Until now, whether you could build one depended entirely on your city. Some allowed them, some allowed only an apartment inside the house, and some allowed nothing you could live in. From October 1 there is a statewide floor.

What the law requires

A covered city must adopt rules that permit a detached ADU on any lot or parcel that:

• is 11,000 square feet or larger,
• has a single-family home on it, and
• is in a zone where a single-family home is a permitted use.

Cities may go further and allow detached ADUs on smaller lots. Some already do: Salt Lake City has no minimum lot size at all.

Which cities it covers

The law applies to "specified municipalities": every city of the first, second, third or fourth class, and fifth-class cities with 5,000 or more people in a county of the first, second or third class. That covers 82 Utah cities, including Salt Lake City, West Valley City, Provo, West Jordan, Orem, Sandy, Ogden and St. George. Unincorporated county land is not covered.

See every covered city.

What a city can't require

A covered city may not:

• require a conditional use permit for a detached ADU in a primarily residential zone;
• require more than one on-site parking space for a detached ADU under 650 square feet, or more than two for one of 650 square feet or more.

It must also give owners a way to convert a legally built accessory building, like a detached garage or studio, into a detached ADU, and it must require ADUs to meet building, health and fire codes.

What a city can still decide

The law sets a floor, not a design. Cities keep control over:

• size, height and lot coverage;
• setbacks, and design that fits the home;
• owner occupancy, meaning the owner lives in the house or the ADU;
• one ADU per lot.

A city may also prohibit a detached ADU that is larger than the home, sits in a front yard or on a recorded easement, lacks adequate utility access, or is rented for less than 90 consecutive days.

That is why the rules differ so much from one city to the next, and why we research each city's ordinance from its own documents. Utah ADU rules by city has what we've verified so far.

What to do now

1. Check your lot. We find your county tax parcel, draw it, and apply the rule for your city.
2. Read your city's rules, or call its planning office. Many cities are adopting or changing their ordinance right around October 1.
3. Design the building. A backyard home still needs a building permit, and the drawings have to meet your city's size, height and setback rules.

The full text is in the enrolled bill, S.B. 284 (2026), and our summary of the law covers it section by section. This post is a summary, not legal advice.

How it works

Type your street address into the lot checker, which is also on our homepage. In a few seconds it:

1. Finds your parcel. It matches the address to your county's tax parcel through the state's public parcel data from UGRC, the Utah Geospatial Resource Center.
2. Draws it. The parcel boundary appears on a map, with an aerial view if you want to see the house, the driveway and the trees.
3. Checks the rule. It works out whether your city is covered by the state law, and whether your lot meets the size rule for that city: 11,000 sq ft under the state law, or less where the city allows smaller lots.
4. Puts a building on it. A backyard home footprint drops onto your lot. Drag it into place and rotate it freely. It snaps to your lot's own lines when it gets close.

The result reads as one of a few answers: your lot looks eligible, it looks eligible but your city's ordinance is still pending, it's under the minimum (and by how much), your city isn't covered by the state law, or the county record isn't clear enough to say.

How many lots qualify

Across the 82 cities the law covers, 217,277 residential tax parcels are 11,000 sq ft or larger. That count comes from the same county parcel data, and the checker shows the number for your city with your result.

It's a count of lots that pass on city and size, not of lots confirmed buildable. Zoning, an existing ADU, HOA covenants, easements and the slope of your yard all matter too, and none of them is in the parcel record.

What it can't tell you

The checker uses public tax-year data. A recent lot split or merge might not be there yet, and the county's land use code for your parcel is sometimes blank. When it is, we say so instead of guessing. It's a first answer, not a legal determination. Before you design or apply, confirm with your city's planning office.

Try it

Check your lot. If it qualifies, you can take the lot straight into the design studio and start on the building.

The first three pages are up.

Salt Lake City: already past the state law

Salt Lake City adopted its current ADU rules in April 2023, well before SB 284, and they already go further than the state requires. There is no minimum lot size: a detached ADU is allowed by right on any lot in a zone that permits homes.

• Up to 1,000 sq ft, and no larger than the main house
• 17 ft tall, or up to 24 ft with a pitched roof if setbacks grow with the height
• One parking space, which can be waived near transit or a bike path
• The owner or a family member must live on the property
• It can be rented for 30 days or more, with a business license and the city's Good Landlord Program

Salt Lake City ADU rules

West Valley City: new rules for October

West Valley City adopted Ordinance 26-28 on June 23, 2026, adding a new section of its code for detached ADUs.

• Lots of 11,000 sq ft or more, the state floor
• Smaller than the house, and together with other accessory buildings no more than 25% of the rear yard
• In a side or rear yard; 5 ft from side and rear lot lines in a residential zone, 20 ft from a street
• One parking space under 650 sq ft, two at 650 sq ft or more
• The owner must live on the property, and rentals must be at least 90 consecutive days

West Valley City ADU rules

Sandy: an ordinance still in front of the council

Sandy's detached ADU ordinance is pending. The Planning Commission recommended it on August 20, 2026, and it was before the City Council on September 1 and September 15 with no vote recorded yet. So its page shows the proposed rules, labeled as proposed, not final.

One detail to watch is the minimum lot size. The Planning Commission recommended 10,000 sq ft; the text in front of the council says 11,000. Until now, a detached unit in Sandy was only possible as a small guesthouse on a lot of at least 20,000 sq ft, with no kitchen, and it couldn't be rented.

Sandy ADU rules

How we research a city

• We use only official sources: the city's code, adopted ordinances, council and planning commission records, and the city's own guides.
• Every rule on a page links to the document it came from.
• If we can't find a rule, the page says Confirm with the city instead of filling in a guess.
• Rules that aren't adopted yet are labeled proposed.
• Each page shows the date we last verified it.

More cities are coming, starting with the largest. The index of covered cities shows which ones are done. If you're planning a build now, check your lot and call your city's planning office before you apply.