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Currently, the built heritage presents clear signs of degradation, requiring in some situations an urgent intervention. The majority of defects can be avoided or mitigated at the design and execution stages, but the designers and stakeholders often neglect the maintainability of the buildings and components, thus compromising their performance and durability. It is thus necessary to adopt an integrated approach during the buildings life cycle, evaluating their performance over time, the influence of the degradation agents and mechanisms on their durability and service life, and the adoption of cost-effective maintenance strategies. In this sense, it is crucial to use quantitative information related with the performance of building components over time. This study intends to respond to this need by proposing a methodology for the service life prediction of pitched roofs’ ceramic claddings, which are the most common type of roofing system adopted in Portugal and in many countries around the world. These elements are one of the most vulnerable in a building, more exposed to the degradation agents, and with a higher incidence of defects. The method proposed is validated based on a visual inspection campaign, performed in 85 buildings and 146 claddings located in Portugal, with a total area of 43,991.6 m2. Various degradation patterns are established based on the roofs’ characteristics, evaluating their influence on the roof claddings’ service life. The proposed methodology allows obtaining coherent results, providing relevant information regarding the pitched roofs ceramic claddings’ service life, aiding the adoption of rational and integrated maintenance strategies.

The main goal of this study is to predict the service life of external paint finishes and contribute to the subject of construction elements´ durability. The service life is estimated using the factorial method proposed by ISO 15686, since, despite some criticism, this method excels as a simple and efficient tool with great potential for use in the planning of maintenance operations. The model proposed is based on a field survey of 323 coatings. The factor method estimates the service life of building components by multiplying their reference service life by weighting values applied to several factors affecting the performance of the elements under study. In this study the durability factors are obtained through iterative simulations. The results are analysed based on a set of criteria and statistical indicators. The results are suitable and reliable for most of the deterioration variables considered and the factor method proves to be an efficient tool to evaluate the service life of external paint finishes. This work is intended as a contribution and reference for future developments within the subject of durability in the construction industry as knowledge on the performance of given materials or constructive systems over time allows estimations of when to invest in maintenance/repair and of the amount of resources that will be required.

This paper describes and summarizes the various models previously applied to service life prediction of rendered facades. The main methodologies are divided in four categories: (i) deterministic methods; (ii) factorial methods; (iii) stochastic methods; and (iv) artificial intelligence based models. The estimated service life obtained through these models is analysed and the models compared. The predictive ability of the models is also examined and, using ROC curves, the sensitivity and specificity of the models is analysed, evaluating the accuracy of the models in the classification of the case studies that have or have not reached the end of their service life. This study addresses a comparative analysis of the service life prediction models, regarding the predictive ability of the models, analysing the errors and the probability of failure of each model, the results obtained using the models and their ability to describe the loss of performance of rendered facades.

The knowledge of the service life and durability of building components is paramount to sustainable analysis and decision making since it allows a more rational management of the maintenance of building and provides data for life cycle analysis procedures. Nevertheless, predicting the service life of a building or its components is a complex process with which a number of variables are associated. The main difficulties associated with service life prediction are related to the complexity of the degradation phenomena and to the lack of understanding of degradation factors and mechanisms. This paper aims at establishing a model for the service life prediction of rendered facades using a Takagi–Sugeno fuzzy model. The models proposed include the variables that influence the degradation of rendered facades (render age, render type, building height, facade orientation, exposure to damp, and facade protection level). In this study, the degradation condition of 100 case studies located in Portugal is analyzed based only on in situ visual inspections. The proposed models are able to describe appropriately the degradation of rendered facades and to predict the service life of the sample analyzed.

In the summer of 2015, the existing ceramic cladding of the Girasol Building in Madrid went through an inspection campaign that left all underlying occurrences of detachment exposed. The community of neighbors then decided to renew the facade, therefore marking the end of the service life (SL) of the cladding. A visual assessment of the facade was thus made in order to quantify its overall condition after 49 years of SL. These data are used to provide real life feedback and discuss existing methods of SL estimation. The information gathered confirms that 50 years (or 100 aging cycles) are accurate estimations for the SL of ceramic claddings for a 20% level of degradation. Conclusions are also reached regarding the relationship between SL, threshold limits, and their dependency on human decision making processes.

