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The Construction Quality Assessment System Construction Essay

Paper Type: Free Essay Subject: Construction
Wordcount: 5278 words Published: 1st Jan 2015

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CONQUAS stands for Construction Quality Assessment System. Construction Industry Development Board Singapore now known as the Building and Construction Authority have developed it for the major public sector agencies and the various leading industry professional bodies to measure the quality level of completed project (The National House Buyers Association (HBA), 2009).

The Building and Construction Authority (BCA) is an agency under the Singapore’s Ministry of National Development. The BCA is championing the development of an excellent built environment for Singapore. “Built environment” refers to buildings, structures and infrastructure in our surroundings that provide the setting for the community’s activities.” (Building and Construction Authority, 2006)

At the beginning, the CONQUAS was introduced only to the local construction industry. CONQUAS have been launched since 1989 (Building and Construction Authority, 2006).

Today, CONQUAS is widely recognized and also accepted internationally as a benchmarking tool for quality. CONQUAS is now a registered trademark. CONQUAS have adapted in Singapore, Malaysia, China, Hong Kong, United Kingdom, Australia, South Africa and India, UK and Hong Kong construction industries (Building and Construction Authority, 2006).

The aim of CONQUAS was introduced to have a standard quality assessment system for construction projects. Furthermore, CONQUAS is to enable quality assessment to be carried out systematically within reasonable cost and time. Besides, CONQUAS is used to measure quality of constructed works against workmanship standards and specification (Building and Construction Industry, 2005).

However, CONQUAS is an independent assessment. It is carried out by assessors from BCA Singapore. It was designed to gauge and benchmark the quality of workmanship through the sampling approach. On the other hand, it means not every unit will be inspected or evaluated by the assessor. Random samples will be pre-selected and inspected to represent the quality of the whole project (The National House Buyers Association (HBA), 2009).

Since the launch of CONQUAS in 1989, more than 2,238 public and private building projects have been assessed by BCA. The total cumulative contract value of the assessed projects exceeds 81.9billion Singapore dollar (Building and Construction Authority, 2006).

In 1998, BCA introduced a number of new features to CONQUAS resulting in the launch of CONQUAS 21 (Building and Construction Authority, 2006). Now, Malaysia is applying CONQUAS 21 into the building projects.

Problem Statement

The standard quality of the building product becomes the significant issue that is always discussed and disputed by the contractors, developers, and investors or house buyers. Quality assessment of the building before the developer vacant possession to the purchaser is the significant issue for the developer. The developer shall delivery the final building product to the purchaser which the building is achieved a standard quality. However, how many will ask: “How should I ensure the quality of the product (property) that I purchased is fairly justified with the amount of money that I paid?” Many of the investors and the house buyer are sacrificing a huge money to appoint a famous Feng Shui master, to conduct a property surveys and engaged property agent prior making decision to invest the property. Has the quality standard of the building product been assured and same as the show unit? (The National House Buyers Association (HBA), 2009).

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There are many developers intended to deliver the final product to the end user with free of defects and good in quality. Thus, to achieve the standard quality of the building production, the contractor can adopt the Construction Quality Assessment (CONQUAS 21) in the project to give the quality assurance workmanship of building product. Although, the CONQUAS 21 is applied in construction industry, however, it is brought any benefits to the contractors, developers and end users? Moreover, what are the impact of the CONQUAS 21 toward the contractors, developers and end user? Consequently, the researcher will carry out the research regarding the application of quality assessment system (CONQUAS 21) in construction industry.

Aims & Objectives


To investigate Quality Assessment System (CONQUAS 21) in construction industry.


To study the principle and concept of CONQUAS 21

To find out problems occur when applying the CONQUAS 21

To find out the advantages of using CONQUAS 21

Scope of study

The research will provide a detail description on the standard of CONQUAS 21 and procedures of the system. This is done through literature review on journal papers, conference papers, books and browsing through websites.

Besides that, the researcher aims to the population of local contractors and developers who are adopted CONQUAS 21 in the construction projects. Researcher will investigate the reason of implementing the CONQUAS 21 in construction industry. Moreover, research will in-deep investigate regard the impacts and advantages of CONQUAS 21. Basically, a case study will be conducted to obtain more information regarding the implementation of CONQUAS 21.

Research Methodologies

Literature Research

Cover journals, relevant textbook, and internet research and conference paper is the sources that I obtain my information and doing for my literature research.


Site agent, supervisor and the site manager will be interviewed by the researched to get more details about the CONQUAS 21. The interview is hold at Swiss Garden Residences site.

