Why Phoenix-Area Homeowners Are Building ADUs
Why now
Two things changed. Housing in the Phoenix metro got expensive enough that a second small home on a lot you already own became one of the most practical ways to add space or income. And Arizona's 2024 law required larger cities to allow ADUs on single-family lots, which removed the biggest obstacle in many neighborhoods. The result is that a casita, a converted garage or an attached suite is now a realistic project for a lot of homeowners who could not have built one a few years ago.
What people use them for
The same building serves very different purposes, and the purpose shapes the design.
- Multigenerational living: a parent or adult child nearby with their own kitchen, bathroom and front door
- Rental income: a long-term tenant in a self-contained unit, where the city allows it
- Aging in place: a single-level unit with wide doors and a no-step shower, either for the owner or a caregiver
- A home office, studio or workshop with a bathroom and kitchenette that can become living space later
- Guest quarters that are genuinely private instead of a spare bedroom
What makes a lot a good candidate
Most of the Valley's older neighborhoods were built with generous backyards, which is why so many ADUs are going up in Mesa, Tempe, Phoenix and Scottsdale. The best candidates have room for the unit plus the setbacks the city requires, a way to get equipment to the back of the lot, utilities that can reach the site without heroic trenching, and a main house whose electrical service has capacity to spare. A pool, a mature tree or a septic system does not rule a lot out, but each one changes where the unit can go.
A Mesa-area ADU build
One of our recent projects, the Mulberry Residence, is a detached ADU behind an established Valley home with a pool. The photos follow the job from the start: trenching for water, sewer and electrical across the yard, forming and pouring a reinforced concrete slab, framing the walls and roof, setting cabinetry inside, and paver work that ties the new building into the pool area. It is a good picture of how much of an ADU happens below the ground and inside the walls before the finished casita appears.
See the full photo set on the Mulberry Residence project page.
Questions to settle before you design
A short conversation up front saves redesign later.
- Who will live in it, now and in ten years?
- Will it ever be rented, and does your city allow that?
- Single-level, or is a second story worth the extra structure and cost?
- Should it share the main house's utilities or be metered separately?
- How much privacy do the two homes need from each other?
How to start
Read our guide to what an ADU involves in Arizona for the process in detail, then have us walk the lot. We check what the city and any HOA allow, where utilities can run and where the unit fits, and come back with a design and an itemized estimate instead of a guess.