Utah County · 93,446 residents
Lehi ADU rules
Lehi: internal ADUs allowed (lot 6,000+ sq ft); detached ADUs allowed (lot 11,000+ sq ft). Owner occupancy applies.
Internal ADU (inside the home)
Detached ADU (backyard building)
✓ Checked against city sources on September 24, 2026 See sources
Lehi ADU rules at a glance
| Rule | Internal ADU (basement, attic, inside the home) | Detached ADU (backyard building) |
|---|---|---|
| Allowed? | Allowed | Allowed |
| Minimum lot | 6,000 sq ft. The lot must be at least 6,000 sq ft, and the home must not be in an area on the city's ADU Restricted Area Map. | 11,000 sq ft. Since July 14, 2026, detached ADUs are allowed on lots of 11,000 sq ft or more (down from 14,520 sq ft), matching the statewide floor. |
| Owner occupancy | The home must be owner-occupied; the owner signs an owner-occupancy affidavit that is recorded against the property (new owners must re-record it). | Owner occupancy is required. Lehi's detached-ADU code applies the internal-ADU owner-occupancy rule, with a recorded affidavit, and the city's detached-ADU declaration says one of the two dwellings must be owner-occupied. |
| Parking | One off-street stall of at least 9 x 20 ft, separate from and not tandem with the home's required parking, plus a lighted walkway from the parking to the ADU entrance. | Two off-street stalls for a unit over 650 sq ft, or one for a unit under 650 sq ft (each at least 9 x 20 ft), in addition to the home's parking. |
| Size limits | Lehi sets no size limit for an internal ADU. | Finished living area must be smaller than the main home, and the dwelling portion must be at least 300 sq ft. |
| Height | Not yet verified — confirm with the city | No taller than the main home, with a 35 ft maximum. |
| Setbacks | Not yet verified — confirm with the city | Must be beside or behind the house and at least 6 ft from it. A new or post-2020 building can be 5 ft from a side or rear lot line if that wall has no windows (or two small opaque ones); otherwise 10 ft for a one-story building up to 20 ft tall. Two-story or taller buildings must meet house setbacks. Conversions of pre-2021 buildings need 5 ft from lot lines. |
| Zones | Only in single-family detached homes, and not in areas on the ADU Restricted Area Map (the city also excludes resort and planned communities, townhomes, duplexes and multifamily). | Allowed with single-family detached homes on qualifying lots, but not in areas on the ADU Restricted Area Map; one ADU per lot (internal or detached). |
| Short-term rentals | A property may hold both an ADU permit and a short-term rental permit, but only one of those uses can be active at a time. | The code lets a property hold an ADU permit or a short-term rental permit but use only one at a time; city staff said an approved detached ADU may operate as a short-term rental. |
| Permit process | A Planning Division ADU permit ($25 application fee), a building permit, and an active ADU license while the unit is rented. The unit must keep an interior connection, such as a locking door, to the main home. | A permitted use with no conditional use permit, reviewed by city departments for access, utilities and addressing. Requires a building permit, a $25 application fee, and an impact fee ($4,253 on the city's form). Utilities must connect through the main home, and a 12 ft all-weather access is required. |
What the Lehi council decided
Recorded votes and actions on ADU rules, linked to the public meeting record on OpenUtah.
· City Council
Approved Ordinance 2026-31 amending Chapter 26 detached ADU rules for SB 284: 11,000 sq ft minimum lot, 1 or 2 parking stalls by size, size cap tied to the main home, 6 ft from the house, and no CUP for conversions (5-0).
Read the meeting record· City Council · Approved
City Council approved Ordinance #47-2025 amending Development Code Chapter 26 requirements for detached ADUs.
Read the meeting record· Planning Commission Meeting · Approved
Planning Commission gave a positive recommendation on a code amendment allowing detached ADUs on 1/3-acre lots.
Read the meeting record
State law: detached ADUs from October 1, 2026
Lehi is a “specified municipality” under Utah S.B. 284. Beginning October 1, 2026, it must permit one detached ADU as a permitted use on a lot of 11,000 sq ft or more that has a detached single-family home. The city can still apply setbacks, height, design, owner-occupancy and limited parking rules, and it may allow detached ADUs on smaller lots. How the state ADU laws work.
How our property map screens Lehi lots
The map colors parcels using the rules on this page and the recorded lot size. A color is a planning screen, not a permit; Lehi makes the decision.
- "Likely" above 15,000 sq ft is this site's planning band for a large recorded lot. It is not a sentence in the Lehi code. Owner occupancy, parking, setbacks, zones, and HOA rules below still have to be checked.
