I think this is the crux of the matter: organising tradies to appear on time and complete the job properly in a timely fashion.
We signed a contract in mid March 1975 with a large SA building firm for completion in mid October.
Our building progressed in a series of fits and starts. First the siteworks occurred, then a break of weeks with BS being given as to why no trenching or formwork. Then trenching happened, but no slab or trench filling. It rained and the trenches collapsed. etc etc and so on.
It seemed like the supervisor could only organise one trade at a time and then the project ceased until I got on to him to ask what next.
Finally in the 4 weeks of November we progressed from lock-up to completion with carpenters/electrical/plumbing/tilers, gyprock fixers and painters managing to do their work. Only stuffup was the plumber coughing up the hot and cold taps above the kitchen sink. I said we could live with it as I was (well and truly) over the whole process, and just wanted possession.
Its my belief that if building supervisors cared, or could properly organise themselves and trades a house could be erected in 4 months max.
I don't think many would know what a Gantt chart is (although they may be out of fashion by now).