Last Planner System during the finishing phase in the world of small subcontractors

29 June 2017

The Last Planner System (LPS) is a production planning and control system designed to produce predictable workflow and rapid learning in programming, design, construction and commissioning of projects. LPS has five main elements: (1) Master Scheduling, (2) Phase "Pull" Planning - what should get done, (3) Make Work Ready Planning - what can get done, (4) Weekly Work Planning - what will get done, and (5) Learning - what was done (did) [1]. The collaborative process of LPS promotes participation of those who do the work to plan the work. During the weekly work planning, the correct amount of work and the right sequence of make-ready tasks are selected. Root Cause Analysis of the failures from the previous week are then discussed between Last Planners. The Percentage of Promises Completed (PPC) is a performance indicator that measures conformance of promises and team dynamics which promotes improvement.

LPS has been documented in many IGLC Conference Papers. In the Peruvian context, it has been implemented during the structural phase of a residential building. However, a major challenge still exists to sustain LPS implementation during the finishing phase. At this stage, there are numerous small trade partners who are performing work at the same time or place. More often, individual agendas exist regarding profitability or resource allocation across current projects. Making weekly commitments with the team using a pull process on the project is not their focus. Also, these trade partners lack awareness of Lean Techniques or LPS benefits. In this scenario, General Contractors fail to sustain LPS implementation throughout the finishing phase.

Last Planner System Challenges

To understand how LPS is implemented during the finishing phase, we studied a housing project to identify losses, the production stream, and challenges arising from LPS. It is noteworthy that each main finishing tasks were performed by an independent small trade partner.

We observed that the production unit of many tasks is one “full storey” per week, as shown in Figure 1. The chunks of work are oversized and tasks are not planned at the operational level. This myopia makes it difficult to identify constraints and make-work-ready on time. In the case study the lead time of individual storeys was 7 weeks and for the whole project was to take 15 weeks. However, the finishing phase lasted 22 weeks.

Task	Week 1	Week 2	Week 3	Week 4	Week 5	Week 6	Week 7	Week 8
Painting 1st coat	Storey 1	Storey 2	Storey 3	Storey 4	Storey 5	Storey 6	Storey 7	Storey 8
Door frames		Storey 1	Storey 2	Storey 3	Storey 4	Storey 5	Storey 6	Storey 7
Kitchen cabinet			Storey 1	Storey 2	Storey 3	Storey 4	Storey 5	Storey 6
Closets				Storey 1	Storey 2	Storey 3	Storey 4	Storey 5
Windows					Storey 1	Storey 2	Storey 3	Storey 4
Windows					Storey 1	Storey 2	Storey 3	Storey 4
Floor						Storey 1	Storey 2	Storey 3
Painting 2. coat							Storey 1	Storey 2

Figure 1: Takt-time schedule for the finishing phase

A Value Stream Map was produced so each task could be analyzed. In the case of “painting”, the production unit was a full apartment. The added-value activities constituted just 40% of the lead time of the activity. A huge gap of 40 days was identified during which no sub-process were performed in this production unit.

Table 1 summarizes the challenges of using LPS during the finishing phase of the housing project, evidence for the findings, and possible countermeasures to address these problems:

Challenges of using LPS in the finishing phase of the housing project	Evidence	Countermeasures
Production units are oversized	The production unit is either one full story (e.g. painting) or one full apartment (e.g. tiling, doors).	Production units should be divided into smaller work chunks
Pull planning is performed with very few trade partners	Full attendance only at the first meeting. Small trade partner’s lack of LPS training. Partners have individual agendas, trying to balance their human resources across projects.	Training: Include attendance and participation in relevant pull planning sessions as a compulsory requirement in contracts
Weekly meetings only serve to track achieved progress and plan again	Little analysis of constraints. Tasks are not broken into operations. General Contractor does not know tasks at the operational level.	Training: Conduct workshops with trade partners to analyse and understand their tasks at the operation level, in conjunction with planners and foremen
At some point, pull planning gets neglected	Planners push trade partners to finish their tasks by the contract’s completion date. Conflicts arise in the field.	The general contractor should focus on sustaining Look Ahead Planning (make-work-ready) Process throughout the project
Invisible losses resulting in an extended schedule	On average, during 90% of the lead time of major activities, no subtask is performed	Use of flowlines at the operation level as a visual tool for extended comprehension

Table1: LPS challenges, evidence and countermeasures

Lean Techniques for Improvement

We propose the following steps when planning and controlling tasks during the finishing phase of housing projects:

1. Sign contracts including a clause of compulsory attendance and participation at weekly meetings, engagement in collaborative planning, to track progress and to analyze underperformance.

2. Create several production units within the floor plan. It is necessary to reduce the batch and to plan activities with no interference (barriers to flow), considering the position of several production units. For example, Figure 2 illustrates five production units as follows: PU1: bathrooms, PU2: kitchens, PU3: closets, PU4: doors, and PU5: painting. The first three PUs are in different locations in each storey, so crews could be allocated at the same time without interfering with each other. By contrast, the last two PUs should be scheduled independently, because they require most of the space within the storey.

Figure 2: Production units per story

3. Identify the correct subtasks for the project and visualize these production units at the right level. Figure 3 shows subtasks (make-ready process) included in major tasks (phase “pull” planning)

	PU1 Bathrooms	PU2 Kitchens	PU3 Closets	PU4 Doors	PU5 Painting
Subtasks	Floor tiling	Wall cabinet	Structure	Frames	Sealing
Subtasks	Wall tiling	Base cabinet	Doors	Doors	1st screeding
Subtasks	Grouting	Granite board	Shelves	Frame painting	Sanding
Subtasks	Marble board	Wall tiling	Drawers	Door Painting	1st coat
Subtasks	Sanitary	Sink	Knobs	Knobs	2nd screeding
Subtasks	Cabinet	Faucet	Sealing	Doorpost	2nd coat

Figure 3: Subtasks within production units

4. Create flowlines as a tool for pull planning sessions. Figure 4 shows the flowline of the production unit 5. This level of detail would help Last Planners to visualize the work, detect process clashes, identify constraints, and have better-informed pull planning sessions.

Figure 4: Flowlines for a production unit. Adapted from [2]

5. Intersect flowlines of different production units to avoid time and inventory waste. When intersecting flowlines Last Planners could visualize areas without work and we can allocate crews to optimize the workflow.

Figure 5: In the blank area crews can be allocated to perform activities

We applied these steps in a large community housing project. Contracts with small trade partners were key drivers for participation and attendance at pull-planning sessions. The design of production units was related to project’s complexity. For example, social housing has less finishing works, so work chunks can be divided into more spacious areas. The use of flowlines is beneficial but its potential goes far beyond just a visualization tool. To conclude, it is the General Contractor’s responsibility to promote collaboration and facilitate pull planning sessions to identify tasks at the operational level. Full deployment of these strategies, however, requires training and leadership among the managers of both contractors and trade partners [3].