Budget Breakdown: This $606K ADU in Seattle Tests the Limits of Pure Joy

For architect Ivan Kostic, the caving-in garage on a property he was eyeing struck him as an immediate opportunity—but he didn’t capitalize on it right away. "When my wife and I bought our house in Seattle in 2014, we thought the logical thing to do was take down the garage and build a detached accessory dwelling unit in its spot," recalls Kostic. Several years and two kids later, after launching his firm, 0.blok, with partners Ben Prager and Brian Nguy, he finally got around to it. It’s now an ADU that’s half garage, half house, and, in Kostic’s description, 100 percent joyful. "As architects, we believe in joy," he says.

He used the build as a laboratory for fun-filled ideas that client projects don’t always allow for. And besides getting to experiment, he was able to get a better understanding of construction costs. "I wanted to figure out different assemblies and techniques but also understand the budget impact of those moves," he says. Having spent more than a decade on construction sites but never having built anything himself, he, with the help of his brother-in-law, spent three years replacing the garage and incorporating an 800-square-foot, dual-level dwelling behind it.