Comparative experimental study of fire resistance ratings of timber assemblies with different fire protection measures

This paper presents the results of a comparative experimental study to investigate the effects of using three different fire protection measures to improve the fire endurance of timber assembly. The three fire protection measures were fire retardant intumescent coating, gypsum plasterboard and filling the timber assembly void with mineral wool. Compared to the reference timber assembly without any fire protection (fire resistance time = 37 minutes), the increases in fire resistance by using the three different fire protection measures were 6 min (16%), 37 min (100%) and 142 min (384%) for using intumescent coating (specimen F2), using 12 mm-thick gypsum plasterboard (specimen F4) and using in-fill mineral wool (F3) respectively. The specific intumescent coating used in the test failed to expand. Therefore, this specimen (F2) behaved very similarly with the control specimen (F1) without any fire protection. Attaching an additional layer of gypsum plasterboard to the timber assembly on the fire exposed side improved the fire resistance rating by about 30 minutes, which is higher than that obtained from using the current design guidance such as Eurocode EN 1995-1-2. Among these three fire protection methods, filling the void between the top and bottom timber boards gave the best result because the mineral wool not only provided insulation but also stopped direct flame attack of the timber board on the unexposed side.