Cladding & Curtain Walling
21 April 1989

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Corporation. The Development Corporation had carried out tests based on local weather criteria and were satisfied with the system's performance.

However, there were still problems to overcome: the development of the design and detailing of the material, the integration of doors, windows and roof covering and the potential cost increases as a result of these factors.

This is the stage when the contractual problem arose. Most systems are only supplied by the manufacturer or agent. Although part of the system the ultimate "design" is the reponsibility of the erector, who at this point in time is, like the supplier, not yet appointed.

The main contract was to be the result of competitive tender and the client did not wish to nominate any subcontractors or suppliers. It was however permissible to name the product in the tender document but the erector of the system had to be selected by competitive tender.

This made it impossible to develop the detailed design of the system prior to a main contractor being appointed. This meant there could be a potential delay at the start of the contract, and accurate costs would not be known until tenders were received.

Fortunately all external apertures and the roofing element formed part of the one element for tender purposes. All the component parts of this element - the external envelope - could be "named" and their erection carried out by one domestic subcontractor who would be part of the main contractor's competitive tender.

The development of the external envelope design virtually ceased during the design process when input from the erection subcontractor was required. Very little additional information was forthcoming from the supplier at this stage since without financial commitment he was unwilling to give further information on his product.

When tenders were received and a contractor appointed the responsibility for the design of the system had passed to the main contractor. The main contractor was by then satisfied that the cladding subcontractor could carry out what was required and the supplier was satisfied that the cladding subcontractor could erect the system in question.

It is several years since our involvement with the laboratory building. We were ultimately satisfied with the results in the end despite the rather involved contractual/design process.

In early 1988 we were commissioned to the Calders in Edinburgh, to overclad a high rise, local authority, blocks of flats and again the circumstances were very similar to the laboratory building.

The majority of the initial selection of systems were over-budget and a simpler adaptable system which had been used locally consisting of profiled sheeting with coloured flashings was preferred. The client did not wish to nominate a supplier but preferred to name the system to be erected and to state that it be erected by the system designer's approved contractor.

So, like the laboratory building, during the detailed design stage the detailing of the cladding ceased. Full working drawings were not available until the main contract was let.

Is the need for this excessive selection and deign process a result of our client not having adequate funding to select a system which has been developed, tried and tested? And does the continuing development of cladding materials and their use in situations of competitive tender where nominations are not permitted necessitate the processes outlined? The answer must be yes to both questions.

The main contractors in both examples have accepted the naming of systems and have ultimately taken design responsibility for these systems. If these main contractors refused to accept responsibility for named systems, i.e. demanded nomination, then letters of intent could be issued by clients and detailed design could be undertaken at the appropriate stage in the design process.

However, the likelihood of this happening is slight since there will always be a suspicion that taking such a stance will result in exclusion from the tender list.

A united front may help - let's hope it happens before our next cladding project •