Case Study

Site visit to the Swiss Garden Residence would be the best way to figure out the effectiveness of CONQUAS 21. Besides that, it is to figure out the problems occur when applying the CONQUAS 21.

Chapter Outline

Chapter 1: Introduction

In this chapter, the researcher is going to slightly introduce the background of CONQUAS. Besides that, the researcher is going to talk about the aims and objectives for this research.

Chapter 2: Literature Review

In this chapter, the researcher is going to discuss the concept and principle of CONQUAS 21. The information regarding the CONQUAS 21 are obtained from the literatures from books, articles, journals and web site. Moreover, the researcher is going to comment on the advantages of CONQUAS 21 and the impact of applying the CONQUAS 21.

Chapter 3: Designing the case study and research methodology

The researcher is going to use Swiss Garden Residences as the case study for CONQUAS 21. The researcher is going to interview the project manager, site manager and site agent for obtaining the relevant information.

Chapter 4: Analysis of the secondary data

After collecting the information, the researcher is going to do the analysis for the information obtained. The researcher is going to argue on the information obtained and give some opinion regarding the CONQUAS 21.

Chapter 5: Conclusion and further studies

In this chapter, the researcher is going to make a conclusion for the whole research and state out the further studies for quality assessment.

Plan and Schedule

Planned Schedule



Second Semester

First Semester

Second Semester












Literature Review

Designing case study



Actual Schedule



Second Semester

First Semester

Second Semester












Literature Review

Designing case study



Chapter 2

Literature Review

2.1 Quality Philosophy

Definition of Quality

Different party defines the quality in different way. Some people will define it as to meet contract requirements, instead some people define it as the satisfaction of customer and others also define as it reaches the required standards. ‘Totality of characteristics of an entity that bear on its ability to satisfy stated or implied needs’ is the definition that The National Organization for Standardization (ISO) defines quality (Chung, 1999). The aims or requirements have been fulfilled or reached by any party, mean the quality standard has been achieved.

Furthermore, quality also can be defined based on own opinion such as ‘providing customers with products and services that consistently meet their needs and expectations’ (S.L. Tang, 2005), ‘performance to the standard expected by the customer’ (S.L. Tang, 2005) and ‘fitness for purpose’ (Chung, 1999).

However, the definiton of quality is based on how a party to define, it can be defined is several way.

Basic Concept of Quality

Quality is the most important factor to be concerned in every field including construction field. In order to achieved the quality, the industries have come out with there are assessment system and guidelines to be carried out to ensure the works done in the construction industry can achieve the quality. ISO 9001:2000, Quality Assessment System in Construction (QLASSIC) and Construction Quality Assessment (CONQUAS) is the assessment system that always used by constrction industry to ensure the works done reach the quality standard requirement. Case study of CONQUAS will be carried out in more details later.

Quality can be quantified as follows:-



Q = quality

P = performance

E = expectation

If Q is greater than 1.0, then the customer has a good feeling about the products or services (Besterfield, 1998).

Furthermore, There are nine dimensions in the quality. All dimensions are independent, which means that an end product can be excellent in one dimension but poor in others (Besterfield, 1998). These nine dimensions details and their terms is the following:-

Table 1: Nine dimensions of quality and their terms




Primary products/service characteristic such as time, cost and workmanship aspect.


Secondary characteristic, added consideration such as creativity in design and attractivenes.


Meeting specification or industry standards, workmanship and client’s requirement in contract.


Consistency of performance over time, average time for the unit to fail.


Useful life period with less maintenance or repair.


Resolution of problems and complaints, ease of repair.


Human to human interface such as efficiency during meeting, fast decision making, effective human resources management.


Sensory characteristics in design such as exterior finishes.


Past performance such as being ranked first in the tendering process.

Adapted from Garvin, 1988, Managing Quality: The strategic and Competitive Edge, New York: Free Press.

Furthermore, there are always the relationship between quality with cost, value, cycle time and productivity. The details of the relationship is shown as following:-

Quality and Productivity

Productivity increase will influence the quality by improvement

Productivity = Salcable output / Resources used

Quality and Costs

Cost will increase if the quality of conformance increase

Cost will increase if the quality of design increase

Quality and Cycle Time

The cycle time will be reduce if there is improvement of quality effort

The cycle time to complete the activities is the key parameter

Quality and Value

Organizations must evalute the value they provide, relative to the competition

Value = Quality / Price

(S.L. Tang, 2005)

2.1.3 Quality Management

Quality management will influence the quality directly. The principles of quality management are applicable to every industry, within all organisations and at every level (McCabe, 1988). The basic goal of quality management is the elimination of failure: both in the concept and reality of products, services and processes (Juran, 1989).

