BIM and DFMA

Photo © Portakabin Group / Yorkon

Building Information Modelling (BIM)

BIM has its roots in CAD and CAD/CAM as a highly cost effective software tool to plan and to control the detail of manufacturing processes. The application of BIM to the construction industry has taken a long time but has now arrived and is being developed and exploited at different levels of complexity across the industry.

The construction industry clearly has a long way to go and it is curious that so much of the industry is still almost totally dependent on 2D paper drawings even if these have to be delivered from an otherwise paperless software environment. Is construction alone in still thinking that this is good practice?

BIM has typically been used at the design stage of a construction project to enable the design brief to be tested and the proposed construction solution to be changed at minimum cost. At the detailed level the Model has been used to optimise design solutions, to avoid clashes and to require issues of buildability to be dealt with well before work and spending starts on site. Use of a BIM model is also a very convenient device to engage with client requirements for a sustainable building, minimisation of waste, embodied carbon and predictable cost of ownership.

However, a BIM model has the potential to deliver so much more and increasingly leading clients, designers and constructors are starting to use BIM as a project management device to support the management and delivery of the construction stage. Before any work starts on site the project team will enjoy a very high level of certainty as to precisely how the building will actually be built, the associated issues relating to logistics, health and safety considerations, environmental considerations and also time and cost.

At the cutting edge the digital model is also starting to be used as an asset management tool to support the operation of the building in use by the FM Team based on much greater certainty regarding performance in use.

Buildoffsite is very supportive of the implementation and growth in the intelligent application of BIM as a mechanism to develop mindsets to think challengingly about innovation in the process of construction and the opportunities to introduce offsite components of increasing complexity into design and construction processes. BIM is a tangible mechanism to encourage the consideration of offsite solutions as early as possible in the project planning process.

Find out more: BIM: People matters 14 questions with Richard Ogden

Design for Manufacture and Assembly (DFMA)

In the context of the construction industry, Design for Manufacture and Assembly (DFMA) is an approach best described as ‘improving quality through the application of efficiency.

Seeking to find the most efficient way of delivering a project inevitably reduces the resources required (whether this is measured in cost, time, carbon, waste or labour) while increasing positive aspects such as health and safety, quality, certainty. In other words, DFMA breaks the traditional relationship between cost, quality and time: a DFMA solution can be achieved to a higher quality at lower cost and in less time.

DFMA takes a number of forms, but the common factor is the application of factory (or factory-like) conditions to construction projects. This is critical for many reasons including:

  • Health and safety: factory condition are 80 per cent safer than site conditions
  • Cost: site labour is approximately 2.2 times more expensive than factory based labour
  • Productivity: factory productivity reaches 80 per cent compared with 40 per cent for a typical site
  • Sustainability: waste is reduced to just two or three per cent in efficient factories and almost all can be recycled

A DFMA solution starts by understanding the end product – site, brief, constraints and key drivers – draws upon the range of suppliers and systems available. Varying degrees of “granularity” can be used according to the project requirements. Volumetric solutions create as much of the finished product as possible in the factory, with on-site labour completely minimised. “Flat pack” or panelised create a kit of parts that can be quickly assembled on site.

Often prefabricated sub-assemblies (M&E services, for instance) are deployed in conjunction with more traditional build elements. In all these instances, the factory may be remote from site or located in an adjacent or nearby facility.

For some situations, traditional build elements are used (dylining etc) but the site is effectively turned into a factory. Pre-packed “fit out kits” are delivered to site with everything required for the element of the works, eg for an apartment this might include pre-cut boards and studs, tested and terminated ‘plug and play’ wiring looms, volumetric or flat pack bathrooms and prefabricated services units (comprising boiler and water tank, under floor heating manifold, electrical distribution board, whole house ventilation unit etc). Waste is virtually eliminated, together with the most common causes of delay on site including lack of materials and labour, sequencing of follow on trades, reworking etc.

DFMA also allows for building to be deconstructed more safely, with components or even entire buildings able to be reconfigured or redeployed elsewhere. This is the ultimate form of sustainable construction; re-using available parts expends far less resource than creating new ones.

 

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