Cargo containers, long a staple of international trade, are designed to be affordable, sturdy and water-tight. …What’s new is that the enormous Corten steel boxes are now gaining mainstream popularity as building blocks for affordable homes in a variety of sizes and types. …“Once you do all the work involved in designing and building a container home that meets building code requirements, the cost is actually about the same as for building a comparable traditional home,” she says, estimating the final cost to be around $150 per square foot. …And because the containers were meant to withstand marine conditions, they have plywood flooring heavily treated with formaldehyde. The flooring must be removed and replaced to avoid off-gassing once the structure has been insulated and sealed for use as a home, Strauss explains.