It is hard to know where
modular housing ends and
prefab building begins. Probably they, as well as the
manufactured homes and the building
kits we discussed earlier, can all be placed on a continuum we can call
"factory assisted" housing. In some cases the factory just assists more than in
others.
What is usually thought of as a modular house is two or more three-sided
structures that are shrink-wrapped at the factory and shipped by truck or train
to the building site where each is lifted by crane on to a prepared foundation
then joined together. The modules are usually shipped with windows, doors,
cabinets, electrical, plumbing and HVAC systems in place and take very little
time to finish on site. Some modular homes look, from the outside, very
much like manufactured housing except for the foundation that links them to the
land and enables them to be deeded with the land. However, modular building has
advanced to a state that enables the building of elegant two (or more) story
homes in virtually any architectural style and with interesting design features
that make them indistinguishable from their stick-built neighbors.
Hard construction prices have been
difficult to come by, which is understandable when one considers the many
variables such as finish quality, shipping, and customization that go into a
project. One modular manufacturer, however, has provided a little guidance with
price estimates for a 1,600 square foot home, exclusive of
land. Many of the site-related numbers below can be used to arrive at
rough estimates for other types of factory assisted
construction.
| Modular home, including shipping |
$ |
89,000 |
| Garage (also modular) |
|
20,000 |
| Permits |
|
15,000 |
| Utility connections (if close to site) |
|
8,000 |
| Site prep & foundation |
|
15,000 |
| Set up on foundation |
|
17,000 |
| Engineering and survey (if needed) |
|
3,500 |
| |
|
|
| Total |
$ |
167,500 |
This is about $104 per square foot but does not include any finish work or
landscaping and is going to vary according to location. Generally, estimates
vary on the overall cost savings from modular construction. Estimates are out
there that range from 10 percent to 50 percent.
Other types of prefabs need a good deal more work at the site than
modulars.
If you watched volunteers assemble 67 homes for shipping to the Gulf on the
Today Show this past week you have seen a form of panelized
home construction. The frames of the homes were assembled by hundreds
of volunteers then taken apart (probably into four separate walls although that
detail wasn't mentioned) and shipped to Louisiana where other Habitat for
Humanity volunteers will assemble and finish the homes. On-site finish work was
estimated at 30 days per house, but this work is being down with sometimes
inexperienced workers.
The Today Show houses are an example of open panels. When factory-built, open
panels usually have plywood cladding on the exterior of the frame but interior
studs are exposed. Insulation, wires and pipes, and wallboard are installed on
site. With closed-panel construction, each panel is finished and inspected at
the factory with insulation, pipes, and wiring enclosed behind the interior
drywall.
Many stick built homes are actually partially panelized. Roof trusses and
floor trusses are increasingly built in factories in controlled environments and
checked for compliance with building codes and blueprints then shipped to the
site.
Panels, once at the site, are typically assembled by local construction
crews, however, some manufacturers ship their product complete with an
experienced crew which does the assembly work on site.
One manufacturer of building panels estimates that the units
can cut the process of closing the home to weather from 10 to 14 days to 2 to 4
days, at which point weather, normal weather at least, ceases to be a
construction factor.
Wooden studs are not the only materials used in panelized home
construction. Lightweight steel or concrete are also used in the place
of much of the wood. In one interesting variation expanded polystyrene panels
can be snapped together to create walls of any thickness in 2 to 4 inch
increments. Space between the panels is then pumped full of concrete which
hardens into a strong monolithic core. Any exterior or interior finish can then
be applied. The polystyrene panels can be cut to allow for arches or other
architectural details. According to the manufacturer this construction method
provides significant energy savings, noise reduction and a four hour fire
rating. The construction method can be used to build to any seismic or hurricane
standard and won't support growth of mold or mildew.
There are other processes and materials in use and an Internet search on prefab,
panelized construction, and concrete
home construction will keep you busy for days.
Any of these alternatives to totally site built construction offer the
benefit of factory conditions mentioned earlier ¨C greater adherence to
standards, computer-assisted construction, freedom from weather delays, and the
greater buying power of a mass-market purchasing. One manufacturer pointed out a
cost benefit that we hadn't thought about. Back in 1996 the National Association
of Home Builders estimated that a 2,000 square foot home results in 8000
pounds of "waste" that ends up in dumpsters and eventually in
landfills. At that time builders were paying an average of $511 for disposal not
to mention the labor costs involved in policing the site. Panelized construction
supposedly virtually eliminates waste on the site and material
waste is also reduced because the manufacturer pre-determines the most efficient
use of materials when designing the panels.
Prefabs and modulars have long been an accepted form of building in Europe
and some of the most exciting new concepts are heading here from European
builders and designers. IKEA, the innovative Swedish design
company, is now doing homes in boxes for large scale developments in Scotland
and other areas. Imagine the day when you can pull up your Penske truck at the
IKEA loading dock in Atlanta or Elizabeth, New Jersey and load it up with not
only tea candles, a couple of wastebaskets, and the furniture you need for the
living room, but the whole new house, assembly instructions included.