Integrating buildability in ISO 9000 quality management systems: case study of a condominium project

Building and Environment 36 (2001) 299±312

www.elsevier.com/locate/buildenv

Integrating buildability in ISO 9000 quality management systems: case study of a condominium project Low Sui Pheng a,*, Belinda Abeyegoonasekera b a

School of Building and Real Estate, National University of Singapore, 10 Kent Ridge Crescent, 119260, Singapore b APCO Architects and Town Planners, 23 Duxton Hill, 089606 Singapore Received 13 April 1999; received in revised form 5 July 1999; accepted 26 November 1999

Abstract Productivity and quality are two inter-related issues of utmost importance in the construction industry. The buildability concept and ISO 9000 quality management systems are used to help raise productivity and quality standards in construction. However, both buildability principles and ISO 9000 quality system elements are frequently considered separately in many consulting and construction ®rms. Many of these ®rms have also developed and implemented ISO 9000 quality management systems in their organisations. To achieve synergy, this paper argues by means of a case study of a private condominium project that buildability principles can be integrated within ISO 9000 quality management systems. 7 2000 Elsevier Science Ltd. All rights reserved. Keywords: Buildability; ISO 9000; Quality; Productivity; Integration; Synergy

1. Introduction With the need for better buildable designs, the implementation of ISO 9000 quality management systems can help to enhance the buildability of a project. The ISO 9000 standard establishes the policies and procedures that require proper documentation for a minimum level of management commitment to quality. Hence, with documented procedures which consider and ensure conformity of buildability in building processes, as well as encourage buildability reviews and corrective actions, ®rms can be made more aware of buildability principles which will, in turn, lead to improved buildability of a project. With improved internal communications, feedback and training, the ISO 9000 standard can help to enhance a company's con®dence in its ability to consistently deliver buildable designs and construction methods. This paper does not suggest that the linkage between * Corresponding author.

quality and productivity is an entirely new consideration. The linkage was already considered to synergise the relationship between quality and productivity in a generic sense [10,15]. Buildability, which can help to raise both productivity and quality standards, deals however with separate, albeit closely related, issues. It is believed that the integration of buildable concepts with ISO 9000 quality system elements is dealt with for the ®rst time in this paper. As more consulting and construction ®rms obtain certi®cation to meet the ISO 9000 standard, this paper proposes that the ISO 9000 quality management system can serve as an important working platform for achieving buildability. The thrust of this proposition is shown in Fig. 1. There is currently no study on the application of ISO 9000 on buildability nor any research work which evaluates the e€ectiveness of using ISO 9000 quality management systems in enhancing the buildability of a project. While the buildability concept is now slowly making an inroad into the construction industry, there is still a lack of understanding of this concept and its underlying principles. While more and

0360-1323/00/$ - see front matter 7 2000 Elsevier Science Ltd. All rights reserved. PII: S 0 3 6 0 - 1 3 2 3 ( 0 0 ) 0 0 0 0 4 - 4

300

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

more ®rms are being certi®ed to meet the ISO 9000 standard, many are still blissfully unaware of the usefulness and e€ectiveness of ISO 9000 quality management systems in achieving and enhancing the buildability of a project. The objectives of this paper are therefore: 1. To brie¯y present the buildability concept.

2. To brie¯y highlight the application of ISO 9000 quality management systems in the construction industry. 3. By means of a case study, to examine the relevance of using ISO 9000 quality management systems for integrating buildability principles at the design and construction stage of a project.

Fig. 1. Theme of paper.

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

2. Buildability concept Buildability is related to all aspects of a project which enable the optimum utilisation of construction resources. It ensures that there is continuity of work by managing labour, plant and equipment in such a manner that the ¯ow of materials, components and sub-assemblies into the growing building is maintained and optimised to achieve ecient and economic production. It is concerned with activities on site and speci®cally with the logical sequence of operations and construction methods. Good buildability can improve

301

design empathy for production, encourage more e€ective communication between the design/construction parties, simplify construction techniques and optimise the approach to construction management. In a demanding market, the client expects his building to be completed on time and within the anticipated budget, to be of good quality and not too troublesome or expensive to maintain. Experience has shown that many clients have complained of building designs which do not provide value for money in terms of the eciency with which the construction process was executed [14]. Good buildability is known to be able to

Table 1 Principles of buildability Principles

Key aspects

1. Investigate thoroughly

The investigation of site conditions and other circumstances likely to a€ect the course of the project should be thorough and complete to avoid the risk of subsequent costly delays and alterations after construction has commenced. The location of access to and around the site during construction should be carefully considered at the design stage. Consideration should be given at the design stage to the location of material storage and unloading facilities. Consideration should be given to minimise the amount of time taken by the work in the ground, particularly where the ground is poor, wet or hazardous. The construction and detailing of a building shell, including the roof, should facilitate the enclosure of the building at the earliest possible stage so that work can be carried out without hindrance from inclement weather. Select robust and suitable products and materials which utilise normal site assembly methods and sequence, with subsequent operations as well as wear and tear in mind. Design must include a realistic assessment of the level of skills likely to be available from appropriately chosen contractors and specialists. Designers should endeavour to produce the simplest possible details compatible with the overall requirements for the building to achieve ecient and defect-free works. The design of building elements and details should encourage appropriate repetition and standardization so as to reduce learning time, construction duration, costs and increased risks of error from construction of special projects. The site layout should allow for the maximum use of mechanical plant, particularly for the movement of materials. The design of the building assembly should recognize the tolerances which are normally attainable in site conditions, making allowances for di€erences between factory tolerances and those of normal site construction. The method of construction should encourage the most e€ective sequence of building operations. The design should arrange work sequencing in such a way that a trade can complete all its work at one location with as few return visits as possible. The design should enable work to be carried out in a workmanlike manner without risk of damage to adjacent ®nished elements and with minimum requirements for special protection. The design should be arranged so as to facilitate safe working in foundations and earthworks, when materials and components are being handled and wherever traversing for access is necessary. Buildability is assisted by the thorough and clear presentation of information before the start of construction. Complete project information should be planned and coordinated to suit the construction process and to facilitate the best possible communication and understanding on site.

