Gypsum board fall-off for fire resistance modelling

This paper presents and discusses the results of an attempt that was made to determine the gypsum board fall-off temperature criterion from 80 full-scale fire resistance tests conducted at the National Research Council of Canada in accordance with ULC-S101/ASTM E119 standard fire exposure using floor assemblies with wood joist, wood-I joist, steel C-joist and wood truss protected with either one or two layers of Type X gypsum board and with and without insulation in the floor cavity. The proposed temperature criterion is based on the sudden temperature rise on the back side of the fire exposed gypsum board that is caused by either the board fell-off or board sagging. Extensive statistical analysis of the gypsum board fall-off temperature will be presented. A comparison of the fall-off time based on the temperature criterion and observed board fall-off from fire resistance tests will also be presented.Peer reviewed: NoNRC publication: Ye