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WHEN I WAS A COLLEGE STUDENT struggling with an architecture major, I attended a lecture by Buckminster Fuller, inventor of the geodesic dome. “Does anyone know how much this building weighs?” he asked, looking up at the huge concrete gymnasium where we sat. “If this were an aircraft, an aeronautical engineer would know the weight down to the last pound, but architects continue to design buildings as if the earth had unlimited resources.” Fuller was convinced the earth could provide more than enough for everyone if we would only use its resources wisely and efficiently.
Factory-built housing is a step in that direction. Houses which are made all or partly in factories now account for nearly 40 percent of all new single family homes sold in the United States. And the trend is upward. Factory-built housing (also called manufactured, prefabricated and industrialized housing) is a generic term which includes manufactured (mobile), modular (sectional), panelized and pre-cut (kit) houses. The terms are confusing. Manufactured housing, one of the sub-categories of factory-built housing, is sometimes used as the generic term for all types of factory-built housing.
The Evolution of the Factory-Built Home
The factory-built housing idea isn’t new. Sears Roebuck offered a prefabricated “modern home” in their spring 1908 general catalog, which was shipped by train. Trailers began appearing on the newly-paved highways in the 1920s and became low-cost dwellings wherever people decided to park them. The trailer evolved into the mobile home, and mobile home parks emerged after World War II to provide much-needed housing for returning veterans.
In the 1960s, the mobile home category made an evolutionary split. One branch evolved into recreational vehicles (RVs) to the point where the house now tows the car. The other branch evolved into manufactured homes, 95 percent of which now become permanent dwellings once they are towed from the factory to the site. Factory-built housing has been popular in Europe and Japan for years.
Today, even conventional site-built homes are using an increasing amount of factory-assembled components. Roof and floor trusses, pre-hung doors and windows, modular cabinets and fiberglass bath and shower units are standard prefab items. I once saw a semi truck deliver a load of prefabricated concrete fireplace chimneys to a new housing subdivision in Southern California.
The Factory-Built Advantage
Because factory-built houses are built all or partly within factory walls, construction continues year round. Assembly line workers don’t need to be skilled carpenters and are paid about half of what carpenters make, but they have steady jobs with benefits and can afford to buy the products they make.
Factories are located to make the most efficient use of transportation, materials and labor. Therefore, the houses can be built better, faster, more efficiently and more economically. Also, there is less waste and none of the pilferage, vandalism and weather damage common with site-built construction. After delivery to the site, all factory-built housing can be assembled, closed in and occupied in a matter of days.
The precision machinery used in fabrication will accept only high quality kiln-dried lumber, unlike the “green” boards which often go into site-built houses. Joints are both nailed and glued. The resulting tight construction makes the houses stronger and more energy efficient. Prefabricated components are built extra rigid to hold up during shipping and assembly, which makes the houses better able to withstand earthquakes and severe storms. I have heard stories about modular sections falling off truck trailers and sliding down hillsides with little or no damage. In factory-built homes, the floors don’t squeak and the doors and windows don’t stick, and you don’t see nail pops or wall cracks.
The four types of factory-built homes, listed in order of their completeness of prefabrication, are described below. In general, houses which are shipped nearly complete offer the most cost savings compared with conventional homes.
Manufactured (Mobile) Homes
Of the four types of factory-built housing, manufactured homes are the most completely prefabricated, least expensive and most common type of home built home today. On average, they are about 20 percent less expensive than an equivalent site-built home. In the past, they have also suffered the most criticism for their tacky design and appearance, and have been the bane of zoning boards and the butt of rural jokes. However, the modern manufactured home has evolved far beyond the old flat top tin box “trailer park” stereotype.
Manufactured homes now make up almost one-fourth of new housing starts and nearly one-third of all new homes sold in the United States. In California, nearly two-thirds of new manufactured homes are constructed on conventional lots, mainly because of outdated zoning regulations biased against “trailer parks.” Recent manufactured home purchasers are also younger, more affluent, more educated, have larger families and are less likely to be retired than those who purchased manufactured homes only 10 years ago.
Laws in California and many other states now allow manufactured homes to be installed in any area which allows conventional single family homes, providing they meet local standards. Covenants, conditions and restrictions (CC&Rs) adopted after January 1, 1988 in California can’t prohibit manufactured homes as long as they meet the same basic architectural standards as site-built homes.
High quality manufactured homes now look just like conventional site-built homes and are superior in many ways. They come with conventional siding and roofing materials, pitched roofs with overhangs, vaulted ceilings, bay and dormer windows, custom kitchens and bathrooms, sunken bathtubs, skylights and even fireplaces. Architectural styles range from Cape Cod to California ranch.
Because manufactured homes are getting better, they are beginning to appreciate in value the same way that site-built homes do. As a result, more lenders are willing to finance them and interest rates are falling to the level of site-built homes. By law, new manufactured homes must be sold by manufactured home dealers, while real estate brokers and agents normally handle manufactured home resales.
