Off-site fabrication is playing a key part in high-profile projects, including the use of regional construction hubs as part of Heathrow's expansion. Could it benefit your next project?

What is off-site fabrication?

Off-site fabrication refers to the process of manufacturing or assembling elements of a structure away from the site where it will be built. Use of off-site fabrication ranges from small components, decorative features or structural elements (examples of non-volumetric fabrication) to whole units, such as bathrooms or kitchens (volumetric fabrication) to fully modular buildings.

While off-site fabrication is not a new practice, it has grown in popularity in recent years. The types of projects that use off-site fabrication are far more diverse than previously, in part because of advances in computing and manufacturing.

What are the benefits of off-site fabrication?

Developers and contractors who have adopted off-site fabrication in their projects report the following benefits:

  • Higher quality and consistency: Off-site manufacture, often using CAD systems and specialised personnel, can mean fewer defects and shorter snagging lists. Modules and components are tested for quality before leaving the factory.
  • Labour advantages: Less on-site labour is required and for shorter periods. Fabrication at off-site warehouses allows developers flexibility to build in areas with local shortages of skilled labour.
  • Less waste: The use of precision equipment and standardised processes in a controlled, factory environment generates far less waste, which has both financial and environmental advantages.
  • Reduction in programme times: With more of the work being carried out off-site, programmes are less likely to be impacted by weather stoppages or site congestion. Build time tends to be considerably shorter because of efficiencies such as the ability to carry out ground works simultaneously to fabrication of key elements of the eventual structure.
  • Less disruption: Reductions in dust and noise, fewer vehicles on site, fewer risks (for example, because working at height can be minimised) and more controllable interface risk all contribute to a general reduction in disruption, when compared to traditional builds.

Practical considerations

If you are considering incorporating an element of off-site construction into your project, the following issues may be relevant:

  • Timing: To be effective, off-site fabrication must be “baked in” from the start. If you are putting your project out to tender, you should make clear whether and to what extent you are open to an off-site solution. Although it is likely to save time on-site, adoption of off-site fabrication is likely to lead to a longer lead-in time and this should be considered during the planning phase.
  • Transportation of materials to site: How will those components which are manufactured off-site be transported to the site and, once there, how will they be stored if they are not immediately incorporated into the project? This may be less of an issue for smaller elements but will be an issue for larger modules and components.
  • Access to the site: How will the site be accessed? Will you need to access or oversail neighbouring properties? Where larger modules are to be incorporated, cranes or other lifting equipment are likely to be required.
  • Price: Off-site fabrication may offer fewer cost benefits for a bespoke, one-off project but may offer more certainty of price. Savings are more likely to be associated with economies of scale or projects that contain repetitive elements. When comparing the costs of traditional construction with those of a project incorporating off-site elements, it is best to take a holistic view as outlays and economies will fall in different areas depending on the approach. There are assessment tools available to aid in this exercise.

Legal considerations

The legal considerations involved in any construction project will be influenced by many factors, including the nature of the project, the manner in which it is being funded and the priorities of the employer. However, some issues of particular importance where elements of work will be carried out off-site include:

  • Title: The parties will need to agree who owns the relevant components while they are off site and when title in them passes. The employer may need to pay for goods and materials early on in the project and will wish to ensure that it is protected if the supplier or manufacturer becomes insolvent prior to their delivery to the site.
  • Risk: Unless otherwise agreed, risk in goods will pass at the same time as title. The parties will wish to allocate liability for the risk of damage to the goods while in the factory and during transit.
  • Monitoring, testing and inspection: Adequate arrangements to ensure that the employer (or a representative) can satisfy itself as to quality prior to delivery will need to be put in place. The appropriate regime will depend on the nature of the work being carried out off-site.
  • Collateral warranties: If there is no direct legal relationship between the employer and the off-site manufacturer, the employer may require a collateral or product warranty, as may any potential funder, purchaser or tenant.
  • Interface and co-ordination: In any project it is important to ensure that all of the parties involved understand the extent of their duties and responsibilities and how they interact with each other. Not all of the project team will be familiar with the off-site fabrication model and design responsibility will not necessarily sit with just one party. It will be particularly important that each party’s liability is clearly defined and that there is no scope for confusion on this point. Co-ordination and co-operation between the parties will also be crucial. For example, if a change in design will affect the manner in which other services are carried out this should be communicated early so that the full impact can be assessed and addressed.