ADUs and In-Law Suites in Utah: Cost, Rules and What Changed in 2026

Current as of October 2026. ADU law in Utah is changing quickly. This article reflects state law and city ordinances as of that date.

An accessory dwelling unit, or ADU, is a second, self-contained home on the same lot: a basement apartment, an in-law suite, a converted garage or a separate cottage. On October 1, 2026, SB 284 (2026) took effect and opened detached ADUs to many more Utah lots. Here is what changed, what each type costs, what your city and HOA can and cannot require, and what an ADU does for resale. Every cost figure is a researched market range, not a quote.

What changed for Utah ADUs in 2026?

Under SB 284, detached ADUs are now allowed on lots of 11,000 square feet or more in most Utah cities. Cities can no longer require more than 2 parking spaces for the property. Before this change, many cities allowed only internal ADUs by right and left detached units to local discretion, so a backyard cottage on a typical quarter-acre lot was often not possible. Now, on an 11,000 square foot lot, it usually is.

Can my HOA stop me from building an ADU?

This is the rule that surprises almost everyone. Under Utah law, an HOA cannot ban an internal ADU, and it cannot ban you from renting one. A basement apartment or in-law suite inside the home is protected. An HOA can ban a detached ADU, so check your CC&Rs before designing a backyard cottage, even if your city allows it.

What can Utah cities still require for an ADU?

Internal ADUs, those inside the footprint of the main home, are permitted by right under state law. Cities can still:

• Ban internal ADUs on lots of 6,000 square feet or less.
• Require one additional parking stall.
• Require the owner to live on the property.
• Set a 30-day minimum rental term.
• Require a rental license.
• Restrict internal ADUs in up to 25 percent of their residential zones.

Internal ADUs are exempt from impact fees, which is one reason a basement ADU is usually the lowest-cost route.

How much does an ADU cost in Utah?

Market ranges by ADU type run as follows:

ADU type	Typical market range
Internal or basement	$60,000 to $150,000+
Garage conversion	$60,000 to $175,000+
Attached addition	$150,000 to $275,000+
Detached	$200,000 to $400,000+

Permit fees typically run $1,500 to $4,000. A detached ADU costs the most because it needs its own foundation, roof, utility connections and often a separate meter. A basement ADU reuses structure that already exists, though egress windows, a separate entrance and fire separation still carry real cost.

What are the ADU rules in Draper, Holladay, Salt Lake City and Lehi?

City	Types allowed	Key rules
Draper	Internal and detached	12,000 sq ft lot for detached. ADU no more than 50% of the home. Owner-occupied. 1 parking stall. 30-day minimum rental.
Holladay	Internal and external	Lot at least twice the zone minimum or half an acre for external units. Owner on site. 1 parking stall.
Salt Lake City	Detached on any lot size	Up to 1,000 sq ft. Owner-occupied. Short-term rental banned.
Lehi	Internal and detached	Detached on 11,000+ sq ft lots. Internal on 6,000+ sq ft lots.
Orem and Provo	Pending	Updated ordinances still pending as of October 2026.

Lehi applications go through Lehi Building and Inspections. Draper, Holladay and Salt Lake City publish their ADU rules through each city's planning department.

Can I rent my ADU on Airbnb?

Usually not as a nightly rental. Cities may require a 30-day minimum for internal ADUs and a 90-day minimum for detached ADUs. Salt Lake City and Cottonwood Heights ban short-term rental of ADUs. Holladay allows it only by conditional use permit in the R-2 and R-M zones. Long-term rental is the normal use.

How long does it take to build an ADU?

• Basement ADU: 3 to 5 months.
• Attached ADU: 5 to 8 months.
• Detached ADU: 7 to 12 months.
• Permits: 6 to 10 weeks, inside those totals.

Does an ADU add value to a Utah home?

Mountain-region 2025 Cost vs Value data puts ADU cost recovery at 45.5 percent at resale. On that measure alone, an ADU is not a resale play. The stronger financial case is usually rental income an appraiser can count, or a lot where the ADU changes the property's permitted use. Both depend on your city, your lot and the rental market, and we are not making a projection about either.

Many families build an ADU for reasons no spreadsheet captures: a parent moving closer, an adult child coming home, a guest suite with its own door. For larger in-law suites built onto the house, see luxury home additions.