and your city has 5,000 or more residents: as of October 1, 2026, the city cannot require a conditional-use permit for a conforming detached ADU and cannot cap its size below the size of your primary home. The discretionary hearing that used to be the main risk in a backyard-unit project is gone for qualifying lots. Local setbacks, height, parking and owner-occupancy rules still apply, so the design still has to fit the envelope your city defines.
If your lot is under 11,000 square feet: the detached mandate does not reach you. Utah Code 10-9a-530 and its by-right internal ADU is your path, and it has been available since 2021. A basement or interior conversion is a genuinely different drawing set from a detached cottage, and it is worth scoping it as what it is rather than chasing a statute that does not apply.
If your city has not updated its ordinance yet: it is required to adopt a conforming policy by October 2026. Ordinances across the state are in motion for that reason, which is why every figure on a Utah ADU page needs a date attached to it. We verify against the text in force for your jurisdiction rather than repeating a summary.
On timing: starting drawings now is almost always right. Design, engineering coordination and revision cycles take time regardless of the statute. October 1 changes what a city can deny, not how fast a set gets produced.
Working on a Utah project right now?
Send us the lot and what you want to build. We'll confirm which local rules apply to your parcel and come back with a firm number, at no cost.
The drafting work Utah projects need most
A statewide by-right rule changes what makes sense to draw. When the discretionary hearing disappears, the bottleneck moves to the completeness of the submitted set.
ADU Plans & Design
Detached units under 10-21-304 and internal units under 10-9a-530 are different drawing problems. We scope which statute applies to your lot before anything is drawn.
Permit-Ready Drawings & As-Builts
With the discretionary step removed for qualifying units, a complete, correctly formatted submittal is what stands between you and an approval. As-builts matter for interior conversions with no current drawings.
Custom House Plans
Utah's custom-build submarkets reward plans drawn around the lot. If you intend to add an ADU later, the primary-home set is where that gets designed for.
An internal ADU is frequently a home addition or remodel in disguise, and a detached unit meant for aging parents belongs in multigenerational and universal design. Stock house plans start at $799 where a proven layout fits the lot, 3D renderings help when a second structure has to be sold to a household or a lender, and energy-efficient design is drawn into the set rather than bolted on. Full menu on the services page, numbers on the pricing page.
Utah markets we cover in depth
Each city page digs into that market's own ordinance, permitting counter and neighborhood detail instead of repeating the statewide summary.
St. George
Washington County reached 209,129 residents in 2025, up 2.32%, with 87% of that from net migration. The city issued 2,515 building permits in 2024 valued at $481.5 million, including about 800 single-family permits. City Code section 10-17A-3 requires owner-occupancy and prohibits short-term rental of an ADU, and it was amended by Ordinance 2025-059 in August 2025.
Utah is one of several states we draft for. The full list is on the service areas page.
How a remote Utah project runs
Three steps, no office visit, the same standard everywhere in the state.
Send the lot and the scope
Tell us what you want to build, the parcel, and the jurisdiction. We pull the governing rules: the state statute that applies, plus the city ordinance text currently adopted.
We draft to the local standard
Plans are drawn to the submittal requirements of the office that will review them, with revisions handled over phone, video and email until the set is right.
You submit a complete set
You receive digital, permit-ready files formatted for your permitting office and ready for your builder. More about how we work is on the about page.
Utah ADU and drafting questions, answered
Can I build a detached ADU anywhere in Utah after October 1, 2026?
Not anywhere, but in far more places than before. Utah Code section 10-21-304, created by SB 284 and effective October 1, 2026, requires municipalities of 5,000 or more residents to permit a detached accessory dwelling unit on lots of 11,000 square feet or larger that hold a single-family dwelling where single-family is a permitted use. Two thresholds decide whether it reaches you: your city's population and your lot's size.
What did HB 82 already change for internal ADUs?
HB 82 (2021), codified at Utah Code 10-9a-530 and effective October 1, 2021, made internal accessory dwelling units a permitted use by right in most residential zones statewide. A conforming internal ADU needs no conditional-use permit and no discretionary hearing. The law removed the statewide owner-occupancy mandate while letting cities keep their own, and defined internal ADUs as rentals of 30 days or longer, which excludes nightly rentals.
My city does not have an ADU ordinance. What happens in October 2026?
Cities without a conforming ADU policy must adopt one by October 2026. In practice, ordinances across Utah are being rewritten right now, so any ADU figure that predates this year should be treated as unverified until it is checked against the currently adopted text. We confirm the code language in force for your jurisdiction before drafting.
Should I wait until October to start drawings?
Usually no. Drafting, engineering coordination and revisions take time, and the October 1 date changes whether a city can deny a qualifying detached unit, not how long a set takes to produce. Starting now means the drawings are finished when the statute takes effect.
Does SB 284 mean my city cannot regulate the ADU at all?
No. The statute removes the conditional-use requirement for a qualifying detached unit and blocks any maximum size other than the size of the primary home. Setbacks, height, parking, owner-occupancy and design standards remain local. In St. George, for example, city code still requires owner-occupancy and still prohibits short-term rental of an ADU. The state sets the floor on whether. The city still governs how.
How does remote drafting work for a Utah project?
The whole process runs on phone, video call and email. You share the lot, the scope and any existing drawings. We pull the rules that govern the parcel, draft the plans, handle revisions, and deliver digital files formatted for the office that will review them. Stock house plans start at $799, and custom sets are quoted against your specific lot.
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Tell us what you're building and we'll scope it, confirm the timeline, and give you a firm number before any drafting starts. Every plan set is drafted to your local jurisdiction's documentation standards.
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Get Utah-ready house plans
Tell us the city, the lot size and the project. We will confirm which statute governs it, quote the work, and deliver permit-ready drawings, all remotely. Questions first is fine: the FAQ and contact page are both open.