How Prefabricated Homes Operate

Manufactured homes often receive a negative reputation, especially when jokes are made about being stuck behind a truck hauling a house. The term "trailer-trash" has become part of the modern lexicon. However, just as Starbucks transformed the coffee industry and "Who Wants to be a Millionaire" redefined game shows, prefab modules are reshaping the landscape of assembly-line homes. Supporters of prefab houses highlight advantages such as lower costs, superior construction, environmental benefits, and faster move-in times. Prefabs are also expanding in size. Once limited to small, two-room cottages without plumbing, modular homes now range up to thousands of square feet with multiple floors and basements. The prefab industry was expected to surpass $10 billion in 2007, according to money-zine.com. Furthermore, after Hurricane Katrina, prefab homes gained popularity as sturdier and more appealing alternatives to FEMA trailers.

The process of building a prefab house mirrors the concept of manufacturing a car. Just as Henry T. Ford's assembly line made the Model T affordable for the masses, mass production and bulk buying reduce the costs and construction time for prefab homes. These homes have evolved over time and now offer many varieties, along with a range of optional features. Similar to how you can equip your car with satellite radio or heated seats, you can add features like hot tubs and crown molding to your modular home. Welcome to the world of prefab.

What exactly defines a prefab house? How are its components crafted and assembled? How does the cost of building a traditional house compare to installing a prefab on a plot of land? And what kind of instruction manual accompanies the ultimate model kit for such a construction?

In this article, we will explore the world of prefabricated houses.

The History of Prefabricated Homes

Prefab homes have a deep-rooted history in the U.S. The concept dates back to the 1600s when a prefab home was shipped from England, but mass prefabrication didn’t take off until the introduction of 'house kits.' These kits included all the parts needed to build a home, allowing owners to either assemble the homes themselves or hire help. The Aladdin Company began offering the first house kits through its catalog in 1906. One of the most prominent sellers of early house kits was Sears, Roebuck and Co., which sold over 100,000 homes between 1908 and 1940 [source: Sears archive].

Several factors contributed to the rise in popularity of kit homes. Companies like Aladdin, located in Michigan, benefitted from the thriving automotive, iron, steel, and coal industries in their regions. Wealthy individuals sought to build homes for their families outside of city limits, and with improved roads, they were able to build in rural areas. Additionally, similar to the automotive sector, prefabricated homes thrived thanks to assembly-line manufacturing. Instead of having carpenters construct parts onsite, housing components could be mass-produced on conveyor belts and shipped to the construction site, significantly reducing costs. Items such as drywall, plumbing, and electrical wiring could all be produced cheaply in factories rather than by skilled laborers on location.

The reduced costs meant that middle-class Americans could finally afford to build their own homes. For under $2,500, buyers received a kit containing about 30,000 parts, including everything from lumber and nails to paint and shingles, along with a manual to guide them through the construction process.

Kit homes were not just for first-time homeowners; they also attracted the more affluent, who wanted vacation properties or beach cottages. For those who desired to take their vacation homes on the go, “trailer coaches” were introduced in the 1920s. However, after the stock market crash of 1929, fewer people had the financial means to purchase homes, and kit home sales began to decline.

Mobile homes were the first type of prefab homes to recover after World War II. With returning veterans in need of housing and the new highway systems facilitating travel, mobile homes became an affordable option. Over time, many individuals stopped relocating their mobile homes and settled into them permanently, using them as their primary residences.

In the 1970s, the federal government moved to regulate manufactured homes for safety reasons. In 1976, the U.S. Department of Housing and Urban Development (HUD) introduced a building code, now known as the HUD Code. This code established standards for heating, plumbing, electrical systems, structural design, construction, fire safety, and energy efficiency. The code was later updated in 1994 to raise the standards for prefabricated housing even further.

Over time, manufactured homes became an affordable housing solution. However, in recent decades -- especially during the ongoing housing downturn -- new innovations have allowed these homes to cater to a wealthier market and those interested in sustainable living. Additionally, individuals in densely populated countries seeking affordable and durable housing have increasingly turned to prefab options.

Next, we will explore the world of modern prefab homes.

Contemporary Prefabricated Homes

Although the idea of modern prefab design dates back to the 1960s, it wasn't until the early 2000s that the architectural movement truly gained momentum. With advancements in technology, such as SIP panels (pre-cut structural insulation that locks together), and growing interest in residential design, architects began focusing on prefab houses. Their objective was to develop a home that could be easily transported to a construction site, assembled quickly, and resemble modern architectural styles, all while staying within an affordable price range.

