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1. INTRODUCTION
Modular buildings are buildings which are made from prefabricated three dimensional
components made in a factory. A simple modular building may be made from a single
section, while more complex structures are made by attaching several sections
together. Modular buildings can be used for a wide variety of purposes, from
temporary housing after a natural disaster to establishing a permanent facility such as
a gymnasium on a school site.
When a modular building is ordered, it can be a custom building, or ordered from a
company's existing line of products. In either case, constructions occur indoor in a
factory environment, with the factory creating one or more modules, depending on the
size of the building. Each module is totally self contained, including everything from
the roofing to the electrical wiring, and the modules are totally finished inside. The
size of the modules is generally limited by ease of transport, with companies not
making modules which are too large or too dangerous to move easily.
Once modules are finished, they can be shipped to the location where the modular
building will be installed. Off-frame modular dwellings differ from mobile homes
largely in their absence of axles or a frame; however, some modular dwellings are
built on a steel frame (on-frame modular) that can be used for transportation to the
site. The site can be prepared with a temporary or permanent foundation, depending
on how the building will be used and the building can be locked onto the foundation
and to other modules to make it ready for use. A modular building may be temporary,
semi-permanent, or permanent in nature.
One of the big advantages to modular construction is that it is very rapid, and it tends
to be less expensive than a site-built structure. Modular buildings are also known as
manufactured or prefab structures. In some regions of the world, this building
technique has faced considerable consumer opposition, with consumers viewing such
structures as cheap or tacky. In fact, modular buildings run the gamut from very lowcost structures which are of poor quality, to very solid, elegant buildings which
feature the latest in modern design innovations. Some companies actually opt to
specialize in high-end modular construction, offering features like increased
environmental friendliness during the construction process, and finished structures
which are specifically designed to be more energy efficient.
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2. MODULAR HOMES
Because of similarities in the manufacturing process, some companies (for example,
Palm Harbor Homes, among many others) build both types in their factories. Modular
homes are transported on flatbed trucks rather than being towed and lack axles and an
automotive-type frame. However, some of these homes are towed behind a semi-truck
or totter on a frame similar to that of a trailer. The home 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 home. Once the home has reached its location, the axles and the tongue of
the frame are then removed, and the home is set on a concrete foundation by a large
crane.
Most zoning restrictions on the homes have been found to be inapplicable or only
applicable to modular homes. This occurs often after considerable litigation on the
topic by affected jurisdictions and by plaintiffs failing to ascertain the difference.
Most modern modulars, once fully assembled are indistinguishable from site-built
homes. Their roofs are usually transported as separate units. Newer modulars also
come with roofs than can be raised during the setting process with cranes. There are
also modular’s with 2 or 3 stories. As the legal differentiation between the two
becomes more codified, the market for modular homes is likely to grow.
Fig.1 Modular homes
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2.1 USES
Modular buildings have a variety of uses. They may be used for long-term, temporary
or permanent facilities such as construction camps, schools and classrooms, civilian
and military housing, and industrial facilities. Modular buildings are used in remote
and rural areas where conventional construction may not be reasonable or possible.
For example, the Halley VI accommodation pods used for a BAS Antarctic
expedition. Other uses have included churches, health care facilities, sales and retail
offices, fast food restaurants and cruise ship construction.
Modular buildings are used for purposes ranging from singular guard shacks to family
homes to whole hospital complexes.
1. Small Uses for small modular buildings include portable buildings such as
guard houses, on-site construction offices, temporary storage facilities and
portable classrooms. Other small-building uses are residential garages and
carports, backyard storage and garden sheds playhouses, home studios or guest
houses, gazebos and small cabins in remote hunting areas.
2. Medium residential or small farm uses for medium- size buildings can be used
for living quarters and homes, barns, workshops and large garages for multiple
vehicles and RV storage. Commercial uses range from business or office
buildings, real estate sales offices, banks, machine enclosures, clean rooms,
stadium press boxes, smoking shelters and outdoor seating for employees,
cafeterias, and many other uses that are usually associated with brick-andmortar buildings.
3. Large modular building uses include one- and two-story office complexes,
retail shopping centers, agricultural buildings, churches, government facilities,
fire stations, barracks and entire educational campuses with libraries and
science labs. Other uses are aircraft hangars, riding and show arenas, body
shop repair bays, correctional facilities, and medical and health care
complexes.
4. Disaster Relief Earthquakes, hurricanes and other world calamities require
emergency shelters and housing for displaced persons and operations. Modular
buildings for this purpose come in single-family units, multi-person bunk-style
units and empty shells. Portable restrooms, showers and mess halls are also
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prefabricated. These units require no foundation or assembly and can be run
on solar power. The empty shell units can be utilized for clinics, staging
operations and other necessary applications.
