Everything homeowners need to know about building an accessory dwelling unit in Salt Lake City - size limits, setbacks, permits, and how a 2021 Utah state law and the city's own 2023 ordinance work together.
Last verified: September 2026
7/10 · ADU-friendly
1,000 sq ft*
Max ADU size
24 ft*
Max height
Required
Owner-occupancy
By-right
Permit type
This page summarizes Utah Code § 10-9a-530 (the statewide internal ADU law) and Salt Lake City Code § 21A.40.200 (Accessory Dwelling Units) for general reference - it is not legal advice. Regulations change; always confirm current requirements with the Salt Lake City Planning Division before designing or applying for permits. See sources below.
Zoning & size requirements
What you're allowed to build
ADU type
Max size
Max height
Notes
Internal ADU (basement, attic, or space within the existing home)
No maximum size cap since Salt Lake City's 2023 ordinance update (previously 50% of the primary structure)
Same as primary structure
Protected as a permitted use statewide under Utah Code § 10-9a-530, in an owner-occupied, detached single-family home
Detached ADU (new build or garage conversion)
1,000 sq ft gross floor area
17 ft base; up to 24 ft with increased side/rear setbacks (roughly 1 extra ft of setback per ft of added height)
Limited to 17 ft if within 10 ft of a corner side lot line
Allowed zoning districts
Internal ADUs are a statewide-protected use in owner-occupied, detached single-family homes under Utah Code § 10-9a-530. Salt Lake City also allows detached ADUs by-right in single-family residential zones citywide, after a 2023 ordinance change eliminated the conditional-use (Planning Commission) requirement. Confirm your parcel's zoning with the Planning Division.
Additional standards
Setbacks, parking & other rules
Setbacks
Detached units: 3 ft minimum from interior side and rear lot lines; corner side setback of 10 ft or 20% of lot width, whichever is greater; taller units need additional setback
Parking
One off-street space is typically required per ADU, waived if the property is within a quarter mile of transit or a half mile of designated bike infrastructure
Units per lot
One ADU permitted per lot, regardless of lot size, in addition to the primary dwelling
Owner-occupancy
Required - the property owner or a qualifying family member must occupy either the primary residence or the ADU. The City Council kept this rule in its 2023 update but committed to revisiting it
Building code
Must meet the 2021 Utah State Residential Code (based on the 2021 IRC), adopted via HB 532 and effective statewide since July 1, 2023
Rental license
A city business license is required to operate any rental dwelling, including a rented ADU; owner-occupied properties with 4 units or fewer are exempt from the per-unit fee
Short-term rental
Prohibited - ADUs may not be used for stays under 30 days
Ordinance history
How Salt Lake City's ADU rules got here
2018Earlier ordinance debated, stays narrow. City Council discussions on a broader ADU ordinance stalled over neighborhood carve-outs and conditional-use requirements; ADUs remained capped at 50% of the primary structure and required Planning Commission approval.
2021Utah passes HB 82. The state legislature enacted Utah Code § 10-9a-530, requiring every city and county to allow at least one internal ADU by-right in an owner-occupied, detached single-family home - a statewide floor that local ordinances can't fall below.
2023Salt Lake City overhauls its local ordinance. On April 4, the City Council voted unanimously to eliminate the conditional-use requirement for detached ADUs, remove the 50%-of-primary-structure cap for internal ADUs, and keep the citywide owner-occupancy rule with a commitment to revisit it in three years.
2023Utah's 2021 Residential Code takes effect. Statewide construction standards based on the 2021 International Residential Code became effective July 1 via HB 532, governing how ADUs must be built.
2024West-side ADU loan program launches. The Salt Lake City Community Reinvestment Agency, with CDC Utah, set aside about $2.9 million for low-interest ADU construction loans (up to $200,000 per household, 3% fixed, 30-year terms), concentrated in the 9 Line Community Reinvestment Area and other west-side neighborhoods.
Worth knowing: Utah's state law creates a strong floor for internal ADUs everywhere in the state, but detached ADUs still depend on each city's own ordinance - Salt Lake City's rules are notably more permissive than many of its suburbs. The owner-occupancy requirement remains the biggest limit on using an ADU as a pure rental investment; confirm with the Planning Division whether the three-year policy review has produced any changes.
Permit process
How Salt Lake City ADU permitting works
1
Confirm zoning eligibility
Check your zoning district and confirm your property qualifies using the city's zoning map, or contact the Planning Division directly.
2
Choose a design path
Use one of the city's pre-approved ADU Standard Plans (several options in the roughly 650-800 sq ft range) for a faster review, or submit a fully custom design.