The quality management is defined as “all activities of the overall management function that determine the quality policy, objectives and responsibilities, and implement them by means such as quality planning, quality control, quality assurance, and quality improvement within the quality system” (McCabe, 1988)

The quality management have four stages in evolution, known as: Quality Inspection, Quality Control (QC), Quality Assurance (QA) and Total Quality Management (TQM) (UTM, 2003). Inspection and Quality Control are retrospective; their aim is find out the occurred problem by detection mode. Instead, the aim of Quality Assurance and Total Quality Management is reduce and to avoid problems occuring (McCabe, 1988). The characteristic of the different stages in Quality Management as shown following:-

Figure 1: The four stages of quality management





Adapted from Dale, Boaden and Lescelles 1994: Levels of total quality management adoption

Figure 2: The four stages of quality management

Quality Assurance

Quality systems development

Advanced quality planning

Comprehensive quality manuals

Use of quality costs

Involvement of non-production operations

Failure mode

Total Quality Management

Policy deployment

Involve suppliers and customers

Involve all operations

Process management

Performance management


Employee involvement

Quality Control

Develop quality manual

Process performance data


Product testing

Basic quality planning

Use of basic statistics

Paperwork controls



Sorting, grading, relending

Corrective actions

Identify sources of non-conformance

Adapted from Steven McCabe 1988: Quality Improvement Techniques in Construction

Stage 1 : Inspection

The first stage of quality management is inspection. The inspection is defined as “activity such as measuring, examining, testing or gauging one or more characteristics of an entity and comparing these results with specified requirements in order to establish whether conformity is achieved for each characteristic” (McCabe, 1988).

Inspection is used by most of the construction industry to ensure the conformance. The site supervisor will carried out the inspection of the construction project. The supervisor will make the comparison the architectural works and structural based on the specification and drawing. If there is any defective works found by the customers, the contractor need to rectify the defective works until fulfill the customer’s requirement.

Stage 2 : Quality Control (QC)

Quality control will be carried out after the inspection done. Quality control is considered as a system of routine technical activities, to measure and control the quality of the inventory as it is being developed (Mangino, 1996).

The procedure of Quality control is very complicated. QC mostly is based on the statistical analysis. Collection of data is required in QC to maintain the quality by statistical techniques.

Stage 3 : Quality Assurance

Quality assurance is defined as “all the planned activities implemented within the quality system, and demonstrated as needed, to provide adequate confidence that an entity will fulfill requirements for quality” (McCabe, 1988).

The objective of Quality Assurance (QA) is to provide adequate confidence that a service or product will fulfill customers’ requirement by performing system audit, Failure Mode and Effect Analysis, design of experiment and similar initiatives (UTM, 2003). In other words, QA is more specified on planning. The prevention of poor quality and defects is based on detection activities.

Stage 4 : Total Quality Management

The final stage of quality management is Total Quality Management. The implementation and understanding of quality management principles and concepts in every aspect of business activities are involved in this stage. The best service or product will be provided to the customer at the lower cost by using these activities.

However, TQM is less formal; having either procedures or system, and it is hard to be described due to it is less in formality (McCabe, 1988). Normally, only guidance will be provided by TQM and it consider as a philosophy.

Concept and Principles of CONQUAS 21

2.2.1 Introduction

Recently, the requirement of customers towards the building that they purchase is quality. They wish to get the best quality of the purchase building as possible. In this condition, the developers have to play an important role to ensure the quality of the building project. The developers overcome the problem by using Quality Assurance (QA) and Quality Control (QC) into the construction project to maintain the standard of quality as the requirement. CONQUAS 21, ISO 9001:2000, QLASSIC will become the choice for the developers for their assessment system. Case study about CONQUAS 21 will be carried out by the researcher in more details.

2.2.2 Objectives of CONQUAS 21

There are three objectives in the CONQUAS 21 system:

Act as a standard quality assessment system in construction projects.

Inspecting quality assessment by:

Measuring the specification and standard of the workmanship in the works done

Randomly selecting the sample as represent the whole project

To enable quality assessment systematically take place within reasonable cost and time

(Building and Construction Authority (BCA), 2006)

Scope of CONQUAS 21

In CONQUAS 21 system, all the works done will be given points based on the quality standard. All of the given points will be added together to get the total quality score which also known as CONQUAS score for the construction project (Building and Construction Authority (BCA), 2006). The quality workmanship is better, the higher of CONQUAS score will be obtained. 100% is the maximum CONQUAS score in construction project, but our human being is unable to construct a work with zero-defects.