Planned communities, PRDs and PUDs
Lehi City's ADU FAQ says an ADU is not allowed in a Resort Community or a Planned Community, or on a townhome, duplex, or other multifamily property. The map applies that sentence when the assessor class or subdivision name says planned community or resort community, at any lot size. The same FAQ still describes an older detached lot size; the July 2026 lot-size change is recorded separately and does not remove this community limit. A generic PUD label that does not say planned community stays on the unconfirmed planned-community screen. Source: Lehi City ADU FAQ, lehi-ut.gov, read September 22, 2026.
Sources
We link only to government sources and public meeting records. Codes change; confirm the current version with Lehi before you apply.
- Lehi City Development Code Chapter 26 — Accessory Uses (updated Sept 15, 2026)
Current codified 26.030 (internal ADUs) and 26.040 (detached ADUs, amended 07/14/26): lot sizes, owner occupancy, parking, size, setbacks, height, permitted-use review.
- Lehi City Council, July 14, 2026 — Ordinance 2026-31 Chapter 26 DADU amendment (OpenCity)
Staff report (state-required changes, no CUP, short-term rental note) and 5-0 approval.
- Lehi Application for Detached Accessory Dwelling Unit
Application fee and impact fee amounts; owner-occupancy declaration ('one of the dwellings must be owner occupied'). Lot size and parking on this 2024 form are outdated.
- Lehi Application for Internal Accessory Dwelling Units
$25 application fee and owner-occupancy declaration.
- Lehi Accessory Dwelling Units FAQ
No size restriction for internal ADUs; exclusions for resort/planned communities and attached housing (2022; detached details outdated).
- Utah S.B. 284 (2026), enrolled copy
Enacts Utah Code 10-21-304 (effective Oct 1, 2026): specified municipalities must permit a detached ADU on single-family lots of 11,000 sq ft or more; defines 'specified municipality'.
- Utah Code 10-2-301 — Classification of municipalities
City class population thresholds.
- Utah Code 17-60-104 — Classification of counties
County class population thresholds.
- U.S. Census Bureau Vintage 2024 subcounty population estimates
July 1, 2024 population estimates for Utah places and counties.
- Official Lehi website
Common Lehi ADU questions
Can you build an ADU in Lehi?
Lehi: internal ADUs allowed (lot 6,000+ sq ft); detached ADUs allowed (lot 11,000+ sq ft). Owner occupancy applies. This is planning guidance, not a permit. Confirm the zone on your parcel with Lehi.
What lot size does Lehi require for an ADU?
Internal ADU: 6,000 sq ft minimum. The lot must be at least 6,000 sq ft, and the home must not be in an area on the city's ADU Restricted Area Map. Detached ADU: 11,000 sq ft minimum. Since July 14, 2026, detached ADUs are allowed on lots of 11,000 sq ft or more (down from 14,520 sq ft), matching the statewide floor.
Does Lehi require the owner to live on the property?
Internal ADU: The home must be owner-occupied; the owner signs an owner-occupancy affidavit that is recorded against the property (new owners must re-record it). Detached ADU: Owner occupancy is required. Lehi's detached-ADU code applies the internal-ADU owner-occupancy rule, with a recorded affidavit, and the city's detached-ADU declaration says one of the two dwellings must be owner-occupied.
How much parking does a Lehi ADU need?
Internal ADU: One off-street stall of at least 9 x 20 ft, separate from and not tandem with the home's required parking, plus a lighted walkway from the parking to the ADU entrance. Detached ADU: Two off-street stalls for a unit over 650 sq ft, or one for a unit under 650 sq ft (each at least 9 x 20 ft), in addition to the home's parking.
Can an ADU in Lehi be a short-term rental?
Internal ADU: A property may hold both an ADU permit and a short-term rental permit, but only one of those uses can be active at a time. Detached ADU: The code lets a property hold an ADU permit or a short-term rental permit but use only one at a time; city staff said an approved detached ADU may operate as a short-term rental.
What does it cost to build an ADU in Lehi?
Wasatch Front planning bands are often about $55,000–$145,000 for an internal suite, $70,000–$175,000 for a garage conversion, and $95,000–$250,000 or more for a new detached unit, before unusual site work. These are planning ranges, not bids.
Can an HOA block an ADU in Lehi?
City approval does not override CC&Rs or plat notes. Read the HOA documents and your subdivision plat before you design. A private restriction can stop a unit the city would otherwise allow.
Before you design: general checks for any Utah ADU
General planning advice, not Lehi code.
- Confirm the zoning district on the city zoning map. The county assessor’s “residential” class is not zoning.
- Read your HOA CC&Rs and subdivision plat notes; private restrictions can block a unit the city allows.
- Sketch existing and proposed parking. Driveway geometry and access often decide what fits.
- Ask early about sewer, water and electrical capacity; utilities can force a redesign.
- Expanding a building’s footprint usually triggers full setback and height rules.
Nearby city ADU rules
Want to know what fits on your Lehi lot?
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Utah ADU Builder provides educational planning guidance. This page is not legal advice and not a permit. Population: U.S. Census Bureau population estimate (2024). Editorial standards.