A fire barrier material for use in building construction comprising a sandwich structure (1) have a first (2) and second (3) outer layers comprising a high temperature resistant material having corrugations (7, 9) therein and an intermediate layer (5) comprising a flame retardant fibrous material wherein the corrugation (7, 9) are positioned in the outer layers (2, 3) in a manner which enables the barrier material (1) to be rolled into a bundle in a direction substantially perpendicular to the direction of the corrugations (7, 9).