Causes of defects

Below are some common reasons why defects arise; they are not in any particular order of significance.

Water

This is by far the greatest cause of what occupants perceive as a defect, yet it is under-rated as the key agent of decay and destruction.

Renovation

The addition of modern conveniences in older buildings - in particular showers and wet room areas - has a major impact on older properties. The combinations of defects that can arise in such circumstances are too numerous to mention. Surveyors need to remember that the modernisation of buildings can involve many compromises that, when combined, cause complex defects.

Backlog maintenance

Most organisations have an element of backlog maintenance, and a defect can arise because the economic climate is such that it is not possible to undertake the work that is required. Problems can be left from one financial period to the next, until reactive maintenance is the only option. Often surveyors are faced with what looks like incompetent work when inspecting a defect, but that may be a valiant effort in the face of poor funding. Property professionals working for organisations that have taken on property portfolios can inherit huge maintenance deficits, and realistic solutions have to be found, even if the ultimate remedy is uncomfortable.

Lack of responsible supervision

In most texts, lack of responsible supervision is explained as if it were a third party problem. It is quite easy for a project to impose a high demand for supervision at a time when other pressures are also at their height. Many professionals work out of offices and can be too far removed from the reality of the problems faced by the craftsmen on site. Clear direction and guidance are as much the surveyor's responsibility as anyone else's. Regular set days for site visits can be counterproductive, as mistakes and problems can be masked in anticipation of a visit. Do not regard site visits as an opportunity to catch people out, but as an opportunity to resolve problems and set standards at the right time.

Over-confidence (poor application)

Contractors often complain about designers and architects (and vice versa). These complaints may or may not be substantiated; however, both parties often overlook quite how difficult each other's task is. The construction process may not be complex, but it is complicated, and many people revert to tried and tested methods without standing back to really assess what it is they propose to do or ask people to do. With repetitive maintenance work for example, a case may arise where the standard response will not work. The defect therefore arises not because what was contemplated doesn't work, but because the alternative was not explored. Confidence is beneficial, but over-confidence contributes to poor design and execution.

Bad design

It is often said that a main cause of defects is bad design, but this can be used unfairly as a sweeping commentary on the sometimes complex and deadline-driven construction industry. Many design details are drawn up very close to the time that a craftsman has to carry out the work. Short cuts can be undertaken not only in the build process but in the drafting of the plans and specifications. Superficially everything is in order, but on closer inspection the omission of key information can lead to significant problems on site. Problems become masked, and the inevitable occurrence of a defect long after everyone has left site is set in place.

Surveyors needs to be keenly aware that sometimes on site things do not go to plan, and there is very little time to remedy problems with certainty. On most occasions the skill and experience of the designers and contractors resolves difficult problems with great success; but occasionally even the most careful consideration and application can result in a defect arising many years later.

Bad design may not be so much to do with negligence as the way we design and communicate among the myriad of consultant designers, contractors and subcontractors. By understanding how some of these communication errors can occur, the surveyor can be mindful not to repeat such practices.

Some key problems in detailing are:

• Providing a drawing with overall dimensions on it while the intermediate dimensions, such as window size or spacing, are missing. When the building is set out, the intended dimension that is missing from the drawing may be nothing like the actual size of the building.
• The use of calculators and computers to fine-tune dimensions that, in practice, are virtually impossible to achieve on site. An example of this is the gradient on guttering and on flat roofing, which can be calculated on a computer to a much greater tolerance than could ever be practically achieved on site.
• A single line on a plan drawn by computer that represents 3 separate materials coming together in one place on site. A typical example of this is when floor details are drawn, where the soil meets the concrete and masonry and the damp-proof membrane. In reality these surfaces rarely meet in a perfectly straight line, and minor variations can accrue to be quite a significant misalignment.
• During calculations of overall room dimensions the significance of the thicknesses of materials is overlooked, so that when the materials are installed on site they do not match the control dimensions on the plan. A commonly missed dimension is the thickness of skirtings. Often when free-standing floor units are installed on site, the skirting thickness has not been accounted for.
• For restoration work, the use of a computer to create the plans usually results in a vague assumption that the existing building is perfectly square and perfectly plain and perfectly flat. This is seldom the case. The 'snap to grid' feature on computer-aided design packages is often the main culprit, as it does not intuitively suggest to the draughtsman that the original surveyor's dimensions are in fact correct and the room is not square.

Specifications can be too vague in areas of work that require detailed information. Key phrases in specifications to watch for are:

• Make sure surfaces are clean and free of grease.
• Apply, install or fix to the manufacturer's recommendations.
• All in accordance with BS XXX.
• Access by way of mobile access equipment.
• Fix as appropriate.
• The contractor is to make good contingency for breakage.

Obsolescence

Something that is broken is clearly a defect, and the remedy of replacing it is clearly the correct option. However, the problem of how this is to be achieved can be easily overlooked. Many products and replacement parts are not produced for any length of time. High-quality products can be damaged for any number of reasons, and therefore being able to repair them economically is intrinsic in cost planning. Components such as PVCu window ironmongery, light fittings, door handles, lock casings and fan parts are typical of such products.

Obsolescence is becoming a key problem for life-cycle costing and day-to-day facilities management. When observing some defects, consider whether the cause is due to replacement components that were, at the time, the best available alternative. These situations manifest themselves when defects recur in components that are in constant use (e.g. doors, windows, switches). There comes a point when constant replacement of a component is less cost effective than complete replacement of the whole element with a new one that has readily available spares.

When detailing maintenance programmes it is good practice to check on the availability of key components. Designing an element to have a long lifespan based on normal wear and tear may be completely undermined if the item is deliberately damaged, and subsequently cannot be replaced because it is unobtainable.

Complex defects

In isolation, defects can be easy to quantify, diagnose and remedy. However, some symptoms are a result of combinations of defects that can frustrate normal lines of enquiry and investigations.

Complex issues may be at work that frustrate attempts to resolve what at first glance seemed to be a straightforward issue. For example:

• There is more than one defect creating the same symptom.
• There is a concealed space indirectly related to the defect area, e.g. voids in pipe boxing.
• The symptoms only occur in certain conditions, none of which have been collectively assessed.
• The assumed construction detail is not the actual build detail.
• There is an area that is difficult to inspect and no one has checked it.
• The symptom has recurred after several remedial repairs.
• Anecdotal evidence is inconsistent or has been given with an ulterior motive.
• The presence of damp is assumed to only have one root cause.
• Other work has taken place elsewhere that has not been analysed in respect to the current defect.
• The initial remedy was an over-reaction that has caused further complications.