Winefred, I can tell by your other posts that you clearly have some sort of axe to grind, but you really are talking nonsense, I'm afraid.
It would be suspicious if a Chartered Architect did nothing but extensions, because there's bugger all money in it, so it would imply that they're fit for nothing else.
Yes, Architects go through 7 years of training, but what you've got to remember is that while they spend 5 of those 7 years attending a couple of hours lectures a week and getting drunk, most of the Architectural Technologists you're disparaging are spending 40 hours a week actually designing and technically detailing buildings.
You are right about one thing: Professional Indemnity Insurance pays out against an Architect's Certificate/PCC if the designer turns out to be negligent.
The trouble with that is that insurance companies will fight tooth and nail to avoid paying out, so you will be expected to prove, [i]to a standard acceptable in a court of law[/i], that the building defect results from something that the professional should have reasonably been expected to spot during their scheduled site visits while construction was under way.
You've be taking the consultant that you've built up a relationship and possibly friendship with to court, to try to prove that they are an incompetent liar. Meanwhile his or her professional body will be closing ranks and defending their member to the best of their ability, in an attempt to protect their own reputation and standing.
I have been in a position on numerous occasions where I have had to make claims against Architects' PI, so I know that of which I speak.
Compare that to a proper Structural Warranty, where if there is an identifiable defect, the Warranty provider pays out - simple as that; no court case, no question of apportioning blame - and you'll understand why I am saying that you'd be a fool to rely on a PCC.