You've probably seen them stacked high to the sky at city ports, left empty after traveling around the world carrying furniture, appliances and other household goods.
But the next time you see a shipping container, it might be far from the waterfront and serving a purpose for which it was never intended: housing.
Originally developed as an artistic experiment, shipping container homes are moving into the mainstream, as architects and builders recognize the economic and environmental benefits of working with the giant Lego-like steel boxes.
"It's not just a bunch of mad scientists tinkering in a garage making these buildings," said Peter DeMaria, principal architect of DeMaria Design Associates, a Manhattan Beach, Calif.-based firm that has designed several container-based suburban homes. "It's people who understand the economics and understand the environmental benefits."
Each year, millions of shipping containers arrive on American shores. Because it's so expensive for empty containers to make a return trip across the ocean, DeMaria estimates that up to half never make it back. Some industry experts say the number of containers available for reuse hovers around 100,000, but can reach 700,000.
In addition to the several modern homes DeMaria's firm has already completed in southern California, it will launch a new line of shipping container homes in the coming weeks.
In the last year, he said, 25,000 people have inquired about these Logical Homes through the company's Web site. Each day, he said, about 10 others approach the firm by telephone or e-mail.
Although architects and builders have been experimenting with shipping container homes for the last few years, questions about structural integrity and legality have continued to nag.
But, DeMaria said, a home he designed for a family in Redondo Beach, Calif., last year changed the landscape for his company and others in the field.
Its completion demonstrated that a container-based building could conform to local building codes, he said, and proved that "it isn't going to fall down, rust away. The technical, functional issues have been put to bed."
Adam Kalkin, a New Jersey-based artist and architect, was one of the first people to experiment with shipping container homes more than 10 years ago.
Now, he has about 12 container-based homes under his belt, in addition to a new crop of prefabricated Quik Homes. But, when he started, building homes from the steel shells -- 40 feet by 9.5 feet by 8 feet -- was more performance art than practical enterprise.
"For me, it was an intriguing idea. I like their very sculpture in nature. [They're] beaten up. They've had this history," he said. "God knows where they've gone, what they've done and what they've seen."
"I loved the idea that you've taken something that has been all around the world and you localize it," he said.
When Kalkin first started, builders were so reluctant to join his experiments in construction that he had to take hammer to nail himself and recruit his friends.
But now, he said, two forces are contributing to the growing acceptance of container-based homes: a slumping economy and increasing environmental awareness.
Founded two years ago, SG Blocks (for Safe Green blocks) is one of the companies at the front of the field working to source and convert shipping containers for construction.