"I felt really trapped," she said. Moving to a 120 square-foot space enabled them "to live in a different way, take control of our lives."
Postings on online marketplace Tiny House Listings have increased in volume since 2011, while the site's Facebook fan count hit 182,000 on July 8, up 5,500 from the previous week. Google trends shows national interest in the search term "tiny house" surging since May.
"Since I got into the small-house game 15 years ago, every year seems like it's the biggest ever," said Shafer, who founded the Tumbleweed Tiny House Company in 1999 and started another, Four Lights, in 2012. "The need for it just becomes increasingly apparent."
Some advocates are refugees from the recent real-estate bust. Macy Miller's 2,500-square-foot Idaho home was foreclosed on in 2007, following her divorce. "I have absolutely zero interest in tying myself up with that kind of loan ever again," she wrote in an email.
In 2011, Miller literally took matters into her own hands, building a 196-square-foot timber home on a trailer in Boise, Idaho. She completed it in 18 months for $11,000 with zero debt, pays $200 a month to rent the land and shares the space with her partner, their baby and a 100-pound Great Dane named Denver.
Aspirants to the lifestyle tend to "skew female," according to Tumbleweed's web traffic, said Debby Richman, the Sonoma, California-based company's chief marketing officer.
"Tiny houses are no longer strange," she said. "They are now 'cute.' The cultural mores have changed."
The largest share of inhabitants, 23 percent, are between ages 31 and 40, according to "The Tiny Life" blog, which surveyed more than 2,600 dwellers in the U.S. Almost 90 percent said they had at least some college education and 61 percent had zero credit-card debt.
"This is the second coming of the Sears Roebuck house," said Richman, referring to the ready-to-assemble mail-order kits. Sears sold about 70,000 of these homes between 1908 and 1940, according to the company archive website.
There are several geographic hot spots, according to Richman. While it's easier to build in rural areas where zoning laws are less restrictive, Portland and Seattle have attracted builders because of their "open-mindedness," she said.
"Wherever you find expensive housing on the East Coast or the West Coast, you find a higher concentration of tiny houses because people understand the need," Shafer said.
In Washington, D.C., Boneyard Studios advocates mini homes as a solution to underutilized spaces, known as infill. The site showcases three places in a triangular alley lot, once filled by illegally parked cars. There's a communal fire pit, hot tub, outdoor oven and garden. Boneyard has a legal address, electricity and uses incinerator toilets and a rainwater- collection system with RV-like water pumps.
The homeowners, who lead tours every few weeks for approximately 50 guests, can't call these structures permanent legal residences because of zoning restrictions. To get around that, Boneyard's builders constructed the houses on wheels, making them technically travel trailers.
The codes exist to maintain standards, said Ellen McCarthy, director of the city's Office of Planning, as she praised Boneyard's "high-quality" and "environmental stewardship."
"We need some level of controls so people aren't setting up squatter camps in alleys," she said. "We're trying to recognize that people's situations require a variety of different living arrangements." The planning office recently proposed easing restrictions that could pave the way for legalizing tiny houses in backyards.
Until recently, the movement was so small-scale it flew under the radar of local, state and federal authorities. The lack of legal parameters might be the biggest barrier to growth, said LaVoie. "People feel intimidated by zones and coding," she said.
Pent-up demand will drive legislation, said Matthew Campbell, co-founder of Frontier Fortress, a Wyoming-based tiny- house company. "The laws are going to change. They will have to."
On a personal level, the psychological hurdle of parting with one's possessions restrains a large number of people from going tiny. While liberating for some, dramatic downsizing can prove too taxing on the psyche for others.
Shafer, the movement's champion, said it took him "years" to figure out how to thrive with less.
Immel, the schoolteacher who finished his home in late 2013, said he wasn't sure the lifestyle would suit him long- term. He built the house with resale in mind, "just in case."
His home, which has a façade that's 20 percent glass, doesn't feel claustrophobic, he said, and heating it through the harsh winter was next to free. With total expenses about $900 a year, including about $112 for propane and the rest for electricity, his $40,000-plus salary easily sustains him — and his savings account.
The best thing about his little house, he said, is how it gave him "complete peace of mind."