5. Residential and commercial modular buildings are not mobile homes. Modular
buildings are built to state and local building codes, unlike mobile homes,
which fall under federal building codes. Modulars will look like stick-built
buildings when completed on site and in essence, become real property just
like a house. Mobiles must be attached to a permanently fixed foundation
before they are considered real property. Modular buildings have much
quicker construction times than on-site built structures at less cost due to the
control factors of building in a factory and the cost of materials, which are
usually steel, preformed concrete or other less costly building materials.
Outside labour costs are also reduced.
Fig.2 Modular home in Sutton, Alaska
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2.2 ADVANTAGES
Modular buildings are very affordable because of the factory construction of these
buildings. They are cost effective compared to conventional construction. These units
are typically constructed in an enclosed facility; therefore weather is not a factor in
the construction timeline. Material delivery fees are also out of the equation because
an ample amount of material will always be available at the facility, as opposed to
being delivered in limited quantities to the job site, nearly eliminating construction
delays, and theft of building materials from the site.
Such dwellings are often priced lower than their site-built counterparts and are
typically more cost-effective to builders and consumers. Homes can be constructed in
less time than it takes to build a home "on-site."
Manufacturers cite the following reasons for the typically lower cost/price of these
dwellings:
•
Speed of Construction/Faster Return on Investment: Modular construction
allows for the building and the site work to be completed simultaneously,
reducing the overall completion schedule by as much as 50%.
•
Indoor Construction: Assembly is independent of weather, which increases
work efficiency and avoids damaged building material.
•
Favourable Pricing from Suppliers: Large-scale manufacturers can effectively
bargain with suppliers for discounts on materials.
•
Ability to Service Remote Locations: Particularly in countries such as
Australia there can be much higher costs to build a site-built house in a remote
area or an area experiencing a construction boom such as mining towns.
Modular homes can be built in major towns and sold to regional areas.
•
Low Waste: With the same plans being constantly built, the manufacturer has
records of exactly what quantities of materials are needed for a given job.
While waste from a site-built dwelling may typically fill several large
dumpsters, construction of a modular dwelling generates much less waste.
•
Environmentally Friendly Construction Process: Modular construction reduces
waste and site disturbance compared to site-built structures.
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•
Flexibility: Conventional buildings can be difficult to extend, however with a
modular building you can simply add sections, or even entire floors.
3. STANDARDS AND ZONING CONSIDERATIONS
Typically, modular dwellings are built to local, state or council code: 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
customised for local zoning codes. For example, homes built for final assembly in
a hurricane-prone area may include additional bracing to meet local building
codes.
Some US courts have ruled that zoning restrictions applicable to mobile homes
do not apply to modular homes since modular homes are often assembled with a
permanent foundation. Additionally, in US, valuation differences between
modular homes and site-built homes are often negligible in real estate appraisal
practice; modular homes in some market areas be evaluated the same way as
traditionally built dwellings of similar quality. In Australia manufactured home
parks are governed by additional legislation that does not apply to permanent
modular homes. Possible developments in equivalence between modular and sitebuilt housing types for the purposes of real estate appraisals, financing and zoning
may increase the sales of modular homes over time.
4. CONSTRUCTION OF MODULAR HOMES
Modular components are typically constructed indoors on assembly lines. An
assembly line track moves the modules from one workstation to the next. Initially the
panels
for
produced
flat
floors,
for
both
roofs,
efficiency
walls
and
and
ceilings
safety."Flow
Line"
are
all
principles
are employed in the factory, the floors and bathroom pods are brought together before
moving on to have walls and ceilings erected to form a rigid box. The module then
continues along the line becoming increasingly more complete as it is flush jointed,
painted, wired, plumbed and over-clad.
The completed module then emerges from the end of the flow line for delivery to
site. Independent building inspectors are on site to supervise the construction and
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ensure that all building codes are adhered during assembly. While modules can take
one to three months to be constructed, they can take only 10 days. They are
transported to the building site and assembled by a crane. The placement of the
modules may take from several hours to several days. Once assembled, modular
buildings are essentially indistinguishable from typical site-built structures. While
mobile manufactured buildings often decrease in value over time, a well-built
modular building should have the same longevity as its site-built counterpart,
increasing in value over time.
Fig.3 Walls Attached To Floor
Fig.4 Ceiling Dry walled In Spray Booth
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Fig.5 Roof Set In Place
Fig.6 Roof Shingled and Siding Installed
Fig.7 Ready for Delivery to Site
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5. CHARACTERISTICS OF MODULAR BUILDINGS
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 . The
different charecteristics of modular buildings are described below.
