Achieving Sustainable Urban Renewal in Hong Kong

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serious problem of building dilapidation in the old urban areas. On account of the high-rise high-density built environment in Hong. Kong, this problem poses ...

Case Study

Achieving Sustainable Urban Renewal in Hong Kong: Strategy for Dilapidation Assessment of High Rises Daniel Chi Wing Ho1; Yung Yau2; Sun Wah Poon3; and Ervi Liusman4 1


Abstract: Approximately 4% of the private buildings in Hong Kong are older than their design lives of 50 years. In addition to the engineering factor, the lack of timely maintenance and proper management has led to a serious problem of building dilapidation in the old urban areas. On account of the high-rise high-density urban setting in Hong Kong, the problem has engendered severe safety and health hazards for the local community. Although different ways of urban renewal or regeneration exist to revitalize the urban environment, it appears that redevelopment is most frequently used. However, the speed of dilapidation would probably exceed the economy’s capability of absorbing redevelopments. In addition, redevelopments have detrimental effects on the social fabric and create a large volume of demolition and construction waste that greatly surpasses the current landfill capacity in Hong Kong. A sustainable strategy for urban renewal is, therefore, urgently needed. This research aims to establish an existing profile of the building conditions in Hong Kong and evaluate the suitability of various urban renewal strategies for different buildings through the establishment of a structured building assessment scheme called the Dilapidation Index (DI). In total, 393 private residential buildings randomly selected from 4 districts in Hong Kong were assessed by using the DI. The results indicated that the assessed buildings in Sham Shui Po were more problematic than those in other districts. The results also suggested that physical conditions and management factors play nearly equal parts in differentiating the well-performing buildings from the dilapidated ones. The DI developed in this research is beneficial to different parties with an interest in the quality of the urban built environment because it can help people identify problematic buildings for further actions. DOI: 10.1061/(ASCE)UP.1943-5444 .0000104. © 2012 American Society of Civil Engineers.

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CE Database subject headings: Urban development; High-rise buildings; Rehabilitation; Hong Kong; Sustainable development. Author keywords: Urban renewal; Building conditions; Redevelopment; Building rehabilitation; Decision tool.


The stock of buildings plays an important role in determining a city’s sustainability. However, much academic and policy attention has been drawn to the design and construction of new developments rather than the performance of the existing building stock. In fact, new developments comprise only a small portion of the overall building stock throughout the world. Because they are subjected to deterioration over time, the stock can undermine the sustainability of the built environment if not properly managed (Chew et al. 2004). Similar to many other developed cities, Hong Kong has suffered from the plight of urban decay (Lee and Chan 2008a). In the territory, approximately 4% (or approximately 2,200 buildings) of the 55,000 private buildings are older than their design lives of 50 years (Home Affairs Department 2010). In addition, the predominant coownership arrangement of most private 1 Associate Professor, Dept. of Real Estate and Construction, The Univ. of Hong Kong, Hong Kong, PRC. E-mail: [email protected] 2 Assistant Professor, Dept. of Public and Social Administration, City Univ. of Hong Kong, Hong Kong, PRC (corresponding author). E-mail: [email protected] 3 Associate Professor, Dept. of Real Estate and Construction, The Univ. of Hong Kong, Hong Kong, PRC. E-mail: [email protected] 4 Senior Research Assistant, Dept. of Real Estate and Construction, The Univ. of Hong Kong, Hong Kong, PRC. E-mail: [email protected] Note. This manuscript was submitted on November 3, 2010; approved on October 12, 2011; published online on October 17, 2011. Discussion period open until November 1, 2012; separate discussions must be submitted for individual papers. This paper is part of the Journal of Urban Planning and Development, Vol. 138, No. 2, June 1, 2012. ©ASCE, ISSN 0733-9488/2012/2-0–0/$25.00.

buildings in the city renders homeowners’ participation in building upkeep more prone to free-rider dilemma (Yau 2011). Eventually, the lack of timely maintenance and proper management has led to a serious problem of building dilapidation in the old urban areas. On account of the high-rise high-density built environment in Hong Kong, this problem poses severe safety hazards (e.g., fires and falling objects) and hygiene problems for their occupants and passers-by (Walters and Hastings 1998; Ho et al. 2008). The increasing number of reports about building danger received by the Buildings Department over the past 15 years suggests that the deterioration of the built environment in the city has aroused concerns among the local community (Table 1). To revitalize the urban built environment, Hong Kong has 2 adopted different approaches of urban renewal or regeneration such as redevelopment and rehabilitation. Redevelopment generally refers to complete reconstruction on a site after the demolition of the existing structures. Rehabilitation means any efforts to repair, improve, and upgrade buildings to comply with the current standards. These approaches have their own merits, limitations, and side-effects, but the public sector and private real estate developers in Hong Kong apparently incline toward redevelopment. In this regard, a growing number of studies call for a balance between different modes of urban renewal (Yau and Chan 2008; Fung and Yau 2009). Given that information regarding the existing conditions of the building stock is necessary for an informed formulation for a forward-looking strategy for sustainable urban renewal or building stock management, this article attempts to develop a decision tool on the basis of a structured building assessment scheme.


