Solution Summary: Lean Construction
Lean construction processes are streamlined to eliminate operational inefficiencies and enhance the value on projects.
Lean construction processes are streamlined to eliminate operational inefficiencies and enhance the value on projects. This is achieved by eliminating all forms of waste and non-value adding activities. Non-value-adding activities, such as re-work, interruptions and productivity losses, are undertakings that consume time and resources but do not directly or indirectly add value or progress to the project. These activities lead to schedule delays and cost overruns in design and construction projects. The removal of these excesses during operations ensures reduced timescales, errors and rework, improved product quality, optimized costs and enhanced productivity throughout the construction work processes.
Established on the principles of lean production, lean construction aims at maximizing value to the client by minimizing wasteful activities on construction projects. Waste is any human activity or component that absorbs resources of materials, equipment and manpower, but creates no value to the customer. Lean practitioners therefore seek to minimize wastes from system operations and continually improve the efficiency of construction processes. The eight basic types of waste identified in lean are defects, waiting, transportation, motion, inventory, overproduction, unnecessary process steps and making-do. They are explained briefly as follows:
- Overproduction: This occurs when there is production of a quantity greater than required or earlier than necessary. This results in an excess of products, products being made too early and increased inventory.
- Waiting time: This is sometimes referred to as queuing. It refers to idle time or periods of inactivity caused by non-integration of material flows and pace of work by different groups or equipment.
- Transportation: This is concerned with the unnecessary movement of materials from one operation to another on site. This results in handing damage and increases processing time during which no value is added.
- Processing: This involves extra operations during conversion activities such as rework, handling or storage that occur because of defects, overproduction or excess inventory.
- Inventory: This can be a result of lack of resource planning or uncertainty on the estimation of quantities. It includes all inventories that are not directly required to satisfy the client’s current orders. Excessive and unnecessary inventories lead to material waste, additional handling and space, and monetary losses due to the capital that is tied up.
- Motion: This refers to unnecessary or inefficient movements made by workers during work tasks to accommodate inefficient layout, ineffective work methods, defects, reprocessing, overproduction or excess inventory.
- Defects: These are intermediate or finished goods or services that do not conform to the quality specifications or customer’s needs, thus leading to rework and ultimately customer dissatisfaction.
- Making-do: This refers to a situation where a task is started without all its standard inputs, or the execution of a task is continued although the availability of at least one standard input is lacking.
Lean conveys efficiency, prudence, and minimizing the usage of resources on construction projects by using less to achieve more. Lean construction brings about a change in the traditional conceptualization of project management in the construction industry through lean thinking. Lean thinking is implemented to maximize performance at the project level and is anchored on five principles of Value, Value Stream, Flow, Pull and Perfection. While value must be understood from the client’s perspective, value stream allows for remarkable process improvements by reducing variability and waste. The concept of flow is related to the ideal of flowing work processes without interruptions which reduces the lead time of generating desired outputs. The employment of pull technique generates timely feedback from the job site which can be used to drive related work activities off-site. Lean Thinking achieves perfection through standardized work, which defines precisely, the sequence, flow and allowed inventory of construction activities. These lean principles address communication, workflow, variability, and other production issues.
Lean practitioners have developed many tools and techniques that help facilitate the lean system of production and address the peculiarities of construction. Some of the techniques used in Lean construction include the Last Planner® system, Lean Collaborative Planning and Project Management, Just in Time (JIT), Structured Problem Solving, Visual Management, Process and Operations Improvement, the 5 S’s (sort, set, shine, standardize, sustain) and Work Structuring. Success in implementing lean principles requires a profound change of the company’s culture regarding production management. Also essential for a positive outcome is close collaboration among project team members, which includes the involvement of safety and health professionals in the development of lean initiatives. Furthermore, as the construction industry moves towards integrated project delivery methods, the utilization of lean construction presents great benefits to construction stakeholders. These methods integrate construction knowledge into design which results in efficient work methods, high quality structures and improved safety performance.
