The Lean Design Process

The design process of a building is often a complex one as it involves numerous decisions, in a highly uncertain environment, sometimes over a long period and with many interdependencies. In addition, the design process may require trade-offs between multiple competing design criteria characterised by schedule constraints, intense budget and inadequate information. It is at this phase that client's ideas and expectations are conceptualised into a physical model. The client's needs and specifications are also defined by technical specifications, drawings and procedures. The impact of the design phase on project outcome is significant, both economically and technically. Due to the immense impact of the design phase on overall project outcome, the design review process forms a critical part of the process. However, the control or review of the design process may be faced by a number of problems such as erratic decision-making, chaos and improvising, insufficient documentation, inadequate communication, deficient or missing input information, poor coordination between disciplines, and unbalanced resource allocation. These issues are particularly common in the traditional design process that fails to take account the uncertainty and complexity that cause inconsistencies in the construction process. In response to these challenges, modern organisations introduce Lean design to improving value generation in the design phase, minimise waste and reduce unnecessary uncertainty

Keywords: construction, design, process, review, organisation.

Introduction

The Toyota Production System or the lean philosophy and its derivative approaches are applied by several organisations in different sectors across the world to improve performance and to increase productivity. The system guarantees the empowerment of the team members in the adopting organisations to increase the quality of the goods and services they offer through the constant improvement of processes and the elimination of avoidable wastes in natural, human and corporate resources (Leite and Vierra, 2012). In several organisations today, the Toyota Production System influences different aspects of the organisations resulting in overall product and process improvement and the optimisation of quality. The production system comprises a range of values, procedures, and information that allow the achievement of organisational goals. Furthermore, the system entrusts the workers with different responsibilities in the company processes and encourages the participation of all members to improve the quality.

One of the sectors where the lean philosophy is currently used is construction. According to Sarhan, Xia, Fawzia and Karim (2017), lean construction encompasses different mechanisms of designing the systems of production to reduce the wastage of human effort, time and material with the ultimate aim of generating value and reducing costs. In most construction processes, lean involves the complete pursuit of continuous improvement in designing, construction, salvaging, maintenance and recycling in building projects. Aziz and Hafez (2013) explicate that lean construction takes the form of identification of strategies and setting the milestones of long lead items. It also encompasses the specification and identification of hands off and identification of operational conflicts as well as planning to ensure that with the aim of carrying out work perfectly.

One of the processes of construction where the lean philosophy is applied is design. According to Bonnier and Ose (2015), the design and engineering processes in the construction organisations play a vital role throughout the life cycles of the construction projects. Although it accounts for a little proportion of the overall cost of the production process, the design can have significant consequences on the construction phase and the overall life cycle of construction projects. Consequently, a good design process is important in the construction of sustainable buildings (Ćatić and Vielhaber, 2011). Furthermore, the increased market competition in the construction sector which has resulted from globalisation and the increased complexity of building designs calls for more efficient design processes. It is, therefore, essential for the construction companies to ensure that their experts spend more time on value-added activities which increase quality and reduces costs and time wastage.

The lean process in product design is characterised by a number of steps that involve various reviews and continuous brainstorming by the designing team. With some few adjustments, the process can be replicated in architectural design. This paper evaluates the current construction design review process of a local organisation. Further, different concepts of the lean production process are employed in the design review phase of the project. Particularly, the paper employs the value low to identify the concealed causes of waste in the organisation's current workflow. Lean concepts are then used to develop a lean design process to ensure that the review process addresses the concerns of the organisation. System dynamics is used at the end of the paper to authenticate the viability of the proposed lean process. The improved process is expected to improve design reliability and correctness, hence increasing the value to the organisation.

Critical Evaluation of the Current Process

In the recent years, construction projects have increased in complexity following the advancements that have been made in the architectural field. Gould and Joyce (2009) explicate that the increased complexity of the building projects has resulted in the impossibility of a single architect to claim expertise over a particular project. Consequently, a number of defects occur in the design phase that can only be detected in the construction phase. Günhan, Arditi, and Doyle (2007) claim that while some of the defects can be detected easily and solved through the collaboration of the general contractors and architects, more complex problems require changes in order to define which may be time-consuming and costly. In several places within the UK, improper building designs have led to various accidents. This section appraises the current design process in a local construction company in the UK.