2. Consider access at the design stage 3. Consider storage at the design stage 4. Design for minimum time below ground 5. Design for early enclosure 6. Use suitable materials 7. Design for the skills available 8. Design for simple assembly 9. Plan for maximum repetition and standardization

10. Maximise the use of plant 11. Allow for sensible tolerances 12. Allow for a practical sequence of operations 13. Avoid return visits by trades 14. Plan to avoid damage to work by subsequent operations 15. Design for safe construction 16. Communicate clearly

302

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

ful®l these objectives through speedy construction, improved quality and lower costs. Key aspects relating to buildability principles are explained in Table 1 [1]. The bene®ts achieved through a good buildability programme were noted to extend across the total design/ construction process as shown in the literature by Gray [7]; the Construction Industry Institute (CII) [5]; Adams [1]; Ferguson [6]; as well as Grith and Sidwell [8].

action; handling, storage, packaging, preservation and delivery; control of quality records; internal quality audits; training; servicing; and statistical techniques. These 20 elements are generic in nature and their interpretation for implementation can vary from organisation to organisation as well as from industry to industry [9,11]. An ecient and e€ective quality system can help a construction-related organisation reap many bene®ts [12].

3. ISO 9000 quality management systems

4. In¯uence of ISO 9000 on buildability

The ISO 9000 is a series of standards which specify requirements and recommendations for the design and assessment of a management system. It sets out a framework for the systems which an organisation should have in place to control its internal processes [11]. It has also been described as an essential building block towards the implementation of Total Quality Management (TQM) [13]. As a ``model'' for quality systems, it can be applied under di€erent circumstances. The ISO 9000 standard is a series of ®ve international standards on quality management, quality assurance and quality systems. They deal with the structure, procedures, requirements and the elements of quality management, quality assurance and quality systems. The ®ve international standards are:

Like ISO 9000 quality management systems, buildability can be a key driver in the construction industry. ISO 9000 quality management systems can be used as a tool in enhancing the buildability of building projects by integrating buildability principles within the ISO 9000 processes. The policies and procedures in ISO 9000 quality management systems can be extended to incorporate buildability principles. The quality management system can be used to encourage buildability reviews to ensure that only the most ecient construction solution is adopted. Any non-conformity with buildability principles can be identi®ed and resolved through the adoption of corrective and preventive actions in a systematic way. ISO 9000, which encourages communication, can be used to ensure coordination between design and construction, and among the di€erent trades. It also gives an organisation the capabilities and tools to implement continuous improvement programmes on buildability that will ultimately be translated into more buildable designs and higher quality products. Following the key buildability principles of Adams [1] as shown earlier in Table 1, the matching of these principles with relevant ISO 9000 quality system elements is summarised in Table 2. This matching was carried out by comparing each buildability principle (in Table 1) with the speci®cations of all 20 quality system elements required by ISO 9000. Where the buildability principle can be incorporated into a particular quality system element, a note was made of this match. The end result of this conceptualisation process formed the basis for the match shown in Table 2. It should, however, be noted that the matching shown in Table 2 is by no means exhaustive as this could vary from one organisation to another depending on their nature of work. As more and more construction ®rms worldwide secure certi®cation to meet ISO 9000 requirements, ISO 9000 quality management systems can therefore play a useful role to enhance the buildability of future construction projects. The buildability of a construction project can be achieved through integration with the relevant ISO 9000 quality system elements. Again, through the conceptualisation process explained above, the relevant

. ISO 9000 Ð Quality Management and Quality Assurance Standards Ð Part 1: Guidelines for Selection and Use. . ISO 9001 Ð Quality Systems Ð Speci®cation for Quality Assurance in Design/ Development, Production, Installation and Servicing. . ISO 9002 Ð Quality Systems Ð Speci®cation for Quality Assurance in Production, Installation and Servicing. . ISO 9003 Ð Quality Systems Ð Speci®cation for Quality Assurance in Final Inspection and Test. . ISO 9004 Ð Quality Management and Quality System Elements Ð Part 1: Guidelines. An ISO 9000 quality management system can include up to 20 system elements documented in a pyramid of inter-connected policies, procedures and work instructions. Of the three system models (namely, ISO 9001, ISO 9002 and ISO 9003), ISO 9001 requires compliance with all 20 system elements. These 20 elements are management responsibility; quality system; contract review; design control; document and data control; purchasing; control of customer-supplied product; product identi®cation and traceability; process control; inspection and testing; control of inspection, measuring and test equipment; inspection and test status; control of non-conforming product; corrective and preventive

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

ISO 9000 quality system elements are interpreted for buildability in the design and construction stage as shown in Tables 3 and 4 respectively. These interpretations should be kept in mind when reading the case study presented below. 5. Case study This paper analyses a condominium project to examine the extent to which the quality elements of ISO 9000 were applied to the project to enhance its buildability and to determine the e€ectiveness of integrating buildability in ISO 9000 quality management systems.

