If you are going to rely on the design expertise of a specialist subcontractor, it's up to you to check it has what it takes to do the job – or run the risk of …
I confess to uttering, very quietly, a very rude word when I read what this architect expert witness impressed on the court in the case of Bellfield Computer Services Ltd and E Turner & Sons Ltd vs Horace D Watkins and Alan Best.

The judge said: "I accept Mr Forbes Bramble's evidence … that the detailed design of the fire lining including its upstands could properly be left to the design expertise of the specialist supplier or specialist subcontractor."

That's when the rude word was uttered.

Look, do be careful about assuming a putter-upperer has design expertise. And above all, don't let crucial design elements leave the hands, hearts and minds of those who have spent year after year gaining formal qualifications. By all means, let contractors and subcontractors take on a huge burden of design, but only if they have the staff with formal design qualifications. Mr Forbes Bramble is right to say detailed design can be left to specialist suppliers and subcontractors, but only if you add: "provided they have – and have been checked to have – formal qualifications for that design".

The trial was about a disastrous fire at Unigate's dairy in Marshfield, south Glamorgan. The damage ran to £6m. Unigate blamed the builder of 10 years before, E Turner & Sons. The building was a typical portal frame shed with an office inside at one end. It is ever so ordinary to put up compartment walls between the office and factory area and get on with business, and Unigate happily bottled and delivered their milk until the fire. The fire is said to have spread because the hot gases and smoke escaped over what ought to have been the compartment wall and under-purlin lining at roof level.

It is wrong to assume that the subcontractor’s staff are specially trained or have formal qualifications, especially when it comes to fire

The notion is to screw non-combustible composition board to a galvanised grid and form upstand returns between the lining and crinkly tin roof. That is supposed to produce a two-hour fire-resistant lining. Hmm! Anyway, the lining was hopeless; it let the gases through. By now the putter-upperer subcontractor was out of business, so E Turner & Sons had to pay Unigate. Then Turner turned on its architect, Horace D Watkins (HDW), and sued it for negligent design work.

Turner had been in a partial design-and-build agreement with Unigate, so it had done what a lot of builders do: call on a firm of architects to help out. That, too, was a loose arrangement – the judge said it Turner had bought "partial architectural services". HDW had identified the need for a two-hour fire-rated lining and wall between the office and the factory. When Turner asked the architect about the fire barrier detail, the reply was: "Fire barrier, two hours, to cover this area, [the subcontractor] to sort out methods of supports for suspended ceiling." So, Turner and the architect did no more detailed design; they just left it to the ceiling contractor, Boddy-Moir Ltd.

At the trial, when Turner was trying to pass on its losses to the architect, it was apparently agreed by everyone that Boddy-Moir was a specialist subcontractor for this type of work. The judge said: "I am satisfied that, as specialists in this field, Boddy-Moir would have been fully aware of the need to provide suitable upstands to the fire lining so as to comply with the relevant regulations and make it fire resistant." He went on: "There was no reason to doubt that as specialist subcontractors, Boddy-Moir would have been able to carry out detailed design of the fire lining … to achieve the required fire resistance." The judge accepted the expert evidence of Mr Forbes Bramble that such specialist subcontractors have "skilled operatives with specialist know-how", to whom the architect issues directions "at his peril". The expert architect was totally confident that architects can rely on specialist subcontractors.

The proof of all that pudding was in the eating. The confounded work and detailed design of the fire lining was a total mess. No, that's not HDW's fault. It was not asked to produce detailed design. So, Turner couldn't pass on the bill. Both architect and builder happily believed that they could leave detailing to the subcontractor.