Defects and Deterioration in Buildings

A Practical Guide to the Science and Technology of Material Failure

Barry Richardson

• Publisher: Routledge
• Year: 2002
• ISBN:
  9781135803681
• Edition: 2
• Topic: Tecnología e ingeniería
• Subtopic: Construcción e ingeniería arquitectónica

A professional reference designed to assist surveyors, engineers, architects and contractors in diagnosing existing problems and avoiding them in new buildings. Fully revised and updated, this edition, in new clearer format, covers developments in building defects, and problems such as sick building syndrome. Well liked for its mixture of theory and practice the new edition will complement Hinks and Cook's student textbook on defects at the practitioner level.

1
Defects and deterioration

1.1 Introduction

The purpose of this book is to assist architects, surveyors and engineers to recognise, diagnose and avoid problems in buildings, and to decide to obtain specialist assistance if appropriate. Where a problem leads to litigation or arbitration a much more critical assessment is required, usually resulting in comments on the problems in relation to the contract documents and normal good practice, as represented by British Standard specifications and codes of practice and other readily available sources of guidance. Where an action is against an architect, surveyor or engineer, an expert in the same discipline will be required to give an opinion on professional duties and the actions that a reasonably competent and diligent person should have taken in the circumstances, but the architect, surveyor or engineer employed as the expert may not necessarily be responsible for the actual investigation, which may involve unusually critical site inspections, laboratory testing and extensive knowledge of building science in order to make a reliable diagnosis of the causes of the problems. Such investigations are the province of the building scientist, usually working in close cooperation with the architects, surveyors or engineers who are also engaged to give expert evidence. It is the thoroughness of these investigations that makes them so interesting and instructive, as they frequently disclose matters which would not be considered in normal structural surveys. It is this more detailed information that is presented in this book, in the hope that it will assist in better understanding of building problems.

It is not intended that this book should be a comprehensive account of defects and deterioration encountered in buildings. Instead the book describes some of the problems that seem to present the greatest difficulties to architects, surveyors and engineers, and which are therefore most frequently referred to building scientists for investigation. The defects described arise generally through lack of care or knowledge in specification or workmanship; this book is not concerned with obvious design defects, such as inadequate beam sections in relation to design loads.

1.2 Legal aspects

Problems and failures in buildings can be broadly attributed to either defects or deterioration. Defects arise due to error or omission, that is, breach of contract or negligence by a designer or contractor, but deterioration is a natural process which may be unavoidable, although minimised by care in design and the selection of materials. However, where the rate of deterioration is excessive it may be due to a defect, such as the selection and use of unsuitable materials, or an event, such as a water leak resulting in fungal decay. A defect in such circumstances may be due to a breach of contract or negligence during construction or repair, or it may be a failure by a building owner or tenant to maintain the building adequately or to repair it promptly after accidental or weather damage.

When a problem or failure arises and a building owner or tenant decides to seek compensation, it may be very difficult to establish that a breach of contract or negligence has occurred, rather than normal deterioration, lack of maintenance or failure to repair promptly. One difficulty is that a cause of action can only arise if a person or firm has suffered an actual loss. The implications are best illustrated by an example, perhaps of a building with inadequate foundations. If the faulty foundations are discovered soon after construction, the owner can claim against the contractor for breach of contract if the contractor failed to observe the design requirements which formed part of the contract. However, litigation must commence within the statutory limitation period, that is within 6 years of practical completion for a normal building contract, but within 12 years for a speciality contract, that is a contract made by deed or under seal. Generally, a building owner has retained an architect to design the building and supervise construction, so that a contractor might claim in defence that the inadequate foundations were installed to the satisfaction of the architect. A building owner may therefore claim also against the architect for breach of contract for failing to supervise construction properly, or alternatively for failure to design the foundations properly, if it is found that the contractor actually followed the design. The situation may be further complicated if the relevant work was subcontracted; an architect might subcontract or assign foundation design work, to an engineer, and a contractor might use a subcontractor for specialist foundation work, such as piling.

