The application of prefabrication in documented construction history took form as early as 1579, with the execution of the Nonesuch House on London Bridge. The four-storey prefabricated structure was originally constructed in the Netherlands, then entirely dismantled and shipped to London, where it was later reassembled with the help of precise markings. What may have been regarded as extravagant back then, however, is gradually emerging as a pertinent, present-day requisite.

Prefabricated constructions comprise buildings that use manufactured components, modular sections (modular homes) or movable sections (manufactured trailer homes, popular in America). The basic premise of prefabricated constructions is that sections and parts of structures (walls, floors, roofs, etc.) are built in a controlled factory environment and transported to a project-site on completion, where they are assembled and anchored on a conventional foundation. Modular constructions with multiple storeys are lifted with the help of cranes and bolted together. This means that there is minimal field-work required onsite with core construction work taking place at a heightened pace.

After years of association with temporary and shoddy constructions, prefabricated houses today, fortunately, boast of clean-line minimalism, sustainable use of materials and modern design principles. They are increasingly being seen as resource- and cost-effective, revealing not only their sustainable and green credentials, but also their relevance in providing low-cost, durable shelters to India’s teeming masses. Sunaina Gera, VP—Product Development, Marketing and Business Intelligence, Gera Developments, reveals that large infrastructure projects that require sound aesthetics and adherence to timelines for project delivery—flyovers, stadiums, metro stations and the like—are increasingly choosing prefabricated solutions in cement, steel or a combination of both.

Manifold Benefits
One of the benefits of prefabrication is the propagation of green construction. Prefabricated construction is green because manufacturing components in controlled factory environments allows for accuracy with material planning and utilisation, resulting in very little waste as compared to standard constructions. The method also allows bulk acquisition of rare green building materials which can be used over several projects, while minimising procurement time and ensuring use of correct, first-preference materials. Economical bulk procurement of a precise number of items to construction sites dramatically reduces the pollution resulting from transportation as well as associated costs.

Low construction costs, lesser installation time and faster ROI are driving prefabrication to opularity. Estimates suggest that prefabrication reduces overall project completion time by as such as 50 per cent. Costs can be controlled due to savings in time and cost arising from the grouping of similar activities. Moulds for precast components can be used for several repetitions, reducing the cost of moulds. In the case of conventional reinforced cement concrete (RCC) slabs, props and shuttering have to wait until slabs are removed. In the case of prefabs, finishes may be done immediately despite the slab. Ideally, prefabricated materials must lead to overall savings of between 15–20 per cent.

Skilled labour may be effectively used offsite,while reducing manpower congestion onsite. The process also minimises delays and damage due to harsh external conditions. Prefabricated construction provides for disciplined delivery and quality control, ensuring optimal use of steel and cement in structural designs. However, one must outweigh the additional cost of transporting fragile and complicated modules and the ease of transportation and onsite assembly. The method also circumvents other restricting environmental conditions such as lack of power and water supply or populous environments. This enables prefabricated constructions to grace remote or rural locations.

 

Building Materials
Materials used in prefabricated constructions are by and large the same as those used for site-built constructions. Like the latter, they also use wood-frame floors, walls and roofs and sometimes even brick or stone exteriors and granite counters. In prefabricated construction, foundations and floors are constructed the traditional way.

Floors and roofs together account for a large chunk of a building’s cost. Conventional cast-in-situ concrete roofs featuring temporary shuttering increase cost and build time. Some convenient and low-cost prefabricated roofing/flooring elements are precast reinforced concrete (RC) planks, precast hollow concrete panels, precast RB panels, precast RB curved panels, precast concrete/ferrocement panels and precast RC channel units. Precast foundations with insulation and combined interior walls that may be installed in a day while maintaining indoor air quality and material-efficiency are now available. Casting a super structure takes only about a week, as opposed to one to four weeks when casts are made onsite. Moulds made of steel are preferred to timber, despite costing three times more, as they can be used much more.

Prefab roof systems may also be incorporated on-field after the basic installations are completed. The hydrostatic roofing system is popular in India and relies on the strength of spanning structural members sans support of any substantial roof deck. The availability of roofing materials such as aluminium-made Kalzip offers flexibility for concave, convex curved and tapered surfaces. Materials that look like and possess the properties of natural building materials and are resistant to UV degradation, thermal shock, water, chemicals, fire and rot are now being used. Cement-based glass-reinforced concrete (GRC) with alkali-resistant fibres has adaptable applications, for example, in domed roofs and wall claddings, as it does not use steel reinforcement. Light-gauge steel framing with reinforced polyurethane for lightweight and quick installations is also popular. Ceramic bricks with thermal insulation properties are another breakthrough. Prefab wall and roof elements that possess facilities for insulation, wiring and plumbing are increasingly being used. Surface treatments for exterior walls can be determined during the manufacture. In the case of brick/stone veneers, builders may prefer field applications.