The general building works is covered by CONQUAS 21 system. There are 3 components in the assessment:

Structural Works

Architectural Works and

Mechanical & Electrical (M&E) Works

There are different item to be assessed in the different component stated above (Building and Construction Authority , 2005).

CONQUAS 21 is considered as ‘first time right’ inspection approach (Building and Construction Authority , 2005) means that the rectification works will not take into consideration in CONQUAS 21 score for the assessment. Furthermore, sampling system is the assessment system used in the CONQUAS. The assessor will choose the unit according to the average, 1-in-4 apartment units in a residential development for the assessment (Building and Construction Authority , 2005). Thus, which unit will be chosen is unknown so the contractors have to ensure all of the constructed works are in good quality condition. If there is any defective found, the works will be considered as failed.

Besides, the heavily equipment-base such as heavy foundation, sub-structure works and piling is not available for assessment and the work separate contracts or sub-contracts are not included in the assessment (Building and Construction Authority (BCA), 2006).

The inspection is different with the inspection done by the site supervisor. Normally, the contractors have to purposely do an arrangement for the inspection which form a specific team for the inspection. There is a guideline have to be followed for the assessment.

Components to be assessed

Structural Works, Architectural Works and M&E Works are the components under CONQUAS 21 assessment.

Structural Works

Structural Works can be considered as ‘body’ for a building, the stability of the building will be affected if there is failure or defect in structural works. Thus, maintain its quality is necessary due to the cost of rectification is very expensive. Below show the details of the assessment of Structural Works:-

Inspection of finished concrete, formwork and steel reinforcement have to be carried out on site during the construction site. If any component constitutes exceed 20% of the total structural cost, the pre-stressed concrete and structural steel are included in the assessment. If found the precast concrete volume more than 20% of structural concrete volume, the precast elements have to be assessed.

Tensile strength of steel reinforcement and testing of compressive strength of concrete will be carried out on laboratory testing.

Non-destructive testing of the uniformity and the cover of hardened concrete.

(Building and Construction Authority (BCA), 2006)

Appendix 1 shows the quality standards of Structural Works.

Architectural Works

The components and finishes are classified in Architectural Works. The workmanship and quality can be easily seen and found. Below are the details of assessment of Architectural Works:-

After the building have complete, the assessment have to be carried out on roofs, external works, external walls and internal finishes. All the assessment have to be carried out on site. Internal walls, doors, components, windows and floors are classified under the internal finishes.

Functional and material tests such as on external walls and adhesion of internal wall tiles and water-tightness of window.

(Building and Construction Authority (BCA), 2006)

Appendix 2 shows Architectural Works quality standard.

Mechanical & Electrical (M&E) Works

The progress of whole building will be influenced by M&E Works. Air conditioning & Mechanical Ventilation Works (ACMV), Electrical works, the basis M&E fittings and Fire Protection Works are classified under the progress of the building. Below are the stage of assessment:-

Concealed pipes, ACMV ductworks and electrical conduits are classified as installed works, the inspection on the item have to be carried out before embedded on site.

The cooling tower, fire alarm control panel and Air-Handling Unit (AHU) are the final installed works which the assessment have to be carried out on site.

Dry Riser Test, Earthing Test and Water Pressure Test are considered as selected works. The performance tests are carried out on them.

(Building and Construction Authority (BCA), 2006)

Appendix 3 show the quality standard of M&E Works.

The Weightages

CAT A (Commercial, Industrial, Institution and Others), CAT B (Condominium, Institution and Others), CAT C (Public housing), and CAT D (Landed properties) are the four categories of building that distribute the weightages for M&E Works, Architectural Works and Structural Works in CONQUAS 21 system.

The objective of weightage system is making the quality of a building is based on the CONQUAS score, it is a compromise between the cost proportions of the three components in the various buildings and their aesthetic consideration (Building and Construction Authority (BCA), 2006).

In general, M&E works consist 10% for four categories of building in average, 35% is consisted by the Structural works and the highest percentage is consisted by Architectural works which 50% in average for the four categories of buildings. The quality of Architect works is the most important with the highest percentage, second is represented by the Structural works and M&E works is the lowest.

