'The concept of a latent defect is not a difficult one. It means a concealed flaw.' So said the court in Baxall v Sheard Walshaw Partnership, writes Kim Franklin.
In that case, the defendant architect under-designed the roof of a warehouse, which caused unexpected flooding as a result of ordinary, expected rainfall. But, as the court pointed out in Murphy v Brentwood: 'It is the latency of the defect which constitutes the mischief'. If a person has the opportunity to inspect the product before using it and becomes aware of the defect, they have no remedy. So, if a latent defect causes loss or damage, there may be a claim.
But if the defect is discovered, it becomes patent and capable of remedy.
In the Baxall case, the court went one stage further and held that where the building is inspected by a surveyor who ought to have unearthed the hidden flaw, the defect is deemed to have been revealed, whether or not the surveyor actually spotted it. In that case, the architect avoided liability because, although the claimants had not, in fact, discovered the defect, they had had an opportunity to do so.
Latent defects are of concern to designers who may be responsible for any damage they cause for up to 15 years from the construction of the building. Throughout that time, the building may be inspected by various interested parties.
Does the designer owe a new duty to each occupier, even if the defect has been discovered by, or was discoverable to, previous occupiers?
This far from straightforward problem was considered in detail by Technology and Construction Court Judge Thornton QC in the recent case Pearson v The Charter Partnership. That case concerned a warehouse roof designed by architects CPL.
During a storm in July 2002, 140m 3 of water damaged more than two million stored books. Reprinting costs exceeded £1.3 million. The roof, which comprised four double-pitched modules, required a siphonic rainwater drainage system. CPL designed for a rainwater intensity of 75mm an hour, whereas the experts agreed the design capacity ought to have been for not less that 150mm.
Between 1990 and 2002, the warehouse was owned, insured, leased and sub-let by various concerns. In 1994 there was a severe flood and the roof was inspected by loss adjusters who reported on the inadequate drainage system.
However the occupiers, who subsequently assigned their lease to the claimants, never learnt of the defect.
The judge found that a purely visual inspection of the building would not reveal the under-capacity of the siphonic drainage system and that the claimants knew nothing of the previous flood, or its cause, when they acquired the building. He rejected the architects' contention that if one person discovers the defect, it ceases to be latent to subsequent parties. He concluded that 'the latent quality of the defect survives for everyone unless and until the defect becomes obvious to all'.
In this case, the architects were found liable because, although someone had previously discovered the defect, the claimants had not.