1. Behavior of wood in fire

Already in ancient times, wood was widely used in buildings designed to shelter people. Solid posts and beams were assembled to form load-bearing frameworks. Flat elements (shingles) were used for roofs and facades. But it was already commonplace to use wood as a domestic fuel, and the dramatic fires that occurred throughout history (Rome in 70 BC, Brussels in 1967 causing 322 deaths and Moscow in 2003 causing 40 deaths, for example), led to uncertainty in people's minds about the ability of wooden structures to meet fire resistance requirements.

However, wood is naturally fire-resistant. In fact, as the outside temperature rises during a fire, wood begins to brown and dry out on the surface. It's only when the temperature rises above around 300°C that the wooden element begins to pyrolyze and carbonize. The outer layer of charcoal thus formed acts as a thermal...