Influence of board joint configurations on the fire performance of CFS walls

Cavity-insulated cold-formed steel (CFS) wall lined with double-layer sheathing and staggered board joints on both sides is a common wall configuration in mid-rise CFS structures. Such staggered board joints become a laborious task during the construction and may not be always achieved, resulting in overlapped board joints in practice. In this study, six 1.1 m × 1.1 m specimens were prepared using gypsum plaster (GP) board and calcium-silicate (CS) board as the sheathing boards, and rock wool as the cavity insulation. Four specimens were exposed to ISO834 fire conditions for testing and giving a quantitative assessment on the adverse effect of overlapped board joints on the fire performance. It was found that the overlapped board joints reduced the fire resistance time against the insulation failure and structural failure by 16.9% and 29.4%, respectively, for the present cavity-insulated GP-GP sheathed CFS walls. The other two specimens adopted different configurations to the overlapped board joints i.e. additional board strips and steel sheets. The results showed that steel sheets were able to mitigate the adverse effects of overlapped board joints, with improved fire performance of CFS walls. In addition, infrared thermal imaging technology was practiced in the experiments to report the temperature development on the unexposed surfaces of specimens. Significant non-uniform temperature distribution on the unexposed surfaces was quantified and the unexposed surface area corresponding to the stud became a weak area for the insulation failure of CFS walls. Some direct suggestions were proposed on the determination of the fire-induced insulation failure of CFS walls.