Table 1. Numbers of Reports Received by the Buildings Department about Dangers from Buildings Year

Dangerous advertising signs

Dangerous buildings

Dangerous hillsides

Unauthorized building works

Total number of reports

1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010

230 165 350 250 614 260 178 135 181 303 331 564 322 563 478 242

1,974 2,567 3,658 3,851 4,730 4,280 6,671 5,956 8,665 10,407 13,999 6,758 4,566 6,138 5,566 8,028

38 91 130 53 130 71 41 52 48 146 208 183 128 313 219 256

8,203 9,913 12,427 12,577 16,999 13,911 12,764 21,844 24,870 21,123 25,683 24,861 24,633 24,942 25,102 28,148

10,445 12,736 16,915 16,731 22,473 18,522 19,654 27,987 33,764 32,069 40,221 32,366 29,649 31,956 31,365 36,674

Note: (Buildings Department 1996, p. 8; Buildings Department 2001, p. 8; Buildings Department 2006, p. 8; Buildings Department 2011, p. 8).

probably exceed that of redevelopment (Yau 2009). Moreover, redevelopment may destroy the existing social fabric and create a large volume of demolition and construction waste (Itard and Klunder 2007; Yau and Chan 2008). On the other hand, building rehabilitation has less severe negative environmental and social effects but brings about smaller positive externalities to the neighbourhoods. Perhaps, the difficulty facing the decision-makers lies in the absence of a one-size-fits-all solution. Different renewal projects have dissimilar characteristics and involve stakeholders in different compositions. In this regard, different criteria are involved in the decision-making for the sustainability of the projects (Walbaum et al. 2011). For example, the constraints and concerns for the renewal of a densely populated estate and the revitalization of a derelict but abandoned area are unlike. The social effects on the original residents and local businesses should receive more considerations in the former scenario. Common decision-making criteria for a renewal project include sense of community of the local residents, creation of new jobs, and environmental friendliness 3 (Lee and Chan 2007). With an eye to the sustainability in urban renewal, community involvement in the decision-making process is necessary (Burke 1968; Ng et al. 2001). Yet, precise and 4 up-to-date information is always necessary for informed decisionmaking to achieve sustainability (Verghese and Hes 2007). To allow the stakeholders to make responsible decisions regarding the approach to urban renewal, different types of information such as building quality profile and social aspirations are required. Accordingly, a longitudinal monitoring of the conditions of building stock in a city or country can provide valuable information on building quality for more informed decision-making (Davidson 2005).


Sustainability in Urban Renewal: Needs and Challenges

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Long-term management of building stock is essential for every city (Kohler and Hassler 2002; Augenbroe and Park 2005; Kohler and Yang 2007), and urban renewal can significantly contribute to the sustainable urban management of a city for various reasons. First, good-quality housing helps reduce health risks facing the local community (Krieger and Higgins 2002). From the perspective of economic sustainability of the built environment, timely repair and maintenance can arrest building dilapidation, which may result in excessive depreciation. It was estimated that a value amounting 34% of Hong Kong’s gross domestic product was lost because of building depreciation in the city in 2005 (Yiu 2007). In addition, excessive dilapidation of buildings can result in building abandonment and reduce the efficient use of the building stock and land resource in the city (Scafidi et al. 1998; Simmons-Mosley 2003). Moreover, urban renewal projects, if properly designed and implemented, can improve urban competitiveness profoundly (Teng et al. 2006). A sustainable strategy of urban renewal should take the entire life cycle, from design and construction to operation and maintenance, of urban structures and the life quality of the residents into consideration (Fischer and Amekudzi 2011; Walbaum et al. 2011). That explains why in addition to public health, economic, and environmental concerns, social needs have to be duly observed in a sustainable renewal project (Percy 2003). Urban renewal projects should be designed and implemented with due care because of their high execution costs and significant but irreversible effects (Garrett 1995). In reality, nonetheless, many renewal projects have been uncoordinated, sporadic, and profitbased so that they failed to achieve sustainability in the urban built environment (Lee and Chan 2008a). In addition, the choice between different renewal modes, particularly redevelopment and rehabilitation, has received much academic attention (e.g., Itard and Klunder 2007; Juan et al. 2010). Generally speaking, redevelopment can eradicate substandard buildings, incompatible land uses and environmental nuisances, and release underutilized urban land without compromising the city’s natural environment (Thomas 1977; Fung and Yau 2009). Nevertheless, redevelopment involves a lengthy land assembly process so the speed of dilapidation would

Development of a Tool for Benchmarking Building Dilapidation Decision Tool for Sustainable Management of Building Stock In practice, periodic surveys are conducted on the housing conditions in some countries. For example, the English House Condition Survey (EHCS) was run every five years from 1971 to 2001 and


hazard-based rating mechanism is too technical or “scientific” for operation and interpretation (Stewart 2002; Department of Environment, Transport and the Regions 2005). Although the EHCS and AHS can be used for mass evaluation of housing quality, they lack a mechanism to aggregate the survey findings to give scores or grades for easy comparison between buildings. In addition, the two schemes may not be applicable to the Hong Kong context. For example, the EHCS puts much weight on heating, insulation, and dampness, which are not big issues in subtropical Hong Kong. Also, evaluations of means of escape and fires services installations are missing in the AHS. The EHCS does not address the conditions of elevators. These services or elements are actually very common in high-rise housing in Hong Kong so they should not be ignored in building assessment in the city. Principles and Construction of the Dilapidation Index In light of the aforementioned gaps, this study develops a Dilapidation Index (DI) for more informed decision-making in urban renewal in Hong Kong. The principles and frameworks of the DI model those of the Building Health and Hygiene Index (BHHI) and Building Safety and Conditions Index (BSCI) developed by the Faculty of Architecture, University of Hong Kong, with necessary consolidation and simplification (Ho et al. 2004; Yau et al. 2008). Reference is made to these two assessment protocols because they are tailored for first-tier screening of the building health and safety performance of private apartments in Hong Kong. Unlike the BHHI and BSCI, the DI serves to indicate a building’s level of and proneness to dilapidation. Given that obtaining the profile of a large number of buildings within a relatively short time frame is essential for the purpose of sustainable management of building stock or urban renewal, the DI assessment should be practicable in terms of the resource consumption and the level of knowledge or technology required. Therefore,

