ADU Construction in Utah: Rules, Costs, and Permits for 2026
ContractorLink Team May 1, 2026
ADU Construction in Utah: 2026 Guide
Accessory Dwelling Units (ADUs) — also called in-law suites, basement apartments, or backyard cottages — are booming across Utah. State law now requires most cities to allow ADUs on single-family lots.
Types of ADUs
- Attached ADU: Addition to main home
- Detached ADU: Separate structure (backyard cottage)
- Basement ADU: Separate entrance from existing basement
- Garage conversion: Convert attached or detached garage
Construction Costs
- Basement conversion: $40,000–$90,000
- Detached ADU (400–600 sqft): $120,000–$220,000
- Garage conversion: $50,000–$100,000
- Attached addition ADU: $150,000–$280,000
Zoning & Legal Requirements
Utah's ADU law (SB 82, updated 2023) requires cities to allow at least one ADU per single-family lot. However:
- Setback requirements still apply (typically 5 ft side/rear)
- Maximum size limits vary by city (usually 50% of main home or 1,000 sqft)
- Owner-occupancy may be required in some cities
- Separate utility connections may be required
Permit Process
Expect 4–12 weeks for ADU permit approval. Required documents:
- Site plan showing setbacks
- Floor plans and elevations
- Structural drawings (engineer-stamped)
- Utility connection plan
Peaking E&C (pec-ut.com) provides ADU engineering and permitting support across Utah.