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Buildability is concerned with the activities on site and specifically with the sequence of operations and building methods. It is about the dynamics of building works and the difficulties inherent in putting together a complex combination of building materials, components and sub-assemblies. The term buildability was defined in many ways. In addition, the terms constructability and buildability were often used interchangeably.
There has been a long standing need to integrate designer's intentions and the practicalities of construction and the term 'buildability' was coined in an attempt to describe the desired end point or result of the integration process. The term buildability has only recently appeared in the literature relating to construction and project/construction management. The term appears to have been first used by the United States firm Proctor and Gamble Company (Proctor and Gamble,1976) in an in- house practice manual. Various groups of people within the industry have subsequently viewed the process of achieving buildability from different perspectives and a number of definitions has been proposed. Two definitions of significance have been identified.
This definition strongly emphasises construction involvement in the design function to achieve project success. The infusion of construction knowledge into various decisions and activities, particularly those preceding the construction phase, will, therefore, improve the efficiency of construction operations. The integration of design and construction functions should, however, occur throughout the whole building process, hence buildability is brought about by a continuous process of integrating the knowledge and experience of the designers/consultants, the builders, subcontractors and suppliers from inception to completion of a project.
The second definition of significance was proposed by the Construction Industry Research Information Association (CIRIA) in the United Kingdom who see buildability as:
" ........ the extent to which the design of a building facilitates ease of construction, subject to the overall requirements for the completed building." (CIRIA, 1983)
This definition suggests that the buildability of a project is a direct consequence of design intentions and therefore the major key to buildability is believed to lie in the early phases of a project. The authors claim that the definition has two further implications. Firstly, buildability is thought to exist on a scale ranging from very good to very bad. A design which gives careful consideration to the methods in which the building is going to be erected, and the practical conditions under which this process necessarily has to take place, would be considered to have good buildability. A design which has characteristics incompatible with the practicalities of the building process represents bad buildability. Secondly it is not always possible for a design to exhibit good buildability due to particular constraints of the project such as some design features. The acceptance of less than very good buildability is unavoidable if buildability will compromise or perhaps change the quality or appearance of the building. The client's and designer's requirements therefore ultimately influence the buildability of a design.
CIRIA's definition was criticised for its narrowness in scope, in that it essentially confined buildability to the design process (Wong et al., 2007). Based on a comprehensive literature study, Wong et al. (2007) concluded that constructability is concerned with the whole process of project development to facilitate construction efficiency and achieve project goals. By contrast, buildability deals mainly with construction efficiency seen at the design stage. In other words, Buildability and constructability are both connected with 'ease of construction' which is highly relevant for an evaluation of risk of defects. However, buildability further is connected with 'design' and 'efficient and economical construction', while constructability is connected with 'integration of construction knowledge and experience' and 'optimisation'. Hence, constructability embraces the concept of buildability.
Nevertheless, the achievement of good buildability depends upon both designers and builders being able to see the whole construction process through each other's eyes (Adams, 1989).
Besides these two major definitions, many other definitions have been proposed which illustrate a diversity of opinion as to what buildability means.
Illingworth (1984) recognizes the danger associated with the word 'ease' in CIRIA's definition and defines buildability as " .... design and detailing which recognise the problems of the construction process in achieving the desired result safely and at least cost to the client."
Tatum and Teague (1981) attempt to describe buildability in terms of several objectives. For example, they suggest that buildability is a consequence of the effort and consideration given to a project with the objective of reducing the construction difficulties. They recommend that effort and consideration should be given to the determination of construction methods, site access, working conditions, facilities, quality requirements and other design and construction aspects of the project. When these matters are properly resolved the efficiency of construction would be improved and project cost and time savings would result. Ferguson (1989) defined buildability as the ability to construct a building efficiently, economically and to agreed quality levels from its constituent materials, components and sub-assemblies. In the code of practice on buildable design published by the Building and Construction Authority (BCA) in Singapore, in September 2005, buildabilty was simply defined as the extent to which the design of a building facilitates ease of construction. Chen and McGeorge (1994) conclude that a workable concept of buildability needs to recognise the many factors in a project environment which has an impact on the design process, the construction process, and the link between design and construction. They suggest that buildability might be redefined as: The extent to which decisions, made during the whole building procurement process, ultimately facilitate the ease of construction and the quality of the completed project.
Some major construction and engineering corporations in the United States have also developed their own definition of buildability. For instance Proctor and Gamble (1976) define it as "a team building process between organisations designed to decrease costs and increase savings." Bryson (1984) describes buildability as "the planned interaction of construction with project definition and design for the purpose of assessing all factors that affect design and contribute to project cost and schedule."
As it mentioned, constructability and buildability mutually connected to each other. This matter of fact cause hazy boundary to clarify the coverage range of each one. It is obvious that using construction knowledge and experience is common in both constructability and buildability definitions. However, based on broad range of definitions for them, it can be concluded; there are defined levels to show focus area and objectives of constructability and buildability in each project in recent studies. The most important indicators and objectives depicted in Figure 1.1.
