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1. INTRODUCTION
Modular building and modular homes are sectional prefabricated building or houses that
consist of multiple modules or section which are manufactured in a remote facility and
the delivered to their site of use. These modules are assembled into a single residential
building using either by a crane or trucks.
Modular building has a wide variety of uses. They will either be used for long term
temporary or permanent facilities. Such uses include construction camps, schools and
classroom, civilians and military housing needs and industrial facilities. Modular
buildings are a perfect solution in remote and rural areas where conventional construction
may not be reasonable or even possible. Other uses have also been found for modular
buildings include churches healthcare facilities and retail offices, fast food restaurants
and cruse ship constructions.
At this time modular home today can be built to any specification and any size from a
simple one to a complex one. One of the big advantages of modular construction is that it
is very rapid and it tends to be less expensive than a site-build structure. Manufactures are
not limited by issues like inclement weather and because they have a great deal of
experience, they can put structure together quickly and well. And they tend to be more
earthquake and weather resistance than site build structure.
Modular construction concepts can be applied for all types of buildings such as offices,
commercial, residential, hotels and much more. Recently, modular construction was used
in the UK for projects such as Raines Diary, Murray Groove and the micro-flats concepts.
As shown in the case studies, modular construction can save time in the construction
schedule and therefore may result in savings. Also, the generation of construction waste
is reduced on-site due to the off-site prefabricated modules being transported to the site
fully fitted out, hoisted and assembled
2. THEORY
There is an age-old analogy in construction circles regarding how building modules are
much like the basic, living cells found in nature. Take the brick for example. A brick is a
man-made module of elegant simplicity that has been used by home builders for
thousands of years. Although it seems lifeless, assembled piles of bricks stuck together
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with mortar develop into protective structures, just as cells labelled “skin” to combine
and protect our bodies.
Recently, modular building modules have evolved into larger and
more complex cells born to encapsulate smaller functions. In modular design, these
modules now incorporate many of our life support systems: heating, ventilating, airconditioning,waterdelivery,wastesystems,electricity,security,andmuchmore.
And, just as tiny organisms have evolved, so have the small brick modules
formerly used in the buildings of old. Now, sheets of plywood, glass & metal panels and
floor joists (to name just a few) are components that have become pieces of our
sophisticated environment.
3. 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 homes. 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.
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 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; thus, modular homes can in some cities and counties (depending on local
ordinances) 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 site-built housing types for the purposes of real estate apparels financing and
zoning may increase the sales of modular homes over time.
4. 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
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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.
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.
5. CONSTRUCTION PROCESS
Modular components are typically constructed within a large indoor facility on assembly
lines. Such facilities use an assembly line track to move the modules from one
workstation to the next. Independent building inspectors are on site to supervise the
construction and ensure that all building codes are adhered to during assembly.
The modules that will combine to form the house are assembled off-site in a factory.
These modules can take one to three months to be constructed but often take as little as
10 days actually to construct when they are first started. Then they are transported to the
building site where a crane is brought in to assemble the modules together. The
placement of the modules together generally takes several hours or days. Once
assembled, modular buildings are essentially indistinguishable from typical site-built
homes.
Once a potential homeowner has decided to go with a modular home, there are a few
steps to take that are relatively consistent regardless of which modular home building
company one is working with. First a homeowner must select a modular home factory.
The majority of manufacturers are located on the East Coast, and some are very specific
as to what states they will ship their homes
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Since it is usually necessary to include a local builder or developer in the process it
may be helpful to consult with this party for advice on manufacturers. Many local
developers have established relationships with certain manufacturers, so this is a good
place to start. After a local developer and manufacturer have been decided on, the
homeowner must choose a floor plan and select from a wide range of options. When these
decisions have been made and an initial contract is signed, the manufacturer's engineering
staffs overlook the plans and the factory
can go to work on constructing the home. Once
the manufacturer has begun building the home in the factory, it is usually just a matter of
weeks before the units are ready for transport. As the work in the factory is taking place,
on-site construction of the home's foundation by the local builder is being done to ready the
site for the arrival of the home. Because the foundation is being laid on-site as the home is
being built in the factory, the overall construction time is dramatically reduced. The
modular home is then shipped to the site on flatbed trucks. The units are then placed by
crane onto the foundation, and the entire home is fastened together. At this point, the
amount of time until the homeowner can move in depends on a number of things. There are
plumbing and electrical tie-ins to address as well.
Fig .1: Bulk material used for modular building
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Fig .2: Wall attached to floor
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Fig .3: Assembly of the building—exploded view showing the individual modules
Fi
fig .4: Construction of each module by crane in the site
Fig .5: Modular home after construction
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6. 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 basement 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 builder’s choice. Roof systems also can
be apart of - separate from - applied in the field after the basic installation is completed.
7. EXAMPLES OF MODULAR CONSTRUCTION
7.1. MARRIOTT COURTYARD HOTELS
The USA’s Marriott Corporation shows offsite fabricated modular units from
manufactured Kaplan for its courtyard hotel chain. The units comprise two bedrooms
separated by a corridor and measured 18.5m by 4.1m, using a rectangular hollow steel
section frame with steel/gypsum board walls. Even on the first prototype hotel, the offsite
prefabrication approach saved 60 days on the construction programmed, which Marriott
considers in worth around US dollar 1 million
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Fig.7: Marriott Courtyard hotel
7.2 ABN/AMRO BANK EXTENSION, AMSTERDAM
This bank needed 600 to 700 people space. Today the bank occupies 100,000 sq. ft. class
A corporate office space, constructed from prefabricated modular units. The four storied
building has a total GFA of about 1, 15,000 sq. ft. The building was constructed using
675prefabricated modules to create 710 workspaces the floor was made of concrete and
the ceiling height was about 9 ft. In future it is intended that the manufacturer De Meevw
will purchase back and remove the building after a minimum of 5 years should the bank
want to sell it. The building was designed to a last period of 10 to 25 years or more with
proper maintenance. The total project cost were 31% lower than leasing conventional
office space
Fig.8: ABN/AMRO Bank extension
8. ADVANTAGES
Modular buildings are very affordable because of the factory construction of these
buildings. They are a very cost effective compared to conventional construction. These
units are typically constructed in an enclosed facility; therefore weather is not a factor in
the construction time line. 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.