5.1 BUILDING STRENGTH
According to manufacturers, 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. Despite
manufacturer claims that the modular home is initially built to be stronger than a
traditional home, it is difficult to predict the final building strength since it needs to
endure transportation stresses that traditional homes never experience.
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 percent 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.
5.2 DURABILITY AND LIFE CYCLE OF MODULAR CONSTRUCTION
The life cycle expectancy of modular construction is the same as conventional, and in
a world where sustainability is gaining momentum each day, there are also several
basic principles intrinsic to the modular construction process that make it more ecofriendly than conventional construction. The module-to-module combination of the
units appears to have provided an inherently rigid system that performed much better
than conventional residential framing.
The life cycle expectancy of modular construction is the same as conventional, and in
a world where sustainability is gaining momentum each day, there are also several
basic principles intrinsic to the modular construction process that make it more ecoDepartment Of Civil Engineering

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friendly than conventional construction. They spend significantly less on-site time, a
result of a shortened construction cycle, (the outcome of the simultaneous activities of
on-site development and off-site building construction), notably minimises the overall
impact on a site. And finally, modular construction methods and materials allow a
building to be more readily “deconstructed” and moved to another location should
need arise, so complete building reuse or recycling is an integral part of the design
technology.
Many of the life cycle reports and research focus on the environmental life cycle of a
building rather than its economic life cycle. And while non traditional methods such
as modular construction are comparable to traditional methods in terms of economic
life cycle, modular construction provides significant advantages in terms of
environmental life cycle analysis. This advantage is a result of a combination of less
materials waste on the initial site coupled with the fact that modular structures are
designed for deconstruction at the end of their useful life much more so that
traditional buildings, thus reducing the amount of materials waste in landfills upon
demolition.
After Hurricane Andrew hit in 1992, FEMA’s Mitigation Assessment Team
conducted a study of various building types and how well they weathered the storm.
In their summary the Mitigation Assessment team concluded that the masonry
buildings and wood-framed modular buildings performed relatively well.” The report
went on to state that overall, relatively minimal structural damage was noted in
modular housing developments. The module-to-module combination of the units
appears to have provided an inherently rigid system that performed much better than
conventional residential framing. This is documented research from a government
agency attesting to the fact that modular construction is a more durable and rigid
building system than conventional construction. Another example of modular
construction’ durability can be seen in San Antonio. The Hilton Palacio del Rio Hotel
is a 21-storey concrete modular hotel built in 1968, still in use today, this believed to
be the tallest modularly-constructed facility in the United States.
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5.3 COST AND TIME SAVINGS
Modular construction projects continue to become more common as homebuyers
learn more about them and better understand the construction process. Using
streamlined production process it delivers higher efficiency and a higher quality
house. The prefab construction speed is faster than on-site construction since
manufacturers build your house inside a factory and weather cannot cause delays.
Weather delays in site-built construction can greatly increase labour costs. Home
buyers also don't get stuck with the tab for wasted building materials exposed to wind,
rain, snow and general rot at the building site of old fashioned construction. Prefab
home prices will vary depending where you live. A general guide is that stick-built
houses cost upwards of $150 per square foot while mobile or manufactured homes
will cost $40-$80 per sq. ft. Modular housing prices will be about $90-$150 per sq. ft.
For more precise pricing estimates, use our directory of home builders. These veteran
builders will be able to give you accurate construction prices based on personal
building situation and your preferred floor plan. Custom appearance like traditional
home prefabricated modular homes allow you to afford the home that has all the
options you want. You can have a basement, multiple levels, extra bedrooms,
increased energy efficiency and additional insulation. Modular builders allow you to
select different custom options so you can have the floor plan of your dreams.
Modular housing looks just like traditionally built homes. The big difference is that
these prefab homes are pre-built in factories and assembled on-site. This process
provides time savings since construction on the modular building can begin in the
factory while the site preparation work is being done (leveling of ground, laying
foundation, etc.) and weather delays don't slow down the factory construction.
5.4 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 multifamily 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 finalize in the plant production process or in the
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case of brick/stone veneers field applications may be the builder’s choice. Roof
systems also can be a part of separate from applied in the field after the basic
installation is completed.
6. CE MARKING
The CE mark is a construction norm that guarantees the user of mechanical resistance
and strength of the structure. It is a label given by European community empowered
authorities for end-to-end process mastering and traceability.
All manufacturing operations are being monitored and recorded
•
Suppliers have to be known and certified
•
Raw materials and goods being sourced are to be recorded by batch used
•
Elementary products are recorded and their quality is monitored
•
Assembly quality is managed and assessed on a step by step basis
•
When a modular unit is finished, a whole set of tests are performed and if
quality standards are met, a unique number and EC stamp is attached to and on
the unit.
