Prefabrication in construction involves the use of components manufactured in defined industries, wherein sub-assemblies or complete assemblies are transported to the site. This differs from conventional construction methods, for which raw materials are transported to the site for each component to be built there.
Prefabrication comprises of a wide range of components — from manufacturing of windows, staircases, rooftops and trusses to manufacturing of complete building units. In cases where the entire building is prefabricated, only the foundation is constructed onsite. All other parts like walls and windows are transported to the site and bolted together.
In some form or the other, prefabrication has always been a part of society. The oldest documented prefabricated building is ‘The Nonsuch house’ on London Bridge, which was originally constructed in Netherlands. It was dismantled, shipped and reassembled in London in 1579. In fact, the oldest operating McDonald’s restaurant built in California in 1953 is also a prefabricated structure.
A recent breakthrough for prefabrication technology is the 57-storeyed skyscraper, Mini Sky City, which was constructed by Broad Sustainable Building in China within 19 days. It has been a huge success and the company intends to construct more high-rises in this way.
Prefabricated structures almost resemble conventional buildings but present added advantages such as significantly reducing construction time as well as providing sustainable and better quality. Since the components are manufactured in controlled environments, they offer human and environmental benefits like site safety, waste reduction, improved air quality and quality management. Although, in case of smaller volumes, they come with a high price tag and limitations in flexibility.
In India, prefabricated structures came into prominence after the establishment of Hindustan Housing factory in the 1950s (now Hindustan Prefab Limited) by then-PM of India, Pandit Jawaharlal Nehru. The company introduced the use of precast concrete and pre-stressed concrete railway sleepers to the Indian market to provide immediate low-income housing solutions in large volumes. It was an effective option as the units were low rise and standard in size, with minimal requirement of flexibility. The price differential was 30-40% when compared to conventional construction.
In the context of the Indian construction industry, prefabrication is yet to gain popularity and is not widely practiced because:
• Cost still takes precedence over speed
• Not many companies offer complete building solutions (apart from industrial and warehousing units)
• Assembly requires skilled labour
• Involves heavy transportation costs and risk of damage while in transit
• Requires careful handling of components and limitation to the size of modules
• Limits the option of alterations in the design scope of the building
There is an immediate need for popularisation and extensive use of prefabricated structures to increase the efficiency, quality and speed of construction. In India, due to the lack of skilled labour and high transportation costs, the technology is not as feasible. Some of the efforts that can help overcome this challenge are:
• Establishing prefabrication factories at various locations to allow accessibility for easy transportation
• Providing labour with adequate training
• Conducting quality checks at the factories producing prefabricated components
• Recognising readily available materials that cut down the cost of construction and make the final product environment friendly
• Avoiding design modifications of structures
Alternatively, to allow for customisation, small units should be prefabricated and bolted onsite, rather than creating entire modules in factory. Prefabrication should not only be limited to high-rise residential buildings but should also extend to small scale housings as well.