The current proposal process can largely be categorised into two stages; the preliminary and detailed design phases. According to Ko and Chung (2014), the preliminary design phase of the construction process involves the preparation of all the required documents and the drawing of the desired building design. The process requires the evaluation of the exterior perspective, the interior, the floor designs and the sectional and the elevation plans. At the end of this process, responsible professionals generate a design report which is followed keenly during the building stage.

As part of the requirement of the building industry, the local construction company ensures that the preliminary design process is undertaken. During this stage, the preliminary architectural designs are drawn and presented for approval. In this organisation, the preparation of the preliminary architectural drawing is done by the architect without any consultations. The architect researches different designs that are appropriate for the building to be constructed, selects the appropriate design, draws the preliminary design and presents it for approval.

The selected plans then proceed to the detailed design phase. At the detailed design phase, revisions to the design are made to suit the organisation's needs and specifications. The services of a structural engineer are sought in order to come up with detailed drawings of the structure. The next step involves the checking of the blueprints for error before signing and authorisation. An analysis of the organisation's capacity is then conducted by the relevant engineers. After the analysis step, the design is signed and approved for the second time. Lastly, the footprints obtained from the processes are integrated by the architect. To reduce costs, the local construction organisation seeks the help of structural engineers who offer substandard services at cheaper prices. When presented to the structural and equipment engineers for approval, they conduct a rough overview of the drawing to estimate the design correctness ratio. In many cases, the structural engineers approve construction designs with 80% correctness ratio upwards.

While the design process appears smooth, it has serious underlying problems. Each stage of the preliminary proposal phase is the duty of the draftsman with the exclusion of the mechanical and project designs that are delegated to other parties.

Value Stream Mapping of the Current State

This essay uses the value flow mapping to determine the different causes of waste in the design process of the life cycles of construction projects in the local organisation which was chosen. According to Layeequddin and Khatoon (2017), the value stream mapping refers to a field of mapping in which the flow information and material is used in the coordination of diverse activities performed by the manufacturers, suppliers and distributors to deliver products to the consumers. In the construction sector, the value stream mapping is an important tool which is used in the elimination of wastes in different processes in the construction companies. The tool does not only highlight the inefficiencies in organisations which have an adverse impact on the quality of the construction projects, but also provided mechanisms that can be used for the improvement of the identified areas.

Lack of Job Sharing

The value stream mapping of the design process shows that the architecture independently completes each part of the design process. Therefore, the upstream work is solely undertaken by the architecture. Structural and project engineers have to wait until the upstream work is complete in order to analyse and inspect the design. The construction company then begins building and turns it to the organisation upon completion. In the case any design error is identified in the erection phase, the blueprint is returned back to the designer for modification. The current design workflow and process and value stream mapping show a significantly large part of the drafting process is completed solely by the planner. The architect is entirely responsible for resolving errors and making revisions arising from design problems identified in the construction phase. As a result, the practices translate to schedule delays and consequent budget overruns.

Miscommunication of Information

The second issue which was identified from the value stream mapping process of the construction design process in the organisation which contributes to waste is the miscommunication of information. According to Zero Waste Scotland (2016), the design process in the building industry relies heavily on communication between the architects, the structural engineers and the owners of the proposed projects. Communication is important in the design process as it helps in the facilitation of handoffs and the transfer of information from one person to another (Bølviken, Gullbrekken, and Nyseth, 2010). While explaining the importance of communication in the design process, Millard (2001) states that in an ideal world, it would be better if an individual had all the information and knowledge required to perform a task. However, since that is not the case, communication becomes vital to facilitate information sharing and efficiency in organisations (Westin and Paivanitra, 2011).

The current design workflow is characterised by poor communication among the members of the building project design team. While it is indispensable for the architect to be in constant communication with the owner to increase the chances of producing designs that meet their needs, the current workflow process puts all the responsibility on the architects, limiting their communication with the owner. The result is the wastage of both time and resources as the architects have to redo their designs in most cases to satisfy the needs of the customers. The lack of efficient information sharing between the architects and the structural engineers in the organisation also makes it difficult to achieve 100% design correctness. In most cases, the company produces designs with less than 100% correctness leading to the construction of unsustainable buildings. In cases where the owners of the proposed projects insist on the efficacy of the design, architects have to redo the work, causing both time and financial problems.

Lack of Necessary Competence

Thirdly, the value flow plotting of the current planning process in the company reveals the construction drafting process is characterised by the lack of the necessary competence which leads to waste generation. The competence of the design process personnel is important in the construction companies as it helps in determining the overall sustainability of the buildings and the levels of satisfaction of the customers. According to Oehmen and Rebentisch (2010), one of the problems which arise from the absence of competence of professionals is the need for additional communication to acquire the necessary knowledge to perform the tasks assigned. The result is wastage of project time in putting measures in place to ensure the increased competence of the staff.

