Our first homes were three, 4-Star Green Builder homes built simultaneously—without looking at the Green Builder ratings criteria. (see here) At the time our homes were in the top one-half of one percent of all homes ever rated in this program.
They were built in a factory to the Texas Industrial Building Code (Modular Code). Not to be confused with trailer house code (HUD Code), Modular buildings are built to standard site-built codes, except they are built in a factory, then transported to their permanent location on a transportation dolly and lifted off with a crane and placed on a concrete foundation.
They are built with 2 x 6 walls and 2 x 12 floors and a concrete retaining wall foundation just like site built homes. Workers glue, nail and staple all connections creating a structure that significantly exceeds the structural strength of traditional site built homes.
We ordered them without trim, siding and doors and installed our own upgrades along with extensively fabulous porches, all in classic Craftsman style.
Typically, we would not consider building single homes unless they are substantial in any number of ways. But we would consider multiple units simultaneously.