Jay Shafer sweats the small stuff.

Hopping into a waist-high metal bathtub smaller than a shower stall, Shafer swung a faucet over his head to demonstrate how one bathes in the combination tub/shower/sink.

"It's better than a regular-sized tub because you can fill it with water up to your shoulders," he said.

Gesturing at the composting toilet a foot away, he added: "This bathroom is the part of this house I'm proudest of. It was inspired by the Japanese model of being very compact and very efficient. The whole room is 11 square feet, smaller than a standard closet."

Thinking small, targeting simplicity and paying meticulous attention to detail exemplify Shafer's craft: designing tiny houses.

The Sonoma County resident is considered a father of the tiny house movement, a burgeoning trend to live more efficiently in less space. It taps into several contemporary obsessions: green living, the maker ethos, urban homesteading.

'Live debt free'

"Jay articulated and popularized a philosophy of live small, live debt free, and have more time and freedom to pursue your life's passions," said Ryan Mitchell, editor of TheTinyLife.com, a website dedicated to living in small-scale structures. "He backed it up with some really attractive designs."

From a 119-square-foot house in Graton, Shafer, 49, writes books about small dwellings; whips up blueprints for Craftsman-style houses ranging from 98 to 288 square feet; plans weekend workshops for DIYers; and sketches out his latest brainstorm: an entire village with dozens of tiny dwellings, each less than 400 square feet, plus a larger common house and other shared amenities, to be erected in Sonoma County.

With typical wry sensibility, he's dubbed it the Napoleon Complex - Cohousing for the Antisocial. The idea has support from Sonoma County officials who see it as a way to address the urgent need for affordable housing.

Sonoma County hotbed

In fact, the county is a hotbed of the small-house movement, with an annual exhibit at the Sonoma County Fair, several small-house companies and at least 100 tiny dwellings.

About 3,000 of Shafer's house designs have gone out into the world. Like a latter-day Johnny Appleseed, the art-school graduate doesn't know how many have taken root.

True devotees live in them full time, while others plunk one in their yard as a guest house, office or in-law unit, or park them lakeside for a vacation cottage. A 120-square-foot house costs about $45,000 to build, evenly split between labor and materials, Shafer said.

Mitchell, who lives in Charlotte, N.C., is just putting the finishing touches on a house based on a Shafer design that is 130 square feet plus a loft. It took him six months to build and cost about $25,000 in materials.

"I've never built anything in my life since shop class in eighth grade," he said. "But you get 60-some pages of architectural drawings, blueprints, wall-framing instructions, interior detail; it's very comprehensive."

While there are no official counts on tiny dwellings, a survey by TheTinyLife.com last year drew 2,600 responses from Americans living in very small houses.

Barriers to growth

Lots of impediments keep the small movement from getting, well, big.

"Land, laws and loans are all issues," Mitchell said. "You need a place to put it - land is expensive - and the legal compliance for a tiny house to be allowed in the eyes of the city. Banks usually won't give loans on tiny houses because they are 'nontraditional assets.' "

Tiny, of course, is in the eye of the beholder, and it's relative to the number of occupants.

"A small house is one in which all the space is used well," Shafer said. "A 5,000-square-foot house could be a small house if 20 people lived there."

Some of his designs are 119 square feet to comply with zoning laws letting people build structures under 120 feet in their yard without permits. Another loophole: Many tiny homes are built atop flatbed trailers, so they are considered either RVs or "loads" and exempt from building codes.

The mild-mannered Shafer turns ferocious when it comes to zoning and size requirements.

"It's ridiculous," he said. "I came out with a manifesto in my 'Small House Book' about how dumb it is that these codes exist, how weird that there are so many McMansions, and that the average American house is not affordable to the average American."

A self-proclaimed "OCD type," Shafer clearly marches to his own drummer. He dissed Oprah Winfrey, refusing to truck his tiny house to Chicago when he appeared on her show because he didn't want it battered by winter storms.

Very supportive

Fourteen months ago, he walked away from the company he founded, Tumbleweed Tiny House Co., because his business partner "wanted to go big and I wanted to stay small," he said.

"We are very much supportive of Jay's identity and mission, and the community he wants to launch," said Debby Richman, chief marketing officer for Tumbleweed in Sonoma. Tumbleweed sells ready-made tiny homes on trailers starting at $57,000. They are certified as RVs so buyers can get standard RV loans with 10 percent down and interest rates around 6 percent.

Every square inch counts in Shafer's dwellings, which blend aesthetics and functionality. With a steeply pitched red metal roof above a cedar-clad exterior and knotty pine paneling inside, his Graton house resembles a fairy-tale cottage. It has a main room with a cathedral ceiling that's 10 feet tall at its peak, a gallery kitchen, a loft sleeping area big enough for a very intimate couple, built-in storage galore and the closet-size bathroom. Abundant windows and skylights admit natural light and provide long sightlines. Heat comes from a toaster-size propane-powered metal fireplace. City utilities provide water and electricity.

Sitting at the ample desk (in other models, it might be a couch that doubles as a bed), Shafer swept his arms around the main area, where he can host six dinner guests.

"Each of my houses has a 'great room' - I call it the Elbow Room," he said. "I always try to make one space that is volumetric."

"Jay does beautiful tiny houses that are very appealing to a segment of the population who love that idea of paring away all the excess and living in the scale of a boat," said Sarah Susanka, author of the "Not So Big House" series, which explores living "better rather than bigger," albeit not in quite as minuscule dimensions as Shafer. "What he's doing is really thought-provoking."

Inspired by Thoreau

In fact, inspiring people to consider alternatives may be the tiny house movement's ultimate legacy.

"Living in 100 or 200 square feet is an extreme, and most people would not be OK with it," Mitchell said. "But if it gets people's minds whirling and they end up living in a somewhat smaller space with more financial stability and more time to spend with family, that will be the biggest impact."

Now that Shafer has a wife (Marty, a veterinarian in Sebastopol) and two sons (Emerson, 4, named for Ralph Waldo Emerson, and Kaldar, 1 1/2), he lives in his version of a mansion - a whopping 500-square-foot two-bedroom - and uses the 119-square-foot place in the yard as his office.

"I spend all my waking hours here and just bunk in the big house," he said. "All you really need is a desk, a bed and storage - that's all that Henry Thoreau had. He was one of the earliest small-house people."

Learn more DIY workshop: Dec. 14 to 15 in Emeryville. Details online: Go to www.fourlightshouses.com.