In the current design workflow, the lack of competence has adverse impacts on the design process. Both the architects and the structural engineers responsible for the design process lack insight on time management and the prioritisation of tasks, leading to wastage. For instance, instead of focusing on problem-solving and the development of design solutions that meet the needs of the owners of the proposed projects, many working hours are spent on non-value adding undertakings such as writing the status reports, database updates, attending lengthy meetings and making presentations. This situation causes the inappropriate use of the competence of the engineers and architects as they focus on tasks which they are not trained for. Consequently, the construction design process professionals produce poor results such as the design incorrectness and within longer time frames.

Lack of Clear Authority and Responsibility

Fourth, the value stream mapping of the current workflow process in the selected construction organisation also revealed the lack of clear authority and responsibility in the design process team. In the organisational setting, a responsibility refers to the legal or moral obligation of an individual to perform a task while a role refers to the duty of a person in an undertaking. A rule, on the other hand, is defined as a custom which guides the behaviour of individuals in the workplace.

Having perceptions and knowledge of what is expected of people in company processes is an important step towards the realisation of the desired outcomes. According to Wibowo et al (2017), complicated systems such as the design process requires all participants to have clear perceptions of their roles and responsibilities and also to understand the duties of others. Understanding the role structure is vital in construction design processes since it helps in limiting the challenges associated with overlapping competencies and disagreements among the team members which is likely to result in lower productivity. The ambiguity of the job roles of the members of a project team also results in the levels of job satisfaction and more time is wasted in conflict resolution rather than the development of building design solutions. The current design process in the organisation is characterised by poor definition of the roles and responsibilities of different team players. Consequently, many conflicts arise from the process causing time delays as much time is wasted on conflict resolution.

Underutilization of Resources

Notably, the value stream mapping of the organisational design process revealed that the resources allocated for the process were underutilised. Resource allocation remains one of the most critical managerial tasks in different phases of the construction projects. Efficient allocation of resources in the performance of diverse tasks is efficient to ensure the success of the organisations and satisfaction of the customers. However, there are instances where resources can be underutilised, leading to the reduction of productivity and the wastage of time.

The design phase of the construction process can face resource underutilisation, thereby affecting the levels of job satisfaction and productivity. The resources that can be underutilised in the design processes of the construction companies are the tools, man-hours and competency. The current state shows that the resources allocated for the design process in the organisation are underutilised. Bauch (2004) mentions that the core task of structural engineers and architects in the design processes is the development of building designs and design solutions, solving existing building problems and the implementation of change. However, in the current state, the design engineers spend more time on activities that do not add value including the database and schedule updates and the preparation of project status reports. Such activities lead to the underutilisation of the skills and competencies of these professionals as they engage in duties outside their jurisdictions.

Apart from the underutilisation of the skills and competencies of the professional who drive the design process in the organisation, the management of the company does not provide the necessary support for the staff who work in the building project design phase. For instance, both the architects and the structural engineers perform duties without assistants or trainees. Consequently, they have to move around looking for tools, seeking information on the desired building project designs and consulting each other on the sustainability and correctness of their designs. This situation causes wastage of time which would have been allocated to other tasks. Time wastage, in most cases, translated to longer project periods and poor outcomes.

Over-engineering

Lastly, the other inefficiency which was identified in the current state of the design process through the value stream mapping is the over-engineering of designs. Within the building and construction context, the term over-engineering refers to the act of exceeding both the internal and external requirements of the design. According to Bauch (2004), it encompasses the addition of unnecessary accuracy, features and details to a building design.

In the building and construction sector, the requirements vary both in specification and accuracy. This lack of clear definition of the requirements often leads to assumptions. In most cases, producing a building design which is beyond the internal and external specifications is considered value addition as it results in the increased robustness of the design. Exceeding the required value also adds value in cases where the additional information satisfies the unknown needs of the customer.

While most of the information produced through the addition of unnecessary features is important, exceeding the requirements of a building design is disadvantageous and causes wastes in the design process. In the event where the over-engineered parts of the design process are incorporated into the final solution, it is considered waste due to the additional information. With the increased complexity of the designs of buildings in this century, such additional information can lead to an increase in the production costs which may lower the value of the solution delivered to the customer.

