The combustibility of cladding panels is a hot topic, and it's left one architect facing millions of pounds in damages and building owners struggling to afford insurance
A number of high-profile fires have emphasised the risks associated with composite cladding panels, also known as "sandwich" panels. The implications of these fires are being felt by building owners far and wide.

Composite cladding is made up of a metallic outer skin and a foam insulating core. The combustibility of the different types of core, and therefore the perceived risk, varies. Polyurethane (PUR) and expanded polystyrene (EPS) are seen as a greater fire risk than polyisocyanurate (PIR), and mineral wool fibres are regarded as the least hazardous form of core. But the less combustible cores tend to be more expensive, so specifiers need to balance the perceived fire risk against the relative costs. However, awareness of the risks has grown over time, and today's solution may not be the one arrived at when the panels were specified.

The nature of the problem is well illustrated by a recent case in which an architect, Paskin Kyriakides Sands, was found liable for up to £17m of damages as a result of the use of EPS panels (14 March, page 14). The case involved a fire in 1998 in the factory of Sahib Foods Limited, that produce chilled and frozen foods. The fire started in room G49, where a gas-heated pan known as a "bratt pan" was being used to caramelise onions. The fire was plainly caused by the negligence of Sahib's employees. However, the key question was who was responsible for the spread of the fire from room G49 to the rest of the factory.

The court heard expert evidence that if the room had been built with non-combustible panels the factory would not have burned down.

It also heard that in 1994, when the panels were specified, a perfectly competent architect might not have known of the combustibility of EPS panels when exposed to a serious fire. However, it became clear from PKS' evidence that it had, in fact, been aware of at the time of specification that the EPS core would rapidly degrade if enough heat was applied to it. The maker had written to PKS expressing concern at the use of EPS panels in areas where frying would take place. PKS nevertheless specified the panels.

Consequently, PKS was found liable for all the loss, except that which would have occurred if the fire had been contained within room G49.

One irony is that many occupiers and funding institutions impose lists of ‘deleterious materials’ that actually forbid the use of the more insurable insulating cores. This places the designer in an invidious position

It is clear that by 1994 the risk of using combustible panels was known, even if it had not been disseminated throughout the architects' profession. On the other hand, insurers have only recently hardened their stance on these panels, with the result that many building owners have been faced with massive increases in premiums when renewing their building insurance. In some cases, insurers have refused cover altogether.

No doubt this has a lot to do with the insurers' heightened perception of risk following the events of 11 September 2001, as well as the cumulative effect of the fires that have occurred.

The insurance industry's policy on the use of composite cladding panels is based on technical advice from the Loss Prevention Council, which certifies approved composite cladding products. However, many existing wall and roof panels containing PUR or EPS cores are not LPC approved.

Building owners that feel aggrieved at the dramatic increases in insurance premiums may seek to recover the excess costs from the designers. Obviously, in any given situation, the chances of success will partly depend on the terms of the contracts with the designers. It does not, however, follow that the designers have breached their obligations simply because the premium has increased dramatically. If the panels were specified before the recent increase in premiums, it is difficult to see how designers could be expected to have anticipated the change in insurers' attitude. On the other hand, now that it is known that combustible panels may be difficult to insure, it would surely be negligent to specify them in the knowledge that there is a more readily insurable alternative.

One irony is that many occupiers and funding institutions impose lists of "deleterious materials" that actually forbid the use of the more insurable insulating cores, such as polyisocyanurate and man-made mineral fibres. This places the designer in an invidious position, and may prejudice the position of the building owner – yet another reason why the use of such lists is best avoided.