Building a Casita in Tucson: How ADU Plans Become Dream Spaces in 5 Practical Steps

Turning a vision into a fully built Accessory Dwelling Unit (ADU) takes more than a sketch or a Pinterest board—it takes a thoughtful, well-guided process. Whether you’re imagining a cozy guest house for visiting family or adult children, a retreat to support aging parents, a quiet office or studio space, or a compact rental that brings in extra income, building an ADU requires clarity, coordination, and a clear understanding of your goals.

In Tucson and Southern Arizona, these smaller, independent living spaces built on the same lot as your primary single-family home, are often called casitas, Spanish for “little house,” reflecting the region’s Southwestern roots and Spanish-inspired architecture. With their own entrance, bathroom, and kitchenette, they offer the comfort, privacy, flexibility, and independence of a full multi-generational living space. Casitas are seen as a modern, versatile solution to a wide range of needs. Beyond functionality, their smaller size often means a smaller footprint, lower maintenance, and improved energy efficiency.

For homeowners in Pima County, casitas offer a unique way to expand space, improve quality of life, and adapt to evolving needs, while also increasing property value. The key is knowing how to take that idea and turn it into something livable, functional, and beautifully designed.

Here’s how a successful ADU build typically unfolds, step by step.

Step 1 – Start with the Purpose, Not the Floor Plan

Before browsing layouts or comparing costs, start with a simple but powerful question: “Why am I building this casita?”

That answer drives everything else.

If you’re planning a cozy in-law suite to keep aging parents nearby or a comfortable space for a loved one with mobility needs without sacrificing their independence, accessibility features like no-step entries and wider doorways are likely non-negotiable. If you’re going for a rental unit that generates steady income without the hassle of major renovations, privacy and durability should be your top priorities. As for a home office away from distractions, it might call for natural light, airflow, soundproofing, and connectivity. Each purpose points to different design priorities, and keeping that clarity upfront makes every other decision easier. By designing with flexibility and functionality in mind, you’re future-proofing your investment and saving yourself from costly changes later on.

At Aaron & Co, this is where every project begins. Their collaborative Needs Analysis helps homeowners clarify their goals and distinguish between must-haves, nice-to-haves, and long-term priorities. That early conversation becomes the blueprint for everything that follows.

Step 2 – Choose the Right ADU Plan for Your Space and Your Budget

Once your “why” is clear, it’s time to consider the “how.”

That usually starts with a floor plan that fits your lot, lifestyle, and budget. Some homeowners prefer the speed and affordability of premade casita floor plans, which balance comfort, style, and functionality, and can be adapted to meet local zoning and lot configurations. Others may need something more custom and prefer the ability to tweak the layouts, finishes, and features, especially if the casita has a unique purpose or needs to match the architecture of the main house.

With smart layouts, your casita can feel bigger than it actually is. Elements like open floor plans, efficient storage, natural light, and thoughtful room flow can elevate the feel of the entire space. Even details like where the windows are placed or how the kitchen connects to the living area can make your new home addition feel spacious, livable, and efficient. Also, features like energy-efficient systems, clever storage solutions, and open-concept living areas help ensure your casita is as sustainable as it is stylish.

In Tucson, ADU builds can vary greatly in cost. One of the biggest pricing variables is the condition of your existing utilities and whether they need to be replaced, extended or upgraded to serve the new unit. The next major factor is finish selections. You might opt for high-end fixtures and materials or lean toward more economical options that still deliver comfort and quality. The final price also depends on square footage, level of customization, and site-specific considerations. A skilled design-build team like Aaron & Co starts with your budget in mind and works backward from there. That way, they’re never overdesigning a project, and every recommendation is grounded in what matters most to you. The result is a streamlined process that balances functionality and comfort while keeping the project aligned with your timeline, priorities, and financial goals.

Step 3 – Understand the Permits, Zoning, and Prep Work

Even the best design won’t move forward without the proper approvals.

In Tucson and Pima County, ADU zoning rules can vary from one neighborhood to the next. Setbacks, lot size, utility access, and easements are just a few of the factors that can influence what’s possible on your property. Permitting itself typically takes between 2 to 8 weeks, but additional government approvals can sometimes add more time to the overall process.

That’s why many homeowners choose to work with trusted local ADU contractors who know the ins and outs of the process and can manage it on their behalf. At Aaron & Co, permitting, zoning research, and site evaluations are all handled in-house. This streamlines timelines and removes one of the most frustrating hurdles in the building process.

Step 4 – From Groundwork to Finishes

Once approvals are in hand, the construction process — and real transformation — starts.

Most casita builds follow a similar construction flow:

• Site prep and grading
• Underground utilities
• Foundation work and framing
• Installation of systems like plumbing, electrical, and HVAC
• Interior finishes, including fixtures, cabinetry, flooring, and final details

On average, construction takes about 5 to 7 months, depending on the size and scope of the project. Clear, consistent communication throughout this phase is key. Homeowners want to know what’s happening, what’s coming next, and when their input is needed.

Some of the most defining moments happen at the very beginning. Whether you’re choosing custom cabinetry, sleek bathroom features, or thoughtful lighting and energy-efficient upgrades, these touches turn your construction project into a true home.

You can check out Aaron & Co’s full process here.

Step 5 – The Real Payoff: A Space That Works for You

At the end of the process, your new casita isn’t just a detached structure. It’s a beautiful, functional living space that supports your life and evolves with you.

Maybe it’s a quiet backyard home where loved ones can live independently but nearby. Maybe it’s a guest house that makes hosting easier and more comfortable. Or maybe it’s a flexible home addition that offers extra space, privacy, or even rental income down the line. Whatever your original motivation, the benefits of a well-designed ADU are long-lasting.

While a well-built casita can increase your property’s value, most homeowners aren’t thinking about resale. They’re thinking about how to solve a need, open new possibilities, and improve everyday life. And when designed with care, a casita does exactly that.

Thinking About a Casita? Start with a Conversation

You don’t need every answer before you begin. The most important part is having a clear goal and the right people to help you build toward it.

Whether you’re early in the planning phase or ready to explore your property’s potential, start by talking with someone who knows the process and the region. Then, you’ll be ready to take the next step with clarity and confidence.

Aaron & Co has helped dozens of Tucson homeowners design and build casitas that are just the right size, shape, and function for their lives. You can be next. Schedule your free consultation today and start turning your dream casita into a beautifully designed reality.