The poor safety record of the construction industry over the decades makes it one of the most hazardous industries worldwide. The poor safety culture among workers on construction sites is a major cause of accidents. The industry has consistently recorded injury and fatality rates that are among the highest of all industries. This is because the complex and dynamic nature of construction projects makes it difficult to maintain injury-free performance on job sites. This may be as a result of unsafe behavior of workers, inadequacy of tools and machinery, nature of the work environment or improper designs, to name a few.
The design process is complex and uncertain. It may be compounded by erratic decision making by the client, time pressure and the numerous interdependencies of the various building professionals. Significant causes of design problems include poor briefing and communication, inadequacies in the technical knowledge of designers, lack of confidence in preplanning for design work, delayed input from the client, changes in design objectives, unbalanced design resources, late engagement of a design party and late decisions. These problems result in slow approvals from the client, insufficient time to complete design documents and late appointment of consultants. The non-sequential progress of the erratic design process impacts the construction stage in the form of delays, inadequate information and poorly constructible design solutions. Final designs may include hidden problems that appear only in the construction phase which may result in deficient planning and resource allocation, missing of vital information and change orders which may reduce performance in the design and construction phases and eventually decrease the value provided for the customer. Efforts made to rectify the situation are considered a type of waste from a lean perspective. They are economically and socially costly and add no value to the client.
Problems also arise in construction due to an exclusive focus on the goal of task completion without paying adequate attention to the equally important goal of value generation and work flow management. This adds variability to the construction process in the form of change orders, rework, decreased constructability, cost overruns, and delays which result in major disruptions to the work process. This consumes extra resources and negatively impacts the overall system performance in terms of budget, schedule and quality. An important component of lean construction is its focus on the system rather than component processes. Stability of the work flow in construction is done through planning and control systems and the integration of the design and construction phases.
The safety of workers on job sites attracts much attention and is usually prioritized on construction projects on projects. Also, the pursuit towards sustainable development in the nation puts a huge responsibility on the built environment to design and construct buildings which address the concerns of environmental degradation, resource depletion and the creation of a healthy and safe environment. Consistent with the lean principle of eliminating waste is the removal of safety hazards and the risks associated with it. Implementing lean techniques efficiently reduces variability in construction which results in better safety performance.
How Risks are Reduced:
The overall philosophy of lean provides a focused approach for continuous process improvement and utilizes various tools and techniques such as the Last Planner® system, six sigma, value stream mapping and the five S’s to bring about such improvements. The application of these tools also promotes safety on construction sites. In order to achieve a safe workplace, lean plans the construction process and the working environment in a way that reduces workers' exposure to hazards. In addition, work procedures, decisions and actions are carried out to overcome the effects of risks and the major obstacles in work processes.
Eliminating incidents, injuries and accidents is a fundamental goal of lean construction. Utilizing lean techniques ensures safety during work operations on construction sites. Also, improving the construction process through the application of lean principles naturally leads to enhanced worker safety.
The last planner system (LPS) is based on the principles of lean construction to minimize the waste in a system through assignment planning, control and scheduling. Planning and controlling of the construction processes are done at weekly and monthly levels which aid the elimination and mitigation of risks and hazards caused by poor planning and control. Production planning is achieved in lean construction by continuous evaluation, learning and adjustment to reduce wasteful actions and idle time and cutting down on interdependencies thereby improving work flow in the process. The Production Plan reduces rework in the design and the movement of operatives on site. It also ensures that materials are received when needed. Clarity in design and scheduled operations reduces rework and allows for a more flexible response to changes in the client’s requirements. At the planning stages, the different risks and hazards are identified, and decisions are made on how to manage them. The planning stages in the LPS include the master plan stage, the six-week look ahead stage and the weekly work plan stage. Safety is incorporated into the production planning and control processes at these three stages .
At the master plan stage, appropriate work methods are selected by the construction management team, provision for safety tools and equipments are made and a schedule of tasks based on individual workers’ abilities are developed. This minimizes accidents caused by poor work methods, workers’ incompetence and inadequate safety equipments.
