Abstract: A fire resistant floor and ceiling assembly comprising in combination; a plywood layer; a gypsum floor underlayment extending adjacent below said plywood layer; a series of steel joists located below said underlayment and supporting the plywood and underlayment; a space-apart multiplicity of self-drilling self-tapping screws extending downwardly through the plywood and underlayment, and engaging said steel joists thereby attaching the plywood and underlayment to the steel joists, said screws having upper threads and lower threads with an interrupting non-threaded mid-portion therebetween, the non-threaded mid-portion extending a distance substantially the same as the thickness of said plywood layer; and, at least one layer of third generation fire resistant gypsum board connected to, and supported below, said steel joists by connecting means; whereby said assembly contains no combustibles in the plenum between said underlayment and fire resistant gypsum board, and whereby said assembly attains at least a one

Abstract: A fire resistant ceiling furring system comprising support joists in generally parallel alignment, furring clips attaching furring channels to the joists, furring channels in generally parallel alignment at substantially right angles to said joists thereby forming a generally grid-like configuration, said furring channels connected at grid intersection points to said joists by means of said furring clips, fire resistant gypsum ceiling panels affixed at lower attachment surfaces of said furring channels, and, mineral fiber insulation provided for substantially the full expanse of the ceiling being disposed above, and supported by, said furring channels forming a continuous layer beneath said joists. Whereby upon exposure of the fire resistant ceiling furring system to heat from below the furring channels continue to support the mineral fiber insulation and remain engaged to said ceiling panels during heat distortion by means of said furring clips retaining the furring channels.