Thinking about turning your Aurora backyard into a flexible living space that pays you back? An accessory dwelling unit can create room for family, generate rental income, or boost resale appeal. The key is designing it right for Aurora’s rules, climate, and lots. In this guide, you’ll learn what is allowed, what it costs, how to pick the right ADU type, and smart design moves that make a small space live large. Let’s dive in.

ADU rules in Aurora today

Colorado’s new state law sets a baseline for ADUs across many cities, including Aurora. It requires an objective, administrative review and limits rules that used to slow projects, such as mandatory owner occupancy or extra parking in many situations. You can review the state’s overview on accessory dwelling units for high-level guidance and timelines. Explore Colorado’s ADU overview.

Aurora’s existing Unified Development Ordinance historically governed things like lot size, alley access, setbacks, and materials for detached ADUs. Local text is being updated to align with state law, but it still informs current placements and size caps. Check the ADU section of the UDO before you sketch. See Aurora’s ADU standards in the UDO.

What this means for you:

• Expect an administrative approval path guided by objective standards.
• Jurisdictions must allow ADUs in the 500 to 750 square foot range, at minimum.
• Owner-occupancy requirements and some parking mandates are limited by state law, but you should still confirm local guidance.

Check your lot and location

First, confirm whether your property is inside the City of Aurora or in unincorporated Arapahoe County, because the process differs. The county has its own ADU permit application and fee guidance for properties outside municipal boundaries. Review Arapahoe County’s ADU permit page.

Next, note the site features that affect design:

• Lot size and coverage. Aurora historically required larger lots for detached ADUs and limits accessory building coverage.
• Access. Detached ADUs were historically favored on alley-served lots.
• Setbacks, height, and materials. These shape the envelope and curb appeal.

If you are unsure how new state rules affect your lot, ask Planning for the current administrative checklist before finalizing a design.

Choose the right ADU type

Internal conversion

Converting a basement or attic is often the least expensive path. You can move faster if ceiling heights, egress, and ventilation meet code. A separate entrance and good sound separation make the space more livable for guests or renters.

Attached addition

An addition shares a wall and utilities with the main home. It typically costs less than a detached cottage and can be designed with one-level living in mind. If your rear yard is tight or setbacks are limiting, an attached layout is a practical middle ground.

Detached backyard cottage

A detached unit offers the most privacy and strong market appeal. It usually costs more because it needs a new foundation and utility runs. Historically, Aurora supported detached ADUs on alley lots, and state law may broaden your options. Confirm setbacks, height, and placement early.

Design for Aurora’s climate and code

Layout and light

In 500 to 750 square feet, open plans work best. Keep living and kitchen areas open, use built-in storage, and choose a stackable washer and dryer. Place larger windows in living areas to capture Aurora’s abundant sunshine, then add shade where afternoon heat can build. For local climate context, review typical sun and seasonal conditions. See Aurora’s climate snapshot.

Energy and comfort

Aurora enforces the 2021 IECC, so expect modern insulation and energy performance requirements. Consider high-efficiency heat pumps for heating and cooling and an electric or heat-pump water heater. If your roof is suited for solar, prewire now to save costs later. Review Aurora’s adopted codes.

Privacy and access

Give your ADU a clear, well-lit entry and consider a zero-step threshold if you are planning for long-term accessibility. Use sound-isolation details where an ADU shares walls or floors with the main home. Place windows and outdoor areas to protect privacy for both households.

Utilities, parking, and access

Plan for water, sewer, and electric needs early. Some properties require new taps or service upgrades, which add time and cost. The county’s permit materials highlight potential tap or connection fees, and similar considerations apply within Aurora. Check county guidance on fees and utilities.

Parking rules are shifting under state law. If your property already has off-street parking or a driveway, added spaces may not be required. Document existing parking and ask Planning how current standards apply on your block. For broader context on what the state allows, review Colorado’s ADU page. Learn how state law affects parking.

Budget, financing, and grants

Costs vary by type and site conditions:

• Conversions often range from about $60,000 to $175,000 based on scope and finishes.
• New detached ADUs in the Denver–Aurora area commonly run $150,000 to $350,000+ depending on size, utilities, and foundations. See typical ADU cost ranges.

Watch the big drivers: utility tap or meter upgrades, foundation and site work, permit and plan review fees, and finish level. For help on the financial side, Colorado created an ADU Grant Program for supportive jurisdictions and directed CHFA to offer financing tools for eligible borrowers. Keep an eye on grant cycles and local fee reductions. Read about Colorado’s ADU Grant Program.

Pro tip: Ask if pre-approved plan sets are available. Standard plans can lower design costs and move permits faster when jurisdictions adopt them. Explore the state’s ADU Toolkit.

Step-by-step game plan

• Confirm your jurisdiction so you follow the correct process for Aurora or unincorporated Arapahoe County.
• Schedule a preliminary call with Planning or the Building Division to understand the current administrative ADU checklist.
• Map your site: measure the lot, check for an alley, note easements, and verify setbacks and accessory building limits.
• Call your water, sewer, and electric providers to discuss taps, upgrades, and meter requirements.
• Get ballpark estimates for conversion vs detached options, then speak with lenders about HELOCs, cash-out refis, construction loans, or CHFA-supported options.
• List your must-haves: accessibility, energy efficiency, separate entry and egress, storage, and solar readiness.

Final thoughts

A well-designed ADU can bring flexibility, income potential, and long-term value to your Aurora property. Start with clear rules, choose the right type for your lot, and design for comfort and efficiency in our climate. When you are ready to plan your next step or want local insights on value and rental demand, connect with Kerri Dowling for a friendly, no-pressure conversation.

FAQs

Are ADUs allowed in Aurora?

• Yes. Aurora’s code provides for ADUs, and Colorado law now requires an administrative approval path in jurisdictions that allow single-unit detached homes.

How big can an ADU be in Aurora?

• State rules require jurisdictions to allow ADUs between 500 and 750 square feet at minimum. Aurora’s local caps are being updated to align, so verify current limits before you design.

Do I need a permit for an ADU in Aurora or Arapahoe County?

• Yes. All ADUs require building permits, plan review, and inspections. Expect fees and utility coordination, and follow the correct process for your specific jurisdiction.

Can my HOA stop me from building an ADU?

• Colorado law limits HOA covenants that prohibit ADUs, but HOAs may apply reasonable restrictions that do not effectively prevent construction. Check your HOA documents early.

How much does an ADU cost in the Denver–Aurora area?

• Conversions often range from about $60,000 to $175,000, while detached ADUs commonly run $150,000 to $350,000 or more depending on size, utilities, and finishes.

Are there grants or financing to help pay for an ADU?

• Yes. Colorado’s ADU Grant Program supports local jurisdictions, and CHFA is directed to offer financing tools for eligible borrowers. Watch for local fee reductions or pilot programs.