The six-week look ahead planning under lean is the progressive reduction of uncertainty to ensure that constraint-free assignments are available. A comprehensive plan for supervision schedules is developed by safety supervisors to avoid accidents that may occur due to poor supervision. This results in reduced variation in workflow which allows both time and cost to be reduced. In addition, constraints, risks and hazards associated with the tasks are identified and minimized to promote safety.
At the weekly work plan stage, tasks to be performed the following week are planned and assigned to different workers based on their competence and commitments. Tasks that could cause delay to the master schedule or restrict access to movement or resources are rescheduled. This action prevents accidents that may occur as a result of workers’ inexperience or incompetence. The safety measures incorporated at each stage buttresses the fact that safety is an integral part of lean construction.
In addition, a poorly organized workplace is one of the major causes of accidents on sites. The five S’s (Sort, Set in Order, Shine, Standardize, and Sustain) technique which is aligned with good housekeeping practices aims to promote cleanliness, organization and standardization and thereby improves safety performance and productivity in the workplace . This is achieved by removing materials and machines or items that are not required to be used for the performance of immediate work tasks. Clearing away such items and maintaining a clean site reduces confusion, needless motion and congestion. It also eases movement and circulation on the site, reduces the probability of slipping and tripping, and minimizes the likelihood of accidents.
Effects on Productivity:
Construction processes are characterized by high contents of non-value adding activities such as defects, rework, design errors and omissions, change orders and excess consumption of materials. The increased processing time as a result of these activities leads to a decline in productivity with increased overheads.
Variability, which is a deviation from scheduled performance could also occur. This leads to more work-in-process or longer lead times. Thus, stabilizing the work environment through the implementation of planning and control processes results in substantial performance improvement and increased productivity. In lean construction, these processes are considered complementary and dynamic and are maintained during the course of the project.
Lean construction utilizes a distinct set of objectives to optimize the construction delivery process aimed to maximize value and performance for the client through the application of project control methods throughout the life cycle of the project. This ensures that customer needs are met, while using less of everything to maximize value and reduce waste. In addition, variability is reduced in lean construction to improve performance and labor flow reliability for better productivity.
The last planner system is a useful tool in the management of construction processes and continuous monitoring of planning efficiency, to facilitate value generation and information flow among project team members. It also develops proactiveness among team members, smoothens workflow and reduces the uncertainties that typify construction processes.
Shielding is also carried out in lean construction by selecting only assignments that can be successfully completed and for which all materials are readily available, and all pre-requisite work have been completed. Many benefits can be derived through overlapping, splitting and reducing the transfer time between different activities. Project team members have the opportunity to discuss problems faced during the performance of tasks and share their views, achievements and concerns in daily huddle meetings. The root causes of failures to complete scheduled activities are identified and addressed in such meetings to avoid reoccurrence.
Lean thinking is also applicable to information management. Information utilized in the overall process of construction is well organized, visualized and represented. Value is maximized in the content and flow of information from the client to the project team through the process of exchange, sharing and collaboration. Wastes in lean may include the periods of inactivity during a work task that may happen as a consequence of not providing accurate and up-to-date information, in addition to efforts employed to surmount the challenges of retrieving or accessing information, or the activities required to confirm and correct inaccurate information.
Managing flow in work processes is achieved by cooperation within multi-skilled ad-hoc teams along the value chain of construction. The flow of relevant and accurate information among team members improves effective communication, enhances work flow and encourages collaboration and learning across the different stages of the construction process.
Lean construction also incorporates concurrent engineering in its processes. Here, various tasks are aligned and executed side-by-side by multidisciplinary teams to obtain most favorable results pertaining to functionality, quality and productivity. Concurrent engineering focuses on team efforts, effective communication and information sharing aimed at discovering new ideas for continuous improvement.
Effect of Building Information Modeling (BIM) on Lean Construction and Value Generation
Building Information Modeling (BIM) has succeeded in changing work processes and removing much of the waste considered in lean construction. Given the dynamic nature of construction sites, it is usually difficult to visualize the flow of the work in progress on a construction project and identify workers’ exposures to hazards, highlighting the need for transparency of construction activities and a continuous proactive risk assessment of work processes. Such process transparency is possible with the aid of visual techniques used in conjunction with a Building Information Model (BIM) for production management during construction. BIM is defined as a collection of tools, processes and technologies facilitated by digital, machine-readable documentation about a building, its performance, planning, construction, and operation. BIM-based visualization interfaces are important tools for driving process efficiency. BIM extends the basic concept of a 3D or 4D model to incorporate other information about the project, including integration of a construction project’s management information. This results in process transparency and ensures a quick and flexible response to changes in work orders or the sequence of construction when the need arises.