303

The second author was the architect for this project and therefore has had privileged access to information as well as intimate knowledge of work progress. The case study discusses the application of ISO 9000 quality management systems on buildability during the design and construction stage. These were undertaken by the structural engineer and main contractor respectively who have both achieved certi®cation to the ISO 9000 standard. Although buildability has been considered in the design during the conceptual stage by the designer, the integration of ISO 9000 with buildability will not be examined here because the designer was not ISO 9000 certi®ed at that point in time. The discussion below will highlight the buildable features

Table 2 Buildability principles and relevant ISO 9000 elements Buildability principles

Relevant ISO 9000 elements

1. Investigate thoroughly

Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Document and data control (4.5)/Process control (4.9)/Inspection and testing (4.10)/ Control of nonconforming product (4.13)/Corrective and preventive action (4.14) Quality system (4.2)/Design control (4.4)/Process control (4.9) Design control (4.4)/Control of customer-supplied product (4.7)/Product identi®cation and traceability (4.8)/Process control (4.9)/Corrective and preventive action (4.14)/Handling, storage, packaging, preservation and delivery (4.15)/Control of quality records (4.16) Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Purchasing (4.6)/Process control (4.9)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Control of customer-supplied product (4.7)/Process control (4.9)/Inspection and testing (4.10)/Inspection and test status (4.12)/Control of nonconforming product (4.13)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Purchasing (4.6) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Control of customer-supplied product (4.7)/Process control (4.9)/Control of inspection, measuring and test equipment (4.11) Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14)/Training (4.18) Quality system (4.2)/Contract review (4.3)/Design control (4.4)/Process control (4.9)/Corrective and preventive action (4.14) Contract review (4.3)/Design control (4.4)/Process control (4.9)/Inspection and testing (4.10)/Inspection and test status 4.12)/Corrective and preventive action (4.14) Contract review (4.3)/Design control (4.4)/Control of customer-supplied product (4.7)/Process control (4.9)/Inspection and testing (4.10)/Inspection and test status (4.12)/Control of nonconforming product (4.13)/Corrective and preventive action (4.14)

2. Consider access at the design stage 3. Consider storage at the design stage

4. Design for minimum time below ground 5. Design for early enclosure 6. Use suitable materials

7. Design for the skills available 8. Design for simple assembly 9. Plan for maximum repetition and standardization 10. Maximise the use of plant 11. Allow for sensible tolerances 12. Allow for a practical sequence of operations 13. Avoid return visits by trades 14. Plan to avoid damage to work by subsequent operations 15. Design for safe construction 16. Communicate clearly

304

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

which arose from the application of ISO 9000 and the barriers encountered. Other in¯uencing factors which have also contributed to the buildability of the project will also be examined. The pro®le of this condominium project is given below: . Project name Ð Sillert Towers . Project description Ð One Block of 30/24 storey residential condominium comprising 384 units with basement carparks and communal facilities . Site area Ð 17,635.90 m2 . Gross ¯oor area Ð 69,989.00 m2 . Building height Ð 103.375 m (Tower 1 and 2) 30 ¯oors; 83.875 m (Tower 3 and 4) 24 ¯oors . Construction period Ð 30 months (excluding piling) . Construction cost Ð S$107 million. Sillert Towers is among the tallest private residential block in Singapore. It is situated at Street 1 in Toa Payoh and bounded by public housing estates on three sides, i.e. to the north, east and west with the frontage (south) facing the Pan Island Expressway. This luxurious housing condominium complex comprises of two 30-storey towers 103 m high and two 24-storey towers 83 m high. The 30-storey towers and 24-storey towers are linked at the ®fth storey. In addition, the two 30storey towers are also linked at the 25th storey. The

condominium project comprises of 384 units with basement carparks and extensive facilities such as swimming/wading pools, tennis courts, golf simulator and KTV lounge. The site was originally occupied by a seven-storey factory/showroom and oces, a ®ve-storey factory/ warehouse, a dilapidated single storey factory, a confectionary factory and some smaller buildings. The initial proposal was to retain and upgrade the sevenstorey factory/showroom and oce block while the rest of the dilapidated buildings were to be demolished to make way for a new eight-storey industrial building. However this proposal was rejected by the local Planning Authority because it was contradictory to the long term plan for this site which has been rezoned for residential usage. The planning concept was to phase out all industries in this area. Faced with a new set of planning requirements, the design architect was required to maximise the plot ratio by designing a 30storey residential block. One of the brief requirements was for the adoption of a buildable design for the project. The main emphasis for the superstructure was on ease of construction, speed, buildability and good quality ®nishes. Investigations were required to determine the most cost e-

Table 3 Interpreting ISO 9000 elements for buildability during design stage Relevant ISO 9000 Elements

Interpretation for buildability

Clause 4.3 Ð Contract review

Ensures that the company has the necessary resources and expertise to meet the client's requirements for buildability. . The design control process includes checks at strategic points to ensure that the design solution satis®es the brief requirements of buildability. . Design reviews enable one to review and verify the design for buildability in terms of standardized, simpli®ed and single integrated design element. . The procedure for design control allows for value engineering analyses of alternative solutions and investigation of new construction techniques and materials which could enhance buildability. . Speci®cations are checked in details for compatibility, appropriateness and completeness and to ensure these promote eciency in construction operations. . The process ensures that design and speci®cation documents are reviewed for completeness, errors and omissions before issue. Evaluation and auditing of consultants ensure that the services of consultants with technical expertise and experience on buildable designs are engaged. . Inspection of drawings, speci®cations and contract documents ensure that these documents are complete and well co-ordinated before issuing out. . Application of the Buildable Design Appraisal System enables the designers to obtain an initial assessment of how their designs contribute towards buildability. . Design elements which do not conform to buildability are identi®ed, analysed and corrected to meet the requirements. . Non-constructable details, inappropriate speci®cations and incomplete drawings with discrepancies are examined to determine their causes so that appropriate corrective actions can be taken to prevent recurrence. . Training improves one's knowledge of the latest materials, innovative technologies and construction methods available in the industry. . Post-construction analysis and feedback can enhance the buildability of similar future projects.

Clause 4.4 Ð Design control

Clause 4.6 Ð Purchasing Clause 4.9 Ð Inspection and testing

Clause 4.13 Ð Control of nonconforming product Clause 4.14 Ð Corrective and preventive action Clause 4.18 Ð Training

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

cient structural system to be adopted. External loadbearing walls with modular formworks, wire mesh reinforcements instead of rebars and precast components like staircases, party walls, etc. were encouraged. The brief requirement for few variations in the unit types was also to encourage the repetition and standardization of the design. Speed and early completion of the structure was crucial to the developer as this enabled the early certi®cation of the structure by the architect

305

for the collection of progress payments from buyers to ®nance the project. Another main objective of the project was its emphasis on achieving high quality standards for this luxurious private condominium. With its close proximity to the surrounding public housing estates, it was of great importance to make the project attractive by providing high quality design and ®nishes to distinguish it from the surrounding public housing ¯ats.

