The following is the first of two posts written to detail findings from a case study of lean design in two construction projects built in Norway during the years of 2018/2019.

In this case study, two large scale construction projects were designed using an LOD-based framework made with the intent to standardize the often chaotic process that is our current approaches to building design.

Although the study uncovered several valuable insights as to how lean construction design can be accomplished, most of these findings will be discussed in detail in another post. The following article serves as a theoretical introduction to the topic of achieving lean processes in construction design engineering.

The challenge of modern building design management

Traditional construction design management has struggled with an ad hoc approach to design, increasing the amount of rework and cost, in addition to reducing the ability to produce efficient designs according to customer needs.

Although many improvements have been made in construction design over the last decades - most notably being that of Building Information Modeling (BIM) - these improvements are more often than not simply tools for designers, and does not address the underlying problem with construction design today, that is: the lack of an orderly process of work which can be managed towards clear goals and thus value creation.

Learning from Toyota: What is Set-Based Design?

One of the many great insights revealed from the lean practices of Toyota is the way they design cars, often referred to as Set-Based Design (SBD).

Set-Based Design comes with a radical new insight as to how to approach the design process itself. Instead of starting with a presumption as to roughly how the designers think the design should be and iterating upon said design (the strategy of which is often referred to as “Point-Based Design''), designers using SBD instead takes the following approach:

Define the broadest possible amount of different design concepts that could possibly satisfy the end goal of the product, then to gradually develop all the concepts simultaneously. While continually testing the performance of concepts against each other, potential concepts that prove to be underperformers are scrapped in favour of more development on the best performing concepts.

In contrast to traditional point-based approaches, Set-Based Design takes a slower, more methodical approach to design. The graphs above can be understood as two axes, with different designs on the vertical axis and degree of completion of said design on the horizontal axis.

How does Set-Based Design enable lean design?

At first glance, Set-Based Design might seem like a slow and cumbersome process, so how does it produce better results than Point-Based Design? There are a couple of reasons:

1. Develop for testing. During the development, designs are only developed to the minimum viable product that can be tested for vital performance metrics relevant to the customer experience of the final design. Once proven to be underperformers, designs are quickly scrapped and do not consume more time and energy during development.
2. Clear goals. In contrast to Point-Based design, SBD has a clear end goal: Reducing the possible solutions down to the best solution (which at that point is close to finalized). On the other hand, Point-Based approaches have no such end-state. In addition, Point-Based design processes often include a lot of rework as a result of flawed assumptions in picking “the correct” concept before any testing has been done. The end result is a design process that is impossible to manage towards clear goals.
3. Better designs. The vast majority of cost related to a product usually comes from its production cycle, not from the design process. Seeing as SBD has a higher likelihood of producing efficient and cost-effective solutions according to customer needs, the entire project lifecycle of the product is often completed a lot more effectively, and at a lower cost.

Why is Set-Based Design difficult to apply in construction?

Sadly, the analogy of a car which you can build multiple different prototypes of, testing for fuel-efficiency, noise, pollution and so on does not easily translate to construction development. Construction projects are large and unique, whereas cars are mass-produced at a level in which the relatively minor cost of building different prototypes are negligible.

Construction design projects also see greater involvement by the customer, which influences the design process in several ways:

1. The customer is often involved in establishing a base concept during the start of the design process, making it less relevant for designers to test many different concepts.
2. The design process is expected to be completed in a short duration of time, further stressing this critical phase of project development.

Although construction projects are not able to test multiple different designs of the same building, the principles of Set-Based design are still relevant to achieve a lean design process. As described in the introduction, the primary challenge of managing construction design is the lack of an orderly process. By understanding design development as increasingly mature designs as described by Set-Based thinking, design managers can solve this issue by formalizing the design development as a series of increasing steps of maturity.

How maturity-related management enables Set-Based Design in construction

In recent developments in the Norwegian AEC-Industry, one attempt to describe the building construction design process in a way that enables lean principles of Set-Based engineering has been created in the form of an LOD-based framework referred to as Model Maturity Index (MMI).

The framework was a set of levels describing the attributes of increasingly mature (although not yet complete) building designs, in an effort to use the levels as milestones in planning. In this way, designers can avoid the trap of Point-Based Design by allowing for designs to gradually develop into complete designs, and the design managers can (for perhaps the first time ever) have a tool to systematically describe design and model development in a predictable and systematic way conducive to sound principles of project management.

One can draw parallels between Set-Based Design and MMI, seeing as the increasingly mature designs gradually converges towards a final design, rather than forcing the design based on presumptions made by the designers:

Learn how to use MMI effectively from Case studies

This post was an introduction to the concept of model maturity and the theoretical background of how it was made using principles from Set-Based Design. For a more detailed post on the practical challenges and experiences from using MMI in actual case studies, watch out for the next post!