To further fuel the growing interest, Dwell magazine hosted a modern prefab invitational in 2003, aiming to design an affordable prefab home that could be mass-produced. Allison Arieff, Dwell's former editor and author of the 2002 book 'Prefab,' which explored modern prefab prototypes, was approached by Nathan Wieler and Ingrid Tung for insights into creating a modern prefab home. Instead, Arieff proposed that the couple use their land in Pittsboro, N.C., as the location for a design competition. With a starting construction budget of $200,000, the couple agreed, and they soon collaborated with the magazine to establish home criteria and judge the designs [source: Boston Globe].

The Dwell invitational presented an opportunity to turn the modern prefab concept into a reality, aiming to introduce mass-produced prefab homes with a modern architectural touch. However, challenges persisted. The architectural firm Resolution: 4 Architecture delivered the design, but the project exceeded the budget by $50,000, forcing a reduction in the home's size to meet the budget constraints [source: Dwell].

The price of a modern prefab home is still a common complaint, with an average cost ranging from $175 to $250 per square foot [source: BusinessWeek]. Dwell magazine now offers modern prefab homes through its company Empyrean. Supporters of the prefab movement argue that while many prefab homes cost as much, or even more, than traditional stick-built homes, they offer savings in design and construction. Many architect-designed homes exceed $300 per square foot, excluding design fees [source: The New Yorker]. After all, the designs are not one-of-a-kind; the architect is reselling the design, and modifications, if needed, usually add only minor costs.

When it comes to mass-producing affordable modern prefab homes, Rocio Romero is a well-known name. Romero’s company in Perryville, Mo., produces flat-packed, cubelike homes with sleek, modern exteriors. The price of house kits ranges from $23,650 to $45,255 [source: Rocio Romero]. Finishes and additional features can affect the price. Romero uses interlocking panels for easier construction, and the company provides a videotape along with instructions for contractors or even DIY homeowners.

While some prefabs are considered 'traditional homes' by mortgage companies because they use some methods from stick-built homes, others do not. However, many new modern prefabs are being introduced to homebuyers. The Swedish company IKEA launched its modern prefab home, the BoKlok, in the European market. In 2006, the Walker Art Museum showcased an exhibit on modern prefab, titled 'Some Assembly Required: Contemporary Prefabricated Houses.' As the demand for environmentally and budget-friendly housing increases, the modern prefab market is expected to expand its offerings.

In the following section, we will explore the various types of traditional prefab houses.

Next, we’ll dive into the different categories of prefab houses.

The term 'prefabricated housing' is a broad category that includes both manufactured and modular homes.

Manufactured homes, once referred to as mobile homes, are constructed on non-removable steel frames known as chassis, which are used for transportation and provide permanent support. These homes are built to meet the Manufactured Home Construction and Safety Standards (HUD Code) and can be placed on permanent foundations, thereby qualifying as real estate. They are generally considered an affordable alternative to conventional construction due to their assembly-line production methods.

In contrast, modular housing is considered a more upscale version of manufactured homes and is closely linked to the 'prefab' movement. Modular homes are made up of individual units, or modules, which are built in factories and assembled on-site. They often use higher-end materials and are typically larger than manufactured homes. Modular homes also offer a greater variety of customization options, including premium features like granite countertops and bespoke flooring. In some cases, these homes can be more expensive than traditional site-built homes, especially after customizations. Unlike manufactured homes, modular houses must comply with state, local, and regional building codes, which surpass the standards of the HUD Code. Once installed, these homes are classified as real estate, and unlike manufactured homes, they don’t rely on steel frames but are constructed with wooden beams supported by steel posts. Their modular nature allows for multi-story designs and basements.

Panelized and precut homes are subsets of modular housing, though some people might consider modular homes to fall under the category of panelized and precut homes. In panelized homes, walls are pre-fabricated in a factory and then transported to the site, much like how rooms are delivered in modular homes. Precut homes consist of pre-cut units that are assembled on-site, but these homes have a more structured approach, with pieces designed to fit together like a puzzle, as opposed to the more flexible, a la carte construction style of modular homes. Log homes are typically included in the panelized or precut category.

