ADU Rules in Lehi, Utah

Lehi has undergone a transformation unlike almost any other city in Utah over the past two decades. Positioned at the Point of the Mountain — the strategic corridor between the Salt Lake Valley to the north and the Utah Valley to the south — Lehi became the geographic center of Silicon Slopes, Utah's booming technology industry cluster. With major campuses for Adobe, Ancestry, Qualtrics (SAP), Vivint, Domo, and dozens of other tech companies, Lehi has experienced population growth that regularly ranks among the fastest in the United States. This growth creates intense housing demand that makes ADUs an attractive investment for property owners.

Utah Statewide ADU Law: HB 462 (2022) and SB 174 (2023)

Utah's landmark housing reform legislation changed ADU rules statewide. HB 462 (2022) requires municipalities to permit ADUs by right in residential zones — through ministerial (administrative) approval, without discretionary hearings or neighbor notification for compliant applications. SB 174 (2023) further strengthened these protections.

Key provisions for Lehi property owners:

• ADUs are permitted by right in residential zones — compliant applications must be approved without public hearings
• The city cannot require owner-occupancy as a permit condition
• The city cannot restrict ADU size below 50% of the primary unit's floor area or 1,000 sq ft (whichever is less)
• Reasonable development standards (setbacks, height, design) remain in effect but cannot function as an effective prohibition

Lehi's fast-growing city has updated its zoning code to reflect state requirements. Given rapid development, always verify that you are reviewing the most current version of the Lehi City Code.

Silicon Slopes: Housing Demand Context

Lehi is at the geographic and economic heart of Silicon Slopes — the tech corridor stretching from Salt Lake City through Lehi, American Fork, Orem, and Provo. Key Silicon Slopes employers with major Lehi presence include:

• Adobe (Adobe Lehi campus on Thanksgiving Way)
• Ancestry.com (Lehi headquarters)
• Qualtrics (SAP Qualtrics campus)
• Vivint (headquarters in Provo area)
• Domo (American Fork, near Lehi)

The concentration of high-wage tech employment within miles of Lehi residential neighborhoods creates sustained rental demand. ADUs in Lehi can command premium rents from tech workers who want proximity to their employers without paying single-family home prices.

Local Zoning and Permitted ADU Types

Lehi's residential zoning — including R-1-8, R-1-10, and newer planned development zones throughout the city's many subdivisions — permits ADUs pursuant to state law. Both attached ADUs (garage conversions, basement apartments, casitas) and detached ADUs (backyard cottages) are recognized.

Lehi's newer housing stock — built primarily from the 1990s onward — often features larger lot sizes and home footprints than older Wasatch Front communities, creating good opportunities for both attached and detached ADUs.

Important consideration: Many of Lehi's newer subdivisions are governed by HOAs with CC&Rs that may restrict accessory structures. Utah state ADU law does not preempt private HOA deed restrictions. Review your HOA documents before investing in ADU plans.

Typical local development standards (verify current code):

• Setbacks: Detached ADUs typically 4–5 ft from side and rear property lines
• Height: Detached ADUs generally limited to one story or 16–20 ft
• Parking: One additional off-street space may be required; verify current requirements
• Lot coverage: ADU may not cause total impervious coverage to exceed district maximums

Seismic Considerations: Wasatch Fault

Lehi sits at the Point of the Mountain on the Wasatch Fault system. The Wasatch Fault runs along the mountain front, and both Salt Lake County and Utah County are designated Seismic Design Category D under the Utah State Construction Code. The Utah Geological Survey (UGS) maps fault rupture hazard zones along the mountain base on both sides of Lehi.

New ADU construction must comply with IBC seismic provisions. A geotechnical investigation is advisable for new detached ADU foundations, particularly for hillside or bench-area parcels. Check UGS maps for fault rupture hazard zones before designing a new structure near the mountain front.

Flood Considerations

The Jordan River headwaters are in Utah Lake, and several water features and drainage channels run through Lehi toward the river. The Point of the Mountain area has some FEMA-designated flood zones associated with these drainages. Check the FEMA Flood Map Service Center (msc.fema.gov) for your specific parcel.

Permit Process

Lehi's Building and Planning departments have grown substantially to keep pace with development.

1. HOA check: Review CC&Rs if applicable before spending on plans
2. Zoning verification at Lehi City Planning (lehi-ut.gov)
3. Building permit application online via Lehi's permit portal, with site plan, architectural plans, and structural documentation
4. Plan review: May take 3–6 weeks given Lehi's high permit volume
5. Inspections: Foundation, framing, MEP rough-in, and final
6. Certificate of Occupancy upon passing final inspection

Planning: lehi-ut.gov | Phone: (801) 768-7100 | 153 N. 100 E., Lehi

Disclaimer: Lehi's rapid growth means zoning codes and development standards change frequently. Utah's statewide ADU laws (HB 462, SB 174) establish the baseline. HOA restrictions in Lehi's many planned subdivisions are private matters not governed by state ADU law. Always verify current requirements with Lehi City Planning and your HOA before beginning any ADU project.