Utah S.B. 284, plainly: what changes for backyard homes on October 1.

“Specified municipality” — does this cover my city?

The bill defines it as a city of the first, second, third or fourth class, or a fifth-class city with a population of 5,000 or more. In practice that is every city along the Wasatch Front and St. George. Small towns and unincorporated county land are not bound by this section, though counties have their own ADU rules.

What actually changes

Today many Utah cities allow a detached ADU only as a conditional use — you apply, a planning commission holds a hearing, neighbors comment, and the city can attach conditions or say no. Some cities restrict detached units to overlay zones; a few don't allow them at all. On October 1 those discretionary steps go away on qualifying lots. The unit becomes a permitted use, which means a building permit, not a hearing.

What doesn't change

The city still decides the envelope. Setbacks, height, lot coverage, and design consistency with the main house all remain local. So does owner-occupancy — most cities require you to live in one of the two homes — and the 90-day minimum tenancy, which means an ADU is a long-term rental, not a nightly listing. That is why Arena keeps one page per city with that city's actual numbers, each marked verified, confirm-with-city, or moving-now.

The number that decides it: 11,000 square feet

A quarter acre is 10,890 sq ft — just under the line. Many older lots on the east benches, in Holladay, Sandy and Draper, clear it comfortably; many lots in the Avenues, Sugar House and newer subdivisions don't. Your county parcel record shows the figure. The estimator asks for it, and if you're not sure, an Arena advisor pulls it when they run your address.

Every service-area city, in one place

Salt Lake County

• Salt Lake City — Salt Lake City already allows ADUs. The new law removes the discretion.
• Draper — Draper's rules are proportional — and that's the part worth reading.
• Sandy — Sandy runs ADUs through a Special Use Approval — and that's exactly what the statute targets.
• South Jordan — South Jordan's own minimum lot is larger than the state's — so the state threshold is what changes here.
• West Jordan — West Jordan is one of the few Wasatch Front cities without an owner-occupancy rule on the books.
• Herriman — Herriman is still writing its detached ADU ordinance — and the clock runs out October 1.
• Riverton — Riverton regulates the building, not the dwelling — ADUs sit inside its accessory-structure rules.
• Murray — Murray asks for a recorded affidavit before it will even accept your application.
• Holladay — Holladay has the lot sizes. The question is what its amended ordinance says.
• Cottonwood Heights — Today a detached ADU here is a conditional use. On October 1 that becomes illegal.

Utah County

• Lehi — Lehi has already passed its new rules — and eligibility jumped about 20%.
• American Fork — American Fork's older core has the lots. The ordinance is being amended now.
• Provo — Provo allowed detached ADUs only inside overlay zones. That ends October 1.
• Orem — Orem did not allow detached ADUs at all. On October 1, it must.
• Pleasant Grove — Pleasant Grove is amending its ordinance ahead of the October 1 deadline.

Davis County

• Bountiful — Bountiful has an ADU ordinance already — the detached rules are what's moving.
• Layton — Layton's detached minimum is 6,000 sq ft — already well under the state line.

Summit County

• Park City — Park City is the hardest market on this list — and the 90-day rule is why.

Weber County

• Ogden — Ogden's 800 sq ft cap is the number that shapes your plan choice.

Washington County

• St. George — St. George usually requires a conditional use permit for detached units — and the statute overrides it.