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operated on a continuous basis from 2002 to 2008 in the United Kingdom (Department for Communities and Local Government 2010). It appraised the physical conditions of housing on the basis of information obtained from household surveys and inspections by trained surveyors. Similarly, the biannual American Housing Survey (AHS) evaluated the quality of sampled housing in the United States on both national and metropolitan-area bases. It was a household survey in which Census Bureau interviewers visited or phoned the households occupying the sampled housing, asking questions about the quality of the latter’s housing (United States Census Bureau 2008). These two periodic surveys were usually followed by a wide range of analyses that provided information on the housing stock. However, similar regular mass evaluations of housing conditions are absent in Hong Kong. Without an overall picture of the stock conditions, it is difficult to prioritize buildings or areas for actions according to their levels of or proneness to dilapidation. In other words, rational allocation of the limited resources to tackle the contemporary building problems in Hong Kong is practically impossible. In this light, a tool for benchmarking buildings is necessary for public administrators or urban managers to decide on an appropriate strategy to regenerate the building stock in the city. A first-tier classification system for identifying seriously problematic buildings is lacking in Hong Kong. Although numerous building assessment tools exist around the world, nearly all of them are positioned as protocols for comprehensive or detailed building assessment. For example, around 380 assessment parameters exist in the Intelligent Building Index Version 3.0, and the evaluation of numerous parameters necessitates stimulation or laboratory testing (Asian Institute of Intelligent Buildings 2005). Most of these tools target new developments, predominantly nondomestic buildings. Although the Housing Health and Safety Rating System introduced by the British Government is tailored to existing housing, its

Table 2. Building Factors Assessed under the DI and their Relative Weightings Level 1



Weight (%)





Level 2



Level 3

Weight (%)

Health and hygiene


Fire safety


Structure and fabrics


Incompatible uses


Responsibility delineation Evaluation and documentation

8.39 4.36

Planned maintenance and operations Emergency preparedness


Financial arrangement





Cleanliness Drainage Plumbing Exit routes & accesses Fire compartmentation Services & hazards Structural safety Unauthorized appendages External building elements Dangerous trades Wet market Deed of mutual covenant Record drawings Incident records Resident survey Regular inspection Daily operations Emergency plans Fire drills Insurance policy Maintenance reserve

Weight (%)a 3.49 5.00 2.79 8.11 5.22 4.21 11.71 4.50 5.53 3.48 1.68 8.39 1.93 1.31 1.12 9.28 4.93 4.09 3.03 4.22 6.00

Because of the round-off problem, the sum of the weights is equal to unity. JOURNAL OF URBAN PLANNING AND DEVELOPMENT © ASCE / JUNE 2012 / 3

because they affect the likelihood of a building to perform well. To put it another way, if the homeowners know their rights and responsibilities, the building structure and services are regularly inspected and resources to finance repair or remedial works are adequate, the building is more likely to be well-serviced and kept in good condition. In other words, the Management branch gives an indication of the proneness of an assessed building to dilapidation or dereliction in the future. The weightings of the building factors were assessed by an expert panel by using the analytic hierarchy process (AHP). The panel consisted of 48 local building-related experts and experienced practitioners. Before the commencement of the AHP interviews, the participants received clear instructions on the pairwise comparison process and definitions of the key terms in the questionnaire. They were also allowed to ask questions to resolve any doubt. These procedures were crucial so as to ensure that all the respondents had a common understanding of the building factors being weighed. As Table 2 shows, the AHP computer package 5 Expert Choice 11.5 extracted the factor weightings from pairwise comparisons of the relative importance of all the pairs of factors under the same category or branch in the hierarchy. One of the most attractive merits of the AHP is the checking of the internal consistencies of each interviewee’s answers (Saaty 6 1980; Lee and Chan 2007). Inconsistencies might occur for various reasons such as random judgments and human errors. The interviewees were asked to revise their answers if inconsistencies were spotted. If an interviewee still failed to achieve the acceptable internal consistency ratio recommended by Saaty (i.e., 0.1) after revising the inputs, their responses would be omitted for the subsequent AHP analysis. The weighting of each building factor can be acquired by averaging out the weightings of that factor derived from all consistent responses. Fig. 1 and the Appendix show the detailed procedures of the AHP interviews and the mathematical operations of the AHP technique, respectively. To make the factor evaluation easier and more consistent, the DI framework breaks down some building factors (Level 3) further into some measurable or easily assessable parameters (Level 4), and the building assessors use predetermined scoring tables to assign factor or parameter ratings. In the DI assessment framework, the rating of each building parameter or factor falls on a continuous scale ranging from 0 (for best practice) to 100 (for the worst practice). The best practice is set with the reference to the highest standards available currently or in the near future, including those proposed by the government, professional institutes, and relevant international guidelines. For instance, despite no statutory requirement to perform regular fire drills, the Fire Services Department and Home Affairs Department advise the building owners in Hong Kong to conduct fire drills at least once a year (Ho et al. 2008). The fulfillment of this recommendation implies the best practice and will be rewarded with a rating of 0 for the respective building. This study determines the worst practice with reference to the minimum standard required by the law or trade practice. For the rating of intermediate cases, this study adopts linear interpolation. For example, the rating of the unauthorized appendages is zero if no small-scale unauthorized building work (UBW) is found on the external walls, reentrants, and light-wells in the observed buildings. However, the study considers a ratio of the number of small-scale UBWs on the aforementioned parts to the number of dwellings in the building equaling or exceeding 2 as the worst scenario with a rating equal to 100. For a ratio equal to 1, the rating is 50. Table 3 illustrates the details for unauthorized appendages. When the building factor is qualitative in nature, a different method determines intermediate cases. The binary building factor (i.e., the presence or absence of a certain condition or

