Why Some Codes Use "Objective-Based" Language Instead of Fixed Numbers

Prescriptive requirements give a specific number to hit — a minimum insulation value, a maximum stair rise. Objective-based requirements instead state the outcome the code is trying to achieve — limiting fire spread, for instance — and allow a designer to demonstrate that a proposed solution achieves that outcome even if it doesn't match a prescriptive path exactly.

This is the basis for "alternative solutions" — a design that departs from the prescriptive path but is shown, usually through engineering analysis, to meet the underlying objective just as well. It gives more design flexibility, particularly for unconventional buildings, but it also puts more burden of proof on whoever's proposing the alternative, since "different" has to be demonstrated as "equally safe," not just asserted.