As my profession one of enforcer of Building Code : The local government [adoptive by-laws] [Building] order 1968. Let me pinpoint one principle of building I often encounter challenges in enforcing; curing.
Curing being a process of controlling drying of concrete or mortar by continuous wetting during dehydration so as to attain its optimum strength. For concrete should not be allowed to dry very rapidly, as it will continue gaining strength up to 28 days. It should be at least cured for 7 days, because it will have gained 3/4 of its strength a principle proving a challenge to enforce: For ignorant Clerk of Works do it at night when everybody else retire to sleep.
Another area overlooked is batching; the process of measuring the specified quantities of materials in dry state for making concrete. Most contractors apply by volume method, instead of by mass which is the most accurate especially for storey building.