"The other day was my biggest struggle with being frustrated. I could hear David so loudly through the wall. He was talking on the phone and I was trying to write and create," said Moeller, whose book, "What Are You Waiting For?" was published during the planning of the house. "And it's going to be tougher this winter. At least right now we can go outside if we need to get away from each other."
If living tiny is a challenge, living in one with a roommate is doubly so, says urban design architect John Cetra, principal at CetraRuddy Architectural Design in New York City. In fact, the tiny home movement was originally a single-occupancy concept. But the economic recession and the public's desire for sustainable, eco-friendly housing quickly turned the idea into a flexible solution for a wide variety of people, including retirees, the homeless and young professionals seeking unique and affordable private homes. Nowadays, it is not unusual for two or more people to inhabit a tiny home.
And Cetra knows how challenging that can be, from firsthand experience.
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"We had lights hanging from hooks, bikes hanging from the ceiling," recalled Cetra, who lived in a 250-square foot Manhattan studio with his wife, who was also an architect, for about five years.
"Our books were stored in kitchen cabinets. Because we needed a large drafting table, we sacrificed by getting a small bed. It was so small that every so often my wife would roll out of bed and wind up underneath the drafting table."
The couple eventually moved to into a roomier, 1,500-square-foot home outside the city. "It felt," he admitted, "like we'd gone to heaven."
"We suddenly had two giant bedrooms, an eat-in kitchen, a garden. We could have dinner parties, have relatives stay over. It was fantastic."
Many people who have tried living with limited space and possessions say it is a fun challenge in the beginning but almost impossible to sustain permanently. In addition, people assume tiny homes come with substantial cost savings, but that is not always the case. Enhancements to tiny home design, such as solar panels and retro-fitted interiors can hike up the price significantly.
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"Our house is not anywhere near as cheap as we thought it would be," Moeller said. "We paid $220,000 to build this tiny mansion. Our solar panels were almost $20,000. A lot of the construction costs—excavating the building site, framing the house, the roof and the cost of labor—all that was extra."
A kit to build a house like Moeller's and Cottrell's costs about $75,000 (theirs was purchased from the Miami-based company, cabinfever.com). She said a good rule of thumb for anyone considering building tiny is to double the cost of the kit, which factors in the cost of materials, specialized construction and customized furniture.
"We know another family who lived in a tiny home. They say, 'Those were the best years of our lives.' However, they didn't stay there," Moeller noted. "But for us, this is truly our forever home. It's been a grand adventure, simplifying our lives and getting back to what matters."
—By Linda Federico-O'Murchu, special to CNBC.com.