"Makers and designers of prefab houses promote the magic combination of less construction time and, often, lower building costs, because most of the work is done in a factory. They also appeal to second-home owners who want to avoid constant visits to the construction site. But as the prefab field grows, you need to do your legwork....

With any designer, ask how many homes the firm has built and how many are in the pipeline, and arrange to visit a finished house. The growing prefab field has led many designers to jump in, but not all them actually have designs that have been built....

Finding the right design is about not just visual appeal, but also such practical issues as finding one that can actually be built on the site. After all, the house has to be delivered on a flatbed truck. And it can be nearly impossible to deliver a modular house to a site that is off a windy, narrow road or one off a route with low overpasses."