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The housing market has provided some nasty shocks to developers. What would have been the outcome if most houses were prefabricated?

Did you know that McDonalds outlets use prefabricated structures, and are known for constructing the building and opening for business within 13 hours (on pre-prepared ground works)? That’s the beauty of prefabrication.

Energy efficient prefab construction can vastly help reduce construction time by almost half-time, reduce wastage, and give better quality finish than conventionally constructed buildings.

The structures are prefabricated in factories and delivered to the site near or fully complete. Pre-fabricated structures have significant advantages over buildings constructed using traditional methods in terms of cost, quality and the life cycle management of buildings.

Across all borders

Prefabrication can be used almost across all buildings and small developments. Prefabricated housing became increasingly popular during World War II as there was a need for mass accommodation for military personnel.

The most widely-used form of prefabrication in building and civil engineering is the use of prefabricated concrete and steel sections in structures where a particular part or form is repeated many times. Prefabricating steel sections reduces on-site cutting and welding costs as well as the associated hazards.

It is most commonly used in the construction of apartment blocks, and housing developments with repeated housing units. Over the years, the quality of prefabricated housing units has increased so much that they may not be distinguishable from traditionally-built units.

The method is also used in office blocks, warehouses and factory buildings. Prefabricated steel and glass sections are widely used for the exterior of large buildings. Prefabrication saves engineering time on the construction site in civil engineering projects.

Radio towers for mobile phone and other services are often made from multiple prefabricated sections. It is also used in the assembly of aircraft and spacecraft, with components such as wings and fuselage sections often being manufactured in different countries or states from the final assembly site.

Recently when Marg Group tied up with Surbana, GRK Reddy, chairman and managing director, Marg Group had said: “We are confident that prefab construction will be in huge demand, as it provides unique benefits that are difficult to obtain in any regular construction. Apart from cost advantage, prefabricated construction methods have environmental advantages as well. The assembly line production method tends to produce less waste than site-built construction. The economies of scale allow manufacturers cheaper access to eco-friendly building materials. And with the quick set-up time, there’s almost no impact on the surrounding areas.”

Ashwin Daatey, product manager at Bhargaw Engineering, a Mumbai-based manufacturer and supplier of prefabricated structures, says: “The prefab home or house requires much less labour as compared to conventional houses or homes.

Most of the companies are selling complete pre-manufactured prefab modular homes or houses called mobile homes or manufactured homes. These types of homes are becoming popular in Europe, Canada and United States as they are cheap.

Moreover in most places around the world, local building codes (LBC) does not apply to prefab homes or houses; instead, these houses are built according to specialized guidelines.”

Costs of prefabViral Sheth, director of Viral Corporation, says: “Costs are much lower than the normal construction methods. It depends on the structural integrity of the building. Concrete is definitely more expensive. Moreover, prefabrication on smaller buildings is feasible. Larger buildings will require structural forms.”

Prefabrication avoids the need to transport so many skilled workers to the construction site, and other restricting conditions such as a lack of power, lack of water, exposure to harsh weather or a hazardous environment are avoided.

While there are advantages it must be weighed against the cost of transporting prefab sections and lifting them into position as they will usually be larger, more fragile and more difficult to handle than the materials and components of which they are made.

Quick and easy

The most common are the modular prefabricated building units. The modular steel panel system buildings are used for smaller structures, while warehouses and halls will require wide spanned steel structures that are insulated or non-insulated. The modular steel panels are insulated with glass wool or rockwool and use powder-paint coated galvanised steel on the outer side and white, laminated chipboard on the inside.

Cement bonded particular board can also be used to cover the inner. EPS boards or polyurethane boards are used to provide insulation to adapt the solution to the climate.

Common prefab building materials like steel, aluminium, wood, plastic, fibreglass, concrete etc., are much cheaper than the conventional building materials and are also more durable, therefore, prove to be cheap for the long run also.


Pros and Cons

Advantages

• Self-supporting ready-made components are used, so the need for formwork, shuttering and scaffolding is reduced
• Construction time is reduced and buildings are completed sooner, allowing an earlier return of the capital invested
• On-site construction and congestion is minimised
• Quality control can be easier in a factory assembly line setting than a construction site setting
• Prefabrication can be located where skilled labour is more readily available and costs of labour, power, materials, space and overheads are lower
• Time spent in bad weather or hazardous environments at the construction site is minimised
• Less waste may be generated and in a factory setting it may be easier to recycle it back into the manufacturing process, for instance it is less costly to recycle scrap metal generated in a metal fabrication shop than on the construction site
• Moulds can be used several times

Disadvantages

• Careful handling of prefabricated components such as concrete panels or steel and glass panels is required
• Attention has to be paid to the strength and corrosion-resistance of the joining of prefabricated sections to avoid failure of the joint
• Similarly, leaks can form at joints in prefabricated components
• Transportation costs may be higher for voluminous prefabricated sections than for the materials of which they are made, which can often be packed more compactly
• Large prefabricated sections require heavy-duty cranes and precision measurement and handling to place in position

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Sept 2020
01 Sep 2020