PURPOSE: To improve the waterproofness and facilitate construction execution by charging the recessed part of a surface member having the male and female connection parts having each tongue piece on the both side edges by a core material and integrally forming the back side by the covering by a back surface member.

CONSTITUTION: On the both side edges of a surface member 1 consisting of a metal plate, synthetic resin plate, etc., a male-shaped connection part 3 having a tongue piece 11 and a female-shaped connection part 12 having a tongue piece 12 are formed. The recessed part 18 of the surface member 1 is charged with the core material 19 such as heat insulating material, and covered by a back surface member 20, and formed integrally with the surface member 1. The gap for preventing the capillary phenomenon is formed by properly selecting the connection part structure dimension of the male/female shapes, and the engagement force is increased by forming the insertion edge into a double structure form. Therefore, execution can be carried out by one worker, and the waterproofness and heat insulation performance can be improved.