Prefabs may use open foundations, rib foundations, columns and footings. For low-cost, low-rise structures, conventional methods using in-situ combinations are more practical and economical. Under normal situations, prefabrication for foundations must be avoided. Maintaining an optimum wall block size will not only hasten building speed but also consume less mortar; however, this ideology has not been very successful for low-rise structures. Structural insulated panels (SIPs), are easy to assemble, strong and energy-efficient. Prefabricated countertops are now made from sustainable materials containing recycled content.

For large projects, builders now prefer to manufacture their own materials. It is a common practice for builders today to make their own pre-mixed concrete, small beams, poles, special pipes and bricks. Prefabricated concrete and steel sections requiring repetition are the most popular prefab elements. Factory-made concrete slabs enable hassle-free concrete mix and reuse of moulds. Onsite cutting and welding costs are reduced for prefabricated steel sections. Prefab materials conclusively include fibre cement corrugated and plain sheets, auto-calved aerated concrete blocks, calcium silicate insulation products, fibre cement products. For the green-conscious, pre-packaged solar PV systems are cost-effective and easy to install.

Pre-stressed, prefabricated modular constructions are commonly used today, with new technologies introduced in steel pre-engineered buildings solutions. Technologies in light-frame prefab buildings such as PEB-Lite and Smartbuild pre-engineered solutions, which are well established around the world, are now available in India. PEB-lite framing solutions may be used for low-priority developments, while Smartbuild is predominant in housing. Compared with the conventional method of construction, light-framing technologies provide a list of benefits such as savings of construction time, less maintenance over a building’s life-span, articulation of building specifications according to the project cost and requirements. In steel buildings, one can alter specifications of walls or roofs or insulations for thermal and acoustic benefits, depending upon the end use. Says GB Singh, Chairman and Managing Director, Red Fort Capital Advisors, “Autoclaved aerated concrete (AAC), Aerocon and cellular lightweight concrete (CLC) produced at construction sites using flyash are the most commonly used prefabs.”



The Indian Scope
A system that thrives on the values of economies of scale may be the perfect solution for a housing-starved nation. According to estimates of the urban housing shortage by the Ministry of Housing and Urban Poverty Alleviation, at the end of the Tenth Five Year Plan, the total housing shortage in the country stood at 24.71 million. Thus, housing India’s homeless is no easy task and is definitely not a quick one. A unique problem however, is that of the urban homeless. Problems arising from the relocation of slum dwellers, and providing low-cost and affordable housing, could be alleviated quickly and economically with the use of mass modular constructions. Quality structures may be constructed on a much wider scale to reap their obvious benefits. This construction style, which had gained prominence in the past with similar applications in nations such as Germany, the Netherlands, the Czech Republic, the United Kingdom, the US and Australia, is now gaining popularity in many developing countries of the world. In recent years, India has seen a few inroads in the development of the prefab niche.

New Zealand-based Lockwood International launched a first-of-its-kind project of luxury prefabricated wood houses in India at the Classic Golf Resort, Gurgaon. The structures have been constructed with pre-designed wooden building blocks—sans nails, cement or steel—within two months.

The Delhi Development Authority (DDA) announced plans to develop 65,000 houses for various income groups over the next four years using prefabricated components. The proposal recently submitted to the Ministry of Urban Development is part of the Urban Development agenda. In order to avoid delays, the DDA intends to construct almost 50,000 of these houses with prefab technology.

Minaean Habitat India, a subset of Minaean Building Solutions, Canada, constructed a two-storey residential model building in Solapur, Maharashtra, in the newly formed Bidi Gharkul area. Minaean also executed a project for Bharat Sevashram Sangha (BSS), a charitable institution, for the construction of three training halls and two schools, all located in Jharkhand. Recently, the company has received purchase orders from Shell India Marketing for the supply and installation of eight modular retail buildings for its gas stations.

“We have already built a single-floor guesthouse for Tata in Jamshedpur and a few G+1 buildings at Anand Port in Gujarat. In addition to Shell and National Thermal Power Corporation we also have an agreement with Paradwip refinery, Hindustan Petroleum Corporation Limited, Bharat Petroleum Corporation Limited and Indian Oil Corporation for retail outlets. We are also executing G+2 and G+3 residential and commercial buildings for Lavasa,” says Mrinal Roy, Marketing—Head, Minaean Habitat India. Other instances of visible prefab use have been at the Reliance Corporate Park, Navi Mumbai, as well as at malls such as Nirmal Lifestyle and Oberoi Mall in Mumbai.

