Faulty materials

Materials may give rise to building failures for three reasons:
• Inappropriate use
• Inherent faults
• Deterioration

The first of these is more likely to provide the basis for a claim for poor design than for faulty materials. The second is usually evidence of a materials failure. The third may not indicate a fault at all but, where it does, it may fall under either of the preceding categories.

For example, a timber beam may fail if undersized (inappropriate use) or because it contains a growth weakness (inherent fault). The use of natural materials containing faults may be seen as evidence of underlying poor workmanship.

In the above example, the use of a timber with an inherent fault indicates that the craftsman responsible for the work did not use proper skill and care in selecting and preparing the timber.

Where natural materials are used, faults usually represent poor selection or preparation. Whether the fault is seen to be one of workmanship or of materials may depend on the stage at which it is considered. For example, the roofing slate which contains deleterious impurities is, on the building site, a faulty material but, in the quarry, it evidences a lack of skill in selection and cutting.

All materials deteriorate and as such deterioration would normally give rise to a claim only for faulty materials if the rate of deterioration was exceptionally rapid. This may be due to the inappropriate application of a material or to inherent faults in it.

With man-made materials, the underlying cause of a fault may be in:
• Design
• Workmanship, or
• Materials

For example, when investigating a recent instance of poor performance of a roof, I found the following defects in the man-made slates used:
The elastic behaviour of new slates changed over three or so days due to incomplete curing during manufacture,

A cause of plastic deformation lay in variations in the thermosetting characteristics of the binder.

The cause of discolouration lay in the poor UV stability one of the pigments used exacerbated by the failure of an inhibitor.

Depending on the stage of the process and contractual relationships considered this could be seen as evidence of faults in design and in workmanship as well as in materials.

Under the building contract, the employer has a claim against the contractor for materials which are not in accordance with the contract. The contractor has a like claim against his roofing sub-contractor who in turn has a claim against the manufacturer for failing to supply goods which are fit for their purpose.