Prefabricated home manufacturers have expanded their sales approaches. While some buyers may still visit showrooms to select units or rooms, manufacturers are now experimenting with selling homes on-site. This means prospective buyers can visit a community or a location where prefab homes are already set up, tour the homes, and then order the pieces to be delivered to their chosen site. Additionally, buyers have the option to pick and customize individual rooms and features.

Ordering a prefab home might seem straightforward, but there are additional costs to consider. Let’s explore these in the next section.

Prefab Housing Costs. The next section will provide more information on the costs of prefab housing.

While prefab homes often cost less than traditional stick-built homes, modular homes may include expensive customization options. However, the overall material costs are still reduced due to the factory-based assembly process.

Since components like windows and walls for prefab homes are produced in uniform batches, there’s no need for specialized labor to craft each part individually, which reduces costs. Additionally, factories can purchase materials in bulk, unlike individual tradesmen. Prefabricated homes are assembled indoors, protecting the construction from weather delays and cost increases. Just like stick-built homes, prefab homes do not have a fixed price tag, allowing buyers to negotiate. In general, prefab homes can cost 10 to 25 percent less than traditional construction options.

The largest expense for a prefabricated house is typically the land, followed by construction costs, depending on your level of expertise.

In the early 1900s, individuals who purchased Sears, Roebuck and Co. homes often had carpentry skills. However, most modern buyers would not feel confident laying their own foundation. There are additional building requirements to consider, such as zoning laws, surveys, and necessary electrical and water connections. Some companies offer these services for an additional charge.

Once you have secured the land and selected your desired house, securing financing can present challenges. Since manufactured homes are not considered real estate until permanently placed, obtaining financing can be more complicated. Furthermore, manufactured homes may depreciate over time, making lenders less inclined to offer loans.

On the other hand, modular homes are not typically subject to the same stigma and are financed more similarly to traditional stick-built homes.

Construction of Prefabricated Homes

Prefab homes are built starting from the interior and following a specific process. The general manufacturing sequence usually takes a few days or less, with inspections occurring after each stage (if the buyer requests modifications, the process could take longer):

After the prefab units are built, they need to be transported to the buyer's property. The transport of the modules is limited by factors such as roadways, overhangs, and power lines. Builders need to assess these constraints before delivery. In general, each unit must be no wider than 16 feet, no longer than 60 feet, and no taller than 11 feet. Since travel conditions can be unpredictable, buyers often accompany independent contractors on-site to inspect the units for any potential damage, such as scratches or cracks during transport.

A foundation is necessary to support the house, so before the structure arrives, the land needs to be excavated and a foundation prepared. This can include options such as poured concrete, concrete blocks, basements, or crawl spaces.

When the house arrives, a crane is used to position it on the foundation. Workers use heavy-duty cables to maneuver the units into place, where they connect at the marriage walls. These walls secure the home and make sure it’s level and properly bolted together. If the roof wasn’t pre-installed in the factory, it is placed on top at this stage. Some homes have a hinged roof that is unfolded onto the structure. The delivery and setup process is typically completed within a day, after which decks, staircases, and additional features can be added.

The timeline for completing the home can be influenced by factors such as customization, financing, and factory schedules. However, from selecting the house to finishing the installation, most manufacturers estimate a few months for the entire process.

On the following page, we'll explore trends in prefab homes both in the United States and internationally.

Prefab Homes Worldwide

In the U.S., the Northeast has led the way in adopting modern prefab homes, driven by limited land, a shorter building season, and high labor costs. California has also joined the trend due to environmental advancements (see sidebar) and expensive real estate. Following Hurricane Katrina and the housing crisis, the South has seen a rise in prefab housing, particularly in affordable options. Many of these homes feature eco-friendly benefits, such as energy efficiency, which boosts their appeal. These homes are also praised for their aesthetics, durability—such as withstanding winds up to 150 mph—and affordability, especially compared to the infamous FEMA trailers.

In Europe, prefab homes have been embraced due to land shortages. In England and Germany, cranes are used to place modular units atop existing buildings. In Sweden, the well-known furniture company Ikea has expanded into homebuilding, offering affordable housing solutions. Their 'BoKlok' apartments, designed for workers unable to afford high-cost city living, have sold thousands.

In land-scarce Japan, Toyota, renowned for its efficient auto manufacturing, has ventured into homebuilding. The company’s modular housing plants have gained a reputation for their efficient production. The homes are marketed as being durable enough to withstand earthquakes, which are a common concern in Japan, thanks to the controlled environment of their factory construction.