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the assessment framework is kept as simple as possible. Only those factors or parameters that are conducive to building dilapidation are included. In other words, the framework excludes other factors (e.g., energy efficiency and building automation) because they have little relevance to building dilapidation. Table 2 demonstrates the building factors to be assessed and their relative weightings. For the construction of the DI, an expert panel of members who specialize in building assessment in Hong Kong selected a total of 21 building factors. With an eye to a quick broad-brush building benchmarking, only common parts of buildings are assessed. This confinement is sensible as homeowners are willing to invest in the improvements of their own dwelling units but reluctant to do the same for the common parts of their buildings. Given the public good nature of the outcomes of building care (e.g., safer living environment and shorter downtime), homeowners tend to free-ride on others’ efforts in the upkeep of the common parts (Yau 2011). In general, therefore, the common areas should show most of the physical problems in a private residential building, and their conditions can be taken as a good proxy of the overall degree of dilapidation or physical fitness of the building. For the convenience of dilapidation attribution analysis, the panel hierarchically structured and grouped these selected building factors (Level 3) into nine main categories (Level 2): 1. Health and Hygiene: evaluates the existing hygienic conditions and fitness in a building; 2. Fire Safety: refers to the conditions of the fire safety provisions (e.g., escape routes, fire compartments, and fire service installations) and the existence of fire safety hazards in a building; 3. Structure and Fabrics: refers to the physical safety of the building structure and appendages; 4. Incompatible Uses: concerns whether the usage of the properties of a building or its immediate external environment create health and safety hazards for its occupants; 5. Responsibility Delineation: examines whether the rights and responsibilities of the homeowners regarding the management of the common parts of a building have been clearly delineated; 6. Evaluation and Documentation: refers to the carrying-out of occupants’ evaluation of the building performance and the keeping of documents that are useful for the management and maintenance of a building (e.g., record drawings); 7. Planned Maintenance and Operations: concerns operational issues such as daily management tasks (e.g., cleansing and refuse disposal) and maintenance standards for a building; 8. Emergency Preparedness: indicates the ability of the building occupants or management to deal with emergency situations such as fire outbreaks or epidemics; and 9. Financial Arrangement: refers to the financial ability of the homeowners or building management to pay for planned works (e.g., route maintenance and repair) and unplanned circumstances (e.g., damages to third-party victims of buildingrelated accidents). These nine categories are further classified under two umbrellas (Level 1). Building factors in categories such as Health and Hygiene, Fire Safety, Structure and Fabrics and Incompatible Uses are called Conditions factors because they measure different aspects of the existing conditions of the buildings under assessment. Although the conditions of a building deteriorate over time because of natural wear and tear, they are also subject to the degree of building care the homeowners initiate. The Conditions factors collectively indicate the state of conditions or degree of dilapidation of a building as of the day of assessment. On the other hand, Responsibility Delineation, Evaluation and Documentation, Planned Operations and Maintenance, Emergency Preparedness and Financial Management belong to the Management umbrella


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Fig. 1. Procedures of the DI interviews [adapted from the procedures of BHHI and BSCI in Ho et al. (2008)]

practice) has no immediate case with the rating of either zero or one. Table 4 presents an example of rating a multinomial building factor. For this type of factors, the study clearly explains and describes the meaning of each rating to ensure the consistency among the building assessors. The clear definition of what a rating

means enables more straightforward judgments for both quantitative and qualitative criteria.

Assessment Procedures and Data Procedures in Building Assessment

Table 3. Rating scale for Unauthorized Appendages (Quantitative and Continuous in Nature) Rating 0 25




Description No nonactionable UBW on the external walls, reentrants, and light-wells in the building is observed. The ratio of the number of nonactionable UBWs on the external walls, reentrants, and light-wells to the number of dwellings in the building equals 0.5. The ratio of the number of nonactionable UBWs on the external walls, reentrants, and light-wells to the number of dwellings in the building equals 1. The ratio of the number of nonactionable UBWs on the external walls, reentrants, and light-wells to the number of dwellings in the building equals 1.5. The ratio of the number of nonactionable UBWs on the external walls, reentrants, and light-wells on the number of dwellings in the building equals or exceeds 2.

The DI framework assesses building factors through four main processes. First, desk study offers valuable background information on the buildings under investigation to the assessors. Government departments’ websites provide information (e.g., the age and development scale) on the target buildings. What follows is the on-site visual inspection of the conditions of the buildings and their surroundings. Upon arrival at a building, the assessors start the inspection from the roof, which is a strategic location for inspecting certain parts of a building, such as its light-wells and reentrants, which cannot be easily seen from other angles. Then, the assessors inspect the building’s interior, including lift lobbies, corridors, and staircases, floor by floor starting with the top floor. After the internal building inspection, they survey the facades, external works, and surroundings of the building. If necessary, aiding tools like binoculars and measuring tapes are used. Throughout the inspection process, the assessors record the findings such as locations and sizes of concrete spalling, and materials and conditions of drainage pipes by using a standard inspection form (see Fig. 2 for the items included). The whole visual inspection generally lasts approximately 1.5–2 h, depending on the scale of development. Photographs are taken during the inspection for recording purposes.


