Yes, it is legal to build an Accessory Dwelling Unit (ADU) in your Denver backyard in 2026, provided you comply with updated state and local regulations. Under the implementation of Colorado HB24-1152, building standards for ADUs take effect in 2026 to streamline approvals and make construction on existing lots more feasible.

In Denver, you must adhere to specific Denver metro ADU development codes, which include the following requirements:

• Size Limits: Detached ADUs in Denver are permitted up to a maximum of 800 square feet.
• Setbacks: The structure must be positioned at least 5 feet from the property line.
• Foundation Standards: Denver mandates an engineered foundation. Due to the city’s expansive clay soils and a 36-inch frost depth, specific systems such as helical piers are often recommended or required to ensure structural stability.
• Zoning and Permits: You must verify your property’s specific zoning, allowable lot coverage, and height restrictions. The project will require a site-specific soil analysis and secured construction permits from the City and County of Denver.

Because regulations and building codes are subject to regular updates, it is essential to consult with the Denver local planning department and a licensed structural engineer before beginning your project.

• ADU Regulations Colorado 2026: Essential Guide for Homeowners