An accessory dwelling unit, or ADU, is a second, smaller living unit on a single-family lot. It can be a basement apartment, an attached conversion of part of the main house, or a detached backyard cottage or garage apartment. ADUs have become one of the most talked-about housing topics in Utah, and the rules are shifting right now: a new state law, Senate Bill 284, takes effect October 1, 2026, and cities across the Wasatch Front are updating their ordinances to match. This guide explains what the new law does, the two types of ADUs, the general process for adding one, and where the rules stand in Herriman, West Jordan, South Jordan, and Daybreak.

The Big Change: SB 284 Takes Effect October 1, 2026

Senate Bill 284, enacted in the 2026 legislative session, rewrites how Utah's larger cities must treat detached ADUs. Starting October 1, 2026, Utah Code § 10-21-304 requires every "specified municipality" (the cities over 5,000 people in the state's populous counties) to permit a detached ADU as a permitted use on any lot that is at least 11,000 square feet and already contains a single-family dwelling.

That is the core of the change: cities can no longer outright prohibit detached ADUs on qualifying lots. They may still regulate size, height, setbacks, parking, and utilities, and they can adopt standards that keep a detached unit consistent with the surrounding neighborhood. What they cannot do after October 1 is say no to the use itself on a lot that meets the state's threshold.

The local picture is changing fast. Some cities have already adopted ordinances ahead of the deadline; Lehi, for example, has moved forward with its local rules. Others were still finalizing theirs as of early September 2026, including Provo. If you are planning an ADU, the state law is the floor, and your city's ordinance is what you actually build against, so check your city's current requirements directly.

Two Types of ADUs, Two Sets of Rules

Internal and attached ADUs

Internal or attached ADUs are basement apartments and units attached to the main house. Under state law, these are a permitted use in most residential zones. Cities can still impose conditions: they can require the design to preserve the single-family appearance of the home, condition approval on the owner occupying either the main home or the unit, restrict rentals to stays of 30 or more consecutive days, and prohibit internal ADUs on lots of 6,000 square feet or less. In practice, your city's ordinance determines how much of that discretion is actually applied.

Detached ADUs

A detached ADU is a separate structure on the same lot: a backyard cottage, a garage apartment, or a standalone unit. This is where SB 284 has the biggest effect. For qualifying lots of at least 11,000 square feet with an existing single-family home, cities must allow a detached ADU as a permitted use starting October 1, 2026, while keeping their own controls on size, height, setbacks, parking, and utilities. For smaller lots, city rules still govern whether and how a detached unit can be built.

What It Takes to Add an ADU

Whether you are converting a basement or building a cottage, the general path looks similar across Wasatch Front cities:

Verify zoning and lot size with your city. Confirm that an ADU is a permitted or conditional use in your zone and that your lot meets the minimum size.
Check the site plan and development standards. Expect rules on setbacks, height, and separation. Salt Lake County, for example, generally requires about a 10-foot rear setback and about 6 feet between the ADU and the main house, with height caps often around 17 to 20 feet depending on the jurisdiction.
Obtain a building permit before construction or conversion. Building without a permit creates problems at sale time and with the city.
Comply with building, fire, and health codes. Kitchens, bedrooms, egress windows, smoke and carbon monoxide alarms, and other life-safety requirements all apply.
Get written confirmation from your water and sewer provider that service is available. Many cities require this confirmation as part of the ADU approval.
Meet parking requirements. Cities often require an additional off-street parking space for the unit.
Plan for an owner-occupancy requirement. Many Wasatch Front cities require the owner to live in either the main home or the ADU.
Do not assume short-term rental is allowed. Most cities restrict ADU rentals to 30 or more consecutive days, so a short-term stay under 30 days will not be permitted in most places.

One more angle worth checking before you invest: what the unit does for your property's value. If you are weighing whether an ADU is worth the cost, start with a current estimate of your home's value at our free home value tool, then talk to your city planner about what is actually buildable on your lot.