Table 4 Interpreting ISO 9000 elements for buildability during construction stage Relevant ISO 9000 elements Clause 4.3 Ð Contract review

Interpretation for buildability

. Ensures that the company has the necessary resources and expertise to meet the contractual requirements of buildability. . A site visit report enables one to assess the accessibility to site and information on ground conditions and existing services as well as details of any obstructions which may a€ect the buildability of the project. . The project quality plan formulated during the post-tender/contract stage reviews the accessibility, sequences of operations, selection of materials, plant and equipment, and construction methods which would improve the buildability of the project. . Speci®cations and construction drawings are reviewed during the contract stage to clarify any ambiguities or discrepancies which will a€ect the progress of work on site. Clause 4.5 Ð Document control Document control ensures that documents such as construction drawings, speci®cations, work procedures, project quality plans, etc. are properly identi®ed and labelled to prevent wrong use and loss which could adversely a€ect the progress of the work. Clause 4.6 Ð Purchasing Ensures that sub-contractors are selected on the basis of their experience and technical capability to meet the buildability requirements. Clause 4.7 Ð Control of customer supplied product Enables one to verify that the purchased product conforms to the speci®ed requirements before installation so as to avoid any rejection work. Clause 4.9 Ð Process control . The buildability of the works are monitored and controlled on site to ensure buildability results are achieved and any non-conforming works are identi®ed and recti®ed. . Periodic buildability reviews during the construction stage ensures that the works are analysed continually to derive the most ecient and coste€ective alternatives in carrying out the tasks. Clause 4.10 Ð Inspection and testing . Each of the trades is inspected and checked for its quality and conformance with contract requirements to ensure that it is done right the ®rst time so as to reduce the need for recti®cation or abortive work. . Inspection of materials ensure that defective materials are segregated and disposed of to prevent their inadvertent use or installation which may result in replacement of the rejected works. Clause 4.11 Ð Control of inspection, measuring and test equipment The procedure ensures that equipment in use are inspected, measured, tested and maintained to the required accuracies speci®ed in the manufacturer's speci®cations to prevent breakdowns. Clause 4.13 Ð Control of nonconforming product . The procedure ensures that non-conforming works a€ecting the progress are identi®ed and its likely causes investigated so that the appropriate corrective actions to improve buildability can be adopted. Clause 4.14 Ð Corrective and preventive action . Records of non-conforming items enable one to pre-empt and eliminate potential causes of construction and operational ineciency. Clause 4.15 Ð Handling, storage, packaging, preservation and . Proper storage and protection of material stock minimise rejection of delivery materials and create a neat and ecient site. . The identi®cation of suitable storage areas and reduction of multiple handling of materials improve buildability and encourage operational eciency. Clause 4.18 Ð Training . Training improves skills and one's knowledge of the latest materials, innovative technology and construction methods available in the industry. . Post-construction analysis and feedback can enhance the buildability of similar projects in the future.

306

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

In view of this requirement, the main contract imposed a condition on the main contractor whereby a sum of S$1 million will be withheld from interim certi®cates and will only be released if the main contractor is able to achieve the required overall CONQUAS score of 83 points. (Note: the Construction Quality Assessment System or CONQUAS is used in Singapore for measuring quality standards of building projects [3].) CONQUAS is administered by the Building and Construction Authority (formerly the Construction Industry Development Board), a government agency in Singapore. This penalty is to deter the main contractor from providing a low standard of quality in the ®nished product. 6. ISO 9000 and buildability during the design stage This section should be read in conjunction with Table 3. The ISO 9000 quality management system was adopted by the structural engineer, who was the only ISO 9000 certi®ed consultant, during this stage to determine how the buildability of the structural design can be achieved in order to satisfy the brief requirements and ful®l his organisation's policy for adopting buildable designs. The ISO 9000 process encouraged the engineer, together with consultants from other disciplines, to come together to work on the design, to put together all the di€erent elements of the technical design and to identify potential problems. The intention was to foresee construction diculties right at the start during the design stage. This process helped to facilitate communication among the consultants during this stage and to build up a cohesive project team who will strive to achieve the client's objective for a buildable design. This close co-ordination, together with the architect's design concept for a clean line building which is simple, modular and repetitive in layout contributed to the buildability of the structure whereby standardized structural components were used. The elements of the ISO 9000 standard which were applied during this stage to achieve and enhance a buildable structural design are as follows. 6.1. Contract review There were regular contract review meetings to assess the manpower situation and whether they can meet the commitment and brief requirement for buildability (see Clause 4.3 Ð Contract review in Table 3). 6.2. Design control Regular design reviews were conducted during the design control stage to ensure that a structural system

with improved buildability was adopted to meet the client's requirement for fast-track construction (see Clause 4.4 Ð Design control in Table 3). Designs and drawings were reviewed in three stages by independent reviewers who were not directly involved with the project under review. Design Review No. 1 (DR1) was conducted during the preliminary structural concept and layout stage prior to approval of the structure's conceptual layout for commencement of detailed design. There were brainstorming sessions at this stage to investigate the various alternative proposals available and value engineering was applied to select the most suitable structural system which is not only buildable but also cost ecient. Through further investigation during this stage, it was discovered that the options available for residential buildings were conventional slab and beam system, ¯at slab system and precast system. Although steel structure and hollow core systems are very buildable components, these were found to be unsuitable for residential buildings because ceiling would have to be provided for the whole unit. The client's preference was for the precast system but the cost was found to be about 30% higher than the conventional method and the adoption of this very buildable system would exceed the project budget. There was also a concern that not many contractors are capable of handling precast construction and hence it was decided that any counter proposal for precast system should instead be proposed by the main contractor. The client ®nally settled for the shear wall and ¯at slab system which is just as buildable but cost less than the precast system. The shear wall and ¯at slab system was to be designed in such a manner to allow for the ¯exibility of converting to a precast system if the main contractor chooses to do so after the award of the contract. The structural system and ¯oor layout were reviewed by the project manager and approved by the project's professional engineer to ensure compliance with the client's requirement for buildability before the commencement of detailed design. Design Review No. 2 (DR2) was conducted at the second stage to review detailed layouts such as key plans, sizing of vertical elements, beam framing and pro®les. During this stage, the expertise and experience of precast specialists and contractors were put to the fullest utilisation by seeking their advice on the structural design and sizing of the structural elements so as to allow for any future conversion from the shear wall/¯at slab system to a precast system. The structural elements were carefully studied during this stage to determine how the elements could be simpli®ed and standardized. All shear walls were standardized to a thickness of 250 mm. The engineer considered the omission of edge beams but decided against this for economical reasons as it would involve