Rehearsal of the Lean Principles

Define Value

Among the most important philosophies of lean thinking is the value definition. According to MoreStream (2010), the starting point of lean thinking in any organisation is the identification of the customer and the specification of value. There are two types of customers for organisations that use the lean principles for continuous improvement. Existing customers are entities that are either internal or external to the producing organisations and consume the items or services produced. Potential customers, on the contrary, are entities that have specific needs that can be met through the functions of products and services that an organisation produces.

Value is what the customer wants and is ready to pay for. According to Hines (2010), the customers of organisations define the value of products and services that meet their needs. Producers have the mandate of meeting the value as defined by the clients to guarantee their satisfaction. A product or service is said to have value to the customers if it meets the needs of the customers, and they are willing to pay a particular amount for the product at a specified time. Before purchasing items or service, customers must justify whether these products meet their needs. The more unnecessary a product or service is, the more difficult it is for a client to justify the need for the product, hence its acquisition.

A business that spends a significant amount of time doing other things other than adding value may be spending a large amount of time in wasteful pursuits that the customer does not consider to be things they should pay for. Such wastes are what lean implementation seeks out to eliminate (Chase, 2000). Organisations using lean thinking constantly review their products from the eyes of the customer. How does a product improve the customers' position, accomplish his mission and carry out his tasks? Such questions help decision-makers in determining the unique value that the organisation's products or services provide.

Map the Value Stream

The next process of lean thinking is mapping the value flow. The value flow refers to a series of interrelated processes responsible for producing value. A process is characterised by both values adding and non-value adding steps. Lean thinking only focuses on removing or minimising non- value adding steps. Mapping the value stream can be done by creating state maps of the overall flow. Lean implementation often ends up creating value streams without regard for departments but a flow through the organisation. Once the unique value that each process provides is evaluated, an assessment of how each process leads to the end goal can be determined.

To ensure that the effective identification of the underlying issues that affect value in organisations, the value stream mapping tool comprises a present state map and one or more future state maps that contain advanced improvements to the existing state map. Prior to drawing a current state map, organisations chose certain products, processes or product categories to represent the target for improvement. The current map is considered as the beginning point or the baseline for the organisation and processing of work in a company.

The current state map does not solve any problems with the workflow process. Rather, it helps in the identification of problems within the work streams of an organisation. It captures the way in which things are currently done in an organisation and in the process, facilitate the identification of the problems that might affect the final value of the product. The value stream mapping process does not only help in the identification of the existing problems of an organisational process or product but also helps on devising different ways of meeting the requirements solving them to address the expectations of the customers.

The practice of mapping the value stream enables the lean team to understand how each value flows through the organisation and more essentially, where it gets stuck (Bertelsen, 2004). The outcome of the mapping exercise is a physical skeleton of the organisation that outlines every step of the process. For raw product, questions such as where the raw material goes when it is supplied. Do we cut it to specifications or does it come to the business pre-cut? What happens next? Who is responsible for a specific process? The guiding question used in this lean principle is what happens next and who is responsible?

Create Value Flow

Once the value stream map is ready, the next step is creating value flow. Creating a value flow involves analysing each step that makes up the process in order to identify ways to reduce waste and maximise efficiencies. The creation of the flow process through waste elimination ensures that a product or material moves production to consumption. In the case of building construction design process, the value flow creation principle requires that the transition of projects from the design phase to the construction phase takes shorter periods (Verna, Das, and Erandre, 2011). This type of flow which involves the reduction of wastes is typically known as the continuous flow.

In the case of a manufacturing process, the key questions might include; what tools are needed for each step? Are the tools essential for the process to run smoothly? Would it make sense to abandon the current model of manufacturing and adopt a new way to reduce time lag? What this principle attempts to realise is the "flow" of value or products from a stage to the next, where every step is a value-adding phase. The flow can be achieved through various tools and ideas. The aim of this principle is to optimise flow in all aspects of the organisation. By following every value stream to the customer, it is possible to evaluate steps to determine whether each one of them is necessary. If each is necessary, it goes ahead to identify areas to reduce inefficiencies, stalls and friction in the value flow to the customer. The guiding question that underlies this principle is how the organisation can streamline its steps to provide the most value to customers.

