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Prefabrication

Prefabrication is the practice of assembling components of a structure in a factory or other manufacturing site, and transporting complete assemblies or sub-assemblies to the construction site where the structure is to be located. Some researchers refer it to “various materials joined together to form a component of the final installation procedure“.

Not to be confused with Preproduction.

The most commonly cited definition is by Goodier and Gibb in 2007, which described the process of manufacturing and preassembly of a certain number of building components, modules, and elements before their shipment and installation on construction sites.[1]


The term prefabrication also applies to the manufacturing of things other than structures at a fixed site. It is frequently used when fabrication of a section of a machine or any movable structure is shifted from the main manufacturing site to another location, and the section is supplied assembled and ready to fit. It is not generally used to refer to electrical or electronic components of a machine, or mechanical parts such as pumps, gearboxes and compressors which are usually supplied as separate items, but to sections of the body of the machine which in the past were fabricated with the whole machine. Prefabricated parts of the body of the machine may be called 'sub-assemblies' to distinguish them from the other components.

Moving partial assemblies from a factory often costs less than moving pre-production resources to each site

Deploying resources on-site can add costs; prefabricating assemblies can save costs by reducing on-site work

Factory tools - jigs, cranes, conveyors, etc. - can make production faster and more precise

Factory tools - shake tables, hydraulic testers, etc. - can offer added quality assurance

Consistent indoor environments of factories eliminate most impacts of weather on production

Cranes and reusable factory supports can allow shapes and sequences without expensive on-site

falsework

Higher-precision factory tools can aid more controlled movement of building heat and air, for lower energy consumption and healthier buildings

Factory production can facilitate more optimal materials usage, recycling, noise capture, dust capture, etc.

Machine-mediated parts movement, and freedom from wind and rain can improve construction safety

Homogeneous manufacturing allows high standardization and quality control, ensuring quality requirements subject to performance and resistance tests, which also facilitate high scalability of construction projects.

[5]

The specific production processes in industrial assembly lines allow high sustainability, which enables savings of up to 20% of the total final cost, as well as considerable savings in indirect costs.

[6]

Transportation costs may be higher for voluminous prefabricated sections (especially sections so big that they constitute requiring special signage, escort vehicles, and temporary road closures) than for their constituent materials, which can often be packed more densely and are more likely to fit onto standard-sized vehicles.

oversize loads

Large prefabricated sections may require heavy-duty cranes and precision measurement and handling to place in position.

Off-site fabrication[edit]

Off-site fabrication is a process that incorporates prefabrication and pre-assembly. The process involves the design and manufacture of units or modules, usually remote from the work site, and the installation at the site to form the permanent works at the site. In its fullest sense, off-site fabrication requires a project strategy that will change the orientation of the project process from construction to manufacture to installation. Examples of off-site fabrication are wall panels for homes, wooden truss bridge spans, airport control stations.


There are four main categories of off-site fabrication, which is often also referred to as off-site construction. These can be described as component (or sub-assembly) systems, panelised systems, volumetric systems, and modular systems. Below these categories different branches, or technologies are being developed. There are a vast number of different systems on the market which fall into these categories and with recent advances in digital design such as building information modeling (BIM), the task of integrating these different systems into a construction project is becoming increasingly a "digital" management proposition.


The prefabricated construction market is booming. It is growing at an accelerated pace both in more established markets such as North America and Europe and in emerging economies such as the Asia-Pacific region (mainly China and India). Considerable growth is expected in the coming years, with the prefabricated modular construction market expected to grow at a CAGR (compound annual growth rate) of 8% between 2022 and 2030. It is expected to reach USD 271 billion by 2030. [7]

Prefabricated home

Prefabricated buildings

Concrete perpend

Panelák

Tower block

— an example of a prefabricated school building

St Crispin's School

first prefabricated building

Nonsuch House

Agile construction

Intermediate good