To prevent water from leaking from a damaged part of a non-water permeable sheet by laminating nonwoven fabric on both faces of a space network mat wherein many thermoplastic synthetic continuous polymer filaments having a specific diameter form a irregular loop, and fluid sealing agent is filled inside.

A laminate water imperious sheet 6 is provided wherein a imperious sheet 2 is laminated on both faces of a space network mat 1, and further a nonwoven fabric being a cover material 2 is laminated on its outside both faces. A sealing agent 4 is filled inside the mat. At this time, the cover material is preferably composed of two layers of an outer layer part 3a consisting of nonwoven fabric of a rough fiber density and an inner both path 3b consisting of a dense nonwoven fabric. The space network mat is a bulky space network mat of a large void percentage formed of many synthetic polymer continuous lines of 0.5-2mm diameter, and is preferably a single melt of thermoplastic polymer of polypropylene, polyethylene, etc., or a composite melt of two or more kinds.