In fact, inadequate foundations may not be detected until much later when some event occurs which leads to investigations, such as the development of a settlement crack, often well beyond the period when an action can be brought for breach of contract. However, an action for a latent defect can still be brought in tort, that is a claim for a wrong arising through negligence, as the limitation period is then 6 years from the date on which the damage occurs or, if it is later, 3 years from the date on which the damage was first reasonably observable, with an ultimate limit of 15 years from the date on which negligence occurred, that is usually the date of practical completion. In the case of architects or engineers it is often suggested that limitation should run from the date of completing designs, but if they are supervising construction they are also responsible for reviewing their designs and specifications until the date of cessation of their involvement in the project, usually the date of issue of the final certificate, or even later if they renew their involvement in the project, perhaps through being asked to advise on a problem that has occurred and which is subsequently found to be associated with a defect. These comments on limitation are included to illustrate the way in which lawyers and courts have become dependent on expert witnesses for guidance on limitation matters, as only an investigating expert can advise authoritatively on the dates when damage occurred or was reasonably observable. These comments on limitation are based only on the law of England and Wales as represented by the Limitation Act 1980 as amended by the Latent Damage Act 1986, although similar limitation legislation applies in all states of the British Isles.

Whilst an action for breach of contract can only be brought between contracting parties, an action for negligence can be brought by anyone who is likely to be affected by a negligent act, so that a tenant or user of a building can commence an action, as can a person passing in the street who is injured, for example, by falling masonry. It may seem unfair that an action for negligence cannot be brought until there is a cause of action, that is actual loss or damage, but this seems to be a deliberate decision of English law to discourage unnecessary actions; it is recognised that it is very rare for buildings to be erected strictly in accordance with their designs and current good practice, but it is equally rare for buildings to suffer damage as a result. An obvious example would be a situation where a contractor was unable to obtain the specified roofing tiles and used instead the nearest available equivalent. Obviously the substitution was a breach of contract, but it would not be negligent, even if carried out without approval, unless it resulted in actual loss or damage.

The only exceptions to these general rules arise when a structure is doomed to fail, as in the case of an overloaded component which is progressively distorting, or when there is an imminent threat to health and safety because part of a building is certain to collapse if subjected to wind or snow loads of normally encountered severity, or there is a danger of rapid spread of fire. In such circumstances a cause of action arises because the defect must be corrected immediately, involving a financial loss; indeed, it is necessary to remedy the defect promptly in order to mitigate the loss and to avoid the much greater claim that might arise should a catastrophe occur, such as a structural collapse or fire causing death or injury.

Compensation for defects can be valued in various ways. It may seem obvious that the compensation should equal the cost of repairs and any consequential losses, but a repaired building may never be the same as a properly constructed building, and an alternative method of valuation would be the diminution in the value of the property due to the defects. Diminution in value usually applies to claims arising through negligence in assessing the condition or value of a property prior to purchase, but diminution is difficult to quantify. Obviously, diminution in value is directly related to the cost of necessary works, but the relationship depends on the state of the market when the offer based on the negligent assessment was accepted by the vendor. If the market is buoyant and there is a strong demand for such properties at the asking price, prices will be rising and a prospective purchaser will be reluctant to abandon a purchase and search for an alternative similar property at a relatively higher price. If a survey discloses necessary works, the prospective purchaser will probably be willing to tolerate the inconvenience and perhaps part of the cost of the works. The prospective purchaser is therefore likely to seek a reduction equal to the estimated cost of the necessary works, but may be forced to agree a reduction to only perhaps a half or three quarters of the cost. However, if the market is sluggish with weak demand and static or falling prices, a prospective purchaser would have little to lose by abandoning the purchase and seeking an alternative property, and would not therefore be willing to tolerate either the cost or inconvenience of necessary works. In such circumstances, the purchase would be unlikely to proceed unless the vendor was willing to accept a substantial reduction, such as 100–150% of the estimated cost of the works. Another method of valuation, appropriate to commercial property although rarely used, relies on the loss of profit that has resulted when a building has proved to be unsuitable for the purpose for which it was intended.

These comments on legal liability have been included to emphasise the seriousness of problems and failures in buildings due to errors and omissions, but such problems are not confined to new construction. Obviously, identical problems apply to repair works of all types, particularly perhaps remedial treatments involving damp-proofing, thermal insulation and timber preservation; these introduce their own special problems as they generally involve specialist contractors, who also provide inspection, report and specification services so that they assume professional responsibility as well as normal contractual responsibility for their works. Their professional responsibilities involve the assessment of existing defects and their preparation of specifications for remedial works, but often their approach is too narrow, perhaps overlooking the fundamental causes of the problem that they are investigating. For example, in the case of fungal decay in a modern timber frame building, they may suggest remedial preservation treatment but fail to comment on defects in the internal vapour barrier or external ventilation which have resulted in interstitial condensation causing dampness and consequential fungal decay. Some remedial treatment contractors believe that they are not liable for the professional thoroughness of their inspections and the accuracy of their reports because they do not charge fees for these services; this is not correct. It is well understood that the costs will be incorporated into any charge for remedial works, and some contractors have discovered that they have the same liability for any inspections that they make and reports that they submit as a chartered surveyor or architect. In fact, a contractor is only usually liable for errors and omissions in his inspection and report if it can be shown that he acted negligently; a contract, if one exists, is usually restricted to making an inspection for the purpose of preparing a specification for remedial works which the contractor considers to be appropriate. A contractor can minimise liability by referring in advertisements, literature and letterheads to inspections for preparing estimates, rather than surveys and reports which imply an authoritative and impartial assessment.

