Evaluation of the Reaction to Fire of Historic Scots Pine (Pinus sylvestris L.) from a Historic Building in Poland

Assessing historic timber requires separating service history from material variability, surface condition and sampling limitations. This study characterizes Scots pine recovered during renovation of the historic half-timbered residential building at farm no. 5 in Swołowo, Poland, dated to 1869, and compares it with contemporary pine and previously published oak results from the same building. Twenty-four historic-pine tests and four contemporary-reference tests were analysed by mass loss calorimetry at 35 and 50 kW/m2. The study extends earlier work by examining, within one historic-pine dataset, how area-normalized peak and total heat release relate to heat release normalized by initial specimen mass, while placing the results in a shared building-provenance context with published oak data. Mean ignition times of historic series ranged from 31.4 to 65.6 s at 35 kW/m2 and from 12.0 to 19.0 s at 50 kW/m2, versus 48.0 and 12.5 s for the references. Mean peak heat-release rates (pHRRs) were 8.4–32.1% higher in historic pine, whereas heat release per initial specimen mass (Q0) was 7.5–22.5% lower; these opposite directions show that peak intensity and mass-normalized heat contribution are not interchangeable. Area-normalized total heat release (THR) varied in direction. Published historic oak showed consistently lower THR, while its pHRR response depended on surface condition. The material was obtained from a historic building, rather than from a controlled ageing experiment; all historic pine tests came from one structural member, and the reference groups were small and heterogeneous. Two mass-signal discrepancies and incomplete specimen-level anatomical and density data further limit inference. Accordingly, the results do not establish an ageing effect or a fire-reaction classification. Fire-performance assessment of historic timber should consider ignition time, peak heat release and mass-normalized heat release separately, without attributing observed differences to age alone.