Figure 1.1: Constructability area of coverage
For the purpose of this study, following definition is developed, covering so many factors such as the nature of construction industry in Malaysia and, at the same time, suiting the objectives of this study:
"Using contractors' construction knowledge and experience at the design stage in order to minimise design related problems during construction phase"
1.2 History of buildability and constructability
In the late 1970s buildability emerged as an area of research, based on the assumption that buildability problems exist because of the comparative isolation of many designers from the practical construction process (Chen and McGeorge, 1994). Since, then, buildability has become an integral part of the construction industry. The situation is even more evident in Singapore where legislation was passed in 2001 to make buildability compulsory. Hence, buildability is now an identifiable and recognizable area of research in the construction industry in Singapore (Low and Abeyegoonasekera, 2001a, b).
Various attempts have been made to study buildability among the literature, including the buildability assessment model (BAM) in Hong Kong (Lam et al., 2006), the buildable design appraisal system (BDAS) in Singapore (BCA, 2005a), the multi-attribute system proposed by Zin et al. (2004) in Malaysia, the cognitive models developed for buildability assessment of steel frame structures (Ugwu et al., 2004), the fuzzy quality function deployment system supporting buildable design decision making (Yang et al., 2003), the neuro-fuzzy knowledge-based multi-criteria decision support system (Yu and Skibniewski, 1999) as well as the automatic system of construction planning and buildability evaluation called 'CONstruction PLANning (CONPLAN)', which works under a computer-integrated environment (Hassan, 1997).
Among these measurement conventions, the BDAS in Singapore is the only system that enables whole building evaluation and forms the basis of a legislation enacted to require minimum buildability scores as one of the prerequisites for building plan approvals in the city state (BCA, 2005). Being inspired by the BDAS, the BAM has been developed with reference to Hong Kong context and data and validated for use there. The BAM is used to assess buildability of building designs through scoring different design attributes, e.g. construction systems, building features and site-specific factors.
Lam, Wong, and Chan (2006) in their study about contributions of designers to improving buildability and constructability mentioned that Improving buildability and constructability has long been an issue that attracts the interests of researchers and scholars, mainly in 5 countries as follows:
1.2.1 Buildability of designs in the UK
In the United Kingdom, since the Emmerson Report (1962), numerous researches had been carried out to identify the causes of buildability problems and search for solutions for improvement. The fragmented characteristics of the industry (Banwell, 1964) and inefficient designs produced by designers deficient in construction knowledge without involvement of contractors (Banwell, 1964; NEDO, 1975; CIRIA, 1983; Gray, 1983) were highlighted. In view of these findings, a set of principles targeted at designers under the traditional procurement system was drawn up by the Construction Industry Research and Information Association (CIRIA). In addition, Gray (1983) and Griffith (1984) suggested inviting construction expertise early at the design stage, using contractual arrangements that facilitate the improvement of buildability. Griffith (1984) further pointed out that the capability of project management embracing suitable procurement approaches would contribute to improved buildability with concomitant benefits for overall project performance. The primary aim of the research was to identify those factors in the design of a construction project that have an impact on site construction techniques (Griffith 1984).
More recently, the Egan Report (1998) awakened attentions that the general buildability performance was far from being satisfactory. Contractors were also found to have little input into the design in the UK's construction scene, thus constituting a comparatively lower productivity figure for the industry (Graham and Bird, 2001).
1.2.2 The CII in the US
In contrast to the United Kingdom approach, constructability researchers in the United States have placed emphasis on the management systems and involvement of owners and contractors. For the United States, the benefits to be gained from good constructability were identified as 'approximately 10 to 20 times the cost of achieving it' by the Business Roundtable (Business Roundtable, 1982). Subsequently, the Construction Industry Institute (CII) encouraged construction inputs for all project stages and the examination of constructability savings at different stages of a project. The stages undergoing study were conceptual designs, engineering, procurement and construction. The CII also published guidelines for implementing constructability by companies in the form of the Constructability Concepts File covering 14 defined concepts, i.e. 6 for the conceptual planning phase, 7 for the design and procurement phases and 1 for the field operations phase (CII, 1987). Hitherto, these concepts have not been taken further for assessment in a quantifiable way.
1.2.3 Buildability and constructability considerations in Australia
In Australia, the terms of buildability and constructability were used interchangeably. Buildability, which contributed to reduced construction time, was viewed as a function of project management (Ireland, 1985; Hon et al., 1988). Early construction involvement of construction experts and use of preconstruction planning were regarded essential (Hon et al., 1988). The scope of buildability was also broadened to cover the whole life cycle of a building (McGeorge et al., 1992). In the late 1990s, the CII Australia (1996a) published its constructability principles and guidelines in the form of the Constructability Manual for advising construction project teams on improving constructability. To-date, no attempt has been made to quantify the concept either.
