Combustion Properties of Timber in Historic Structures: Case Study of the São Pedro de Alcântara Chapel Fire

ABSTRACT Timber plays a fundamental role in the fire performance of historic building components, where ageing and environmental exposure can markedly influence its physical and chemical properties. This study presents an experimental investigation of the fire behaviour of Ocotea sp. ( Lauraceae ) wood obtained from a single original historic flooring element preserved in the sacristy of the São Pedro de Alcântara Chapel in Rio de Janeiro, Brazil. The element was not part of the post‐2011 reconstruction and showed no visible fire damage. Both as‐received and oven‐dried samples were analysed to evaluate the effect of moisture content on flammability. Thermal stability and thermal degradation were characterised using thermogravimetric analysis (TGA), highlighting differences in decomposition pathways and residual char yield. Flammability assessments included vertical and horizontal burning tests adapted from UL 94 V and UL 94 HB to examine the influence of specimen orientation on fire propagation. Additionally, limiting oxygen index (LOI) testing quantified the flammability under varying oxygen concentrations, while glow‐wire tests evaluated the response to localised incandescent heating. Under the adopted bench‐scale conditions, the as‐received specimens required a higher oxygen concentration to sustain flaming and yielded higher glow‐wire indices than the oven‐dried specimens. The vertical and horizontal test configurations produced different flame‐propagation outcomes, although the different exposure procedures do not allow this difference to be attributed solely to specimen orientation. These findings provide preliminary material‐level evidence for future element‐scale testing and fire‐dynamics modelling.