Table 4. Rating Scale for Fire Door Conditions (Qualitative and Nominal in Nature)

Survey Findings and Performance Analysis

Semantic rating

Results of the Physical Building Assessment





Above average




The fire doors intercepting the exit staircases and their protected lobbies are kept in place and in fair condition; and not the cases below. The fire doors intercepting the exit staircases and their protected lobbies are wedged open frequently; and not the cases below. The fire doors intercepting the exit staircases and their protected lobbies are unable to close tightly or there are gaps in the door sets exceeding 4 mm; or the fire doors intercepting the exit staircases and their protected lobbies do not self-close; and not the cases below. The glazing of the fire doors intercepting the exit staircases and their protected lobbies has cracked; and not the case below. Any fire door intercepting the exit staircases and their protected lobbies has been damaged, perforated, removed, or replaced by a non fire-resistant door.




DIk ¼

n X

wH;i F H;ik



As the DI operates like a penalty point system, each building factor receives a rating ranging from 0 (for the best scenario) to 100 (for the worst scenario). After rating aggregation, each building’s DI also ranges from 0 to 100. The raw data the trained assessors gathered were transformed into a set of performance indicators representing the existing level of dilapidation of each building factor illustrated in Table 2. Fig. 4 and Table 7 present the results of the physical building assessment of the whole sample. The DI score ranges from 7.77 to 80.26, with a mean of 47.44 and a median of 49.91, and its distribution is left-skewed. On the whole, buildings in Sham Shui Po were found the most problematic among the four districts. The average DI score for buildings in Sham Shui Po is 51.24. On the other hand, buildings in Wanchai performed quite well, with an average score of 41.29, largely because of the younger ages of the assessed buildings in that district. Central and Western has the highest variability in the DI score (σ ¼ 14:78). As Table 7 shows, the DI scores of the assessed buildings could differ at most by 72. Faced with this large variation in building dilapidation, the public and homeowners of the dilapidated buildings would like to know the underlying reasons. It is beneficial for them to know whether they can improve the situation and the best way to make such an improvement. To start with, the study should examine the dilapidation attribution between the two branches (i.e., Conditions and Management). As Table 8 shows, the Management subscore has a larger variation, in terms of standard deviation, than the Conditions subscore. Yet, this statistic may not be able to explain the two branches’ attributions to the overall DI score. In this regard, the study should conduct a variance decomposition analysis to reveal the relative effects of Conditions and Management on the dispersion of the DI score.

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From the principles and scopes of assessment laid down previously, the DI can act as a tool or protocol for benchmarking private apartment buildings with respect to their existing level of dilapidation and proneness to dilapidation in the future. To compute the overall dilapidation, DIk , for building k, one simply needs to aggregate the ratings (F H;ik ) and weightings (wH;i ) of all n building factors as follows:

In parallel with the on-site inspections, the trained assessors interview building management staff and/or residents by using a preset questionnaire (see Fig. 3) to acquire information on the management practices of the buildings (e.g., the frequencies of refuse disposal and fire drills). In cases of doubt, documentary records will be inspected for verification purposes. Finally, the data obtained from the aforementioned processes are consolidated to compute the DI of the assessed buildings. Descriptions of Buildings Assessed

In 2008, the study randomly selected and assessed 393 multistorey residential buildings in four districts in Hong Kong—namely Sham Shui Po, Yau Tsim Mong, Central and Western, and Wanchai—because they cover the target areas the Urban Renewal Authority (URA) set out for action prioritization (Planning and Lands Bureau 2001). 111 (28%) buildings came from Sham Shui Po, 114 (29%) from Yau Tsim Mong, 128 (33%) from Central and Western, and 40 (10%) from Wanchai. Tables 5 and 6 summarize the characteristics of these assessed buildings by district. The oldest and youngest buildings in the study were both located in Yau Tsim Mong (67.3 and 3.8 years, respectively). The average age of the assessed buildings was 32.6 years. On average, the assessed buildings in Sham Shui Po were the oldest (33.6 years old) with those in Wanchai the youngest (27.0 years old). The average number of storeys and flats in the assessed buildings was 10.6 storeys and 38.2 units, respectively. A total of 159 buildings (41%) were not managed by any incorporated owners (IO) or a property management company (PMC). Among the 111 assessed buildings in Sham Shui Po, more than half (51%) had no form of building management. In Wan Chai, only 24% of the assessed buildings did not have any form of building management.