This ID and all the details are recorded in a database dedicated to quality. At any time,
the producer has to be able to answer and provide all the information from each step
of the production of a single unit, - The EC certification guaranties standards in terms
of durability, resistance against wind and earthquakes.
7. COMPARISON OF MODULAR HOMES WITH MOBILE
HOMES
Differences include the 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 exactly the same codes that govern the
construction of site-constructed homes. In the United States, all modular homes are
constructed according to the International Building Code (IBC), IRC, BOCA or the
code that has been adopted by the local jurisdiction.
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Mobile homes (manufactured homes) are constructed according to the HUD Code and
are generally considered lesser quality. The materials are the same as site constructed
homes. Wood-frame floors, walls and roof are the most typical. Some modular homes
include brick or stone exteriors, granite counters and steeply pitched roofs. All
modular’s are designed to sit on a perimeter foundation or basement. Mobile homes
are constructed with a steel chassis that is integral to the integrity of the floor system.
Mobile homes often require special lenders. Most companies have standard plans.
However, all modular buildings can be custom built to a client’s specification.
Today's designs include multi-story units, multi-family units and entire apartment
complexes.
Fig. 9 Modular homes
Fig.10 Mobile homes
8. APPLICATION OF MODULAR CONSTRUCTION IN HIGHRISE BUILDINGS
Modular construction is widely used in Europe for multi-story residential buildings. A
review of modular technologies is presented, which shows how the basic cellular
approach in modular construction may be applied to a wide range of building forms
and heights The combination of modules with steel or concrete frames increases the
range of design opportunities, particularly for mixed-use commercial and residential
buildings.
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Fig.11 Europe’s tallest modular building
8.1 SKY CITY ONE
Chinese construction company Broad Group has announced ambitious plans to
construct the world's tallest skyscraper in an implausibly swift 90days. If the target is
met, the 838-meter (2,750-ft) "Sky City One" will take only a twentieth of the time
that the Burj Khalifa, the world's current tallest building, took to construct, and will
stand 10 meters (33 feet) taller still upon completion. The secret to the rapid
construction is prefabrication. Approximately 95 percent of the building will have
been put together in modular form before work even commences on site. Broad has
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form in the area of rapid prefab construction. The company, which primarily makes
air conditioning, has already demonstrated its Broad Sustainable Building (BSB)
concept, albeit at a much smaller scale. It built the 15-story New Ark Hotel prototype
in one week and a 6-story demo pavilion in a single day. Broad is clearly confident
that the SBS principle can be applied to the 220- story Sky City One, perhaps taking
confidence from a 30-storey prototype withstanding a simulated "magnitude 9
earthquake." Broad has described Sky City one is a self-contained earthquakeresistant carless city which will not only accommodate approximately 100,000 people,
but provide them with retail and leisure facilities too. According to CNN the Sky City
One will contain 1,000,000 sq m (10,800,000 sq ft) of usable floor space and its 220
floors will be connected by 104 separate elevators. Broad CEO Zhang Yue reportedly
claims that the tower will consume only one fifth of the energy of a conventional
building of its size due to sustainable design approaches built into the BSB concept
including 15-cm (6-inch) thick exterior walls and quadruple glazing, both of which up
Sky City's insulation. CNN reports that the Sky City One is projected to cost US$628
million: positively cheap when compared to the $1.5 billion Burj Khalifa. Work is due
to commence on site in November 2012 with completion due the following January,
though final approval from Chinese authorities is yet to be granted.
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10. CONCLUSION
The module-to-module combination of the units appears to have provided an
inherently rigid system that performed much better than conventional buildings.
Modular construction is a construction method in which all of the pieces of a building,
known as modules, are manufactured in a factory and then delivered to a job site to be
put in place by a crane. Modular construction incorporates skilled labor, assembly line
production, high efficiency, consistent quality, and speed. Modular construction is not
a new building method. It has been used to manufacture prefabricated homes,
temporary offices, and mobile homes. Manufacturing takes place in a large factory
where each module is sent down an assembly line. Work is completed at each station
along the assembly line by skilled professionals. Division of labor amongst skilled
laborers ensures that all work is done quickly and with great precision. Modular
construction generates a lot less waste than stick-built construction. Because modular
construction is completed inside a controlled environment, there is no risk of having
materials damaged by moisture penetration. This gives modularly built projects an
interior air quality that is greatly superior to stick-built construction. Because of all of
these things, modular construction is considered much “greener”.
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REFERENCES
•
Claire Swedberg (2007)-Gammon Steel Tracks Modular Components for
Buildings
•
Dru Meadows MODULAR BUILDING "A Green Life Cycle"
•
. Lucy Bodilly. (1992). Modular Buildings Meet Daycare Needs
•
Susan Conbere and Asa Foss; (2006);"Modular Green"; For the Partners.
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