Consequently, it's not a question of whether a fire can damage a structure, but a question of when. It simply takes longer for fire to affect fire-resistant materials. The key is to construct a building in which a fire would take effect slowly, allowing the occupants plenty of time to escape. This is also why materials themselves are rated in respect to how long it would take fire to affect its structural abilities. Even heavy timber can be considered fire-resistant. It's combustible, however, while metals like aluminum or steel aren't combustible -- instead, they tend to buckle under intense heat.