Manufactured home dealers often handle all the details of the sale, including permits, financing, foundations, wells, septic systems, transportation and set-up. They can also arrange for the construction of decks, entries, garages and driveways. Buyers can order custom expansions and a variety of floor plan options, such as a deluxe master bathroom. New manufactured homes often include floor and window coverings, appliances and kitchen cabinets.
The dramatic rise in construction quality was the result of the federal Manufactured Housing Construction and Safety Standards Act of 1974. This law required the U.S. Department of Housing and Urban Development (HUD) to develop and enforce a federal building code for “mobile” homes. All new manufactured homes constructed after June 15, 1976 must conform to strict structural and safety standards. A red HUD seal, certifying compliance with theses standards, must be displayed on each section. After 1976, “mobile” homes were no longer considered to be vehicles. Congress officially revised the term “mobile home” to “manufactured home” in 1980.
The HUD code preempts all local building codes and is also more stringent. Because the HUD code is based on performance standards it tends to encourage construction innovations. In contrast, the Uniform Building Code written by the building trades is based on the use of standard building materials.
Manufactured homes usually have a permanent steel undercarriage and are delivered on wheels with a trailer harness. They normally range from one-section single-wide homes to three section to triple-wides. Transportation costs limit deliveries to about 400 miles from the factory. Most of the manufactured homes delivered to the Mendocino Coast are assembled in Woodland, about 185 miles away.
On wheels, blocks or tie-downs, the manufactured home is financed, taxed and appraised as personal property. However, once it is attached to a permitted permanent foundation on private land, it becomes real estate. Manufactured homes in parks are personal property regardless of their foundation because they are on leased land.
A permanent foundation does not necessarily have to be the conventional concrete perimeter type, although some picky lenders (including FHA) insist on this. The Mendocino County Building Department will issue permits for a variety of less expensive alternative manufactured home foundations, often accepting the manufacturer’s design. When the building inspector finalizes the foundation system, the Building Department completes HCD form 433 (A) and forwards copies to the County Recorder, the County Assessor and the State Office of Housing and Community Devleopment (HCD). This transfers the home to the county’s real property records.
Modular Homes
The second type of factory-built home is the modular or sectional home. Unlike manufactured homes, modular homes must comply with the same local building codes as site-built homes. Only about 6 percent of all factory-built housing starts are modular homes.
Modular sections can be stacked vertically and connected horizontally in a variety of ways. Like manufactured homes, modular homes may have a steel undercarriage during transportation, but it is generally not a permanent or necessary structural component, and can be removed when the unit is placed on a foundation.
Modular homes are designed to be attached to permanent foundations, which can include full basements. Often indistinguishable from regular site-built houses, they are usually financed, taxed and appraised the same as a regular house.
Panelized Homes
Panelized homes are more expensive than manufactured or modular homes because they require more on-site assembly. However, they are second only to manufactured homes in the number of factory-built units constructed today. Panelized homes can be sold as a packaged kit, or they can be custom-made from your own design.
Panels (also called stress skin panels) are large sandwiches of foam insulation and wood (usually plywood or oriented strand board), normally 8 feet wide by up to 40 feet long. The wall panels include wiring chases, and the bottom edges are recessed to fit over the foundation sill. No framing members are necessary. Panels can be designed as wall, floor and roof surfaces. “Open” panels arrive unfinished inside and out. “Closed” panels include the exterior siding and interior wall finish.
Like manufactured and modular homes, panelized homes can often be completely closed in one day. They offer less savings than modular homes, but more design variety. Experienced do-it-yourself buyers can save considerable labor costs.
Pre-Cut Homes
The pre-cut home is the least prefabricated and most expensive type of factory-built home, and requires the most on-site labor. However, many pre-cut homes offer distinctive designs, high quality materials and prefabricated details which can’t be duplicated by local builders. In some cases, skilled do-it-yourself buyers can save labor costs and have the satisfaction of building their own custom home.
Pre-cut homes come in a variety of styles and packages, including pole houses, post-and-beam construction, log homes, A-frames and geodesic domes. They can be shipped longer distances more economically than modular homes, because there is less to ship and the parts are more disassembled and compact. The best bet is to work with a pre-cut home dealer who knows the local area and to hire a contractor familiar with this type of design. Inexperienced construction crews can make costly errors.
The Future of Factory-Built Housing
Manufactured homes are the most common and affordable type of factory-built housing. These homes have helped bring the dream of home ownership within reach of young families, working people and first-time home buyers who would otherwise be priced out of the housing market.
Outdated zoning ordinances still remain the greatest barrier to public acceptance of manufactured homes and manufactured home communities throughout the United States. The negative image of the 1950s “trailer park” still lingers. Large-lot zoning in rural areas has kept land costs high and has produced a pattern of rural sprawl which is as destructive as the urban version.
However, zoning ordinances are gradually changing, allowing innovative planners to design high-quality compact residential communities to make housing more affordable, provide better infrastructure (roads and utilities) and basic public services (police and fire protection, etc.). Compact development also helps build a strong social framework and allows more forests, wetlands and farm lands to be preserved. I’m sure Buckminster Fuller would approve.
For more information on manufactured housing visit the web sites of the California Manufactured Housing Institute (www.cmhi.org) and the National Manufactured Housing Institute (www.mfghome.org).
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