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

thickening the slab further to overcome the de¯ection problem. The orientation of shear walls were adjusted to face outwards to facilitate easy movement of formwork, workers and materials. A piled raft was found to be the most suitable foundation as it was more buildable and economical than pile caps which would have had to be closely located. The piled raft was also selected primarily for its speed of construction. The Buildable Design Appraisal System (BDAS) implemented by the Construction Industry Development Board, Singapore [4] was also used as a checklist to countercheck that the structural elements were able to achieve a high buildable score before proceeding with the ®nal drafting. When sucient drafting works had been produced, a separate Design Review No. 3 (DR3) was conducted to review drafting practice and drawing presentation. Here, the details are standardized for ease of construction. The structural drawings were checked against the latest architectural drawings to ensure that there was no discrepancy among these drawings. DR1 and DR2 meetings were chaired and reviewed by the managing director, senior principal architect or an independent principal from another team. The Design Review Panel checked and ensured that the design output meets the design requirements in terms of safety, durability, cost e€ectiveness and ease of construction. Matters pertaining to de®ciency in design and drawings, alternative proposals and/or comments and decisions made by the review panel were recorded. No detailed drawings could proceed until a highly buildable design has been achieved and all approvals cleared by the design team. 6.3. Process control and inspection During this process, design and drafting were carried out under controlled conditions and carefully checked to ensure that the design complied with the brief requirement before its issue. There was also an established procedure in the form of a ¯owchart for checking detailed drawings. Upon plotting out the checkprint, this was stamped with the checklist rubber stamp which de®ned the drawings items to be checked by the computer autocad (CAD) technician, project CAD technician and design engineer, respectively. The design engineer and CAD technician involved then initialed in the space provided in the drawings. Likewise, the project manager reviewed the drawings and endorsed them as the checker. These drawings were approved and endorsed by the project engineer that they are in order before release. Design validation was also performed to ensure that the materials speci®ed conformed to the de®ned buildability requirements and user needs (see Clause 4.9 Ð Inspection and testing;

307

and Clause 4.13 Ð Control of nonconforming product in Table 3). 7. ISO 9000 and buildability during the construction stage This section should be read in conjunction with Table 4. The ISO 9000 quality management system was applied by the main contractor during the construction stage to explore and select the best innovative construction methods and techniques available which can enhance the buildability of the project as well as to monitor and control the sequence of operations so that the project's desired buildability and quality can be achieved. The project outline, duties and responsibilities, construction methods, inspection checklists and procedures, quality and safety studies were documented in the Project Quality Plan. This documented quality system formulated by the project manager serves as a means to ensure that the building meets the client's requirement for early completion of the structure and to achieve a high CONQUAS score of 83 points. The elements of the ISO 9000 quality management system which were applied during this stage to achieve and enhance buildability are as follows. 7.1. Contract review During the post tender review but before the commencement of actual site works, the main contractor examined the contract documents in detail, studied the degree of diculties involved for the project and carried out thorough studies before deciding on the construction methods, type of materials and plant to be used for the project. In order to meet the project requirements, the project manager realised the need to break away from traditional construction and to adopt improved construction methods in terms of better buildability, safety and cost e€ectiveness in order to achieve higher productivity and quality. Some items in the contract, such as plastering work, required extensive labour and technical skills. However, with the scarcity of skilled labour in Singapore, the main contractor decided to propose alternative construction methods to overcome this problem. Through its in-house Value Engineering Group, the main contractor was able to pool together available resources, knowledge and experience to explore a wide range of construction methods (arising from the value engineering study) and project costs to arrive at alternative designs and innovative solutions which reduced the sequence of works and achieved better buildability and value for money for the project. These alternative proposals, particularly the conversion to

308

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

precast structure, helped to standardize components and maximise manpower utilisation on site. The result of the value engineering study during this stage led to the adoption of the following alternative solutions: 1. Original design 1.1. shear wall construction 1.2. slab formwork system 1.3. staircase construction method 1.4. external plastered brickwall 1.5. conventional bathroom construction 1.6. conventional basement retaining wall 2. Alternative proposal 2.1. precast structural wall 2.2. ``Topec'' slab formwork system 2.3. ``Stairmaster'' permanent formwork system 2.4. precast external wall 2.5. ``Unitbath'' system 2.6. precast basement retaining wall. Apart from construction methods, other considerations such as site layout, accessibility and type of plant and equipment to be used were looked into by the planning department at this stage. The layout of the site and access had to be properly planned in order to facilitate ease of construction and not impede the progress of the works. In order to reduce the transportation cost of precast components and to exercise quality control, the contractor decided to adopt a ``factory on site'' system by locating the prefabrication yard at a corner of the site so that the precast components could be hoisted up directly by tower cranes and installed in place or stored at the stock-stand. The ®rst-storey slab and entrance culvert were constructed early to allow access to all towers. Cranes were also positioned in a strategic manner to facilitate the hoisting of precast components and materials (see Clause 4.3 Ð Contract review in Table 4). 7.2. Process control During this stage, work instructions de®ned the manner in which construction operations are to be carried out and the safety measures considered. The supervisors and workers are required to familiarise themselves with the sequence of activities and to monitor and control the construction process (see Clause 4.9 Ð Process control in Table 4). ``Completion'' meetings among the four project teams, who are assigned to each of the four tower blocks, were conducted to ®nalise the construction methods, to locate plant and equipment and to designate suitable areas for storage in order to ensure the smooth running of daily activities. These items were further ®ne-tuned and ®nalised by the Head of the Planning Department before being documented in the

