In many cases, yes! Whether you can build—and what you can build—depends on whether your property is located within the City of Tucson or unincorporated Pima County, your zoning, lot size, existing structures, setbacks, easements, and other site-specific requirements.

One of the first things we do is evaluate your property to determine what may be possible before you invest heavily in design and construction plans.

The terms are often used interchangeably in everyday conversation, but they can have different meanings under local zoning codes.

An Accessory Dwelling Unit (ADU) is generally a secondary, independent living space located on the same property as a primary residence and includes living, sleeping, kitchen, and bathroom facilities.

In Tucson, ADUs are commonly called casitas. In unincorporated Pima County, guest houses have their own zoning definition and requirements, so it is important to determine which rules apply to your particular project.

It depends on your jurisdiction (City of Tucson, Oro Valley, Marana, unincorporated Pima County) and also depends on your lot, zoning, and the size of your existing home.

Within the City of Tucson, current ADU regulations generally allow an ADU of at least 650 square feet and up to 1,000 square feet, subject to applicable size limitations and development standards.

Pima County, Oro Valley and Marana use different requirements for guest houses and secondary dwellings, so allowable size is evaluated based on the your property’s specific zoning.

Bigger isn’t always better! A thoughtfully designed 600–1,000 SF casita can provide an extremely functional one- or two-bedroom home.

There isn’t a reliable one-price-fits-all answer. Cost depends on the size, design, finishes, site conditions, utility locations, grading, septic or sewer requirements, and how far the casita is located from existing utilities.

A detached casita is essentially a small custom home. It requires a foundation, framing, roofing, insulation, electrical, plumbing, HVAC, windows, doors, cabinetry, countertops, flooring, fixtures, and finishes—plus permits and site work.

That’s why we recommend starting with the property and desired scope rather than relying solely on a generic “price per square foot.”

Yes. A new casita or ADU used as a dwelling requires permits. Permit processing times vary between the City of Tucson and Pima County.

Your project will require construction drawings and a site plan demonstrating the location of the proposed casita, property lines, setbacks, existing structures, utilities, and other relevant site information.

Cornerstone can help guide the project through the design, permitting, and construction process.

This depends on the jurisdiction (City of Tucson, Oro Valley, Marana, Pima County), zoning, property configuration, and sometimes additional overlays or site conditions.

For City of Tucson ADUs, current regulations generally provide for 5-foot side and rear setbacks, although other requirements can apply depending on where the structure is located on the property. Pima County guest-house setbacks are tied to the accessory-building requirements for the property’s zoning classification.

This is one reason we recommend calling us to evaluate your property before deciding exactly where your casita will go.

Absolutely—and this is one of the most common reasons our clients consider building a casita.

Casitas can be an excellent solution for aging parents, adult children, multigenerational living, caregivers, or family members who want to live nearby while maintaining their own private space.

If you’re planning for aging parents, we can also incorporate age-in-place features such as a zero-threshold shower, wider doorways, minimal steps, accessible bathroom layouts, and other universal-design elements.

Yes, but rental rules depend on the jurisdiction, zoning, HOA/CC&Rs, and how you intend to rent the property.

Local zoning approval to construct an ADU does not necessarily override private deed restrictions or HOA rules. If rental income is an important part of your plan, we recommend investigating those restrictions early in the process.

Yes, when it is permitted as an independent dwelling unit. A true ADU includes its own living facilities and can have a kitchen, bathroom, sleeping area, and living space.

This distinction is particularly important in Pima County because a guest house has a specific zoning definition. The type of structure being permitted needs to match how you intend to use it.

Start with the property—not the floor plan.

Before falling in love with a design, we recommend determining:

Is the property in the City of Tucson or Pima County? What is the zoning? Where are the property lines and easements? What setbacks apply? Where are the existing water, sewer/septic, electrical, and gas utilities? Is there adequate access for construction? Are there washes, floodplain issues, or other site constraints?

Once we understand what the property allows, we can work with you to develop a casita that fits your lot, your budget, and—most importantly—how you plan to use the space.