Architects like to have the final say on the design, and we respect that. But we know more about roofs than they do, so how do they feel about that?
Let me start by making my feelings absolutely clear: I think British architects are the best in the world. The best at architecture, that is. They're not the best roofers, the best curtain-wallers, the best lift engineers, or a whole load of other specialised engineering fields involved in the construction and refurbishment of modern buildings – and, of course, they don't claim to be.

At least, most of them don't.

I was involved in a job recently where my company was responsible for submitting the design and specification for a particular flat roofing project. Those of you familiar with the concept of CDP – the contractor design portion – will understand how this works. As techniques of roofing, cladding or lift engineering have grown increasingly complex, it has become unrealistic to expect an architect to have expert knowledge in all of them. Hence the introduction of CDP, whereby the specialist contractor – who does have that expert knowledge – determines the most effective solution and, provided it delivers the right design effect, the architect rubber-stamps the recommendation.

The problem in this instance was that we'd submitted a CDP proposal that matched the brief perfectly – right appearance, right price, right performance – and the architect blocked it. Why? Because he had never been involved in a project using this product before and therefore couldn't be certain that it would work.

Ah well, you might think: he's only being cautious because it's his head on the block. Except, of course, that it wasn't his head on the block at all – it was mine. The whole point of CDP is that it places the design responsibility on the contractor. The architect specifies how they want the roof to look and perform and the contractor has to come up with a solution for achieving it.

If it doesn't work, it's the contractor that carries the can, not the architect. If it fails to satisfy legislative requirements, that's the contractor's problem too.

We had used the product a number of times before, always with excellent results. So why should the client end up paying for a less effective, more costly solution simply on the whim of an underinformed architect?

In this particular case, we knew our proposal was the right one because we had used the product a number of times before, always with excellent results. So why should the client end up paying for delays – or worse, a less effective, more costly solution – simply on the whim of an underinformed architect? Fortunately, in this instance (and after a frustrating delay), wisdom prevailed. The client pulled rank and the architect backed down.

Now, the reason I relay this episode is not to demonstrate what a tough, uncompromising fellow I am (although you don't get facial hair like mine without a great deal of testosterone, let me tell you) but to raise the question: where do you draw the line? Up to what point should an architect be involved in the nitty-gritty of the specialist tasks and at what point should he or she tactfully step aside? After all, the opposite scenario to the one outlined above – in which the architect abrogates all project responsibility to the contractors – could be even more damaging. You could easily end up with jarring design features, incompatible products and everyone blaming each other.

As with so many things, the sensible way forward lies in the middle ground – and in clarifying responsibilities. The architect has a vital role as creative director and arbiter of quality but it's the client, ultimately, who has to call the shots. We enjoy extremely productive working relationships with 99% of the architects we deal with. This is largely because we respect their need to have control over the design of the building and they respect the fact that we know an awful lot more about roofing than they do. So, when we put in a CDP recommendation, they just check that it does what they need it to and then pass it straight on to the client for approval.

That way, the client gets an expert opinion about the best solution for his money; the architect gets the appearance and performance they wanted; the contractor gets the job done right in the shortest time. In short, everybody's happy and life is marvellous.