Quality Plan or Work Instructions. ``Completion'' meetings were also held regularly to monitor construction progress, review construction methods and to resolve any site problems which may have arisen. Discussions, brainstorming and feedback on the most ecient and cost-e€ective alternatives in improving and carrying out the tasks were also encouraged during these review meetings. The minutes of these meetings were recorded for follow-up actions. The works were also planned with safety in mind at all times in order to prevent any downtime which may be caused by an accident or ®re at the work site. Construction methods and materials were reviewed for their safety before these are used. For example, the climbing platform, which was the ®rst to be used in Singapore, is a prefabricated external working platform which climbs according to the construction sequence and provides a safe working enclosure. The precast members were also designed to be above the slab to prevent people from falling o€. Safety work plans and a comprehensive accident prevention programme set out the procedures to ensure that all works were conducted in a safe manner. The construction work schedules were adjusted, where necessary, to avoid having di€erent works in the same location at the same time. It was the responsibility of the contractor's supervisors to ensure that their sub-ordinates carry out the applicable safety precautions for their speci®c areas of work. Arising from the conversion of the shear wall/¯at slab to precast structures, thorough co-ordination was required early in order to conceal the mechanical and electrical services in the precast components. This required the early preparation and approval of shop drawings before work proceeded. This stage set out the procedure for preparing the shop drawings and for monitoring the approval given by the consultants. 7.3. Purchasing Domestic sub-contractors were appointed for their experience and capability in carrying out their respective specialised construction works. Suppliers of materials and construction methods were selected based on their past good performance and the buildability of their products. The performance of these sub-contractors and suppliers were monitored and assessed based on their ability to perform and to deliver (see Clause 4.6 Ð Purchasing in Table 4). 7.4. Inspections and corrective actions Drawings, speci®cations and contract documents were reviewed by the Planning Department to ensure that these documents were complete and everything is integrated together before proceeding with the con-

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

struction work. Should any information be lacking or clari®cations were required of the drawings, a ``Request for Information'' form was issued to the respective consultants for their con®rmation. This procedure ensured that there was continuous communication ¯ow between the contractor, consultants and site sta€. All the latest drawings and information received were inspected before passing these on to supervisors in charge of the relevant construction area. The construction methods were inspected closely to ensure that errors or problems are detected early and arrested immediately to avoid delay to the works. Plant and equipment were given periodic inspections to ensure that they are in good working conditions. Quality of the ®nished works was inspected to ensure that the works are constructed right the ®rst time to avoid unnecessary abortive works. Any non-conforming items were identi®ed and recorded in the ``Defects Analysis Form''. Remedial actions were evaluated and implemented immediately to overcome these problems and to prevent recurrence. Remedial proposals were often provided as feedback to the contractor's headquarter in Tokyo to solicit comments and to con®rm that the remedial proposals are e€ective before implementation. Examples of nonconforming items detected during this process include the distorted precast panels caused by the repetitive use of the moulds and storage of the panels in a horizontal position. Corrective actions were taken to change the moulds more often and to lay the panels vertically. The moulds also needed modi®cations when it was detected that the starter bars were sticking out which made the removal of the panel from the mould dicult. The contractor also maintained an in-house record of non-conforming items from past projects to assist in pre-empting and eliminating potential causes of construction and operational ineciency (see Clause 4.10 Ð Inspection and testing; and Clause 4.14 Ð Corrective and preventive action in Table 4). 7.5. Training Periodic training on buildability was provided by sta€ from the main contractor's headquarter in Tokyo. The purpose of this training was to update the main contractor's project managers on the latest construction techniques and methods available in the industry. Senior sta€ members from Tokyo occasionally gave lectures to pass on their experience and expertise on buildability to their colleagues in Singapore. On-site training was also provided for general workers who were unskilled and lacked the experience in erecting precast components. A mock-up sample of an entire unit was provided on site to train these

309

workers on the erection process before they proceeded with the actual work. Once these workers were familiar with the erection process, their productivity increased. For example, the construction cycle per ¯oor for precast panel installation used to be 11 days. This was eventually reduced to an eight-day construction cycle after training was provided to the workers. Regular safety training was also conducted to educate workers on the correct way to carry out the works in a safe manner and to observe basic safety rules on site (see Clause 4.18 Ð Training in Table 4). 7.6. Statistical techniques Innovative methods adopted in the project were reviewed by management at the end of the project to assess their e€ectiveness in enhancing the buildability of the project. All comments and feedback received were recorded in a database and formalised into a ``Standard Construction Procedures'' manual. This manual highlights the e€ectiveness of the innovative construction methods, the problems encountered and the pre-emptive measures taken. It records the procedures required for checking the buildability of the proposed construction method and ensures that the same mistakes are not repeated in the future. 8. Main buildable features Although the architectural design and layout provided by the architect were typical, simple and repetitive, these value-added features, together with the application of ISO 9000 quality system elements, contributed to the following buildable features in the Sillert Tower condominium project. 8.1. Structural system The structural buildability of the project was achieved through the vertical repetition of all 15 typical ¯oors for each of the 24-storey tower blocks and 25 typical ¯oors for each of the other two 30-storey tower blocks. This repetition resulted in the standardization of most structural components such as the shear walls, edge beams and staircases. The foundation design adopted was the raft foundation instead of the conventional pile cap design. This helped to increase eciency on site where less time was required for erecting and stripping formwork as well as ®xing reinforcement bars. It was both easier and faster to cast the foundation by using the raft system. In order to achieve the brief requirement for speed and ease of construction, ¯at slabs and external load bearing shear walls were designed instead of the con-

