The ideal size for an accessory dwelling unit (ADU) in Denver typically ranges from 600 to 850 square feet, accommodating a versatile one-bedroom layout. However, the maximum allowable size is directly determined by your lot size, personal needs, and specific zoning regulations. This guide provides a data-driven breakdown of Denver’s official ADU size requirements to help you determine the perfect dimensions for your project.
First, What Is Considered an ADU in Colorado?
An Accessory Dwelling Unit in Colorado is a smaller, self-contained home on the same lot as a primary single-family house. To be a legal ADU, it must be a fully functional and independent living space.
Key Components: Kitchen, Bathroom, and Separate Entrance
Every ADU must contain its own kitchen, bathroom facilities, a sleeping area, and typically a separate entrance. This ensures it can function as a standalone residence.
Detached vs. Attached vs. Internal ADUs
ADUs can be detached backyard cottages, apartments over a garage (“carriage houses”), additions to the main home, or even converted basements. The type you choose will influence the design and placement on your property.
The New 2025 Colorado Law: How It Impacts Your Denver ADU Project
Exciting news for homeowners! A new statewide law, Colorado House Bill 24-1152, effective in 2025, is set to make building an ADU in Denver easier by streamlining approvals and removing common barriers.
Understanding House Bill 24-1152
The primary goal of this legislation is to create more uniform standards for ADUs across the state, thereby encouraging the development of more housing options. As outlined in the bill’s summary, key changes for Denver residents may include the removal of previous owner-occupancy and some off-street parking requirements, which have historically been significant hurdles.
Denver ADU Size & Placement Requirements: The Official Rules
While the new state law provides a framework, Denver’s specific zoning code remains the primary guide for your project’s size and placement. These regulations are enforced by the Denver Department of Community Planning and Development (CPD).
Denver ADU Maximum Square Footage: How Big Can You Build?
To determine how large your ADU can be, you must refer to the specific zoning code for the City and County of Denver. The code ties the maximum allowable square footage directly to your property’s lot size, establishing a clear tier system. (For the most current and complete details, consult the [Denver Community Planning and Development website
| Lot Size | Maximum ADU Square Footage |
| Under 6,000 sq ft | 650 sq ft |
| 6,000 – 7,000 sq ft | 864 sq ft |
| Over 7,000 sq ft | 1,000 sq ft |
Denver ADU Height and Story Restrictions
In addition to square footage, the Denver Zoning Code also specifies that detached ADUs are generally limited to 1.5 stories and a maximum height of 24 feet. This allows for creative lofted ADU designs that feel spacious even on a smaller footprint.
How Lot Coverage and Setbacks Impact Your ADU Footprint
Denver has strict rules about how much of your lot can be covered by buildings (lot coverage) and how far your ADU must be from property lines (setbacks). An experienced builder is essential to navigate these rules and maximize your buildable area.
Popular ADU Sizes & Floor Plans in Denver: Real-World Examples
Regulations provide the limits, but real-world accessory dwelling unit examples show what’s popular and practical.
So, What Is the Average Size of an ADU in Denver?
Most ADUs built in Denver fall between 600 and 850 square feet. This range typically accommodates a comfortable one-bedroom layout, which is the most popular and versatile option for both renters and family members.
The One-Bedroom Standard (500-800 sq ft): The Most Popular Choice
This size is the sweet spot. It’s large enough for a comfortable living area, a full kitchen, a separate bedroom, and a bathroom, making it perfect for generating strong rental income or housing a couple. Great one-bedroom ADU designs often feature an open-concept layout and smart storage to maximize the space.
The Two-Bedroom Home (800+ sq ft): For Families or High Rental Income
If your lot allows, a two-bedroom ADU is ideal for a small family, roommates, or as a high-value rental unit that can significantly boost your income.
Analyzing the Cost & ROI of a Denver ADU
The final cost of your ADU depends on size, design complexity, and finish quality. A smaller, high-end ADU can cost as much as a larger, more basic one. Generally, a one or two-bedroom ADU offers the best return on investment due to high demand in Denver’s rental market. An expert can help you analyze the potential ROI based on your specific goals.
Frequently Asked Questions (ADU Sizing in Denver)
What is the ideal size for an ADU in Denver?
The ideal size for most Denver homeowners is between 600 and 850 square feet. This range comfortably fits a one-bedroom layout, which offers the best balance of livability, construction cost, and rental income potential. The final size should align with your property’s specific zoning and your personal financial goals.
What is the maximum size for an ADU in Denver?
The maximum ADU size in Denver depends on your lot size. For lots under 6,000 sq ft, the maximum is 650 sq ft. For lots between 6,000 and 7,000 sq ft, it’s 864 sq ft. For lots over 7,000 sq ft, the maximum size is 1,000 sq ft.
What is the new Colorado law for ADUs?
Effective in 2025, Colorado’s House Bill 24-1152 mandates that local jurisdictions streamline ADU approvals. Key changes for Denver residents may include the removal of owner-occupancy and some off-street parking requirements. This state-level law makes it significantly easier for homeowners to build an ADU on their property.
How much does a typical ADU cost in Denver?
The cost to build an ADU in Denver generally ranges from $250,000 to over $450,000. The final price depends heavily on the unit’s size, the complexity of the design, the quality of interior finishes, and the specific site conditions, such as utility connection requirements.
Ready to Design Your Perfect ADU? Let’s Talk
Finding the ideal size for your accessory dwelling unit in Denver is the first exciting step. The key is to balance your vision with the practical realities of your property and local codes. Navigating the permitting process can be complex, but working with a specialized ADU builder ensures your project meets all requirements from day one.
Schedule a Free Consultation to Discuss Your Project
If you’re ready to explore what’s possible on your property, let’s connect. We can discuss your needs, evaluate your lot, and help you design and build the perfect ADU for your family and your future.
