Fire resistance tests of light steel floor–ceiling systems using steel sheet-laminated gypsum plasterboards

Abstract

Light steel framed (LSF) floor–ceiling systems using cold-formed steel (CFS) joists typically rely on multi-layer gypsum plasterboard ceilings for fire protection, but their fire resistance is often governed by premature ceiling lining fall-off. This study evaluates the use of Sure-Board (steel sheet-laminated gypsum plasterboard) to delay fall-off and improve fire resistance. Three short-span load-bearing fire tests were conducted on: (C1) a two-layer Sure-Board ceiling with steel sheets facing the cavity, (C2) a two-layer Sure-Board ceiling with steel sheets facing the fire side, and (C3) an externally insulated three-layer system with a Sure-Board face layer. A ceiling-suitable two-direction steel lap-joint detail was developed to enable joint overlaps in both directions. Fire tests showed that all three floor configurations achieved 120 min FRL, with structural adequacy-based failure times of 130, 122 and 142 min for C1–C3 configurations, respectively, and without violating integrity and insulation criteria. The results demonstrate that 120 min FRL performance can be achieved for LSF floors without conventional three-layer plasterboard ceilings, and indicate the potential for simplified upgrades using a Sure-Board face layer with a plasterboard base layer in combination with robust joint detailing.