310

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

ventional beam and slab system which is tedious because of the need to construct the beams. The repetitive ¯oor layout, which is typical on a number of ¯oors, was designed primarily to facilitate the use of modular system formwork for the shear walls. These shear walls were oriented in a strategic manner to facilitate easy retrieval of the formwork. Edge beams were also standardized for easy casting. The internal walls were constructed of precision blocks which are less labour-intensive and require the use of less skilled tradesmen than the conventional method of using bricks to build the walls. Being a lightweight material with a density of 620 kg/m3, the autoclaved aerated concrete precision blocks were easy to handle and erect and required only a skim coat ®nish (see Clause 4.4 Ð Design control in Table 3). 8.2. Construction alternatives The contractor's Value Engineering Group evaluated and considered a wide range of alternative designs and construction methods for various elements of the project. The primary motivation behind the search for alternative construction methods was to achieve quality using scarce labour resources, to reduce the volume of work carried out on site and to enhance the productivity and buildability of the project so that both the structure and ®nishing works can be completed early (see Clause 4.3 Ð Contract review; Clause 4.9 Ð Process control; and Clause 4.15 Ð Handling, storage, packaging, preservation and delivery in Table 4). This was achieved through the adoption of the following innovative and buildable solutions. 8.2.1. Precast structural walls, precast beams and nonstructural walls The cast in situ construction of external structures such as the walls, beams, air-conditioning ledges and sun-shading ®ns were converted to precast construction to minimise site activities such as the erection of formwork, ®xing reinforcement bars, laying bricks and noisy concreting works within the building site. These precast elements were cast on site by setting up the prefabrication yard at one end of the site. This ``factory on site'' system reduced transportation costs between the site and factory as well as risks of damage during delivery, reduced storage costs and provided a safer and more ecient working environment. Work eciency was found to increase under these conditions because of better time control, project planning and co-ordination between precast installation and fabrication. Compared with conventional methods of construction, the labour requirement for the entire project was reduced by over 30%. In addition, a majority of the precast concrete workers do not require any special

skills. With this method of construction, the building facades do not require external plastering upon completion. The external panels were painted while the internal panels were skim coated prior to painting. 8.2.2. Precast concrete formwork/basement retaining wall Precast wall panels, 100 mm thick, were produced on site and erected as a permanent formwork for the basement retaining wall. These panels were installed with the o€-form surface facing the carpark and held in place by temporary supports and brackets to the slab. Reinforcements were ®xed and a conventional formwork secured to the other side. Once the basement wall was cast, the precast formwork panels became part of the monolithic structure. The ®nished surface was ready for painting without the need for further plastering. This therefore reduced the need for skilled labour and helped to improve the quality of the ®nished wall. 8.2.3. Steel permanent formwork for staircase ``Stairmaster'', a ready-made staircase system which originated from Australia, was used as the permanent formwork for the construction of staircases. The prefabricated galvanised mild steel permanent moulds were delivered to site containing the stair reinforcements. These are placed in position by the tower crane and are light enough for ®nal positioning to be carried out manually, thus relieving the tower crane for other activities. The staircase was cast together with the slab and can be used shortly after casting for access to the upper ¯oors. The system's main advantages are that quality control can be achieved for the treads and risers because of factory prefabrication and there is a time saving because it does not involve the stripping of formwork. 8.2.4. ``Topec'' slab formwork system The beamless ¯at slab system facilitated the use of the ``Topec'' system which is a ready-made slab formwork system from Germany. The system comes in panels of 900  1800 mm and is small and light enough for a person to handle. Four unskilled workers can erect 100 m2 of the formwork panels a day. Dismantling the formwork after casting was done with the same workers and can be easily transferred to the next level manually, hence freeing the tower crane for other tasks. This is a major advantage over the conventional table-form method or the installation of precast panels which require substantial use of the tower cranes. 8.2.5. ``Unitbath'' system The bathrooms for the project were designed in a modular size of 1850  1850 mm to allow for the use

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

of a prefabricated toilet system by the contractor. The layout enabled the use of the ``Unitbath'' system which was brought in by the main contractor. The ``Unitbath'' system is a toilet system from Japan where the thin metal sheet wall panels used are prefabricated and marble tiles laid in the factory together with sanitary and other mechanical and electrical ®ttings. The ®nished panels were installed on site. This helped to reduce the numerous sequence of works, damage to the completed works and avoided the use of messy wet trades which were often found when bathrooms are constructed in the conventional manner. Construction of bathrooms in the conventional way is usually the most expensive, time consuming and risky phase of the building process. The ``Unitbath'' system, on the other hand, eliminates potential delays due to poor work sequencing and recti®cation works and ensures that the quality ®nish of the products are controlled in the factory. It shifts the onus at this stage to the factory and allows one supplier to take responsibility for the bathroom units, hence shortening the construction time by several weeks. By reducing wet trades, it not only makes the work site cleaner but also reduces the risk of damage to other ®nishing trades. 8.2.6. Climbing platform This method of construction, which is commonly used in China, was the ®rst of its kind to be used in Singapore. This is a prefabricated working platform which climbs according to the construction sequence. It provides a safe working enclosure and reduces the sequence of activities. This system allows the contractor to repair damaged precast panels, to apply the sealant to the joints of the precast panels and to commence painting once the structure of the ¯oor is completed instead of waiting for the roof level to be completed before a gondola can be installed. The advantage of this system is that the completed work below can be inspected immediately and if necessary, the platform can climb down for any further repair or touch up works. 8.2.7. Door subframe system Timber subframe system was used for doors in the apartment units. This system makes use of a subframe which is installed ®rst, hence allowing ®nishing works to be carried out. The main frame is installed at a later stage to minimise the damage to the ®nished surface. 9. Implementation barriers The engineer and contractor were successful in achieving improved buildability through the implemen-

