Flying factory for construction works

Prefabrication in the construction industry refers to manufacturing that takes place off site, under factory conditions, with the completed components then being transported to site for incorporation into the works.

As a technique, prefabrication is particularly suited to high-volume, repetitive components, or products that require factory conditions to achieve the desired level of quality. It can also allow parallel working on different aspects of a project simultaneously. However, transportation costs can be high, there may be storage requirements, and the costs of establishing a long-term facility can be high, posing a significant business risk, particularly where long-term demand may be unpredictable. See Prefabrication for more information.

Flying factories (sometimes referred to as field factories) are temporary facilities used to manufacture prefabricated components. They are different from conventional off-site factories in that they only operate for the duration of a project and are then closed. Operations may then 'fly' to a new location to service another project.

The term is thought to originate with ModCell, a company that uses straw bales to form prefabricated panels. Locating fabrication facilities close to sources of straw has enabled them to remain flexible and reduce their costs.

Flying factories have the advantage of being able to locate close to, or even on construction sites, or close to sources of materials and so reduce transportation costs, disruption and delays. It can also be more flexible, as leases or buildings are temporary, and so facilities can be scaled up or scaled down to suite the demand from a particular project.

In a report about a facility created to build serviced utility cupboards for Phase1 of the Nine Elms development in London, construction and development company Skanska suggested that the barriers to off-site prefabrication were:

• The initial capital investment.
• High transport costs.
• The financial instability of offsite manufacturers.

They believe that flying factories avoid these problems.

Ref. Construction Manager Magazine, Skansa's flying factories take of in Slough 2 October 2015.

Mark Wray, lead technologist at Innovate UK, which provided a £750,000 grant for the project said, “The biggest barrier at the moment is that offsite manufacture is established in a building, tied to a fixed location, with all the associated costs. At present the high level of capital investment needed to establish an offsite manufacturing facility means that it is not feasible unless you have a large funding mechanism.

“Based on the feedback we have received, this is a viable solution that will be well received by the industry. This is not just for the big players like Skanska and Laing O'Rourke, but also SMEs. We believe the lower start-up costs offered by flying factories will appeal to smaller players.”

The disadvantages of flying factories include:

• Property rental is generally more expensive.
• There are repeat set up costs.
• They may not be suited to fabrication processes that require complex machinery.
• They may be constrained by the availability of local space and qualified labour.

NB The BIM Overlay to the RIBA Outline Plan of Work, published by the RIBA in 2012 suggests that a field factory is: 'A factory facility set up near to the construction site. A field factory might manufacture modules from scratch or might preassemble flat pack components before assembly on site. Field factories minimise the logistics associated with transporting modules and also enable larger modules to be manufactured due to the removal of transportation constraints. Field factories also allow the use of local or community labour sources, which can benefit the local economy of a project. Longer term, it is likely that field factories will increasingly involve the assembly of larger preassemblies as construction moves further and further towards fully assembled buildings.'

DfMA Overlay to the RIBA Plan of Work, Mainstreaming Design for Manufacture and Assembly in Construction, 2nd Edition, published by the RIBA in 2021, defines a field factory as: ‘A temporary factory facility set up near to the construction site to manufacture modules or preassemble flat pack components before assembly on site. The work carried out in them counts as offsite construction. They can also help with transportation logistics’

[edit] Related articles on Designing Buildings Wiki

• 3D printing in construction.
• British post-war mass housing.
• BSRIA launches Offsite Construction for Building Services topic guide.
• Flat pack.
• In-situ.
• Just in time manufacturing.
• Kit house.
• Lean construction.
• Modern methods of construction.
• Modular buildings.
• Offsite manufacturing.
• Off-site construction.
• Off site materials.
• Off-site prefabrication of buildings: A guide to connection choices.
• On site.
• Prefabrication.