The last few years have seen expressions of concern about the sustainability of construction from all actors in the sector. The durability of the materials used has, in particular, been mentioned as a determining factor in increasing the service life of structures and consequently in reducing energy consumption and environmental impacts as a whole. With the introduction of new products and/or the adoption of new constructive techniques it has become necessary to develop the fields of durability and service life prediction of construction products, with the purpose of evaluating their performance throughout their life cycle. A model to estimate the service life of natural stone claddings is put forward, based on the factor method initially proposed by the Architectural Institute of Japan. This method involves the appraisal of the degradation phenomena in stone claddings under real use conditions, through a field survey. 269 stone claddings located in Portugal were analysed. The factors that affect the durability of natural stone claddings were examined. The quantification of the factors affecting the durability of stone claddings is affected by some subjectivity. Therefore it does not seem viable to propose standard values that can be applied in all circumstances. Analysis of the scenarios proposed for that quantification shows that the use of generic values for durability factors, such as those in ISO 15686:2000, does not lead to the best results. The best solution is to adopt durability factors adjusted to the reality of the phenomenon to be modelled at a regional or local scale. This is a first approach to applying the factor method to estimate the service life of natural stone cladding. It is considered that the method proposed shows very promising results, though it still needs to be supplemented, particularly in terms of the comprehensiveness of the sample.

The durability of constructions is essential to the quality of life in urban spaces. Recently there has been a growing concern of the construction stakeholders with the durability of the materials used and construction sustainability. In this study, using a multinomial logistic regression technique, a probabilistic analysis of the degradation condition of rendered facades, as a function of age and type of mortar, is performed. The probability of the rendered facades reaching the end of their service life, i.e. the moment after which they no longer comply with the minimum performance requirements, is also evaluated. To that purpose, a sample of 100 case studies located in Lisbon, whose degradation state is determined by in situ visual inspections, is used.

The main goal of this paper is to establish a method to analyse the progressive failure of external thermal insulation composite systems (ETICS) over time, with the aim of devising a mathematical formula that contemplates the mechanisms of degradation, the type of cladding and the characteristics of the system itself. Apart from the theoretical work, the method is based on field work, which consists of the visual inspection of a sample of buildings under normal exposure conditions. The data obtained in the field survey are processed and converted into numeric indicators to allow identification of the degradation patterns and estimation of a reference service life for ETICS.

Service life prediction is assuming a primary role as it allows a more rational use of scarce resources; its methods are useful for defining preventive maintenance plans, thereby increasing performance and reducing costs. A new mathematical model is presented that uses artificial neural networks to evaluate the service life of painted surfaces. The data on facade degradation were collected from field observations on 160 buildings (220 painted surfaces) in Lisbon, Portugal, examining several degradation agents. In service conditions, the mean estimated service life of exterior painted surfaces is found to be 9.49 years, with a standard deviation of 0.633 years. Detailed factors are identified and incorporated into the model, which account for variations in degradation. Some statistical parameters are used to evaluate the validity and efficiency of the model. The values obtained are consistent with the existing perception relative to the durability of painted coatings. These values can be used to evaluate t...

An approach to the evaluation of the service life of rendered facades applying statistical tools is described. Using multiple linear regression analysis and artificial neural networks, mathematical models are established to estimate the degradation of this type of coating. To devise the models proposed, a sample of 100 rendered facades was subjected to meticulous field work to determine their condition. Some statistical parameters are used to evaluate the validity and efficacy of the models proposed. The service life of the sample of rendered facades is also evaluated, as estimated by the various models, and the result is expressed in histograms. The usefulness of these models to evaluate complex problems, such as the degradation phenomena of rendered facades, is thus demonstrated.

Buildings and their elements are designed to be used for a certain period of time (their service life), fulfilling all requirements for which they were designed without excessive maintenance costs. However, buildings begin to deteriorate because the instant they are put into use, they begin to show a progressive loss of performance until they become obsolete, having deteriorated beyond minimal acceptable levels or having failed to meet economic expectations. Nowadays, mostly for economic and environmental reasons, there is a growing concern about the durability and service life of buildings. This paper discusses the service life prediction of natural stone claddings using a Takagi-Sugeno fuzzy model. The models proposed include variables that influence the degradation of the claddings analyzed. To obtain the models proposed, samples of 140 and 203 facades were subjected to meticulous field work to determine their condition. The service life of the samples was also evaluated and the influence of th...

An application of a factor method for stone cladding directly adhered to the substrate is proposed. The quantification of the reference service life and of the sub-factors that influence its durability is described. The methodology proposed is based on a survey of the degradation state of 140 cladding systems. As an innovation to the factor method and in order to overcome some of its well-known shortcomings a multiple linear regression analysis is proposed to identify the most relevant sub-factors that explain the degradation of stone cladding.

