Everything homeowners ask about building an ADU in Salt Lake City — answered with 2026 data.
Yes, ADUs are allowed in Permitted use (P, no conditional-use permit) in every residential district of the 21A.33.020 use table - FR-1/FR-2/FR-3, R-1/12,000, R-1/7,000, R-1/5,000, SR-1, SR-3, R-2, RMF-30/35/45/75 and FBUN-1 - and wherever else Chapter 21A.33 lists 'Dwelling, accessory unit (ADU)'. Detached ADUs stopped needing conditional-use approval on April 4, 2023 (Ord. 17-23; 21A.40.200.N.3). H Historic overlay and Foothills (21A.24.010.P) rules still apply on top (21A.40.200.B). in Salt Lake City, UT. The maximum size for a detached ADU is 1,000 sq ft of gross floor area (21A.40.200.J.1). Only the ADU's floor area counts when the building also holds a garage or other accessory use; stairs to a second-level ADU, loft space under 7 ft and a storage-only basement with no internal connection are excluded (J.3). A covered patio up to 120 sq ft does not count toward the cap but does count toward lot coverage (H.3). Accessory buildings together may cover at most 50% of the rear yard in single/two-family districts (ADU Handbook v2.2). Attached ADUs can be up to No maximum gross floor area for an internal ADU. Salt Lake City has an ADU-friendliness score of 8/10. Check our full Salt Lake City ADU rules page for complete zoning details.
ADU construction in Salt Lake City typically costs $180,000-$350,000. The cost per square foot averages $300-$350. Garage conversions are more affordable at $120,000-$200,000, while prefab ADUs cost $100,000-$180,000. Permit fees add About $3,000-$5,000 in building-permit plus plan-review fees for a $150,000-$300,000 ADU: permit $1,425.97 plus $8 per $1,000 over $100,000 (Code 18.32.035), plan review 65% of that (FY2027 Consolidated Fee Schedule, amended 6/16/2026). Trade permits and a $35-per-unit rental licence are extra. to your budget. See our detailed Salt Lake City ADU cost guide.
Detached ADUs in Salt Lake City can be up to 1,000 sq ft of gross floor area. Attached ADUs are limited to No maximum gross floor area for an internal ADU. Junior ADUs (JADUs) have a cap of No junior-ADU category in Salt Lake City or in Utah law. The code recognises only internal ADUs (inside or attached to the house, no size cap) and detached ADUs (1,000 sq ft cap). A basement apartment is an internal ADU; a converted detached garage is a detached ADU and may keep the garage's existing setbacks if it is not expanded (21A.40.200.E.3 note 2). Maximum height is Detached ADU: 17 ft, measured the same way as the house (21A.40.200.F.1-2). Up to 24 ft with a pitched roof or 20 ft with a flat roof if the side and rear setbacks grow 1 ft for every foot above 17 ft; no extra setback on a side that abuts an alley or a non-residential district (F.1.a). A detached ADU fully inside the buildable area may use the district's principal-building height (F.1.c); rooftop solar may add 4 ft (F.1.d). Internal ADUs follow the house's height limit (F.3). You are allowed up to One ADU per property on a qualifying lot.
Rear setback: 3 ft from the rear property line for a detached ADU (21A.40.200.E.3), rising 1 ft per foot of height above 17 ft (F.1.a). Additions, including a second storey on an existing garage, must meet these setbacks; a conversion with no expansion may keep the garage's existing setbacks (E.3 notes). Second-storey windows on a wall within 10 ft of a rear or side line must be clerestory (sill 6 ft up) unless they face the house, an alley, or a commercial or non-residential lot (K). Side setback: 3 ft from an interior side property line; on a corner lot, 20% of the lot width or 10 ft, whichever is less, from the corner-side line (21A.40.200.E.3). A detached ADU in the interior side yard must sit behind the rear facade of the house; in the corner side yard it may be no closer to the street than the house unless the lot is under 50 ft wide (E.2). Side setbacks grow 1 ft per foot of height above 17 ft (F.1.a). Front setback: Not permitted in the required front yard (21A.40.200.E.2). Anywhere inside the lot's buildable area (the part of the lot outside all required yards) a detached ADU is permitted and may use the district's principal-building height (E.2, F.1.c). Rooftop patios are prohibited and decks over 2 ft high are barred outside the buildable area (H.1-2). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
1 off-street stall for the ADU on top of the house's required parking (21A.40.200.G.1) - waived if the lot is within a 1/4-mile radius of a public transit stop, within 1/2 mile of a city-designated bike lane or path, in a district with no parking minimum, or already has a spare stall beyond the house's minimum (G.1.a-d). The house's own required stalls cannot be removed to make room for the ADU. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Required on single-family lots: a deed-listed owner, a relative by blood, marriage or adoption, or a family-trust trustor must live in the house or the ADU (21A.40.200.C). Not required when the principal use is a duplex, multi-family or non-residential building (C.4.a); absences of up to 3 years for military service or job assignments and moves into medical or nursing care are excused (C.4.b-c). A recorded restrictive covenant carries the requirement and bans short-term rental of both units (P). Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in Salt Lake City is typically Review times are not published. The Handbook shows building-code, fire, Public Utilities, Engineering and Transportation reviews before the permit, then covenant, owner-occupancy and zoning-certificate steps before occupancy; ask Building Services (801-535-7968) for the current residential queue. Plan check: 65% of the building-permit fee (Code 18.32.035, CFS FY2027). Expedited review costs twice the standard plan-review fee (18.20.050); review of an identical plan set is 30% (Utah HB 368, 2025). Review duration is not published. Pre-approved plans availability: Five pre-approved standard plans on the Building Services ADU page (checked Sept 2026): a 650 sq ft 1-bedroom, a 775 sq ft 2-bedroom, an 800 sq ft 2-bedroom, a detached-garage conversion and a second-storey garage conversion, all drawn by private firms. A site review is still required for the permit and all fees still apply. The Planning Division's ADU Handbook (v2.2) is the zoning guide.
Average ADU rental income in Salt Lake City: 1-bedroom units rent for $1,300-$1,650/month, 2-bedroom units for $1,600-$2,000/month. Short-term rentals: No. An ADU may not be rented as a short-term rental (21A.40.200.Q.1) and the recorded restrictive covenant bars short-term rental of both the ADU and the main house (P.3). Expected ROI: Roughly 5-10% gross yield: a 1-bedroom at the HUD FY2026 Fair Market Rent ($1,456/mo, about $17,500/yr) against a $180,000-$350,000 build, before vacancy, tax, insurance and upkeep - 10-20 years to recover the build cost.
The minimum lot size for an ADU in Salt Lake City is None - 'There is no minimum lot size required for an ADU' (21A.40.200.N.1), and an ADU does not count toward district density (N.2). The base district's building-coverage and rear-yard-coverage limits still apply (L). This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In Salt Lake City, a garage conversion typically costs $120,000-$200,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
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