Traditionally, contractors face a large amount of rework due to both poor field planning and poor coordination between engineering and construction. The loss of productivity caused by rework can be harnessed and turned around if the work packaging process is implemented properly. Efforts on work packaging conceptualization have been under research and implementation.
The Last Planner System from Lean Construction is a practice used in many construction sectors to organize work sequence in the field. The field core deliverable for the Last Planner System is the weekly work plan (WWP).
From Lean Thinking to Lean Construction practices
Lean Construction refers to the adaptation of Lean Thinking Principles and Concepts derived from the Toyota Production System (TPS) to construction. Lean production was developed by Engineer Ohno. Lean construction accepts the Ohno’s production system design criteria as a set of standards but that should be adapted to construction. Hence, research has been conducted to define the adaptation of lean to construction based on the construction field requirements and specificities. It is also presented as “a clear set of objectives for the delivery process, aimed at maximizing performance for the customer at the project level, concurrent design of product and process, and the application”.
The Last Planer System is one of the best known Lean Techniques that was developed by Glenn Ballard and Greg Howell as a production planning and control system. LPS system is designed to affect three different characteristics of a project: variations in construction work flow, planning prevision and uncertainty in construction operations. The system is controlling two main project components: the production unit and work flow.
The system at its latest version covers the full planning and schedule development process from master schedule to weekly planning. The Last Planner System is centered on the Weekly Work Plan (WWP).
Figure 1: Planning Levels in the Last Planner System (Adapted from Ballard and Howell, 1998)
As shown in figure 1, the LPS comprises four levels of planning processes with different chronological phases/deliverables:
Master Scheduling: results in the deliverable of the front-end planning that identifies major milestones and incorporates Critical Path Method (CPM) logic to determine overall project duration (Tommelein and Ballard, 1997)
Phase Scheduling: results in a phase schedule that identifies handoffs between the various specialty organizations to find the best way to meet milestones stated in the master schedule (Ballard and Howell, 2004)
Lookahead Planning: At this stage, activities are broken down in operations, constraints are identified, responsibilities are assigned and assignments are ready (Hamzeh et al., 2008)
Commitment Planning: this is the most detailed plan in the scheduling process. It is very close to the construction process and is directly linked to continuous improvement tools.
Other known techniques are also field oriented and may interfere with the Last Planner System to enhance its application: First run studies, 5 S’s, Increased Visualization and Huddle meetings.