The use of service life prediction tools can allow a more rational management of the maintenance of a building and its components by supporting reduced life cycle costs of constructed assets. A study was conducted to evaluate the degradation of facades of buildings located in Lisbon, Portugal, and in which visual in-situ inspections of 140 stone cladding facades were completed. Based on this information, different models were proposed to describe the degradation of masonry stone-clad buildings and a novel approach to predicting service life was developed. A description is provided for the use of artificial neural networks to predict the service life of stone cladding of the type that is directly adhered to a building substrate. With the use of artificial neural networks an analytical expression was established to estimate the degradation of this type of cladding system. The viability of this method was then compared with other methods used for service life prediction including multiple linear regression a...

The research presented in this paper is related to the durability of cement renders on facades, based on fieldwork data relative to the condition and extent of degradation of 100 facades of residential buildings in Portugal. Deterioration paths are obtained for staining, cracking, and detachment that show the loss of performance of the facade over time until a critical minimum acceptance level is reached, which is considered an estimated durability limit. These degradation patterns are analyzed individually to confirm whether any of three types of defects can effectively be considered limit states for the durability of cement renders on facades. The combined effect of all the defects that occur is also modeled as a single degradation path, and the expected service life is quantified. The results confirm that detachment constitutes a limit state of cement-rendered facades because it directly affects the physical durability of renders. Staining and cracking alone do not generally tend to signal the end of t...

This paper aims at establishing a model for the service life prediction of natural stone wall claddings directly adhered to the substrate, based on a survey of the degradation state of 142 buildings in the Lisbon area. The state of degradation is evaluated through visual inspections that allow the description of the extent of the cladding area affected by the different anomalies, thereby enabling the level of severity of the anomalies detected to be established. A numerical index of the degradation severity of stone claddings (Sw,rp) is established; this is intended to express the global degradation level of these claddings, thus allowing the study of the evolution of their degradation with time in order to estimate a reference service life for this type of cladding.

Although ceramic tiling on building facades has a history of long durability and service life, a number of service life anomalies in modern buildings have occurred. To identify the factors and address this problem, a method is developed for the service life prediction of adhesive ceramic tiling systems based on a successful model for render and natural stone cladding. The focus is on the applicability of an empirical method of field data collection to this type of cladding that recognizes the complexity of ceramic tiling systems. A hierarchy of defects is defined to establish levels of degradation and identify the susceptibility to errors in design, execution and selection of materials. Results were validated using in-situ visual inspections of 117 tiling systems in Lisbon, Portugal. The aim is to provide a preliminary tool to estimate the durability of ceramic tiling systems and identify influencing factors. Ceramic tiling systems are particularly sensitive to the inadequacy of the materials as well as e...

The purpose of this research is to assess and quantify the environmental effects on cement-rendered facades in real-life service conditions. A holistic approach is proposed based on the assessment of the visual impact of the actual climatic environment that affects the aesthetic performance and durability of 19 cement-rendered facades located in Lisbon, Portugal. Different degradation indicators are presented and a deterioration path is identified, which points out to the possibility of modeling the overall degradation of facades in similar building and environmental conditions. Although the proposed method reflects the Portuguese building context, it can be easily adapted to other countries and expanded to include various cladding solutions, so that their remaining service life can be integrated in the existing commercial methodologies for service life prediction and asset management.

Factorial methods are cost-effective, quick and easy-to-implement methodologies for service life estimation of buildings and their parts. They also stand as the underlying principle of the International Standard Organisation ISO-15686 for service life planning. However, few guidelines exist on how to relate real-life deterioration phenomena to quantified durability values for use within factorial methods. This paper describes a methodology to quantify the ‘reference service life’ and its modifying durability factors for cement-rendered facades based on fieldwork data of 150 cases located in Portugal. The methodology proposed relies on regression analysis of the overall degradation level of the cases assessed. The results obtained are used as a reference set of data for the statistical benchmarking of five different scenarios for the quantification of modifying durability factors of cement-rendered facades. Although the values obtained relate to a specific building element and material, on the one hand, an...

