PURPOSE: To avoid to disturb the running of a welding machine by the end of the superposing side end of a nonwoven fabric, or by a band steel to press that part, and to improve the workability, by projecting one side side end of a waterproof sheet from the side end of the nonwoven fabric, and placing the other side end by finishing at the inner side from the side end of the nonwoven fabric.

CONSTITUTION: One side side end of a weldable waterproof sheet 2, that is, one end in the width direction, is projected the amount corresponding to the width of welding margine, from one side end of a nonwoven fabric at this side. And the other side side end of the waterproof sheet 2, that is, the other end in the width direction, is placed to finish at the inner side of the nonwoven fabric at that side. And the superposing side end of a neighboring nonwoven fabric extended on a processing object surface is positioned to a place slipping to the side to the waterproof sheet 2 side end, by the corelative positioning between the nonwoven fabric 1 and the waterproof sheet 2. As a result, when the superposing side ends of the neighboring waterproof sheets are welded, the running of a welding machine is made not disturbed by the end of the superposing side end of the nonwoven fabric, or by the existence of a band steel pressing that part. Furthermore, when the side ends 11 of the nonwoven fabrics are connected, the connection is carried out by only turning up the side end of the waterproof sheet covering the side ends 11 of the nonwoven fabric 1.