That school roof that blew off is a classic example of bad building design and construction. All the joists should have been strapped to the walls and the angled eaves design whimsy is ideally angled and sized to catch the wind. That would'nt last in the south, and is pure stupidity in the north. It is also easily forseeable if you take a simple risk assessment view of the building - fire, flood, wind, rain, and subsidence - all common factors in many place in the midlands and north, and often the south. (Bit like picking a camping spot!)
As far as I know, strapping down roof joists is now specified as part of Building Regs, so the designer, the Building Inspector, the structural design engineer, site engineer and the contractor and subbies are all equally guilty.
As an ex-site QS I used to refuse to pay the subbies if they hadn't done the work right, and put in a claim for extra works to the client if the design was at fault. Now I'm a specialist installer the same thing applies for my own work and I'm fine with that. I can sleep with a clear conscience and no concerns.