Establish Pull

In this principle of lean thinking, organisations or lean teams focus on customer's perspective of the final product by assessing the operations of the business on the value stream map, in a reverse way. The concept of the customer being able to ‘pull' the value as required is what primarily revolutionised manufacturing companies when Toyota adopted lean thinking (Leong and Tilley, 2008). Rather than investing in production, materials and storage, customers' needs guide lean teams on the areas to direct resources. A big source of waste that has always been a focus on lean organisations is inventory. Inventory is responsible for a large amount of waste, given that it takes up space, requires storage and transportation. It also holds up capital that could be used by the business in other areas. The ideal system that a business can adopt is one where products are manufactured when the customer makes an order. While this ideal situation cannot always be achieved by every business or industry, it is possible to achieve it through lean thinking. By using different systems, it is possible to set up production in a way that customers' orders can be quickly satisfied. They can be made on demand or parts manufactured from standard components. Alternatively, inventory may be obtained from a small buffer stock and replenished fast as soon as it is drawn. The guiding question to the application of this principle is how a business can transform its approach so as to have the right quantity to satisfy customers' demand in a timely way.

In the construction industry, organisational success is determined by the ability of the company to produce goods and amenities that address the demand of the customers. In the design process, the establishment of a pull involves ensuring that the designs of the buildings developed by the design team meet the needs of the owner or client. Since the organisation in this study deals with multiple projects, it is important to ensure its transformation to meet the demands of the consumers within the specified time.

Seek Perfection

When the lean team has identified different areas of improvements and implemented changes to improve efficiency and reduce waste in order to bring the greatest value to customers, it proceeds to the next principle of lean thinking. Seeking perfection involves constantly analysing every process to increase value (Verma and Dhayagude, 2009). The analysis focuses on elements that add value as well as eliminating those that do not. Eventually, the flow is tightened and value is delivered to meet customers' needs. The ultimate value is not perfection rather the pursuit of continuous improvement. The lean principles have guided the manufacturing and engineering industries for decades. By implementing the first four principles, an enterprise will have prevented a significant amount of waste from appearing in the process. Nevertheless, an organisation should strive towards perfection with the help of employees. The aim is zero waste and the ability to deliver maximum customer value. Employees should be involved in implementing lean tools to help drive continuous improvement. Tools such as Kaizen have been used as a means of achieving continuous improvement. Achieving success is also about improving every other process in the business. The guiding question is whether the plans executed have helped in realising gains in efficiency. Additionally, what other areas can be improved to bring more value to customers (Poppendieck, 2011).

Development of Target Process/System Grounded on Consideration of Alternative Approaches

A target process is developed founded on the recognition that improper designs lead to budget overruns, rework, changes in orders, schedule delays, and low constructability, leading to avoidable wastes. The target process is the development of a Lean Construction Design Model (LBDM) rooted in the lean concept to enhance the project review process and overall design quality. The concept of lean design is an extension of lean thinking that is often employed in the production processes in different industries including healthcare, building and manufacturing (Thyssen et al., 2010). By moving lean thinking upstream, an enterprise creates a substantial potential to deliver value throughout the entire process because much of the quality and costs in construction projects are locked in before the actual building. Thus, the design process is critical. The lean principle is hence recommended due to its focus on reducing waste and maximising value. Lean thinking has already demonstrated substantial results in the manufacturing industry as well as the building industry. There is a distinct difference that exists between the designing process and the building process. Designing can be equated with producing a recipe for meal preparation. On the other hand, the building can be compared to preparing the meal. Without getting it right in the drafting phase, the entire procedure is flawed. The principles of lean can be modified in the design phase as it accommodates the nature of the design process (Ko, 2017).

Implementation Plans

By nature, construction designs are multi-disciplinary efforts that call for a comprehensive analysis of numerous aspects and structural components (Zimina et al., 2012). Due to the complex nature of architectural designs, even the slightest oversight can cost the organisation and require a range of corrections to rectify the initial oversight (Bade and Haas, 2015). In the proposed process, the design stage will comprise a three-stage approach. Unlike the existing process where the process is made up of the preliminary and detail design phases, the proposed process will an extra step, the basic design phase. It will allow early detection of errors before the contractor can receive the drawings. A multiple design feedback cycle will promote the optimisation of the resulting architectural designs. The verification process will be carried out through the use of system dynamics (Ko and Chung, 2014).

Proposals for Instituting Continuous Improvement along with Performance Measurement

Instituting continuous improvement may be done by measuring single or multiple aspects of the design during the review process (Koskela et al., 2002). One aspect of the design review process in construction projects is designed correctness. Design correctness is a metric that assesses the extent to which a building design addresses the user's necessities or application. The concept of design correctly has been widely adopted to improve design quality. The proposed performance measurement is the First Time Pass Ration (FT