The obvious solution is for property owners to rely only on a proper independent professional assessment, but the arguments are not necessarily convincing. An architect or building surveyor will charge for his services, whereas specialist remedial treatment contractors will usually offer to provide survey and report services free of charge. In fact, specialist contractors attempt to minimise their inspection and report costs by limiting their investigations to the remedial works that they would like to carry out, incorporating the inspection and reporting costs in their estimates or quotations for these works. In addition, an architect or surveyor may be reluctant to give an opinion on specialised matters, such as dampness and timber decay, and will recommend in any case that a specialist contractor should be engaged to inspect, report and to carry out necessary remedial works! The situation is thus thoroughly unsatisfactory: architects and surveyors often failing to provide a comprehensive assessment of a building, while specialist remedial treatment contractors are expected to provide professional services although they are, in fact, only contractors inspecting buildings to prepare estimates and quotations for works that they would like to carry out. This situation has been clarified by a case in which a chartered surveyor was found to be negligent for detecting damp conditions likely to represent a fungal decay risk and for failing to make further investigations; he recommended that a remedial treatment specialist contractor should be consulted, but he failed to assess the situation himself.

The most serious situations probably arise in connection with surveys prior to purchase in which the status of the survey is of crucial significance. Where a survey is for valuation purposes alone, it will not necessarily involve any reference to the condition of the building. In an extreme case, the valuation may be based on the site value alone and the building may be ignored, but where the building itself has significant value a valuation surveyor may report structural defects and the need for further investigations, repairs or maintenance where these aspects affect the valuation; this does not necessarily mean that the building is free from other defects which may require attention. A very strange situation arises where a prospective purchaser applies for a mortgage loan and is required by a bank or building society to pay for the valuation survey and report, but does not receive a copy. The legal interpretation of the situation seems to be that the prospective purchaser does not have a contract with the surveyor, but the courts have indicated that a prospective purchaser is entitled to rely on the valuation information and may be successful in a legal action alleging negligence against the surveyor if the valuation subsequently proves to be incorrect. In recent years the Royal Institution of Chartered Surveyors has recommended that surveyors should offer, whilst making a valuation survey for mortgage purposes, to also provide the prospective purchaser with a basic House Buyer’s Report to a standard format, but a report in this form is still very limited in scope compared with a proper structural survey. Clearly an architect or surveyor has a duty of care when carrying out surveys of all types but, when a problem arises, they can only be considered in breach of contract or negligent if it can be shown that the defect should have been discovered by a reasonably competent and diligent surveyor; the most important point is to detail in all reports the areas where access was inadequate and those where further investigations are necessary.

1.3 Investigations

A structural survey is a routine assessment of the condition of the building which is intended to detect any defects or deterioration requiring attention. Structural surveys are sometimes arranged because the owner or tenant of a building suspects a problem, although most structural surveys are for prospective purchasers. Structural surveys are normally carried out by building surveyors or architects; a building surveyor should be appropriately qualified, such as a member of the Royal Institution of the Chartered Surveyors in the building surveying division, rather than in one of the other divisions, such as general practice, quantity surveying or valuation surveying. Guidance on structural surveys is available from various sources such as the book by J.T.Boyer, Guide to Domestic Building Surveys, and the RICS booklet, Structural surveys of residential property, originally issued as a Practice Note in 1981 but described instead as a Guidance Note when a revised edition was issued in 1985. The RICS note emphasises the need for the surveyor to confirm the client’s instructions and to appreciate the client’s requirements. Obviously, a reliable and realistic assessment of the structural condition of the property is required, although it may be reported that defects or deterioration are possible rather than established, and that further investigations are necessary or at least advisable. This is a common difficulty with surveys for prospective purchasers: the permission of the vendor must be obtained before carrying out exposure works, yet the prospective purchaser requires to know the scope and estimated cost of both essential and advisable work, so that this can be taken into account when making an offer to purchase the property.

