Understanding Building Failures

James Douglas, Bill Ransom

• Publisher: Routledge
• Year: 2013
• Print ISBN: 9780415508797
• eBook ISBN: 9781136448782
• Edition: 4
• Topic: Technology & Engineering
• Subtopic: Construction & Architectural Engineering
• Index: Technology & Engineering

Building defects still continue to plague the construction industry. The lessons learned over the last forty years have not been fully applied. Many new or refurbished buildings still leak or crack. Lack of awareness by designers and installers as to the main mechanisms that trigger such failures remains a problem for the industry.

Investigating and rectifying building failures form a major part of building surveyors' bread and butter work. This book provides guidance on this work for typical residential, commercial and industrial buildings – with advice on how to diagnose a wide range of defects with an emphasis on evidence based practice throughout. It considers both modern and older construction methods, together with new and traditional materials. The particular problems of alteration and renovation work are also discussed.

The first four chapters provide information and guidance on the methodology for investigating failures – how to prepare for and conduct an investigation into a building defect and subsequently diagnose its cause in a logical manner.

This fourth edition has been updated and expanded to cover the latest diagnostic procedures and research. It also includes Appendices and a new Bibliography, and provides an extensive list of books on building pathology and related topics in the UK and North America. It is essential reading for all students and practitioners interested in building surveying and building conservation.

Chapter 1

Introduction to building pathology

Overview

This chapter outlines the principles of Building Pathology. It provides the historical and technological background for the systematic study of building problems.

1.1 Context

1.1.1 Problems of building failures

Most building defects are avoidable: they occur, in general, not through a lack of basic knowledge but by non-application or misapplication of it. Such knowledge seems to become mislaid from time to time. Those with long memories, and those whose business it is to make a particular study of building defects, are often struck by the re-emergence of problems which have been well researched and documented. Certain fundamental properties of materials, such as their ability to move through changes in temperature and moisture, seem to be overlooked and a rash of difflculties occurs. A call goes out for more research but, in truth, all that is usually needed is a good system for the retrieval of information, a better procedure for its dissemination and, most important, the realisation that a search for information is desirable.

Current training in design tends to concentrate on what to do rather than what not to do. A similar situation exists in training in constructional techniques, where the craftsman is instructed how best to undertake a particular operation but, to a lesser extent, in the dangers of deviation from an accepted technique. Understanding of the likelihood of defects through inadequate design or construction is taught implicitly rather than explicitly in most built environment degree courses.

The level and nature of defects in building construction currently encountered suggest that more guidance is required on the avoidance of failures. A need is seen, too, for such guidance to be a positive part of a training curriculum. Indeed, there are good arguments for suggesting that, as the first essential in design and construction is to ensure that the structure provided is stable and durable, specific education in the avoidance of failure should be a major part of any design and construction syllabus.

The purpose of this book is to provide such positive guidance in a suitably compressed form. It does not set out to describe every possible way in which a building may become defective: such a task would scarcely be possible and certainly would not be particularly helpful. It seems better to aim at identifying the principal defects and their causes which, if wholly eliminated, would prevent the great majority of the defects which currently occur, save occupants of buildings much annoyance and discomfort, and reduce the national bill on maintenance and repair by scores and, possibly, by hundreds, of millions of pounds annually.

The book aims to identify the nature and cause of important defects occurring in buildings, with emphasis on those affecting the fabric of a building and its associated services. It does not deal with issues of aesthetics, lighting or thermal or acoustical comfort. While concerned primarily with the avoidance of defects, the text, particularly in Chapters 2, 3 and 4, also gives guidance to aid in their correct diagnosis when, unfortunately, the situation demands cure rather than prevention. Except in a general way, the repair of such defects is not covered. Any one specific failure needs a detailed examination to decide on the most appropriate repair, for this depends not only upon technical considerations but also upon the type of building and its age, and upon related economic and social considerations. There are few standard solutions to problems of repair.

Most defects occur through the effects of external agencies on building materials, and Chapters 5 and 6 consider in some detail the nature of these and their effects on the materials commonly used in building. These agencies include the principal components of the weather, namely, solar radiation, moisture and air and its solid and gaseous contaminants; biological agencies, in particular fungi and insects; ground salts and waters; and manufactured products used in conjunction with building materials, for example, calcium chloride. Moisture occupies a central role, as the villain, in many building failures (Rose 2005).

The main sources of moisture and ways in which the amounts present may be minimized are dealt with in Chapter 7. Special emphasis is given to the cause and effects of condensation, and how the risks may be avoided or reduced. Condensation, particularly in local-authority dwellings, can truly be said to have been the greatest single cause of human discomfort in dwellings since the end of the Second World War. The elements of building structure are then dealt with, starting with foundations and progressing logically upwards to roofs and parapets, passing on the way, floors, walls, cladding and external joinery. The avoidance of defects in building services has a chapter to itself. The book concludes with a more speculative chapter dealing with failure patterns and control. It attempts to relate defects to problems associated with the structure of the industry, to the dissemination of information and to particular difficulties which result from rapid innovation. Current control methods are outlined and a possible strategy is suggested for improving control, quality and reliability.

