Preassembly versus prefabrication, what’s the difference?

Preassembly versus prefabrication, what’s the difference?

Ever since the first prefabricated building in Australia was erected in the UK almost 200 years ago, prefabrication and preassembly have been cost-effective methods of building in countries around the world.

The benefits of using prefabricated or preassembled components are tangible. There are cost savings, improvements in productivity, a faster return for investors, less labour and material handling (which also translates to safety benefits) and improvements in overall quality control.

Everything from pipework to factories can be constructed using prefabricated or preassembled parts. The more repetitive or modular a design is, the easier it is to create large components in a factory and have them shipped to the job site.

While prefabrication and preassembly created a construction revolution and changed the way all buildings and other infrastructure are assembled, they are not the same thing. There are important, discernable differences between the two. This article will explore those differences – and what they mean for building companies.

Pre-fabrication: where it all started

It is not known precisely where pre-fabrication began, but it can probably be traced back to the ancient Egyptians and Romans who would put together large components made of stone in one location and move them to another location where construction was taking place. Throughout history, there have been numerous accounts of this primitive form of pre-fabrication being used to save time and money.

The first advertised prefab home in Australia was assembled in South Australia in 1837. Australia was still very much in its infancy so supply chains were not established and all of the materials available abroad were not readily available yet.

So, London carpenters decided to pre-fabricate a home and then ship it over to South Australia in components, hiring a team of UK immigrants to assemble it. It was called the Manning Portable Cottage and it was the first of many. Several of these homes still stand to this very day.

The trend was quickly adopted in the rapidly booming city of Melbourne and pre-fabricated or modular homes started popping up everywhere. In a very Australian twist, corrugated iron was used for the cladding and roofing. Ever since then pre-fabrication has been an attractive option for building homes, commercial premises and industrial estates because of the efficiencies the process delivers.

What are the differences between pre-fabricated and pre-assembled constructions?

While both prefabrication and preassembly are cost-effective, productivity-boosting ways to assemble any structure, they are different processes.

Pre-assembly involves putting together individual systems that can be shipped out for inclusion in major commercial and industrial projects. For example, electrical systems, plant rooms or data centres could be pre-assembled and comprehensively tested for functionality before being shipped for inclusion in a major construction like a factory or a hospital.

Pre-fabrication is a more holistic approach. While pre-assembly is limited to a certain component, pre-fabricated construction tends to be more complete. Pre-fabrication involves the manufacture of individual components of a building which are then put together at the job site.

The two often work hand-in-hand. For example, a pre-fabricated commercial building could be designed and manufactured in a factory. But the electrical, plumbing, data and plant systems could all be pre-assembled and tested separately, so they can be installed into the pre-fabricated final construction.

Then there is the modern fusion of both of these methods of manufacturing commercial buildings off-premises – modular building.

What are modular buildings?

McDonald’s is a prime example of modular buildings. You can walk into a McDonald’s restaurant anywhere in the country and the look and layout are likely to be the same, or very similar. It provides a sense of familiarity which means that the pre-fabricated approach is not only cost-effective, it is great marketing.

Modular buildings are prefabricated constructions where the final building is manufactured in segments or modules before being assembled on site. It has been used extensively in the modern world for housing as well as commercial outlets, leading to many suburbs where the homes all look basically the same.

It also takes the premise of preassembly to another level. Instead of putting together one building or component and then testing it before shipping, one building or component can be tested and then mass-produced.

With the testing component only required once, even greater efficiencies are gained. Entire commercial constructions can be pre-fabricated and entire systems preassembled offsite before being shipped to the location where they are required.

Because these buildings are mass-produced, there are greater cost-cutting benefits, even less material handling and reliable constructions based on a tried and tested template.

Modular construction is the future of building

The future of pre-fabricated and pre-assembled modular buildings is going to be massive. With the success of McDonald’s and numerous housing estates just some of the examples of the success of this formula, construction companies are now looking to the sky to create modular skyscrapers and more.

Addiscombe Grove is a massive 21 story apartment building construction in the London Borough of Croydon. To date, it is one of the largest modular buildings completely manufactured offsite. Another example (again in London) is 101 George Street which is the tallest building on the planet to be pre-fabricated and featuring preassembled components all manufactured in an offsite factory.

While modular building has combined pre-fabrication and preassembly to achieve great things in terms of scale, it is also helping to rapidly roll out modern innovations as well. Homes and businesses are changing. There is more and more smart technology, including everything from the lighting to the HVAC systems and security alarms, all being internet-connected. By preassembling these individual systems and then including them in modules, construction companies are able to mass-produce smart buildings.

Sustainability is also important in the modern world and the modular approach means that environmentally friendly systems can be preassembled and then included in prefabricated modules. This entire process also means there is far less waste generated, fewer emissions from on-site vehicles and machinery and a better solution for modern housing and commercial buildings.

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