LEAN CONSTRUCTION TOOLS

LEAN CONSTRUCTION TOOLS

The lean construction tools which can be applied on construction projects for waste minimization are as follows:

1. Just in Time (JIT)

Just in time (JIT) is a strategy that works in the elimination of waste in all operations and activities. JIT is a production cost system in the specified time for certain productivity within the project; productivity which leads to development and reduced costs. This strategy is an inventory costs system in a timely manner, which deal with receiving materials today and use them up tomorrow. This method can be effected by adjusting the time of material receipt against the time we start using it in production and adjusting the time of completion of project against the time of delivery. The process of controlling stocks systems leading to JIT process.

On this basis, the adjusted time system which works in production cost reduction is by reducing the supply periods.

The important JIT goals:

• Dispensing with all types of stock or reduced to a minimum.
• Reducing time and resources wastage in the productive processes.
• Purchasing in the appropriate quantity and time to meet customer needs in a timely and quality Occasion.
• The development of relationship and trust between the suppliers and the industry through the development of long-term relationship that lead to confidence

To deduce the disadvantages of production costs at the time specified are as follows:

1. Difficulty in achieving some assumptions, such as absence of defects in production, reaching level units with zero. Fault, along with zero inventory, difficulty in achieving in large-scale company or companies with seasonal activity.
2. This system requires cooperation among management, workers and suppliers. This system cannot be applied without integration among these parties.
3. This system requires the need to develop the general accounting systems, general cost concept and special cost system.
4. So many company do not accept the idea of the application of the concept of production costs in time because of it involves high cost, which occur at the beginning of the application of the concept by the preparation of administrators and workers and by changing company dealings with suppliers and customers.
5. Some administrators are not convinced about the change from existing concept to a concept of production costs in time because they fear its application failure.
6. Closure is the biggest problem facing the economic side to provide materials as the stock in this concept is equal to zero, and in the case of the closure, we will not find materials to be used by the contractor and consequently activities are stoped.

2. Last Planner System

Ballard (2000) shows that Last Planner System (LPS) is strategy that shapes workflow and addresses production variability in construction industry. The Last Planner is the person or group of people that is accountable for operational planning such as structuring of product design to facilitate improved work flow, and production unit control, such as the completion of individual assignments at the operational level. The last planner system consist of implementation sequences (master schedule, Reverse Phase Schedules (RPS), Percent Plan Complete (PPC), six-week look ahead, Weekly Work Plan (WWP), constraint analysis and variances analysis).

The specific goal of last planner is to pull activities by reverse phase scheduling through team planning and optimize resources in the long-term. This tool is similar to the Kanban system and production leveling tools in lean manufacturing.

Master Schedule

The master schedule is described as an overall project schedule, with milestones, that is usually generated for usage in the bid package. Based on this master schedule the RPS is produced.

Reverse Phase Scheduling (RPS)

Ballard and Howell (2003) shows that a pull strategy is used to develop a schedule that works backwards from the completion date by team planning; it is also called Reverse Phase Scheduling (RPS). They also indicate that phase scheduling is the connection between work structuring and production control, and the main purpose of the phase schedule is to produce a plan for the integration and coordination of various specialists’ operations.

Reverse phase schedule is developed by a team consisting of all the last planners. This schedule is closer to reality than the preliminary optimal schedule which is the master schedule. However, without considering actual field factors in the RPS, the RPS is more or less accurate than the WWP.

Six-Week Look Ahead (SWLA)

Ballard (2000) shows that the main tool for work flow control is look ahead schedules. SWLA indicate what kinds of work are suppose to be done in the future. In the look ahead schedule, first week is next week, the second week is the WWP meeting. The number of weeks in look ahead schedule varies. For the design process, the look ahead schedule could be 3 to 11 weeks (Ballard 2000). The six-week-look ahead durations and schedules are all estimated based on the results of the RPS, and the constraints are indicated in order to solve the problems before the actual production takes place. SWLA is distributed to all last planners at WWP meetings. Lean manufacturing look ahead planning is the process of reducing uncertainty to achieve possible constraint free assignments (Koskela et al., 2000).

