What is obsolescence? Numerous older buildings have been demolished due to being labelled as obsolete. There is a general understanding that buildings, similar to machinery and durable consumer goods, should be demolished and replaced when they become obsolete. The truth of this assertion is examined and found problematic, as obsolescence is not clearly understood in conceptual or practical terms. Obsolescence presents a serious threat to built property as it rarely accounts for the immobile, long lasting and (financial and natural resource) capitalintensive characteristics of property, nor its societal and cultural significance. Minimizing obsolescence and extending longevity are therefore indispensable for maintaining the physical, economical and societal investments. The characteristics and symptoms of obsolescence are explored specifically to address how can buildings be diagnosed and when and to what extent is demolition an unavoidable consequence. A theoretical/conceptual model is developed which allows for different kinds of obsolescence to be characterised and distinguished. The model distinguishes between physical and behavioural factors and between endogenous and exogenous factors. It also accounts for the often inverse relation between the increase of complexity of types of obsolescence and the decrease of the owner's possibilities to manage it. Through the provision of an interrelational approach, the model explains why obsolescence occurs and it can be used as a basis for structuring an evidence-base on obsolescence.

The choice between replacement and life cycle extension of existing buildings implies a vital but very difficult decision, involving a wide range of aspects and affecting contradictory and often conflicting interests. Originally, building quality and public health played a decisive role in improvement of the housing stock, mainly by slum clearance. More recently, functional and economic considerations tend to dominate the decision-making, resulting in increasing demolition and demolition waste. Although environmental aspects (e.g. energy consumption and building waste) are of growing importance, sustainability does not seem to be a major aspect in the choice between demolition and life cycle extension until now. To address the questions of what is more sustainable: replacement or life cycle extension, the decision-making processes surrounding housing demolition in the Netherlands are analysed and a conceptual framework is created. Sustainability has the potential to be a major criterion in housing stock management and, in particular, on the decision processes about dwelling replacement or life cycle extension. From that point of view, life cycle extension is often a better solution than demolition.Le choix entre le remplacement de bâ timents existants et la prolongation de leur cycle de vie implique une décision cruciale, mais très difficile, portant sur des aspects très divers et affectant des intérêts contradictoires et souvent conflictuels. A l'origine, la qualité des bâ timents et la santé publique jouaient un rô le décisif dans l'amélioration du parc de logements, principalement par l'aménagement des quartiers insalubres. Plus récemment, les considérations fonctionnelles et économiques tendent à dominer le processus de prise de décision, ce qui entraîne un accroissement des démolitions et des déchets de démolition. Bien que les aspects environnementaux (par ex. consommation d'énergie et déchets de bâ timents) prennent une importance croissante, la durabilité ne semble pas être, jusqu'à présent, un aspect essentiel dans le choix entre démolition et prolongation du cycle de vie. Afin de traiter la question de savoir ce qui est le plus durable -le remplacement ou la prolongation du cycle de vie -les processus de prise de décision entourant la démolition de logements aux Pays-Bas sont analysés et un cadre conceptuel est créé. La durabilité pourrait bien devenir un critère essentiel dans la gestion des parcs de logements et, en particulier, dans les processus de prise de décision relatifs au remplacement des logements ou à la prolongation de leur cycle de vie. De ce point de vue, la prolongation du cycle de vie est souvent une solution meilleure que la démolition.

As a result of changes in housing policy in the 1990s, social landlords in the Netherlands operate largely independently from the government. Without direct financial support, with less government regulation and decreasing demand for social housing, they are adopting a market-oriented approach in housing management. In doing so, they may use methods from 'commercial' business theory. This paper focuses on the method of portfolio analysis and answers the question how this method can be used by Dutch housing associations. On first sight, the usefulness of the classic forms of portfolio analysis known from business theory seems to be limited. These analyses put emphasis on financial performance, which is not conclusive for social landlords, and on diversification while housing associations have little possibilities to diversify out of housing. However, financial performance has become more important for the Dutch housing associations since they have to operate without direct financial government support. Furthermore, Dutch housing associations manage a wide variety of dwellings, so the analysis can be useful to diversify within their residential portfolio. The usefulness of the method may improve by using portfolio analyses which have been specifically designed for housing management, but will remain restricted. At a strategic level in the organization the method offers general directions for strategies to follow but does not offer conclusive actions that should be taken. Furthermore, there will always be discussion about the performance measures that social landlords should use, and in particular about how they should weigh social and financial performance against each other. For social housing managers, it might be best to use classic forms of portfolio analysis as a mirror for their decisions. If they choose a path differing from the one suggested by the portfolio analysis, they have to explain why, referring to their social objectives.Social Rented Housing, The Netherlands, Housing Management, Portfolio Analysis,

In Chile, social condominiums are a significant part of housing for low-income households. After decades of occupancy, this housing stock shows signs of rapid deterioration and devaluation due to neglected maintenance. Given the weak governmental support in management practices, third sector organisations are positioning themselves as alternatives to providing technical solutions and contributing to the enhancement of opportunities and capacities among communities that live in deprived areas. However, little is known about the dynamics between these organisations and the communities they work with as well as their interactions with their institutional environment in the context of improving condominium management practices. Employing concepts of intermediation and institutionalisation, we analyse the practice of the organisation Proyecto Propio. We describe the dynamics of the intermediary role as implementer of housing policy and catalyst of social innovation, and the institutionalisation of these practices. The main characteristic of their intermediary role in condominium management practices is a holistic approach as implementer and catalyst for complex interventions, situating the users at the centre of the process. The main challenges are related to institutionalisation: the inclusion of more incentives to scale up and consolidate the third sector as a relevant actor in housing and condominium management.

Purpose – In previous research publications the authors combined the available knowledge about obsolescence in a conceptual model for further research on and appliance in the decision making about demolition. Since evidence-based theoretical research references on obsolescence are rare, the model inevitably had an explorative character. The purpose of this paper is to test and elaborate the model. Design/methodology/approach – A series of case studies were conducted in various residential building estates. In each estate the types of obsolescence (according to the model) and their interrelationships were identified. Findings – The model can usefully be applied; it enables the determination of types of obsolescence. The case studies also show that several types of obsolescence occur simultaneously, and that these types can be interrelated. This touches upon the complexity of cause-effect mechanisms as already mentioned in the introduction. One of the weaknesses is that information is sometimes available for only one point in time, and that the availability of information varies with the type of obsolescence. Research limitations/implications – The study is based on a limited selection of case studies. Further, the causal relationships between the types of obsolescence could not always be revealed. Practical implications – The current model does not distinguish between causes and effects. For further development of the model, cause-effect processes have to be further analysed. Social implications – Actual measurement of the extent of obsolescence per type is not part of this study, but has to be carried out before social implications can adequately be indicated. Originality/value – The paper presents a conceptual classification of obsolescence that turns out to be workable when tested in practice.