Modular and or Manufactured builders must build their new homes to the building code to which the modular structure will reside. 

The term modular simply describes a method of constructing a home in large sections, away from the home site, in a factory. The type of housing constructed is determined by the building code to which it complies and definitively described using the following common housing configurations: Single detached or multi-family, single level or multi-story. The term modular does not describe a type of home, just as the term site-built does not describe a type of home. They both describe alternative construction methods. Therefore, type of homes commonly described as a single family, town-home, duplex, two story, etc, can be site-built, modular-built, or built using a combination of both construction methods.