To ensure waterproofness and workability and, at the same time, to prevent a waterproof sheet from being damaged by a fixing device even if a heat insulation material or suchlike is deformed by, for example, liquid pressure.

The waterproof sheet laying structure 10 includes: a sheet joining member 14 fixed to the housing 12 of the structure by a fixing device 20; and a waterproof sheet 16 laid on the structure jointed to the sheet joining member 14. The sheet joint member 14 includes: a joint member body 22 having a joint face 22a to which the waterproof sheet 16 is joined, and a recess portion 22b formed so as to recede from the joint face 22a and used for the fixing device 20 to be passed through it; and a covering presser plate 24 installed in the recess 22b and covering the head 20a of the fixing device 20. The surface 24a of the presser plate 24, which is on the waterproof sheet 16 side, is not welded by the waterproof sheet 16 by a solvent used to weld the waterproof sheet 16 to the joint face 22a.

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