PURPOSE: To maintain heat insulation performance of a foam for a long period by a method wherein a heat insulation layer consisting of an organic foam and an inorganic material layer is stuck on an outer wall, a solvent type painting material is applied on the inorganic material layer through an aqueous reaction curing type resin layer. CONSTITUTION: A heat insulation layer consisting of an organic foam (a) and an inorganic material layer (b) is stuck on an outer wall (e) with the foam (a) situated on the outer wall (e) side. The inorganic material layer (b) is coated with a water soluble or an emulsion reaction curing type resin layer (c) being excellent in solvent resistance and having solvent sealing ability, the surface thereof is coated with a colvent type painting material to form a finishing material layer (d). This constitution, since the solvent component of a the solvent type paiting material is sealed by the resin layer (c), prevents the foam (a) from being dissolved by a solvent and holds heat insulation performance of the foam (a) for a long period.