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PFI projects are exchanging construction's lowest-cost paradigm for lifetime performance costing. One of the by-products of this is that the issues of whole system performance and performance-related warranties are firmly on the agenda.

Component manufacturers are taking up the challenge and developing complete tested solutions. But what are the implications for system performance and manufacturers' warranties when these are compromised by cost-conscious contractors who substitute cheaper components?

The performance of a building element, such as a wall, floor or ceiling, cannot be viewed in isolation. The way these elements interact when brought together in the building is vitally important when considering the overall building performance. Inevitably each element will comprise a number of individual components: framework, lining, insulation, fixings and possibly decorative finishes. Often the designer will be able to source all of the components from a single manufacturer as a performance-tested warranted system. The warranty will remove the responsibility on the designer to ensure compatibility and combined performance.

Sometimes, however, the specifier is faced with a solution that involves components from a number of suppliers. It is here that problems can start.

While most component manufacturers can quote standards for individual components or performance figures for their tested systems, often the substantiating test will bear no resemblance to the building in which the component or system is to be installed.

A typical example is fire doors. Testing to BS 476 Part 22 Resistance to Fire will give the door a rating of between 30 and 120 minutes. But this often assumes that the doors will be surrounded by masonry – put them in a lightweight plasterboard-based system and a large percentage would not provide the current British Standard level of fire performance.

In short, if you choose a tested system, it will have been developed to maintain its integrity for the specified period. But if you substitute a single component, even a screw, where does that leave the system – and you?

Substitute a single component, even a screw, and where does that leave the system – and you?

And who would take responsibility in such a situation if the system failed? It wouldn't be the door manufacturer – it will have a test certificate that supports its performance claim. It would be difficult, also, to establish which component of the partition had failed, and again, individual components would more than likely have their own test certificates.

So who carries the can? Inevitably deciding responsibility is a matter for the courts, with all the cost and delays that that involves.

Thankfully, the situation isn't as black as it has been painted. Some manufacturers are going the extra mile to provide an integrated package of components that provides a complete solution. Often manufacturers co-operate with each other to ensure compatibility with other components.

These solutions have been extensively tested in full-scale harmonised programmes, they are supported by test certificates and come with a performance warranty that takes the risk out of the job for the specifier and contractor.

Of course, cost is still important, and there are a plethora of products on the market that appear to meet the "equal and approved" criteria and which are just screaming to be substituted.

The responsibility for holding the specification must now fall squarely on the contractor and the specifier. The contractor must be aware that any cost savings achieved by substitution will negate the whole system warranty. They should therefore balance these savings against total system cost, and indeed, with lifetime performance costs in PFI projects with long-term repair and maintenance clauses.