The construction of the Empire State Building took 13 months in the 1930s. Today, a skyscraper of a similar size would take three to four years to complete. What has changed, and could Lean Construction and BIM help in making construction efficient again? Associate Professor Rafael Sacks of Technion, the Israel Institute of Technology, shared his team’s experiences in his presentation today at VTT in Otaniemi, Finland.
The Empire State Building is a great example of a mass construction. The builders worked in tiers and used buffers in the schedule to manage unaccounted variables. There were no critical paths in the project schedule. The building was fairly simple. There were only two floor plan variations throughout the building. The site had 15 to 16 cranes or hoists around the building, which allowed rapid vertical transportation of material.
Process complexity is a major culprit
Modern buildings are much more complex than in the 1930s. A building consists of many different products and systems that did not exist back then. Furthermore, we have many more subcontractors working on the site. But even if you take into account all the complexities of the project, they don’t explain alone why the time spans for construction have increased so dramatically.
Rafael Sacks believes that a major reason why construction takes so long nowadays is process complexity. We have multiple design changes, re-entrance of crews to complete work that they started earlier, reciprocal interdependencies between subcontractors, and so on. Sacks mentioned, as an example, a single building site in London with between 400 to 500 workers on any given day. The workers belonged to 74 different companies, which were working on multiple projects at the same time.
While projects and processes have become more complex, we still manage them basically the same way as in the 20th century. We have management by contract: we tell the contractors and subcontractors what they are supposed to do, and hope for the best. Each crew optimizes their work for their own profit. That sub-optimization is not beneficial when you look at the project as a whole.
Lean Construction and BIM could be the solution
The result of conflicting interests and sub-optimization is waste. The Lean Construction community has identified many types of waste and has developed methods and tools to reduce it. Lean Construction differs from its predecessors, craft construction and mass construction, by making customized products in a very efficient way.
BIM and Lean are coming together to deal with product and process complexity. They require changes in the ways of working, and that is harder than just implementing new technology. Substantial changes demand long-term efforts and a stable business and working environment.
Professor Sacks talked about the Last Planner System, which makes work processes stable and increases predictability. He also described KanBIM, a system that combines the Lean production principle Kanban, and BIM. Based on real-life pilot tests and laboratory simulations, it reduces process waste from a typical 32 % to 11 %, and at the same time makes the standard deviation smaller.
Projects could become virtual companies
In his concluding remarks Professor Sacks said that in order to increase subcontractors’ willingness to collaborate, we need a “virtual company” that works cohesively. A virtual company requires a new kind of management, new types of contracts, and incentives that make business sense to the collaborating companies. One practical idea for increasing cohesion is to create social networks among the subcontractors. Architects should support Lean Construction by providing up-to-date product information, which can be combined with process information.
The initial results from pilot projects and simulations are encouraging, and should inspire the industry to renew its practices. Professor Sacks emphasized the role of the clients and owners in this development.