Structural safety, to be optimal, should conform to a general rationale for all life safety and health in a society. Two rationales are suggested here, one using a principle of time allocation, the other using a social indicator. The Time Principle of risk management states in effect that a “life-saving” alternative, if truly it is to save lives, should return to society more years of life in good health than the years of work consumed to pay for its cost. Alternatively, a risk optimality criterion can be derived from a compound social indicator that reflects general benefit to society and is a function of gross domestic product and life expectancy. To be preferable, an alternative should maximise the social indicator. The Life Quality Index yields the same optimality criterion as the Time Principle, defining “How safe is safe enough.” Although risk must be discounted like finances, it is suggested as an ethical principle that this discounting should not extend beyond the period of financing. It is concluded that the cost-utility of structural codes and standards (and other provisions for public health and safety) should conform to these criteria.