The intention and hope is that this book will provide positive guidance to the student designer, technologist and builder on how to diagnose and avoid the principal defects in buildings. It includes few complex scientific concepts and requires only a little special knowledge of science. Though concerned more with normal building than with major civil engineering construction, much of the text is of relevance to structural engineers also, particularly those parts dealing with the properties of the structural materials, with foundations and with cladding.

The point was made at the beginning that knowledge gets mislaid: a further aim of this book is to serve as an aide-mémoire for practising designers, surveyors and builders. For this reason, it has been kept concise, and is illustrated to give visual emphasis to some of the more important defects which can occur. These illustrations and parts of the text which describe the likely appearance of failures may assist surveyors and maintenance personnel, too, by steering them towards the probable cause of a failure. Though the essential aim is to avoid failure, once it has occurred and maintenance is needed, it is hoped the book will help both in identifying the cause and in preventing the adoption of the wrong remedial action. It may also help the maintenance engineer and surveyor by putting the severity of a failure and its consequences into a reasonable perspective and so prevent over-reaction to the event, which is not uncommon, particularly with foundation problems. If the book succeeds only partly in these ambitions it will, nevertheless, save both money and misery.

1.1.2 What is building pathology?

The scientific and technological discipline underpinning this edition is Building Pathology. The approach is derived from the medical discipline Pathology, which in its simplest terms is the study and diagnosis of diseases. The word ‘pathology’ is derived from the Greek ‘pathos’ (suffering) and ‘logos’ (discourse or study of ).

Another medical term related to pathology is ‘nosology’, from the Greek ‘nosos’, which deals with the classification of diseases. Defects, like diseases, can be classified into three broad areas:

• Aetiology (causes): e.g. poor design, faulty workmanship, neglect.
• Mechanism (the agency/agencies that triggered the defect): e.g. dampness, pollution, fungi, moulds.
• Symptom or set of symptoms (syndromes):e.g. staining, leaks, cracking.

According to CIB (1993) Building Pathology is defined as the systematic study or treatment of building defects, their causes (aetiology), their consequences and their remedies (or therapy). Harris (2001) stated that the term was introduced as a subject in its own right in an architectural programme at Columbia University by JM Fitch in the 1970s. Since that time Building Pathology has gained increasing acceptance as an important part of architectural conservation and building technology.

Building pathology involves a holistic approach to understand how the various mechanisms by which the material and environmental conditions within a building can be affected (Watt 1999). It is therefore comprehensive in scope, covering the investigative process from initial manifestation of the defect through to rectification and monitoring. Prevention, of course, is also a prime objective of Building Pathology, and is addressed in this book.

As highlighted by CIB (1993), the nature of building pathology can be described as follows:

In medical terms ‘pathology’ has specific meanings as when:

• it refers to diseased conditions in relation to their determining causes (pathogenesis);
• it concerns macroscopic and microscopic alterations caused by such diseased conditions (anatomy and pathological histology);
• it refers to general pictures of a disease (special pathologies), both medical and surgical.

Generally this term is related to illness; however, it may also be used to mean material and product alterations, extending also to treatment, prophylaxis and restoration procedures.

Such ‘metaphorical terminology’ is useful in discussing this topic since the medical field is nowadays quite rightly concentrating on ‘prevention’ rather than purely on the ‘treatment’. Such an approach is also to be pursued in the building field.

‘Pathology science’ has recently become of major importance in building, strangely due to the consequence of innovation. In fact, research is quickly applied in practice, with the objective of shortening times which would, otherwise, be devoted to further experiments.

Not surprisingly, much of the procedures for investigating defects have emerged from diagnostics in the healthcare professions. There are, however, major differences between medical and building diagnostics. First of all, medicine as a discipline can involve many diseases or conditions that are extremely complex and hard to diagnose early on (e.g. ataxia, multiple sclerosis, cancer). Some health problems, particularly ...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• List of figures
• List of tables
• Preface to fourth edition
• Acknowledgements
• Disclaimer
• 1. Introduction to building pathology
• 2. Principles of building diagnostics
• 3. Basic investigative methodology
• 4. Diagnostic techniques and tools
• 5. Deterioration mechanisms
• 6. Durability and service life assessment
• 7. Moisture
• 8. Foundations
• 9. Floors, floor finishes and DPMs
• 10. Walls and DPCs
• 11. Cladding
• 12. Doors and windows
• 13. Roofs
• 14. Services
• 15. Failure patterns and control
• Appendix A. Glossary
• Appendix B. Schedule of defects
• Appendix C. Various defects data analysis checklists
• Appendix D. Sample diagnostic report
• Bibliography
• Index