BACKING MATERIAL

PROBLEM TO BE SOLVED: To provide a backing material of excellent air permeability and draining property capable of effectively draining dew condensate and rainwater while maintaining the strength of the backing material to load from the outside. SOLUTION: The backing material 1 disposed between a roofing material and a sheathing surface of a roof is provided with a plurality of grooves 3 on the sheathing abutting side surface. The grooves 3 are opened at both ends and formed in the pitch direction of the roof at every predetermined space in the horizontal direction of the roof. When the cross-sectional area of the backing material 1 when cut in the horizontal direction of the roof is set to S1 and the total area of the cross-sectional areas of space parts formed by the sheathing abutting side surface of the backing material 1 and the internal wall surfaces of the respective grooves 3 is set to S2, the grooves 3 are provided in a range of S1 and S2 satisfying the relation of 3≤[S2/(S1+S2)]×100≤20(%). COPYRIGHT: (C)2007,JPO&INPIT