Modular – Manufactured – Mobile
A guide to understanding your home building choices
Modular homes fall under strict building codes that govern the construction, types of material used and how they are appraised by banks for lending purposes. The codes that govern the construction of modular homes are the exact same codes that govern the construction of any site constructed home. In the United States, all modular homes are constructed according the International Building Code (IBC), IRC, BOCA or the code that has been adopted by the local jurisdiction.
The materials are the same as site constructed homes. Wood frame floors, walls and roof is the most typical. Some modulars even include brick or stone exteriors, granite counters and steeply pitched roofs. All modular homes are designed to sit on a perimeter foundation or basement. Most companies have standard plans. However, all modular buildings can be custom built to a clients specifications. Today’s designs include multi-story units, multi-family units and entire apartment complexes. Because the public is not as familiar with the terminology of a modular home and often associate them with “mobile” or “manufactured” homes which are governed under completely different constructions guidelines that are not the same as site built homes many companies are now referring to the development of a modular home as off-site construction.
Standards and Zoning Considerations
Typically, modular dwellings are built to local state or council code, so dwellings built in a given manufacturing facility will have differing construction standards depending on the final destination of the modules. Steel and/or wood framing are common options for building a modular home. Modular home designs can be customized for local zoning codes. For example, homes built for final assembly in a hurricane prone area can have additional bracing built-in to meet local building codes. Many home buyers are having their modular homes built with earthquake bracing in consideration of earthquake protection.
Modular homes are generally assembled with a permanent foundation. Additionally, in the US, the Uniform Standards of Professional Appraisal Practice allow site-built homes to be used as comparators to modular homes in real estate appraisal.
Modular homes are generally designed to be initially stronger than traditional homes by, for example, replacing nails with screws and adding glue to joints. This is supposed to help the modules maintain their structural integrity as they are transported on trucks to the construction site. When FEMA studied the destruction wrought by Hurricane Andrew in Dade County Florida, they concluded that modular and masonry homes fared best compared to other construction.
Typically, a modular home contains about 10% to 20% more lumber compared to traditional stick-built homes. This is because modules need to be transported to the job site and the additional lumber helps keep them stable.
Surfaces and Finishes
Modular buildings can be assembled on top of multiple foundation surfaces, such as a crawl space, stilts (for areas that are prone to flooding), full basements or standard slab at grade. They can also be built to multi-story heights. Motels and other multi-family structures have been built using modular construction techniques. The height that a modular structure can be built to depends on jurisdiction but a number of countries, especially in Asia, allow them to be built to 24 floors and possibly even more.
Exterior wall surfaces can be finalized in the plant production process or in the case of brick/stone veneers field applications may be the builders choice. Roof systems also can be apart of – separate from – applied in the field after the basic installation is completed.
Modular and manufactured homes are similar in the fact that both are built “off-site” and then transported to their permanent site. The biggest differences come in the governing standards, foundational options and how they are transported. In the United States, the term manufactured housing specifically refers to a house built entirely in a protected environment under a federal code set by the U.S. Department of Housing and Urban Development (HUD). The term “mobile home” describes factory-built homes produced prior to the 1976 HUD Code enactment.
The original focus of this form of housing was its mobility. Units were initially marketed primarily to people whose lifestyle required mobility. However, beginning in the 1950s, these homes began to be marketed primarily as an inexpensive form of housing designed to be set up and left in a location for long periods of time, or even permanently installed with a masonry foundation. Previously, units had been eight feet or less in width, but in 1956, the 10-foot (3.0 m) wide home was introduced. This helped solidify the line between mobile and house/travel trailers, since the smaller units could be moved simply with an automobile, but the larger, wider units required the services of a professional trucking company. In the 1960s and ’70s, the homes became even longer and wider, making the mobility of the units more difficult. Today, when a factory-built home is moved to a location, it is usually kept there permanently. The mobility of the units has considerably decreased.
The factory-built homes of the past developed a negative stereotype because of their lower cost and the tendency for their value to depreciate more quickly than site-built homes. The tendency of these homes to rapidly depreciate in resale value made using them as collateral for loans far riskier than traditional home loans. Loan terms were usually limited to less than the 30-year term typical of the general home-loan market, and interest rates were considerably higher. In other words, these home loans resembled motor vehicle loans far more than traditional home mortgages. They have been consistently linked to lower-income families, which has led to prejudice and zoning restrictions, which include limitations on the number and density of homes permitted on any given site, minimum size requirements, limitations on exterior colors and finishes, and foundation mandates. Many jurisdictions do not allow the placement of any additional factory-built homes, while others have strongly limited or forbidden all single-wide models, which tend to depreciate in value more rapidly than modern double-wide models. The derogatory concept of a “trailer park” is typically older single-wide homes occupying small, rented lots and remaining on wheels, even if the home stays in place for decades. Modern homes, especially modular homes, belie this image and can be identical in appearance to site-built homes. Newer homes, particularly double-wides, tend to be built to much higher standards than their predecessors. This has led to a reduction in the rate of value depreciation of many used units.
Both types of homes – manufactured and modular – are commonly referred to as factory built housing, but they are not identical. Modular homes are transported on flatbed trucks rather than being towed, and lack axles and an automotive-type frame. However, some manufactured houses are towed behind a semi-truck or toter on a frame similar to that of a trailer. The house is usually in two pieces and is hauled by two separate trucks. Each frame has five or more axles, depending on the size of the house. Once the house has reached its location, the axles and the tongue of the frame are then removed, and the house is set on a concrete foundation by a large crane. Most modern modular homes, once fully assembled, are indistinguishable from site-built homes. Their roofs are usually transported as separate units, eradicating the telltale roof line of the factory built home.