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Everything you need to know about building an ADU in Thornton, Colorado — zoning rules, permit process, costs, and typical rental income.
Under Colorado’s 2024 ADU law, Thornton homeowners can now add an accessory dwelling unit to their single-family property with streamlined by-right approval. Owner-occupancy is no longer required, and parking minimums near transit have been eliminated.
Typical Thornton ADU setbacks: 5 feet on sides and rear. Maximum height: 24 feet. Maximum size: 1,000 sq ft.