Weekly Work Plan (WWP)

Should, Can, and Will are the key terms in WWP (Ballard 2000). Weekly Work Plan (WWP) is produced mainly based on SWLA, the actual schedule, and the field condition before the weekly meeting. Along with this plan, manpower from each trade will be adjusted to the need.

•  Should: shows the level of work that is required to be done according to schedule requirements.
• Can: shows the work that can actually be accomplished on account of various constraints on the field.
• Will: This reflects the work commitment which will be made after all the constraints are taken into consideration. The WWP meeting covers the weekly schedule, quality issues, safety issues, material needs, manpower, construction methods, backlog of ready work, and any problems that can occur in the field. WWP promotes two-way communication and team planning to share information on a project in an accurate efficient and way. It can improve safety, quality, material flow, the work flow, productivity, and the relationship among team members. Ballard and Howell (2003) shows that WWP should emphasize on the learning process more by investigating the real causes of delays on the WWP instead of assigning blames and only focusing on PPC values. Variance analysis is also conducted based on the work performance plan from the previous weeks. The causes of variance should be well documented within the WWP schedule.

Percent Plan Complete (PPC)

The measurement method of Last Planner is the Percent Plan Complete (PPC) values. The metrics is calculated as the number of activities that are completed as planned divided by total number of planned activities (Ballard 2000). The upward (positive) slope between two PPC values means that production planning was reliable. According to Ballard (1999), PPC values are highly variable and it usually ranges from 30% to 60% without lean implementation. In order to achieve higher values (60% and above), additional lean construction tools such as first run studies need to be implemented.

3. Increased Visualization

The increased visualization lean tool is all about communicating key information effectively to the workforce through posting of various labels and signs around the construction site. Workers can easily remember elements such as performance targets, workflow, and specific required actions if they visualize them (Moser and Dos Santos 2003). This includes signs related to schedule, safety, and quality. This tool is similar to the lean manufacturing tool, Visual Controls, that is, a continuous improvement activity that relates to the process control.

4. First Run Studies

First Run Studies are usually used for the purpose of redesigning critical assignments (Ballard and Howell et al., 1977), part of continuous improvement effort include productivity studies and review work methods by streamlining and redesigning the different functions involved. The studies commonly use video files, photos, or graphics to show the process or illustrate the work instruction. First run of a selected craft operation should be well examined in detail, bringing suggestions and ideas to explore alternative ways of doing the work. A PDCA cycle (plan, do, check, act) is a suggested way to develop the study: Plan refers to selecting work process to study, assembling people, analyzing process steps, brainstorm how to eliminate steps, checking for safety, quality and productivity. Do indicate to try out ideas on the first run. Check indicates to measure and describe what actually happens. Act refers to bringing together the team, and communicating the performance and improved method as the standard to meet.

5. Daily Huddle Meetings (Tool-box Meetings)

Two-way communication is the most effective key of the daily huddle meeting process in order to achieve employee involvement. With the awareness of the project and problem solving involvement along with some training that is provided by other tools, employee satisfaction (job meaningfulness, self-esteem, sense of growth) will increase. As part of the improvement cycle, a brief daily start-up meeting was conducted where team members quickly give the status of what they had been working on since the previous day’s meeting, especially if an issue might prevent the completion of an assignment (Schwaber, 1995). This tool is similar to the lean manufacturing concept of employee involvement, which ensures rapid response to problems through empowerment of workers, and continuous open communication through the tool box meetings.

6. The 5s Process (Visual Work Place)

• Sort: The first level of housekeeping consists of separating material by reference and placing materials and tools close to the work areas putting into consideration safety and crane movements.

• Straighten: Materials were piled in a regular pattern and tools were also placed in gang boxes. Each subcontractor takes responsibility for specific work areas on the job site.
• Standardize: This level included the preparation of a material layout. The layout contained key information about each workers activity on the job site. The visual workplace helps locate incoming material, reduce walking distance for the crews and reduce crane movements.

• Shine: This step consist of keeping a clean work place. Workers were encouraged to clean job site once an activity has been completed. Housekeeping crew was set up to check and clean hidden areas on the job
• Sustain: This is the final level of housekeeping, it is sought to maintain all previous practices throughout the project time. At the end of the project, this level is not fully achieved, in part because project personnel did not view housekeeping as a continuous effort. They had to be reminded frequently of housekeeping practices.