A survey report may advise that further investigation should be carried out by another professional person, such as a structural engineer, or that a specialist contractor should be asked to inspect and prepare a specification and estimate for appropriate work. Remedial wood preservation and damp-proofing treatment contractors are often invited to prepare specifications and estimates in this way, but so are many other contractors involved, for example, in plumbing and heating engineering, piling and roofing. There is a temptation for the building surveyor or architect responsible for a structural survey to suggest that these contractors should be instructed to ‘survey and report’, but this is not their proper function; they should be instructed to inspect only to enable them to prepare specifications and estimates for work defined by the building surveyor or architect.

Investigations into defects or deterioration in connection with claims or disputes involve a rather different approach, focusing on a particular problem, in contrast to a normal structural survey which is designed to assess the general condition of a property and detect any matters requiring further investigation. The differences between defects and deterioration have already been explained, but only defects can support a claim or dispute, in the sense that deterioration is a natural process which is to be expected. However, when deterioration is observed it must be established whether it is occurring unexpectedly rapidly through some error or omission in specification or construction, or through inadequate maintenance, or through a defect.

A realistic approach to deterioration is perhaps best illustrated by an example. Bituminous felt is often used as a roof covering for permanent buildings, even though the felt has an effective life which is much less than the design life of the building. Damp stains on ceilings beneath the roof will suggest failure of the felt covering. This failure may be due to natural deterioration, such as loss of volatile components causing brittleness and cracking of the felt; the resultant leaks are then attributable to neglect to maintain the roof properly by replacing the felt at appropriate intervals. However, premature development of leaks may be due to poor workmanship or inadequate materials, in the sense that an unsuitable grade of felt or insufficient layers were used. Alternatively, some accidental event might have occurred, such as dropping an item on the roof which penetrated through the felt covering. Localised cracking in felt may also be due to thermal movement in the building which may overstress the covering as the felt ages and becomes more brittle. All these failures involve rainwater leakage through the roof covering, but dampness may also be caused by interstitial condensation beneath the felt covering, a defect in design or workmanship which is described in greater detail in section 4.7. However, whether the dampness is caused by rainwater leaks or condensation, it encourages biodeterioration of susceptible materials, wood decay being a particularly serious problem in some circumstances, as described in section 6.4, and perhaps requiring more expensive attention than repair of the felt roof covering.

It will be appreciated from these comments that, if a roof is designed to avoid the danger of interstitial condensation, a felt covering with a limited life is acceptable, provided that the limited life is recognised and the covering repaired or replaced at appropriate intervals. All building materials deteriorate, but they are only defective if they deteriorate more rapidly than expected. Natural stone or brick masonry is expected to deteriorate very slowly indeed, and premature deterioration is an indication of a defect, such as the use of inadequately durable stone or brick in relation to the conditions of exposure, or unsuitable mortar, or some abnormal effect, for example the development of sulphate attack in the mortar as described in section 7.3. In contrast, paint coatings on wood joinery are recognised as having only limited durability, and it is accepted that they require frequent maintenance.

Investigations into failures in connection with claims or disputes must obviously establish the causes of failure, and whether they can be attributed to normal deterioration or defects in construction or maintenance. Such investigations are not, of course, limited to site inspections but also involve laboratory examination and analysis of samples, as well as assessment of the situation in relation to construction or maintenance specifications, or normal good practice, usually represented by British Standard specifications and codes of practice. It is obviously essential that an investigation is thorough if the resultant report is to be authoritative, and there can usually be no excuse for failing to make a thorough investigation. This obviously involves a determined approach to the investigation, but also the use of appropriate equipment. In fact, equipment does not usually need to be very sophisticated, the most important requirements being suitable clothing, both weatherproof for external inspections in inclement conditions and overalls for internal inspections in dirty areas. Pencils are preferred for writing notes; pens do not write on damp notebooks! Torches are more efficient than lead lights, but they must be adequate and spare batteries must be available. Hand mirrors can be helpful for viewing inaccessible areas; they can usually be borrowed from mother’s spare handbag! Borescopes can be very useful, although the more expensive elaborate models can rarely be justified; the simple Checkscope (Keymed Industrial Limited) is reasonably robust and particularly suitable. A moisture meter is essential but does not need to be particularly sophisticated; most of the simple probe instruments such as the Protimeter range will accurately measure wood moisture contents and will give relative measurements on other materials, enabling areas of high and low moisture content to be located. Temperature measurement facilities on the same instrument can be useful but are not essential. Convenience is perhaps the most important requirement; it may be found that a simple meter reading instrument, such...