Enhancing the fire resistance of light gauge steel framed floor-ceiling systems through external insulation

Abstract

Light Gauge Steel Framed (LSF) floor-ceiling systems, composed of thin-walled cold-formed steel (CFS) structural components, offer a high strength-to-weight ratio and cost-effectiveness, leading to their widespread adoption in modern construction. However, research on the fire behaviour of LSF floor-ceiling systems is limited. The industry-standard approach of using two 16 mm gypsum plasterboards for ceilings achieves a maximum Fire Resistance Level (FRL) of 90 min, mainly due to the significant fall-off associated with gypsum plasterboard. Traditional methods for increasing FRL involve adding more layers of gypsum plasterboard; however, the efficacy of achieving a 120-min FRL with three 16 mm gypsum plasterboards remains uncertain. This paper addresses these issues by developing innovative LSF floor-ceiling systems that incorporate external insulation (rigid stone wool) to mitigate the impact of critical ceiling fall-off behaviour and enhance FRL. The research includes dimensional stability tests of rigid stone wool, thermal and structural finite element modelling, and load-bearing small-scale fire tests. The new LSF floor-ceiling system has been shown to achieve an FRL of 130 min, approximately 45 % higher than conventional floor-ceiling systems, offering enhanced fire resistance and increased thermal comfort as a single, integrated solution.