Performance Attribution By definition, the DI score is the weighted arithmetic mean of the ratings of all the dilapidation-related factors of a building. Because the building factors come under the Conditions and Management branches in the DI hierarchy in Fig. 1, the weighted average of the respective Conditions Index (CI) and Management Index (MI) gives the overall DI score of a building. Mathematically DIk ¼ wC CIk þ wM MIk


where wC and wM = weightings of the Conditions and Management branches, respectively. The DI and MI scores are also computed in a similar fashion to Eq. (1). It follows that the total variation in the DI score is attributable to: (1) the variation in CI score, (2) the variation in MI score, and (3) their comovements. The following equation can, therefore, express their relationships: VðDIk Þ ¼ w2C VðCIk Þ þ w2M VðMIk Þ þ 2wC wM CovðCIk ; MIk Þ ð3Þ




Information to be recorded

Accessibility of the roof

Accessible or inaccessible

Roof-top structure(s)

Number and sizes

External wall finishes

Cladding (Conditions - rating scale refers) Tiles (Total area of debonded tiles)


Rendering or paint (Total area of spalling and detachment) Conditions of approved canopies

Rating scale refers

Unauthorized appendages








extensions, flower racks, drying racks, metal frames, support


Plumbing and

frames for air-conditioner, metal cages and advertisement signs Hygiene conditions

Rating scale refers

Plumbing system

Materials used for the communal supply pipes and conditions (rating scale refers)

Drainage system

Materials used for the communal downpipes and conditions (rating scale refers)

Exit routes

Minimum width of each staircase and corridor; minimum headroom of the exit route; conditions of the exit routes and accesses (rating scale refers) Conditions of the fire doors (rating scale refers); presence of


Fire resisting construction

Fire services installations

Conditions of the breakglass units, fire hydrants and hose reels

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unauthorized openings to staircase enclosures

(rating scale refers)

Structural safety

Locations and areas of concrete spalling; locations, widths and


lengths of structural cracks

Conditions of windows

Rating scale refers

Conditions of wiring

Rating scale refers

Hygiene conditions

Rating scale refers

Incompatible uses

Presence of dangerous trades in the building; presence of wet

market on the ground floor of the building

Fig. 2. Items to be recorded in the building inspections

where Vð:Þ and Covð:Þ = variance and covariance, respectively. Let T be the total variance such that T ¼ VðDIk Þ. The relative importance of each component is given by the following: the percentage of variation purely because of Conditions factors ¼ w2C VðCIk Þ∕T


the percentage of variation purely because of Management factors ¼ w2M VðMIk Þ∕T


the percentage of variation because of their co-movements ¼ 2wC wM CovðDIk ; MIk Þ∕T

Conditions factors and Management factors play nearly equal parts in differentiating the well-performing buildings from the dilapidated ones. In other words, a balanced view of the two aspects is important to the sustainable management of the building stock in the city.


The Venn diagram in Fig. 5 summarizes the results of the variance decomposition analysis. Pure Conditions factors contributed 31.79% of the variations in the DI and pure Management factors contributed 31.86% to the total variation, suggesting that

Discussions As aforementioned, the DI score can indicate how a building performs. This information can, in fact, facilitate the government or other organizations to allocate resources efficiently to the most needy buildings or areas. The use of the DI framework to benchmark individual buildings in this study can be extended to areabased or district-based benchmarking. In principle, the aggregation of the DI scores of all individual buildings within a local area can give the area’s DI score. This information will be very useful for the public sector in prioritizing their area-based actions such as comprehensive redevelopment or area revitalization. Furthermore,




As-built or record

Architectural or general building plans only


Evaluation and


Building services plans only Both

Incidence records


Safety-related issues (e.g. falling objects, lift failure and blackout) only Health-related issues (e.g. bursting of pipes or water stoppage) only Both


Regular tenant

Hygiene issues (Once every __________)

can choose more than


Safety issues (Once every __________)

one item

Regular inspection

Structural conditions (Once every __________) Electrical installations (Once every __________) Lifts and escalators (Once every __________)

one item

Fire services (Once every __________) and operations

Refuse clearance

Yes (Once every __________)

No / Carried out

irregularly Pest control

Yes (Once every __________)

No / Carried out

irregularly Entrance lobbies (Once every __________)

common areas

Lobbies upstairs (Once every __________)

can choose more than

Staircases (Once every __________)

one item


Cleansing of

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Planned maintenance

Fuel supply (Once every __________)

can choose more than

Lifts (Once every __________)



Emergency plans

In case of infectious diseases (e.g. SARS and influenza) only

In case of fire outbreaks and other accidents (e.g. gas leakage) only


Fire drills


Yes (Once every __________)

No / Carried out

Financial Arrangement


Insurance policy

Third party liability





Maintenance reserve ($ _______________)

reserve or fund

Sinking fund ($ _______________)

can choose more than

Special reserve ($ _______________)

one item

Fig. 3. A sample questionnaire for interviews with building management staff and/or residents Table 5. Physical Characteristics of the assessed Buildings in the Four Districts Characteristic


Sham Shui Po

Yau Tsim Mong

Central and western



Building age (years)

Maximum Mean Minimum σ Maximum Mean Minimum σ Maximum Mean Minimum σ

59.3 33.6 4.8 16.5 37.0 8.6 3.0 5.9 370.0 28.9 4.0 40.5

67.3 33.1 3.8 13.5 24.0 11.0 3.0 6.0 410.0 44.7 3.0 66.1

58.3 33.1 4.4 12.7 34.0 11.2 2.0 8.7 267.0 42.0 2.0 54.5

56.2 27.0 10.8 11.1 26.0 12.8 2.0 7.8 108.0 33.7 2.0 29.6

67.3 32.6 3.8 14.0 37.0 10.6 2.0 7.2 410.0 38.2 2.0 53.0

Number of storeys (counts)

Number of units (counts)


Table 6. Modes of Management of the Assessed Buildings in the Four Districts Sham Shui Po