311

tation of ISO 9000 quality management systems. However, some barriers were also encountered during the course of implementation. One of the barriers encountered was that the ISO 9000 quality management system involved too much documentation and created additional paperwork for the sta€. For example, a number of non-conforming items and problems encountered were not documented in this project even though corrective actions were taken. There were also diculties encountered in ®lling in ISO 9000 forms and checklists. Although the application of the ISO 9000 quality management system enabled the contractor to propose various alternative solutions and innovative construction methods to enhance the buildability of the project, the biggest barrier to implementing these systems was getting the client and consultants to accept the alternative proposals. The consultants were not very receptive initially to some of the innovative construction methods, particularly the ``Unitbath'' system, as most of these systems were relatively new to Singapore and have not been fully tested under local conditions. Consequently, they were concerned with the performance of these products because they could not foresee problems which may arise from their usage. They were also concerned that end users would not be receptive to the precast structure as well as hollowness of the ``Unitbath'' and subframe door systems. Nevertheless, because of the consultants' commitment to buildability, these innovative construction techniques and methods were eventually accepted once they were convinced that these proposals will enhance the eciency and the buildability of the project.

10. Other in¯uencing factors The examples from the case study presented above were able to con®rm the in¯uence of ISO 9000 quality management systems in enhancing the buildability of this condominium project. The most in¯uential ISO 9000 quality system elements which contributed to buildability are ``Design review'' during the design stage and ``Contract review'' during the construction stage. Apart from the ISO 9000 quality management system, other factors which have improved the buildability of the project are: 1. 2. 3. 4. 5. 6.

Owner's commitment Value engineering Receptiveness of the consultants Technological expertise of the contractor Experience on buildability Brief requirements and project objectives

312

L.S. Pheng, B. Abeyegoonasekera / Building and Environment 36 (2001) 299±312

7. Local resource availability 8. Management's commitment and policies. It can be noted that the most in¯uential factors in enhancing the buildability of this project are owner's commitment and value engineering. Following the government's recent move to legislate minimum buildable scores [4] for building plan approval in Singapore [2], mandatory requirements of the local authorities could be another factor which can in¯uence buildability of future projects. 11. Conclusion The e€ective and successful application of ISO 9000 quality management systems in enhancing the buildability of a construction project can be demonstrated in this condominium project. The procedures documented in the ISO 9000 quality management system have encouraged both the engineer and main contractor to consider and implement buildability at various stages of the project, particularly at the design review and contract review stage to ensure that the end product satis®es the project requirements for a buildable design, speed and ease of construction, and a good quality ®nished product. The successful result of this case study was re¯ected in the high buildable score of 62.8 points at the design stage [4]. This surpassed the industry's average score of 50 points for private residential projects. However, with the adoption of simple but yet innovative construction alternatives such as prefabrication and suitable buildable materials, the buildable score of this project rose to 73 points, thus earning it the distinction of being the top buildable private residential project in Singapore. The design and alternative construction methods used not only contributed to a highly buildable project but also added to the overall quality of the condominium. A safer and more ecient working environment was also created on the worksite. The buildable design allowed for ¯exibility to convert to the use of prefabrication technology. Bene®ts such as the early completion of the structure, better ®nishes and a higher quality product with lower future maintenance costs were achieved. In addition, the construction period could have been reduced further if the precast system were adopted during the design stage because some time was wasted during the construction stage while waiting for the approval of the converted structural system from the Structural Building Branch. The precast concrete method of construction in the project, which used a high 28% of precast components as compared to the industry's average of only 8%, sig-

ni®cantly reduced the labour requirements for the project. This technology possesses the potential to reduce the reliance on foreign labour and to reduce the construction cycle of the superstructure to 8 days per ¯oor. By utilising prefabricated systems such as the ``Unitbath'' and the ``Stairmaster'', the volume of in situ work on site was also signi®cantly reduced. Hence, a simple design with standardized and repetitive components, proper co-ordination through good communications between the team members, and breaking away from traditional methods of construction by adopting simple but yet innovative construction methods were achieved through the application of the ISO 9000 quality management system. These translate into higher buildability, eciency and cost-e€ectiveness for the condominium project. The case study therefore concludes that the ISO 9000 quality management system can function as an e€ective and appropriate working platform for operationalising buildability principles at both the design and construction stage of a project.

References [1] Adams S. Practical buildability. London: Butterworths, 1989. [2] CIDB. Buildability requirements to be included in revised Building Control Act. In: Construction focus, vol. 11. Singapore: Construction Industry Development Board, 1999. p. 8 January±March. [3] CIDB. CONQUAS 21. Construction quality assessement system. Singapore: Construction Industry Development Board, 1998. [4] CIDB. The CIDB buildable design appraisal system. 3rd ed. Singapore: Construction Industry Development Board, 1995. [5] Construction Industry Institute (CII). Constructability concept ®le. University of Texas, Austin: CII Constructability Task Force, 1987. [6] Ferguson I. Buildability in practice. London: Mitchell, 1989. [7] Gray C. Buildability Ð the construction contribution, Occasional Paper No. 29, Chartered Institute of Building, Ascot, 1984. [8] Grith A, Sidwell AC. Constructability in building and engineering projects. London: Macmillan, 1995. [9] Lam SW, Low CM, Teng WA. ISO 9000 in construction. Singapore: McGraw-Hill, 1994. [10] Lim LY, Low SP. JIT productivity in construction. Singapore: SNP Publishers, 1992. [11] Low SP. ISO 9000. Practical lessons for the construction industry. Oxford: Chandos Publishing, 1998. [12] Low SP, Goh KH. The practice of quality and quality assurance in the Singapore construction industry. Quality Forum 1993;19(1):40±5. [13] Low SP, Peh KW. Beyond SS ISO 9000: Total Quality Management for construction. SISV Quarterly 1997;3(1):17±21. [14] Low SP, Tng LL. Factors in¯uencing design development time of commercial properties. Facilities 1998;16(1/2):40±51. [15] Me€ord RN. Quality and productivity: the linkage. International Journal of Production Economics 1991;24:137±45.