Prefab structures have great potential for rural housing as well. Generally, structures built in the hinterlands require exorbitant sums due to the added expense of organising workmen and materials. Prefabricated homes can become popular in tier II cities, which are flourishing in India and generating demand for new housing. Mr Roy adds that prefab structures may also be beneficial for West India, which abounds in black cotton soil that features a peculiar swell–shrink characteristic dangerous for regular RCC constructions.

The development of infrastructure in large cities has been greatly aided by prefab technologies. “With the introduction of cement/steel pre-stressed, prefabricated flyovers in metros like Mumbai, Delhi, Chennai and other large cities, there are huge savings of time and money. The introduction of pre-engineered buildings (PEB) and solutions in steel has significantly impacted industrial and commercial constructions,” opines Ms Gera. Mr Singh suggests that while working on constructions such as bridges, installing shuttering and scaffolding may present problems. The obvious solution then, is to first make girders onsite, then launch them on piers. To save time in commercial constructions, one can start preparing prefabs onsite even while approvals are in the process of receipt.

“Prefab is successful in the construction of industrial, commercial and infra projects, but not so much in the field of housing,” asserts Mr Singh. However, developers are scouting for solutions in low-cost housing and high-end premium solutions in pre engineered form, where installation is easy and the quality and speed of construction can be controlled. “The middle segment of residential construction may take a little time to adopt pre-engineered solutions, as end-users are more comfortable with standard building options,” says Ms Gera.

Another ancillary issue affected by the growing use of prefab is that unskilled manpower can be put to good use. Since training involves the understanding of a mechanical procedure, the number of activities where skilled and trained masons and the human element are required is reduced. Work is standardised, with little margin for error. Since there is a tremendous shortage of skilled manpower in the country, there is also great opportunity for institutes to start looking at special courses for managing prefab solutions.

Dealing with Impediments
Prefabs are undoubtedly convenient and sustainable modes of construction; however, they are largely hounded by the issue of cost as well as prejudice. Some common issues are discussed below.

Regulatory impact: Since prefab components are generally constructed within a controlled environment, quality control (as performed on assembly lines) is not impossible to incorporate. Quality inspectors or supervisors may be instated to monitor the process and ensure that all building codes are adhered to during manufacturing itself. Mr Singh states that there are codes of practice and standards available by way of Indian Standards (IS) on all kinds of pre-cast elements and components. In the case of prefab buildings, the IS codes apply to the formative materials that have gone into the structure and the foundation. “Standards like IS 800/2007 contain all clauses for this type of construction,” points out Sunil Mantri, Chairman and Managing Director, Sunil Mantri Realty Limited, adding that American codes were followed earlier. “At present, developers are dependent on manufacturers for recommendations. Most government projects press on international standard in lieu of Indian standards. More developers are following a similar path as available technologies are good and have proven themselves in the last decade within India and in other South East Asian countries,” opines Ms Gera. This is in line with building codes in the US that do not apply to prefab homes or houses; instead, these houses are built according to the Federal HUD regulations, mandated for pre-engineered housing.

Under the Maharashtra Housing and Area Development Authority (MHADA) Act, 1976 and the Maharashtra State Housing Policy, the state is mandated to encourage, manufacture and use prefabs, as well as make changes in tender notices and contract documents to suit turnkey lump sum offers and participate with manufacturers of proven prefabs to achieve the objective of adequate mass housing and eradication of slums. This fiscal year, the budget proposed a tax exemption for prefabricated concrete products manufactured at site; this is expected to allow a reduction of 12 per cent in cost.

“Prefab at project sites is a doable thing because it does not really add costs, which might not be the case when you are producing the same in a factory. If you produce components in a factory, you are subjected to the Factories Act, 1948, which has very stringent rules relating to labour, facilities, holidays, etc. If a developer is doing this at a project site, he also avoids the incidences of taxation and duties like sales tax, transportation and excise duty. For instance, brick has no transportation or excise duty, whereas any alternative component meant to replace bricks, if produced in a factory, will incur excise and sales tax/VAT today. Prefab prices cannot compete with bricks made in the unorganised sector. Manufacturers and suppliers are being discouraged by virtue of the policies of the government and the scenario is not competitive for them to survive. Moreover, in an agrarian country, we end up wasting precious agricultural top soil and kiln energy,” insists Mr Singh. An alternative pre-cast component, such as flyash concrete, does not need much energy and contains 33 per cent flyash, a green waste. Economies achieved in saving of steel and cement is therefore, more than offset by extra incidences of transportation and taxation.