Yau Tsim Mong

Management mode



Both IO and PMC IO but no PMC PMC but no IO No IO and PMC Total

32 19 3 57 111

% 28.8 17.1 2.7 51.4 100.0


38 30 9 37 114

33.3 26.3 7.9 32.5 100.0

Central and western N 37 30 5 55 127





29.1 23.6 3.9 43.3 100.0

11 13 7 10 41

26.8 31.7 17.1 24.4 100.0

Overall N 118 92 24 159 393

% 30.0 23.4 6.1 40.5 100.0


Fig. 4. Distribution of the DI score of all assessed buildings

Statistic Maximum Mean Median Minimum σ Skewness Kurtosis

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Table 7. Summary Statistics of the DI Scores of the Assessed Buildings in the Four Districts Sham Shui Po

Yau Tsim Mong

Central and western



80.26 51.24 56.02 17.55 14.65 0:68 0:59

75.69 48.60 49.38 22.85 12.76 0.01 0:77

78.78 45.04 48.22 7.77 14.78 0:38 0:39

70.27 41.29 39.31 15.73 13.29 0:04 0:60

80.26 47.44 49.91 7.77 14.34 0:33 0:59

a regularly conducted DI survey in Hong Kong can help the local government monitor changes in the conditions of the housing stock and evaluate the effects of the government policies that aim to improve the built environment. From the factor hierarchy shown in Table 2, each building can have DI subscores for the branches Conditions and Management in addition to the overall DI score. The former reflects the existing conditions of a building; whereas, the latter measures the potential for the building to achieve good performance. On the basis of the

building assessment results, Fig. 6 maps the subscores of the 393 assessed buildings in a two-dimensional matrix. This subscore matrix can offer decision-makers insights into the actions they should take to achieve a sustainable built environment. With relatively low Conditions and Management subscores, the buildings mapped in Quadrant A do not suffer from a high degree of dilapidation nor do they have a high potential of running down in the near future. Take Building 75340 as an example (see Fig. 7). The interiors and exteriors of the building were well-conditioned. 7

Table 8. Summary Statistics of the DI Sub-Scores of the Assessed Buildings Statistic Maximum Mean Median Minimum σ Skewness Kurtosis

Conditions subscore

Management subscore

Overall DI score

80.73 31.88 32.41 2.01 14.53 0.18 0:25

100.00 65.67 74.68 12.85 18.30 0:56 0:57

80.26 47.44 49.91 7.77 14.34 0:33 0:59

Fig. 5. Contributions of the conditions and management factors to variations in the DI score


Fig. 6. Scatter plot of the conditions and management subscores of the assessed buildings

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In addition, building services were regularly inspected, and management measures like regular resident surveys were in place. In general, buildings in Quadrant A require no special action except for continuing the current good practice of building management. Public resources allocated for these well-conditioned and wellmanaged buildings should be kept to a minimum. For those lying in Quadrant B, their current state of condition is worrisome. With a high potential for eliminating the dereliction, the

government should encourage or coerce the homeowners to undertake improvement works to their buildings by different forms of intervention. For example, if a voluntary building classification scheme is put in place, the performance of different buildings can be readily benchmarked, and properties in better-performing buildings should command a higher value or rental. This provides economic incentives for homeowners to invest in their properties. On the other hand, if the government steps up enforcement against disrepair of buildings, homeowners who voluntarily undertake improvement works to their buildings have a lower chance of prosecution. For buildings with good existing conditions but lacking the potential to maintain their performance for the future (i.e., those buildings in Quadrant C), the government should allocate more resources to educating the homeowners on the importance of building care. In addition, the government can encourage the homeowners to improve the management of their buildings by providing financial subsidies and technical support for the setting up of a homeowners’ association or appointment of a building management agent. At the other extreme, the buildings in Quadrant D are badly dilapidated and lack the potential to achieve good performance in the near future. Building 52645 was a typical example of this type of building (see Fig. 8). On account of the prolonged lack of proper repair and maintenance, obvious defects existed in the 8 building elements such as broken windows, damaged stairs, and 9 concrete spalling. In the absence of management capacity, any efforts paid in the improvement of the building conditions cannot

Fig. 7. Photos of building 75340 10 / JOURNAL OF URBAN PLANNING AND DEVELOPMENT © ASCE / JUNE 2012

f Pr oo Fig. 8. Photos of building 52645

sustain for long periods of time. In this case, the government may need to take an integrated approach to help the homeowners of these buildings. On one hand, the government or other public organizations have to take the lead to carry out the necessary work on the buildings to eliminate the building dangers and improve the living environment. On the other hand, the government should make use of the statutory power conferred by the Building Management Ordinance (Chapter 344 of the Laws of Hong Kong) to require mandatorily the formation of an IO and/or the appointment of a PMC for these buildings. Alternatively, it may also con10 sider redevelopment as a last resort for “upgrading” buildings of this kind. As is evident, the subscore matrix in Fig. 6 can achieve more informed decision-making with respect to the sustainable management of building stock, not just in Hong Kong but also globally.

