What makes construction different from manufacturing is its dynamic nature. Unlike a systemized production plant, a construction site is a mesh of interconnected processes that are far from optimized. The traditional top-down planning practice does not solve problems on the construction site, as recent research reveals. Making planning collaborative is a necessary step in making construction less wasteful.
Everybody in the industry has felt frustration with inefficiencies in construction, but seeing the data is still disconcerting. I’ve had the pleasure of attending several workshops organized by the Finnish Aalto University’s research teams. These eye-opening events both revealed how much waste we have in construction today and suggested solutions to this problem.
Four Aalto University graduate students shared insights from their research at a workshop of the Waste Workgroup of the Building 2030 consortium. They focused on projects where takt production, a lean construction method, had been used. Takt production breaks the work down into equally timed work batches and typically shortens project lead time considerably—up to 50%. However, even these well-planned projects included waste and unnecessary movement, as the researchers found out.
Even the Best Plans Can Be Made Better
Saara Salerto of Skanska used video equipment to record the activities in two corridors of the Urban Environment House construction site in Helsinki. She measured the utilization rate and possible work disruptions for six weeks. It became evident that the work did not follow the original takt schedule. For example, in the third week, only one task was supposed to take place in the area. Instead, two other tasks were still in progress, one of them starting early. In addition, three unplanned tasks went forward in the area.
During the busiest days, up to four contractors worked in the same area, but some of these just for a few minutes. After the rush period, there were times when the corridors were empty for several days.
It is notable that even though takt scheduling led to shortened construction time, the other takt area was empty almost 50% of the time. A paint job that was a specific week’s only scheduled task took just 50 minutes to complete. Despite this, 20% attendance in the takt area was enough to keep the project on schedule.
Another Aalto student, NCC’s Anton Ruohomäki, shared data from the Vallila Folks Hotel renovation site. He used surveys and video cameras to record the interior construction of two adjacent hotel rooms. The takt time was one day, and the takt area around 20 square meters in size.
On average, the rooms were empty for 63% of the workday, which is more than the 41% in the original plan. There was, however, a great deal of movement when work was taking place, but much of it unnecessary.
The events of one particular day in one of the rooms demonstrate this fact. During this day, eight different workers visited the room 62 times in total. One tile installer stepped into the room 27 times, and another 26 times. Ten visits lasted longer than five minutes. The average duration of visits under five minutes was 39 seconds!
Disturbances and Interruptions
Henri Ahoste, a graduate student from Skanska, followed the installation of raised access floors and their underlying electrical installations for three months at the Urban Environment House site in Helsinki. The work took place in three takt areas, each covering an entire floor. Ahoste measured and surveyed disturbances and interruptions in the process, which are factors that cause process waste.
For example, an absence of initial information led to delayed material deliveries. Sometimes the planned workforce was not available. There were also conflicts with the previous task due to a lack of coordination and communication.
“Location-based scheduling in Finland is run-of-the-mill stuff, and we use Last Planner Sessions quite often. Still, the level of scheduling and production planning on construction sites seems to be fairly low,” Ahoste stated.
Collaborative Planning Is the Way Forward
Other studies corroborate Ahoste’s concern. Unclear schedules lead to time pressure, create quality issues, and diminish worker well-being. They are typically the result of a common top-down scheduling practice that has little to do with the realities of construction sites. Collaborative production planning with the Last Planner System (LPS), in contrast, brings rational scheduling practices to the jobsite.
Subcontractors on the Urban Environment House construction site were enthusiastic about planning collaboratively with the LPS. They were able to keep track of the schedule in daily meetings, which gave them a real-time situational picture of the site. They also started to favor takt planning over conventional planning. The condensed takt production schedule proved workable, even if some tasks were not completed 100% as scheduled.
Ahoste believes that future projects should use takt production and collaborative planning. He recommends that a construction site should use a neutral facilitator to run the LPS sessions. Having comprehensible visual guidelines and requirements for LPS participants is also important. In order to maximize the benefits of collaborative planning, it should cover design, production, and procurement.
Based on the day’s presentations, takt production is a step forward, but it needs to be planned and monitored collaboratively when put into practice.
Read my full report of the Aalto workshop at building2030.com.