Your Service Area Snapshot: City-by-City Rules

The rules below reflect each city's ordinance as of September 2026. Every one of these municipalities is updating its ADU rules ahead of the October 1 state deadline, so verify the current requirements with your own city and HOA before planning anything.

Herriman

Herriman allows internal ADUs in its R-1 and agricultural zones on lots of 6,000 square feet or more, with an owner-occupancy requirement. Detached ADUs follow a city permit process and require a lot of roughly 0.2295 acres, about 10,000 square feet, in residential or agricultural zones. Herriman's detached ADU application page, linked in the sources below, is the authoritative starting point for the current permit steps.

West Jordan

West Jordan requires ADUs to have separate living, eating, sleeping, and sanitation areas. Notably, separate utility meters are not permitted: the ADU stays on the main house's electric meter. If you are planning a unit in West Jordan, work from the city's current ADU application, linked in the sources below, rather than assumptions.

South Jordan

South Jordan generally requires a 14,520 square foot lot for a detached guesthouse, with a conditional use process that can allow a smaller lot in some cases, and the owner must live on the property. With requirements shifting toward the October 1 deadline, confirm the current numbers with the city before you commit. South Jordan's current rules are also summarized on our communities index.

Daybreak (South Jordan)

Daybreak is the notable exception in this group. Within the master-planned community, ADUs are only permitted above a detached or semi-detached garage. On top of South Jordan's city code, Daybreak's community master association adds its own rules, so the HOA's approval matters as much as the city's.

The HOA Factor

HOAs and community master associations can impose their own restrictions that sit on top of city and state rules. This is especially true in master-planned communities like Daybreak, where governing documents frequently regulate accessory structures, rentals, and unit occupancy. Before you plan any ADU project, read your CC&Rs carefully and get written confirmation from your HOA or master association that your proposed unit is allowed on your specific home and lot.

Frequently Asked Questions

Are ADUs legal in Utah?

Yes. State law makes internal and attached ADUs a permitted use in most residential zones, and starting October 1, 2026, Senate Bill 284 requires larger cities to allow detached ADUs on qualifying lots. Local ordinances still set most of the practical requirements.

What is the new October 1 law?

Senate Bill 284, codified at Utah Code § 10-21-304, requires specified municipalities, cities over 5,000 people in populous counties, to permit detached ADUs as a permitted use on lots of at least 11,000 square feet that already contain a single-family home. Cities keep control over size, height, setbacks, parking, and utilities.

What lot size do I need for a detached ADU?

Under the new state law, the threshold is an 11,000 square foot lot. Local standards can differ; South Jordan, for example, has generally required a 14,520 square foot lot for a detached guesthouse, subject to change before the October 1 deadline.

Can I rent out an ADU short-term?

In most Wasatch Front cities, no. Cities may restrict ADU rentals to stays of 30 or more consecutive days, and most do, so short-term rentals under 30 days are not generally permitted in ADUs.

Do I need an owner to live on the property?

Often, yes. Many Wasatch Front cities, including Herriman and South Jordan, require the owner to occupy either the main home or the ADU. Check your city's ordinance for the exact requirement.

Does my HOA have a say?

Yes. HOAs and community master associations can add their own restrictions on top of city and state rules, including in master-planned communities like Daybreak. Review your CC&Rs before planning any project.

Disclaimer: This article is for general educational purposes only and is not legal, tax, or financial advice. Utah's ADU laws and local ordinances are changing quickly. Always verify requirements directly with your city's planning department, your water/sewer provider, and your HOA before planning any project.

Planning an ADU or wondering what one could mean for your property?

Adam and Natalie Stark of Stark Group Real Estate know the Wasatch Front's communities, lots, and local rules. Book a free call to talk through your property, and they will point you to the right city resources.

Book a Call with Adam & Natalie

801-613-0038 info@utahcityliving.com

ADUs in Utah: What Homeowners Need to Know Before October 1