Concluding Remarks Although urban renewal can help eliminate, or at least moderate, the problems of urban decay in a city, different approaches could create different effects on the local community and the society as a whole. The interests in economic, social, physical, and other aspects have to be balanced in due course. In this light, a need exists for more informed decision-making on the issue of urban renewal. In Hong Kong, the high-density, high-rise development mode gives the city a unique skyscraper identity. However, this compact

environment also creates far-reaching public health and safety hazards if the built environment does not function well. As shown by the official statistics, the number of buildings past their intended design lives in the territory will grow quickly in the near future; the building stock is at risk of decay or dilapidation. Therefore, this challenge has to be addressed properly without further delay for the sustainable management of the building stock in Hong Kong. The DI assessment framework developed in this study can help the stakeholders of building sustainability, including the government, homeowners, developers, and the general public, to benchmark the degree of and proneness to dilapidation of buildings in Hong Kong and many other high-rise cities. Although the study used the DI framework to assess buildings in a geographically discrete manner, its application to a large number of buildings in a particular district or region can give outcomes with more practical insights. For example, the DI scores (or the subscores) of buildings can be aggregated to give dilapidation scores for street blocks or tracts. Mapping such information into a geographical information system can easily identify problematic buildings or areas for different appropriate actions. In addition, the degree of concentration of dilapidated buildings or areas can be an indicator of inequality in the building quality in a city. It also facilitates further research on the relationship between building dilapidation and health problems. For governments or public organizations (e.g., the URA in Hong Kong and the Urban Redevelopment Authority in Singapore), the DI framework can serve as a policy tool for selecting target buildings or areas for a wide range of actions such as


redevelopment, enforcement against building disrepair, and education. The importance of this application becomes more noticeable especially during the times of financial stringency facing governments in many jurisdictions (Ho et al. 2005). The information obtained from a territorywide evaluation allows screening of problematic buildings. Moreover, it is possible to evaluate the effects of government policies (e.g., incentive schemes for building maintenance) through longitudinal studies on the DI results. Public bodies, housing associations, community-based organizations, or private developers engaging in redevelopment projects can employ the DI to justify that their applications for the exercise of eminent domain or compulsory acquisition stand from the viewpoint of public interest. Homeowners can also make their maintenance and repair decisions on the basis of the DI assessment results. Once the results of DI assessments on a critical mass of buildings are released to the public, value differentials may be created between properties in well-serviced areas and run-down ones. The market forces can then foster a culture of building care among homeowners. This market-driven approach is, in principle, a more costeffective, environmentally friendly and socially desirable way to arrest urban decay in high-rise cities.

Appendix. Mathematical Operations of the AHP

A0 w0 ¼ λmax w0


It may be shown that λmax ≥ λ. The deviation of the principal eigenvalue λmax from λ is used to define an internal consistency ratio (CR) as follows: CR ¼


where CI = consistency index which is defined by λ λ CI ¼ max λ1



and RCI is a figure computed by averaging CI over a large number of random comparison matrices. Normally speaking, CR smaller than 0.1 is considered acceptable because this is close to the situation λmax ¼ λ when the comparison matrix A is totally consistent (Saaty 1980).

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This appendix details the computations of factor weightings and consistency ratios by using the AHP. Without the loss of generality, the weights of n factors will be determined. The nonnegative weighting of factor f i ði ¼ 1; 2; 3; …; nÞ is denoted by wi, and the set of weights of the n factors is given by w where 0 1 w1 B w2 C B C B C w ¼ B w3 C ð7Þ B C : @ A : wn

In the consistent case, λ is the only nonzero eigenvalue of A. Nonetheless, inconsistency in A occurs once a change is made to the ratio wi ∕wj . In this situation, multiple eigenvectors and eigenvalues exist. The degree of inconsistency remains small as long as the change to the ratio wi ∕wj is petite, so that the principal (or largest) eigenvalue λmax is close to λ. In this sense, the principal right eigenvector is still a good approximation of w (i.e., the eigenvector in the perfectly consistent situation). Therefore, with ***A;0 which is an expert’s estimate of A, the corresponding weighting vector w0 can be taken as the eigenvector solution of the following equation:

The relative importance of factor f i compared to f j ðj ¼ 1; 2; 3; …; nÞ is measured by the ratio wi ∕wj . For the ease of understanding, the weightings of all factors sum to unity. The right eigenvector method is used to assess the factor weightings in a standard AHP operation. This method is initiated by combining all n possible pairwise column vectors into a comparison matrix A in the following way: 0 w1 w1 w1 1 … ww1n w1 w2 w3 B w2 w2 w2 … w2 C B w1 w2 w3 wn C B w3 w3 w3 C B w1 w2 w3 … ww3n C A¼B ð8Þ C : : … : C B : B C : : … : A @ : wn wn wn … wwnn w1 w2 w3 The upper-right and lower-left triangular blocks are reciprocal, and the diagonal elements in A are equal to unity. Multiplication of A by w yields 0 w1 w1 w1 10 1 … ww1n w w1 w2 w3 B w2 w2 w2 … w2 CB 1 C B w1 w2 w3 w n CB w2 C B w3 w3 w3 C w C … ww3n CB B A w ¼ B w1 w2 w3 ð9Þ ¼ λw CB 3 C : C : : … : CB B : C B CB @ A : : … : A : @ : wn wn wn wn … wwn w w w 1




The authors gratefully acknowledge the financial support provided by the Research Grant Council of the Hong Kong Special Administrative Region (Project No. 7009-PPR-4), which made this research possible. An earlier version of this paper was presented in the SB10 Conference in Madrid in April 2010. The authors would like to thank the reviewers and the delegates of the conference for their valuable comments and suggestions, which have brought improvements to this paper.


The following symbols are used in this paper: AHP = analytic hierarchy process; AHS = American housing survey; BHHI = building health and hygiene index; BSCI = building safety and conditions index; CI = condition index; DI = dilapidation index; EHCS = english house condition survey; IO = incorporated owners; MI = management index; PMC = unauthorized building work; and URA = urban renewal authority.



where w = right eigenvector of A with an associated eigenvalue λ.

Asian Institute of Intelligent Buildings. (2005). Intelligent Building Index Version 3.0, Asian Institute of Intelligent Buildings, Hong Kong.


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