Construction Diary: How a Tucson Couple Built a $100K ADU—and How You Can, Too

In the summer of 2023, Logan Havens and Gustavo Silva restored a historic adobe in Tucson’s Barrio Kroeger Lane neighborhood. They learned by doing, developing an understanding of the structure and its materials, and how to update the modest home to meet their needs. But before the couple even finished the remodel, they were already plotting their next project. When the City of Tucson introduced a competition for an ADU model plan library, Gustavo, a designer, and Logan, a photographer, developed a design that adapts the adobe vernacular of the Sonoran Desert. Then, at the rear of their plant-filled lot, they built an example where Logan’s niece, an undergraduate at the University of Arizona, is currently living.

To stay within their $100,000 budget, the couple aligned material, aesthetic, and labor considerations. Building with insulated concrete form (IFC) blocks that were plastered and coated with lime wash, for instance, eliminated the need for drywall and painting crews. Visible materials such as wood, construction hardware, and troweled concrete floors are part of the design intent. Kitchen and storage systems are from Ikea. And, not least important, significant sweat equity, along with a tight-knit network of fellow designers and skilled tradespeople, made their financial planning realistic.

The plan for the 650-square-foot, one-bedroom unit, dubbed the Detached Sonoran ADU, is now part of the City of Tucson’s ADU plan library. For those interested in building one, Logan and Gustavo have compiled a step-by-step guide to go with the plan set, which includes a contractor list that can help with a build out. (The couple estimates that with professional help, a unit can be built for around double what they spent.) Here’s how Logan and Gustavo built their ADU, and how you can build one, too.

Home Depot Special

Gustavo: When Tucson opened up a competition for a model plan library, Logan reached out to all of his architect friends, and he was like, "Someone design something good. We just need to have good designs here."

Logan: They were all too busy. And so I was like, "Gustavo, would you do it with me?"

Gustavo: When we were designing the ADU, the code was more stringent than it is now, so our whole thing was that it had to be something Logan could build. We were pushing for nothing to be custom—everything had to be available at Home Depot, or somewhere, so anyone could build one. We also designed it to be built as is. You can change a couple of things, but there is no way of modeling the design beyond that.

Logan: The building is 38 feet wide, and the average lot size is 50 feet, so that would give you the five-foot setbacks required by the city on both sides for the average lot. We designed one side of the house for privacy, and kept the plan as narrow as possible to have more yard space between houses. The ADU has a traditional Sonoran-style three-sided parapet, and then ten feet is the highest we could make the ceiling without having an engineer. So everything is within existing code, including materials and allowances.