When transparency of construction processes is achieved, production planning and control become more effective. Information about the project is displayed clearly, which reduces the propensity for errors that lead to incidents. This visual communication enables workers to locate information effectively and identify workstations and pathways clearly, allowing rapid comprehension of and response to problems and increasing workers’ motivation and involvement in continuous improvement efforts.
The use of BIM and lean design management leads to increased value realization for the customer. The content of design work can be visualized, thus reducing the number of design cycles. In alignment with the concept of lean construction, design tasks that do not create value are identified and removed, while concurrently improving value-adding tasks. The result is a fast, smooth, and more economical construction process.
Resilience Engineering in Lean Construction Systems
Construction activities are characterized by varying levels of unpredictability in work patterns and processes, giving rise to unexpected changes in planned operational workflow, usually influenced by waste, variability and exhaustion of resources. Also, organizational pressure for productivity and the individual urge to minimize effort often spur workers to work near the boundary of safe performance. Therefore, for organizations to successfully adapt to these production demands without the attendant disruptive consequences, a proactive systems approach to improving safety must be employed. Indicators that allow firms to recognize when construction activities go beyond the normal working capacity and into the area where production demands encroach safety can allow advance interventions to avoid dangerous working situations.
Resilience engineering is concerned with how organizations manage, respond, and adapt to unexpected events, how people in these organizations are prepared to cope with unforeseeable events, and the organization’s ability to revert to its original shape after being stressed. Thus, a resilient organization is one that has mastered the art of managing and coping with unexpected events and variations that fall outside the base mechanisms of the normal working range to avert extraordinary failure or disruption. The ability to prevent the recurrence of failure in workplaces with continually changing hazard sources is more profound with an understanding of how safety is created by people and the inevitable compromises they make between safe and productive operations. In line with the principles of lean construction, system resilience is achieved through continuous monitoring of system performance and the pattern of work flow, which is commensurate with coping with complexity, and the ability to retain control in the face of increasing production demands. The principles applied in resilience engineering are readily applicable and aligned with lean systems, where practitioners constantly seek ways to increase efficiency in work processes by eliminating waste at the system level and constantly exploiting the new capacity to increase the tempo, efficiency, complexity, and performance of work in a predictably safe manner.
The logic behind “going lean” centers on waste removal. Waste removal is fundamental to the lean value stream. This is because improved productivity leads to leaner operations, which help to uncover waste and quality problems in the system. At the crux of lean thinking is value maximization for the client, in addition to efﬁciency and capacity utilization.
However, waste exists in relation to value, and value differs for each client. Thus, one client’s value can be another client’s waste. As such, setting out to eliminate waste from a project in isolation from the value goal of the project is potentially wasteful. Therefore, focusing on waste elimination rather than generating value that clients seek increases the likelihood of removing an important component that will facilitate the successful delivery of the project. This is because eliminating apparent waste in a sub-process, such as multiple or redundant safety controls may optimize that sub-process at the expense of sub-optimizing the project as a whole. In this case, the ability to adequately control safety risks will be reduced in the entire project.
Therefore, care should be taken when applying lean principles. It should not result in the removal of capacity from the system such that projects are unable to proceed effectively and become vulnerable to the inherent complexity and uncertainty characterized by most construction projects. A successful project is one which is able to meet its objectives of staying within the stipulated budget, schedule and quality. The ensuing value for project owners will result in more effective waste elimination and lead to better client satisfaction.
Behzad Esmaeili, PhD - George Mason University
Olugbemi Aroke - George Mason University
Babak Memarian, PhD - CPWR The Center for Construction Research and Training
Hyun Woo “Chris” Lee, PhD - University of Washington, Department of Construction Management