Economic viability: Mr Mantri estimates that the cost of constructing a prefab structure is 50 per cent more than that of a conventional one. The reasons may be attributed to the regulatory fiscal burdens mentioned earlier. However, Mr Roy stresses that, for retail ventures, prefabs spell several extra revenue-generating days right at the project’s start. “Light-gauge-steel panels, fiber cement boards, paints, plumbing and electrical works and sometimes, furniture are included in the package. Large companies will normally have to coordinate with their different departments— engineering, design, project supervision; whereas prefab work requires the involvement of only a few high-level persons for coordination. The overall cost is much lower. One can construct a G+2 or G+3 structure within 15–20 days. In case a company has no need for a particular outlet, he does not need to demolish it. He can simply dismantle, transfer and install most elements of the building at a new site and continue activities. So you end up saving a lot of cost. All building materials are reusable and recyclable,” he says. “This is a choice in structures where launch and delivery dates are vital, end-users are already finalised and there are no cash-flow constraints,” adds Mr Mantri. Mr Singh points out, “The shortfall is that prefabs cannot be used in small projects. Getting economies of scale there becomes difficult as you need multiple utility of the same components.”

Structural strength and the burden of maintenance: According to manufacturers, prefab homes are designed to be stronger than site-built homes in order to retain structural integrity despite transportation. Mr Roy insists that the life of a prefab construction is 70 years at best. However, despite claims, it is indeed difficult to predict the final building strength as the stresses endured by the two diverse structures are also unique. “We are an earthquake-prone country. Prefab tends to introduce weaknesses in a structure’s joints. Rectifying these faults during assembly becomes a big issue for the design side. Bridges and sheds for industries are single-storeyed structures in which problems can be solved easily, without adding much to the cost. However, I did a project in Delhi in the 1970s, where we assembled single panels for walls and floors. We faced the problem of water leakage through joints,” adds Mr Singh. Counters Mr Roy, “Since there is no wet construction, there is no chance of seepage or leakage. It is earthquake-resistant so it can be built in tremor-prone and hilly regions. There is no major maintenance as it is not an RCC, brick and cement construction. So, maintenance involves repainting the walls, depending upon paint quality and type, at the most.”

Real estate value: Today, there may be some inconsistency involved in how prefab realty products are seen and valued by end-users. Many buyers do not see prefab structures at par with site-built ones as there is much doubt regarding the former’s durability, appeal and health issues. So, while the constructions may themselves be of equivalent standards, regulatory and psychological factors have hampered the largescale acceptance and use of this technology. Mr Mantri comments that very few projects are being carried out and those that are in progress are mainly commercial, industrial and warehousing projects that feature horizontal spreads rather than vertical high-rises. He feels that the future of prefab-led construction is not very bright for the residential segment. According to Ms Gera, awareness and acceptance by the end-client are key hurdles for prefabs. Manufactures must establish better instances of prefab solutions for easy understanding and execution at various locations.

Forward Glance
Mr Mantri aptly explains the appeal of prefabs. “From a developer’s point of view, all designs suitable for the product can be executed by this one prefab agency—with a one-window system service—from concept, design and stability certification to execution.” With names such as Minaean Habitat, Kirby Building Systems, Tiger Steel Engineering, Tata BlueScope Steel and Everest Industries making rapid progress, much is expected from the industry. Demand is estimated to be around a million tonnes a year, with 10 per cent annual growth. “However, it is difficult to project the viability of prefab in the residential and commercial spaces as it has been applied predominantly in the industrial segment until now,” says Mr Mantri.

“The future of prefabs is very strong in India. This market has been growing at an average pace of 25–30 per cent per annum over the last 4–5 years, barring the recession period. It may not be a solution for all applications, but is sure to help where speed and quality are key criteria. Some concepts of low-cost housing and small dwellings could be focused on in the next couple of years. Developers need to weigh the cost benefits,” advises Ms Gera.

The palpable benefit of quickly housing India’s homeless is possible only if the means of prefab are affordable. Therefore, a revolution in this particular space of construction manufacturing, skill-optimisation, rational taxation and a holistic change of attitude is essential. Regulatory efforts directed at promoting the use and implementation of prefab in public-oriented projects are a pressing need.