Fire resistance is one of the most enduring ideas in fire safety design. This paper charts the emergence of fire resistance, and its rise to ubiquity – with a focus on British codes and standards. Beginning as a method for independent testing of ‘fireproofing’ systems, fire resistance was formalised in the USA, and subsequently in the UK. Minimum fire resistance periods were defined that would allow a structure to resist burnout of the fuel in a compartment; these minimum periods became legislatively empowered in the 1950s. Over subsequent decades the required periods of fire resistance evolved in response to uncertainties and competing motives. It is shown that within UK guidance, where statutory guidance recommends 30 min as a period of fire resistance, such buildings are not expected to resist burnout. Where guidance recommends more than 30 min fire resistance (for offices or residential buildings), it is intended that such buildings should resist burnout. This paper aims to assist those with responsibility for meeting the requirements of the building regulations to consider for themselves whether following the guidance in the approved documents (or technical handbooks in Scotland) is likely to be sufficient to discharge their responsibilities as construction professionals.