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Modular Construction, mobile homes, trailers, campers, doublewides, panelized construction - what are the differences and how are these structures recognized? This article describes the history and characteristics of these different types of factory-built structures.

This set of definitions and identifying characteristics of these homes and construction methods is a supplement to our more detailed paper, Mobile Home Inspections.

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Definitions: What is a Mobile Home, Trailer, Doublewide, Modular Home, Factory-Built Home, Panelized-Construction-Built Home?

The following is the opinion of the author and has not had a technical review by other industry experts. Various trailer, mobile home, and modular housing manufacturers may disagree with some of these views. Corrections and content suggestions are welcome.

Characteristics of Trailers as Living Space

Trailer traditionally describes a usually small, wheeled, home with a history and image of flimsy construction such as wooden 1x3 wall framing clad with aluminum siding, virtually no insulation, and low quality leaky windows.

"Trailers" up until the 1970's (my estimate) included both campers (photo at left) which really were intended to be towed by a car or truck and moved often from site to site (though some were left parked for decades at campgrounds), and also lightweight factory-made homes which were intended to be towed once to a home site and then kept there.

The camper shown in our photo (left) was abandoned but had previously served as a summer camp for many years.

The little blue structure used as an addition to the left of the small house in the photo at the top of this page was undoubtedly a small camper.

No one building "trailers" calls them that any longer because of the "flimsy" image. The closest thing to a "trailer" in current products on the market are motor homes and campers such as these campers parked along Wappingers Creek in our photo (left).

The least-costly campers (such as our pickup truck "slide-on camper") built after 2000 are probably considerably better constructed than the "trailers" of old. In current language (2009), a "trailer" is either a "mobile home" that is more than 20 years old (see below), or it is a camper designed to be moved easily and often from site to site.

(Or in different usage, a "utility trailer" is a utility vehicle intended to haul goods or large items and designed to be fastened to the back of a car or truck, and a "tractor trailer" is of course a larger (typically 40 ft long) hauling system for moving goods by highway from city to city.)

Trailers may have had their wheels left on, but normally they'd be set on a masonry pier foundation and a skirt installed around to hide the under-trailer area.

Characteristics of Mobile Homes as Living Space

In the past few decades (to 2006), "trailer" manufacturers have considerably improved the quality of construction of such homes. The national manufacturing and building code standards for these structures have also been improved.

Perhaps in part to escape the less than wholesome image of "trailer", manufacturers use the term "mobile home" to describe what is usually larger and better made home than "trailers" of old, though perhaps with similar materials.

Mobile homes are built in a factory and are designed to be moved (once and uncommonly, perhaps once again) on its own wheels attached to its own frame to a site where a foundation is prepared and connections to utilities are made.

In the U.S., states have regulations about the siting, foundation, steps and entry, wiring, plumbing, tie-downs for wind and storm safety that apply to these homes. Some examples of mobile home regulations for New York State are this website. Individual state regulations will vary - you'll want to see what your state requires. Even within states regulations vary as wind and weather conditions do also.

Examples of mobile home improvements include stronger overall wall and roof construction, less leaky roof covering, and windows that are less notoriously leaky. In addition newer mobile homes have, for fire safety, bedroom windows that can be pushed out to a wide opening for emergency exit in case of fire - an important safety improvement.

Usually building departments grandfather in older structures, but sometimes they will insist that certain life-safety improvements be made, for example if an older mobile home is being brought to a new site in a new community. If this is the case one or two windows may need to be replaced to provide this important safety improvement.

When there is a severe storm or hurricane, mobile home communities are among the worst damaged as a strong wind can completely turn over or demolish mobile homes. For this reason, mobile homes set up in high wind-risk zones have extra requirements for tie-downs to secure the building against upset during a storm.

Mobile homes may arrive on wheels but they will be jacked enough to be set on some type of approved building foundation, such as masonry piers or a masonry foundation.

In case these terms are not confusing enough, some mobile home makers like to call these "factory built homes". But that use of "factory-built homes" is confusing too since modular homes are also "factory built" but are quite different from trailers or mobile homes.

Characteristics of a "Doublewide" Mobile Home or Trailer

Some manufacturers provide mobile homes constructed to be joined together, side by side to form a double-width living unit.

While a double-wide mobile home is basically constructed by the same materials and methods just described above, the tie-down and connection requirements for these living units may be different in some jurisdictions, since their risk of being blown away in high winds is different.

Other installation and support requirements, such as connection of the two units and placement of foundation support will also have to accommodate this variation.

Modular home construction and inspection are discussed on a separate series of articles beginning at MODULAR HOME CONSTRUCTION.

Characteristics of Panelized Construction

Panelized construction makes use of wall, floor, ceiling or roof "panels" which have been framed off-site and brought to the site by truck. Panels are lifted into place by crane and fastened together on a foundation, and possibly a framed-in floor which have been prepared before the panels arrive.

Some framing panels make use of special materials, such as plywood and foam roof panels for insulated cathedral ceilings

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

DEFINITIONS of Mobile Home, Doublewide, Modular, Panelized Construction
  TRAILERS & CAMPERS
  MOBILE HOMES
  DOUBLEWIDE TRAILERS
  PANELIZED CONSTRUCTION & KIT HOMES
MODULAR HOME CONSTRUCTION
  PANELIZED CONSTRUCTION

...

Technical Reviewers & References

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• Additional technical contributors & reference sources for this article are listed below.
• "Modular Home Construction, special defects and inspection methods" Dan Friedman, NY Metro ASHI Seminar, Holiday Inn, Crowne Plaza, White Plains NY, October 4, 1996
• Mobile Home Inspections
• Trailer vs Mobile Home vs Modular vs Panelized Construction an explanation of terms and how to identify these structures.
• "Modular Home Construction, special defects and inspection methods" Dan Friedman, NY Metro ASHI Seminar, Holiday Inn, Crowne Plaza, White Plains NY, October 4, 1996
• Critique, contributions wanted: Contact Us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

Information Sources for Mobile Home Inspection, Codes, Products, Manufacturers, Standards & More Information on Building Diagnostic Inspections and Repairs

• Mobile Home Inspections
• Trailer vs Mobile Home vs Modular vs Panelized Construction an explanation of terms and how to identify these structures.
• New York State: "Manufactured Homes: an installation guide for the code enforcement official," undated. [Div. of Code Enforcement & Admin. - 518-474-4073, George E. Clark, Jr., Director] - this is a guide tool, not an enforcement code or standard.
• HUD State Administrative Agency (for 36 states) (NY: 518-474-4073) - for complaints
• Manufactured Housing Institute, 2101 Wilson Blvd. Ste. 610, Arlington VA 22201 703-558-0400 www.mfghome.org
• NYMHA, 35 Commerce Ave., Albany NY 12206-2015 518-435-9859 800-721-HOME (they want the Star Program to provide for separate assessment of manufactured homes)
• Consumer Reports: www.consumerreports.org - special report 2/98
• Mobile Home Inspection Checklist, Florida, Town of Lady Lake Building Department

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