Since Chinese historic buildings have a unique wood structure, the fire load is used as the key parameter to determine the fire risk. In this study, the aim is to examine the fire risk of historic wooden buildings in Beijing by identifying the fixed fire load (FFL) and movable fire load (MFL) for a sample of 83 historical buildings. It is found that the fire load is averagely 2847.7 MJ/m² and dominated by the fixed one, which is significantly different from that of conventional modern buildings. The fire load is proven to have an extreme value III distribution. The roof board, pillars, and beams contribute the most to the FFL and the FFL from the roof board has almost a constant value of 482.6 MJ/m². By a K-Means clustering algorithm, it is found that the FFL first decreases and then increases with a greater floor area, which could be explained by the evolutionary process of a historic building’s size. The sample historic buildings are classified by five types of usages to determine the MFL. Finally, an estimation matrix of the fire load of historic buildings is proposed based on the above statistical results.

Historic buildings have significant cultural, scientific, and aesthetic value, and show the accomplishments of past eras. Unfortunately, many of wooden historic buildings are destroyed by fire disasters. The reaction-to-fire performance of timber was changed after several hundred years of natural weathering. In this study, the effect of weathering on the reaction-to-fire performance of untreated and fire retardant treated timber are investigated. The conventionally treated cedars were weathered in accordance with a standard construction material durability test method (JSTM J7001), three accelerated weathering test methods (J60, J20 and J4), and a standard weathering method (NT FIRE 053 Method A), respectively. Then, the effect of weathering on phosphoric acid and paraffin treated timber samples was examined by comparing the reaction-to-fire performance of chemically treated timber before and after weathering. The results show that the use of fire retardant can reduce the ignition time, the peak heat release rate (pHRR) and total heat release (THR). The weathering process increases both the pHRR and THR, but reduces the ignition time, which infer a relationship between the two processes of sufficient pyrolysis.