Difference: Understanding System-Built Homes

Many types of structures are built in the factory and designed for long-term residential use. In the case of manufactured homes and modular homes, units are built in a factory, transported to the site, and installed. In panelized homes and pre-cut homes, essentially flat sub-assemblies—such as system-built panels or system-cut building materials—are transported to the site and assembled. The different types of factory-built housing can be summarized as follows:

Manufactured homes are constructed entirely in the factory under a federal building code administered by the U.S. Department of Housing and Urban Development (HUD). The Federal Manufactured Home Construction and Safety Standards, commonly known as the HUD Code, went into effect on June 15, 1976. These manufactured homes may be single- or multi-section units that are then transported to the site for installation. The federal standards regulate the design, construction, strength and durability, transportability, fire resistance, energy efficiency, and quality of manufactured housing. Additionally, the HUD Code sets performance standards for the heating, plumbing, air conditioning, thermal, and electrical systems. It is the only federally regulated national building code. On-site additions like garages, decks, and porches often enhance the appeal of manufactured homes and must comply with local, state, or regional building codes.

Modular homes are system-built homes constructed according to the State of Michigan Residential National Building Code, the same code that governs site-built homes. Although modular homes were once referred to as BOCA Code homes, this terminology is now considered outdated.

Modular homes can vary from one- to two-story dwellings and are delivered to the home site in two or more sections, sometimes as the shell of a home. While some of the interior and exterior finish work is performed in the factory, most finishing touches are completed by the builder on-site, following local codes for interior amenities.

Panelized homes are another type of factory-built housing where panels—complete walls with windows, doors, wiring, and exterior siding—are transported to the site and assembled. Like other factory-built homes, panelized homes must meet the relevant state or local building codes.

Pre-cut homes refer to factory-built housing where building materials are factory-cut to design specifications, then transported to the site for assembly. This category includes kit homes, log homes, and dome homes, all of which must comply with local, state, or regional building codes.

Finally, mobile homes denote factory-built homes produced before June 15, 1976, when the HUD Code was enacted. By 1970, these mobile homes were built to voluntary industry standards that were eventually enforced by 45 of the 48 contiguous states.