A method of constructing a heat-insulating and water-proof structure by employing a plurality of heat-insulating members and a plurality of water-proof membranes. A first water-proof membrane is placed over a heat-insulating member, and one longitudinal edge of the water-proof membrane is bent about one longitudinal edge of the first heat-insulating member and secured to a base surface. A second heat-insulating member is then laid on the base surface next to the first heat insulating member so that the one longitudinal edge of the first water-proof membrane is held between the first and second heat-insulating members. A second water-proof membrane is placed over the second member and one longitudinal edge thereof is bent and secured to the base surface. The other longitudinal edge of the second water-proof membrane is joined to the first water-proof membrane. This sequence of work is repeated until a predetermined number of heat-insulating members are laid on the base surface, and a corresponding number of water-proof membranes are applied to the heat-insulating members.