The degradation of building materials occurs as a stochastic phenomenon. Service life prediction methods are usually divided into deterministic, stochastic, and engineering methods. Deterministic models are simpler and easier to use, but are unable to capture the random nature of the degradation phenomena. On the other hand, stochastic models are more complex but very efficient in dealing with the uncertainty associated with a building’s performance. In this study, a stochastic approach to the factor method is proposed to predict the service life of rendered facades. The model proposed is based on a survey of the degradation state of 85 rendered facades located in Portugal. The factors that affect the durability of this type of coating are identified and translated into probability distributions. This analysis leads to coherent values, revealing that facades on buildings built with adequate design measures are more durable; facades exposed to adverse environmental conditions are more prone to degr...

This chapter intends to establish the first approach to the service life prediction methods applied to facades claddings, with three main objectives: i) perform an extensive survey regarding the concepts related with the service life and durability of building components, the methodologies and standardization related to this matter; ii) define the information collected during the field-work, to assess the physical and visual characterization and quantify the degradation condition of the claddings analysed; iii) the characterization of the samples collected during the fieldwork.

In this chapter, a comparative analysis of the different proposed models is performed. First the predictive ability of each model is evaluated through the comparison between the values obtained by each model and the data collected in field work, corresponding to the real degradation condition of the facades analysed. In a second step of the analysis, the sensitivity and specificity of each model is evaluated based on ROC curves, to analyse the accuracy of each model to correctly classify the case studies that may have reached the end of their service life. Once the predictive accuracy and the classification capabilities of each model are evaluated, a multi-criteria analysis is performed. This multi-criteria analysis encompasses different criteria that should be taken into account by different stakeholders to choose the best model for a specific application. A sensitivity analysis is performed in order to analyse the best model for distinct decision-making profiles. Based on these analyses, some recommendations are made, referring the advantages and limitations of the models analysed and thus allowing a more rational and informed selection of a service life prediction model as far as the purpose of the model and the profile of the planner and the perspective of the user are concerned.

The degradation of building materials is a complex phenomenon, which starts as soon as construction is concluded, evolves over time, and contributes to end the service life of buildings. In fact, even for identical sets of initial conditions, degradation mechanisms and performance requirements, there are many possible outcomes with different levels of probability. Because of their great exposure to external actions and their role in the protection of masonry, wall coatings on facades are one the elements most subjected to degradation. Painting plays an important role as external coating finishing, nationally and internationally, and is the most frequently used coating in Portugal. In this study an approach to evaluate the service life of exterior surface of painted walls is proposed, based on the evaluation of the degradation state of 220 facades surveyed in the Lisbon area, in Portugal. The influence of the various characteristics of the painted surfaces and of their surroundings on their durability is also analysed. For that purpose, four methodologies are used: (i) deterministic methods; (ii) factorial methods; (iii) stochastic methods; and (iv) computational models. These mathematical models are established to estimate the degradation level of this type of coating and their service life. The predictive ability of the models is examined and some recommendations are made, concerning the advantages and limitations of the models proposed.

Service life prediction assumes a primary role as it allows a more rational use of construction elements. This constitutes a useful tool in the definition of preventive maintenance plans providing an increase in performance. The main objective of this research is the development of a statistical methodology for the service life prediction of external painted surfaces. This research is based on field data collected via a survey of the state of deterioration of in-service buildings. The degradation is defined by a number of factors that together contribute to the deterioration of painted surfaces thus ending their service life. In this study a mathematical model was defined using a multiple linear regression analysis and this enables the coating's deterioration over time to be expressed as a function of various degradation factors. 220 painted coatings were inspected in 160 buildings of varying construction types. Analytical tools were devised to monitor the performance of paint coatings on walls and estimate their service life. This study contributes to the automation of the maintenance of painted facades, allowing a more rational management of the maintenance of buildings, converted into economic and performance gains. First Publish Online: 19 Jun 2015

Exterior wall painting is one of the most widely-used coating solutions in Portugal. It is particularly susceptible to degradation; this affects the quality of public spaces and the image of cities. The study of service-life prediction contributes to a more rational management of the maintenance of buildings. The state of repair of 220 facades in the Lisbon region of Portugal determined through an in-service survey is analyzed. The model proposed to estimate the service life of painted surfaces is a relatively simple method that balances cost and speed, enabling its practical application to any structure. The models obtained enabled degradation patterns to be identified. The method yielded an average (reference) service life of paint coatings of around 10 years. A technoeconomic analysis was then performed that compared various maintenance strategies for a period of time of 20 years, as follows: (1) maintenance every 5 years, (2) maintenance at 15 and 20 years, and (3) maintenance adjusted in acco...