Christopher Smith is building his dream home—in 129 square feet. Exhausted and sweaty, he leans on the frame of the toolshed-size house he’s constructed from scratch. Not bad for a guy with no previous experience with a hammer. “I really, really underestimated how long it would take me to do this,” he says.

The plan formed as his 30th birthday loomed, when Smith—a military kid who moved seven times before he was 18—began to reflect on his idea of “home.” Shortly after, he forked over $16,000 for a five-acre plot near Fairplay and dedicated himself to a less-is-more concept known as the Tiny House Movement, which bucks current housing trends: At 2,349 square feet, the average U.S. home size has doubled since 1950.

Smith is building the mini abode in a friend’s Boulder backyard before towing it to its permanent location. He’s designed space-saving amenities like a sleeping loft and a composting toilet with water he’ll haul up himself. At the suggestion of girlfriend Merete Mueller, he began filming the home’s evolution for a documentary, Tiny: A Story About Living Small, to debut this spring. “We laugh about the early footage,” Smith says, “where I say it’d probably take two months.” Five months in, just the exterior was done.

The film also features tiny-house dwellers across the country. “We found that people who live in small houses prefer it,” Smith says, “because it frees up their lives and resources to focus on other things.” Still, the pair wrestles with the idealism—and realities—of bare-bones living. “I want a foot in both worlds,” Smith admits. Wielding a drill, he turns his left forearm upward, exposing a small tattoo: Go big or go home.

Watch it: View the trailer at tiny-themovie.com.