Mod Vs. Mobile

Know the Differences Before You Buy a Home

When you are buying a home, you will hear the terms site built, modular home, and manufactured home. It's important to understand how these structures differ, no matter whether you are purchasing an existing home or plan to build on a vacant lot that is subject to restrictions.

All Hoopa Modular homes are built to the California Factory-Built housing code.  That code is defined in the Health and Safety Code, Division 13, Part 6, commencing with Section 19960, entitled the "California Factory-Built Housing Law." 2. The Regulations: HCD’s regulations adopted to carry out the law are contained in the California Code of Regulations, Title 25, Division 1, Chapter 3, Subchapter 1, commencing with Section 3000.

The following is taken directly from the State of California Factory-Built Housing Guide For City - County Building Departments Rev: March 2004.

"Factory-built housing should not be confused with manufactured housing or mobile homes. While both products represent a type of a dwelling manufactured in a factory, each utilizes an entirely different set of construction codes and standards. The construction of dwellings using FBH laws and regulations utilizes the California Building Code, while manufactured housing is constructed using federal standards. Factory-built housing products may include single or multi-family dwellings, hotels, motels or dormitory construction.

California law defines FBH as follows: “Factory-built housing means a residential building, dwelling unit, or an individual dwelling room or combination of rooms thereof, or building component, assembly, or system manufactured in such a manner that all concealed parts or processes of manufacture cannot be inspected before installation at the building site without disassembly, damage, or destruction of the part, including units designed for use as part of an institution for resident or patient care, that is either wholly manufactured or is in substantial part manufactured at an offsite location to be wholly or partially assembled onsite in accordance with building standards published in the California Building Standards Code and other regulations adopted by the commission pursuant to Section 19990. Factory-built housing does not include a mobile home, as defined in Section 18008,a recreational vehicle, as defined in Section 18010.5, or a commercial modular, as defined in Section 18012.5.”

Simply put, FBH units are dwellings manufactured off-site, in sections or components which are assembled at the installation site to form a part of, or a complete dwelling. An FBH component may consist of a wall, floor or roof panel utilizing rigid foam insulation enclosed by interior and exterior

sheathing materials; or may also be a conventionally framed closed-system 6 wall or roof panel containing the plumbing, electrical, etc. systems inside the panel.

An FBH dwelling unit may be 2 or more ‘modules’ assembled on site and attached to a foundation.

FBH products do not include “open-framed” prefabricated construction since open-framed type construction allows inspection at the building site without disassembly. A picture of a typical FBH wall panel is provided on page 8.

Following is a recap of the differences between the three types of residential housing.

Modular Homes

  • Modular homes are built in modules in a factory.
  • Modulars are built to conform to all state, local or regional building codes at their destinations.
  • Modular homes are inspected at the factory by a third party inspection agency to ensure that all homes produced by the manufacturer meet prevailing codes and constructed to the approvals received by the state.
  • Modules are transported to the home site on specially designed trailers, then placed on a prepared foundation and joined together at the job site by local builders.
  • Local building inspectors check to make sure the structure meets local code requirements related to finish work that is done on the job site.
  • Modular homes are generally less expensive per square foot than site built homes.
  • A well-built modular home should have the same longevity as its site-built counterpart, increasing in value over time.
  • Formerly referred to as mobile homes or trailers, but with many more style options than in the past.
  • Manufactured houses are built in a factory.


  • They conform to a Federal building code, called the HUD code, rather than to building codes at their destinations.


  • Manufactured homes are built on a non-removable steel chassis.


  • Sections are transported to the building site on their own wheels.


  • Multi-part manufactured units are joined at their destination.


  • Segments are not always placed on a permanent foundation, making them more difficult to re-finance.


  • Building inspectors check the work done locally (electric hook up, etc.) but are not required to approve the structure.


  • Manufactured housing is generally less expensive than site built and modular homes.


  • Manufactured homes sometimes decrease in value over time.


Site Built Homes

  • Built from the ground up; built entirely at the home site.
  • Conforms to all state, local or regional codes where the home is located.
  • Often called a 'stick-built' home.
  • A well-built, cared for site-built home generally increases in value over time (location plays a key role).