Utah's new law tells cities they must allow a detached ADU on lots of 11,000 sq ft or more. It leaves the details to them: how big, how tall, how far from the fence, how much parking, and whether you can rent it. So we're publishing the rules city by city, from each city's own ordinance and planning documents, with every rule linked to its source.
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
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
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.
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.