Table 2: The Weightages in CONQUAS 21


CAT A Commercial, Industrial, Institution & Others

CAT B Commercial, Industrial, Institution & Others

CAT C Public Housing

CAT D Landed Properties

Structural Works





Architectural Works





M&E Works










Note: In general, projects with central cooling system having cooling tower, chiller system, etc are classified under CAT A. Otherwise, it will be classified under CAT B. Appendix 5 provides a guides with listing of building under the various categories.

Adapted from Building and Construction Authority (BCA): CONQUAS 21 manual book

CONQUAS Assessor

In CONQUAS 21 system, only the Building and Construction Authority (BCA) officer can be the assessor to inspect the works done of the project. BCA will conduct a calibration program and training for assessors to attend to ensure competency and consistency in the assessment (Building and Construction Authority, 2006).

Furthermore, CONQUAS 21 system is consider as independent assessment. Therefore, if the building or parts of the building project are acceptable, the architects and engineers are not allowed to use CONQUAS to make any decision unless the building contract specify it (Building and Construction Authority (BCA), 2006).


Sampling system is introduced in the CONQUAS 21 system for the assessment. It is impossible for us to inspect every unit of the works done. Thus, the sampling system is used for the assessment, it helps the accessor a lot by saving the time and make the assessment easier due to the samples will be randomly chosen by the assessor for inspection.

Furthermore, the sampling system want to make sure the inspection is sufficient to represent the whole building by referring to the gross floor area of the building.

The assessment of CONQUAS 21

Assessment approach

Sampling system is used by the CONQUAS 21 as the assessment system, the sample will be randomly selected for the quality assessment according to the location plan and drawing plan and it will be distributed based on the construction stages (Building and Construction Authority (BCA), 2006).

The scoring will be done on the works that are inspected for the first time because the objective of this practice is to encourage contractors “doing things right the first time” is the principle of the CONQUAS 21 system which want to make sure all the contractor do the works well and maintain the quality in first time. Thus, the scoring will not take into account for the rectification works, only the first time works done will be inspected and scored in the CONQUAS 21 system (Building and Construction Authority (BCA), 2006).

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In filling the assessment form, “X” mean the work done do not fulfill the CONQUAS quality standard after inspection on it. Instead, “” consider the inspected work have reached the quality standard stated in the CONQUAS system. Besides, not applicable item will be noted as “-” in the assessment form. The number of “” over the total number of item assessed is the final score of CONQUAS for the whole project.

Structural works assessment

After the whole projects have been completed, the inspection on structural works only can be done. Wall, slab, beam and column can be classified as the Structural works. Below show the details of the assessment of a reinforced concrete structure:-

Table 3: The assessment of a reinforced concrete structure

Reinforced Concrete Structure

Weightage %





Finished Concrete


Concrete Quality


Steel Reinforcement Quality


NDT – UPV test for concrete uniformity


NDT – Electro-Cover meter test for concrete cover




*If total precast concrete volume exceeds 20% of total structural concrete volume, assessment will be carried out for precast concrete construction. The points will be distributed proportionately between formwork/rebar assessment and precast concrete assessment based on the respective concrete volume percentage.

Adapted from Building and Construction Authority: CONQUAS 21 manual book

The structural works assessment is carried out by using sampling system which mean only part of the samples have been chosen to represent whole project for the assessment, not every unit is inspected. Thus, there are some guidelines for the assessment of structural works. The guidelines are shown as below:-

Table 4: Guidelines for Structural works assessment


GFA per Sample

Min Sample

Max Sample



Structural Elements

500 m2



For Non-Housing Project


Strctural Elements

1500 m2



For Housing Project


Concrete Compressive Strength


Declaration by Qualified Person


Steel reinforcement Tensile Strength


Declaration by Qualified Person


NDT – UPV test for concrete uniformity

5,000 m2

2 sets

20 sets

5 structure members per set


NDT – Electro-Cover meter test for concrete cover

5,000 m2

2 sets

20 sets

5 structure members per set

Note: The computed number of elements to be checked must be evenly distributed throughout the entire block and cover at least 50% of floors in a block. They should also as far as possible cover the different types of structural elements.

Adapted from Building and Construction Authority: CONQUAS 21 manual book

The inspection is only site inspection, the inspection cannot be done at precast yard due to all the structure works to be inspected is cast in-situ concrete works, not the precast component. The inspection of the structural works is according to compliance to the standards (see in the Appendix 1, 1a, 1b & 1c).

The further assessment will be required if the structural steelwork in the structural works exceed 20% of the structural cost and the points will be distributed proportionately. The Pre-stressing Works is similar with the str


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