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Such dwellings are often priced lower than their site-built counterparts and are typically
more cost-effective to builders and consumers. These new 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, waste
from a modular dwelling generates much less waste.
•
More environmentally friendly construction process - modular construction
generates less materials waste and less site disturbances than comparable site built
structures.
9. DIS ADVANTAGES
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TRANSPORTATION COST
 Need of modular shipment to the project site for permanent installation.
 Increased shipping cost for the project.
 Requirement of double handling as equipment and materials are shipped
to the site.
•
MODULE SIZE LIMITATION
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 Different restriction for each mode of transport trucks, train.
 Design must consider dividing modules according to transportation
constrains.
•
TRANSPORTATION ACCESSIBILITY
 Modules must be shipped to the site
 Access site constrains should be carefully considered, especially in dense
urban areas.
10. MODULAR HOMES VS. MOBILE HOMES
1) 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. Mobile homes (manufactured homes) are constructed according to
the HUD Code and are generally considered lesser quality.
2) The materials are the same as site constructed homes. Wood frame floors, walls
and roof is the most typical. Some modular even included brick or stone exteriors,
granite counters and steeply pitched roofs. All modular 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.
3) Lending institutions and appraisers consider as they consider a site built home,
with the same life expectancy and modular home the same as value. Mobile
homes often require special lenders.
Most companies have standard plans. However, all modular buildings can be custom built
to client’s specifications. Today's designs include multi-story units, multi-family units
and entire apartment complexes. The negative stereotype commonly associated with
mobile homes and has prompted some manufacturers to start using the term Off-Site
Construction.
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11. ENVIRONMENTAL BENEFITS DURING THE CONSTRUCTION
The main environmental benefits during the construction operation are derived from the
shorter construction period,which lessens the impact on the local environments. Waste is
drastically reduced because of efficient factory production, and the reduced damage or
use of packaging materials on-site.There are other local environmental benefits of the
construction operation, which are identified as follows:
•
•
•
•
•
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Site installation of the modular units is a rapid and quiet operation that can be
done ‘just in time’, with no requirement for site storage or additional noisy
equipment.
The delivery and installation of the modular units can be timed to observe any site
working or road traffic constraints.
The delivery of a large number of relatively small amounts of site materials is
much reduced.
Less waste is created so dumping of material waste from site is much reduced to
less than 30% of a conventional project.Foundation excavation is minimised and
there are fewer potentially wasteful site activities.
Materials are used more efficiently, with considerable economy of use in
production than is achievable on site.
The main construction operations are less disruptive to adjacent or connected
properties in terms of pollution and associated nuisance, etc.
11.1 ENVIRONMENTAL BENEFITS IN USE
The environmental benefits in use concern the high level of performance that can be
achieved economically, as follows:
• Good acoustic insulation is provided due to the separation between the modules.
• Good thermal insulation can be provided easily in light steel framing by creating
a ‘warm frame’.These buildings are very efficient thermally, leading to
reductions in energy use and consequent CO2 emission.
• Modular units are very stiff and strong, due largely to requirements for lifting and
transportation, and therefore have a solid ‘feel’.
• All light steel framed structures require minimal maintenance and no call-backs
for shrinkage, etc.
11.2 ENVIRONMENTAL BENEFITS IN REUSE
The benefits in terms of re-use are:
• Modular buildings can be extended easily (or reduced insize) as demand changes.
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Modular units are fully relocatable at modest cost, withconsequent reduced
energy cost in dismantling, and nowastage of materials.
Long-term use of scarce resources is reduced.
12. CONCLUSION
Modular buildings are a perfect solution in remote and rural area where conventional
construction may not be reasonable or even possible. Other uses have also been found for
modular buildings include churches healthcare facilities and retail offices, fast food
restaurants and cure ship constructions. According to manufactures, modular homes are
generally designed to be initially stronger than traditional home by, for example,
replacing nails with screws and adding glue to joint. The generation of construction waste
is reduced on-site due to the off-site prefabricated modules being transported to the site
fully fitted out, hoisted and assembled. Therefore modular buildings are good for
construction nowadays.
REFERENCES
1) Automated post simulation visualization of modular buildings production assembly
line,Automation in construction,Science Direct
2) Hybrid light steel panel and modular systems,R.M.LAWSON,Thin walled
structures,Science Direct
3) The benefits of modular construction,by DEVIN M.REFFIT,renal Business
today,October 2007
4) DonShulman”Reality Development Associates Announces Expansion” Easton
Journal
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5) Osama M Mohson, Paul J Knytl, Basel Addulaal, Jack Olearezyk and Mohammed Ali
Hussein, “Simulation Of Modular Building Construction”,University Of Alberta
Edmonton Journal.
6) Chehayeb.N And Abourizk.S, 1998,”Simulation-Based Scheduling With Contours
Activity Relationships,”Journal Of Construction Engineering And Management,
ASCE Civil Engineering Journal.
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