Makers and designers of prefabricated metal buildings promote the magic combination of less construction time and, quite often, low steel building prices, as most of the work is done in a factory.

They also appeal to buyers who don't live that close by and who wish to avoid visits to the construction site on a regular basis. But as the prefab field grows, a buyer needs to do his or her legwork.

Prefabricated metal building is an umbrella term that covers any steel building constructed in a factory.

It includes everything from modulars that arrive in just a few sections — complete with attached walls, flooring and even finishes — to what are called panelized homes, which are delivered in smaller pieces.

With any designer, ask how many homes a firm has built and how many are in the pipeline, and arrange to visit a finished facility.

The growing prefabricated metal building business has led many firms to jump in, but not all actually have designs that have been built.

Finding the right design is about not just visual appeal, but also practical issues - such as finding one that can be built on site.

Prefabricated metal building firms also offer levels of hand holding to take prospective owners through not only the design phase, but also the permit process and the final construction.

In some cases, the owner is responsible for hiring a general contractor.

In Los Angeles, where designs from one steel building manufacturer start at $235,500 for a 660-square-foot metal building to be used for residential purposes - as a one-bedroom house with a deck (not including delivery or the cost of the foundation), builders take a comprehensive approach.

“We offer a full suite of services,” said one firm’s chief. “We not only design a house but we own our own factory, and we are a licensed general contractor.”

Also ask what changes can be made to plans and how complete the steel building is when it arrives from the factory, a variable that can affect construction time - and the metal building prices.

Some steel buildings arrive 90 percent finished, with light fixtures in place; others need considerably more work from a contractor.