3
Prepare your plan set
You'll need a site plan, floor plans and elevations, and documentation supporting the owner-occupancy requirement.
4
Site plan review & building permit
Building Services and Planning review your submission for zoning and code compliance. By-right ADUs don't require a Planning Commission hearing.
5
Construction & inspections
Schedule required inspections through construction. Separate utility metering is allowed as long as the property owner remains billed for both units.
6
Business license (if renting)
Apply for a rental dwelling business license before renting the ADU or the primary home long-term. Short-term rentals under 30 days aren't permitted.
The Planning Division can be reached at 801-535-7700 for zoning and ADU Handbook questions. Fees and review timelines vary by project - confirm current figures directly with the city.
Budgeting
What it costs to build an ADU in Salt Lake City
Garage conversion
Roughly $60,000-$160,000, the least expensive path since the shell already exists
Basement conversion
Roughly $90,000-$200,000, depending on existing ceiling height, egress, and utility access
New detached ADU
Roughly $130,000-$290,000 for a code-compliant, fully insulated freestanding unit
Business license
Base fee around $193 plus a per-unit fee (discounted for landlords who join the city's Landlord/Tenant program); owner-occupied properties with 4 units or fewer skip the per-unit fee
These are general ranges from local contractor estimates and regional reporting, not quotes - actual cost depends heavily on lot conditions, finishes, and utility access. If your property is on Salt Lake City's west side, ask about the city's Community Reinvestment Agency ADU loan program, which has offered low-interest construction financing (up to $200,000 at a 3% fixed rate) to eligible homeowners in specific neighborhoods.
Before you apply
Tips for a smooth approval
Decide between internal and detached early. Internal ADUs get the strongest legal protection under state law and now have no size cap, while detached units are capped at 1,000 sq ft and follow the city's own zoning rules.
Plan around the owner-occupancy rule. You or a qualifying family member must occupy either the primary home or the ADU - a standard permit won't let you rent out both units as a pure investment.
Check whether you qualify for reduced parking. Properties near transit or bike infrastructure can skip the one-space requirement, which can free up yard space for a larger unit.
Ask about the west-side ADU loan program. If your property is in an eligible neighborhood, the city's CRA financing can meaningfully offset construction costs.
Budget for the business license if you plan to rent. A separate rental dwelling license, with its own per-unit fee, applies on top of your building permit costs.
FAQ
Common questions
Do I need to live on the property to build an ADU in Salt Lake City?
Yes. Either the primary residence or the ADU must be occupied by the property owner or a qualifying family member. The City Council kept this requirement in its 2023 ordinance update, though it committed to revisiting the issue.
Is there a state law that guarantees my right to build an ADU?
Yes, for internal ADUs. Utah Code § 10-9a-530, created by 2021's HB 82, requires every city and county to allow at least one internal ADU as a permitted use in an owner-occupied, detached single-family home. It doesn't guarantee a right to build a detached ADU - that depends on your city's own ordinance.
What's the maximum size for a detached ADU?
1,000 sq ft of gross floor area. Height is capped at 17 ft, or up to 24 ft if you provide additional side and rear setback (roughly an extra foot of setback per foot of added height above 17 ft). Units within 10 ft of a corner side lot line are limited to 17 ft.
Is there a size limit for an internal ADU?
No, not since Salt Lake City's 2023 ordinance update removed the previous 50%-of-primary-structure cap. It still has to fit within the existing home and meet building code requirements for a dwelling unit.
Do I need extra parking for an ADU?
Usually one off-street space, but it's waived if your property is within a quarter mile of transit or a half mile of designated bike infrastructure.
How many ADUs can I build on one lot?
One, regardless of your lot size, in addition to the primary dwelling.
Can I rent my ADU out on Airbnb or a short-term rental platform?
No. Salt Lake City prohibits renting an ADU for stays under 30 days. Long-term rentals of 30 days or more are allowed with the appropriate business license.
How much does an ADU cost to build in Salt Lake City?
Garage conversions tend to run roughly $60,000-$160,000, basement conversions $90,000-$200,000, and new detached units $130,000-$290,000, based on local contractor estimates and regional reporting - not counting permit or business license fees.
Is financial help available for building an ADU?
If your property is on Salt Lake City's west side, the Community Reinvestment Agency has offered a low-interest ADU construction loan program (up to $200,000 per household at a 3% fixed rate over 30 years) in partnership with CDC Utah, concentrated in the 9 Line Community Reinvestment Area and nearby neighborhoods.