1.2.4 The BDAS in Singapore
In the Asian arena, Singapore has pioneered with quantifying buildability based on a scheme known as the Buildable Design Appraisal System (BDAS). It has culminated in statutorily requiring building designs to fulfil a Minimum Buildability Score since 2001. Under the Building Control Act, the requirement is a prerequisite for approval of submitted building plans. The 3 key design principles based on which a design is judged for buildability include Standardisation, Simplicity and Single integrated elements. The Buildability Scores are given according to the relative extent of labour saving that can be achieved by the use of different construction systems. Designs with higher scores are generally more buildable and fewer site workers are needed by the same contractor.
The BDAS was developed by the BCA as a means to measure the potential impact of the building design on the usage of site labour. The appraisal system results in a "buildability score" of the design. A design with higher buildability score will result in more efficient labour usage in construction and thus having higher site labour productivity. The legislation of buildable designs took effect on January 1, 2001 in Singapore, following amendments to the Building Control Act to facilitate the introduction of regulations to enhance the efficiency and standardization in designs, processes, construction techniques, products and materials in the construction industry. The regulations affect new building works as well as additions and alteration works. With this, a proposed project needs to achieve a minimum buildability score before its building plans can be approved by the authorities for construction. New projects (including additions and alterations to existing buildings) with a gross floor area (GFA) equal to or greater than 2,000m² falls within the legislative requirements. The minimum score requirement is approximately about 60. The minimum buildability score for mixed developments would be pro-rated according to the GFA of each type of development.
(3) Other design considerations. This section of the BDAS examines the design of the building at a detailed level. Basic design characteristics, namely standardization of columns, beams, windows and doors, structural grids and usage of precast components are considered. The use of these buildable design features will be awarded with points directly. In addition, bonus points would be given for the use of single integrated elements. The maximum buildability score for this section amounts to ten points.
The maximum score that can be achieved is 100 points. Different types of systems will be assigned a different "labour saving index" based on site observations. As an example, Table 3 shows the labour saving index for wall systems. If no labour saving index is indicated in the code, the BCA will determine the value when required.
The total buildability score for the structure is determined by taking the fraction of the structure to be constructed by each method, multiplying by the relevant index, summing the result and multiplying by 50. A similar calculation is performed for the walls (multiplying the result by 40) and finally the "other features" score (up to a maximum of ten) is added in and the total cannot exceed 100 (BCA, 2005). The calculation of the Buildability Score is based on the formula as shown in Table 4 (BCA, 2005).
Table 3. Labour Saving Index for Wall Systems
(Source: Ying and Pheng, (2007), Enhancing buildability in China's construction industry using Singapore's buildable design appraisal system, Journal of Technology Management in China)
1.2.5 The CIRC in Hong Kong, China
In Hong Kong, the construction industry has acknowledged a number of knotty problems that exist in the building process as well as the built products. Being set up to suggest measures to improve the identified problems, the Construction Industry Review Committee (CIRC) (2001) believed that early and greater emphasis on buildability of designs will bring about wider adoption of cost-saving and labour-saving construction technologies and minimise material wastage. Management personnel were hence advised to use a total 'systems' approach from conception to project completion, provided that the necessary authority has been delegated. Fundamentally, the CIRC encouraged more detailed and thoughtful planning at the outset of a project.
1.2.6 Constructability in Malaysia
The preliminary researches on constructability issue in Malaysia have been done by Nima, M. A. and Abdul-Kadir et al. (2001). Rosli M. Z. (2004) focused more on this issue specifically during design phase. Bambang Trigunarsyah (2004) believed that constructability is a unique concept and there seems to be a need to explore this critical issue in construction industry not only in Malaysian construction industry, but also in any other country, especially developing countries in order to have a review on their performance. However, as it can be seen, in Malaysia, there is a few studies have been done related to process implementation, integration and assessment of constructability concept during design phase (Nima et al. 2001; Rosli et al, 2004 and Siong, 2006).
Saghatforoush et al., (2009) in their study about Constructability Implementation Among Malaysian Building Contractors concluded that the term "constructability" was heard by most of Malaysian G7 building contractors, and then they were aware of its earlier implementation because their participation are approximately reduced from conceptual planning phase to construction phase generally. After that they mostly think the constructability efforts are not specifically belonged to any specific type of project.
Based on the obtained results, probability of being familiar with constructability issue among Malaysian sub-contractors is more than main-contractors whilst the main-contractors can be more effective in inserting constructability efforts into the projects. Unfortunately it also is found that main contractors are not still aware of implementation of constructability activities on earlier stages while the sub-contractors are more interested to do it. Then, there are still some contractors who do not believe in constructability benefits on small projects whilst it is not a right belief.
This familiarity probability with constructability issue is almost the same for different kinds of contracts among Malaysian building contractors. It is also obtained that the traditional contractors are more aware of earlier constructability implementation in the projects than the other type. It is completely in contradiction to this expectation that believes traditional contractors are not familiar enough with constructability activities and its implementation. The results also show the traditional and turnkey contractors are not still aware of constructability implementation at small projects, so more efforts are required to make them familiar with this matter.