PURPOSE: To prevent the generation of dew condensation positively by utilizing the advantage of simplicity on the execution of works and the security of simple fire resistance in a framework construction method, adopting an external heat- insulating system and installing an internal permeable layer and an external permeable layer on both sides of a heat-insulating material while holding the heat-insulating material.

CONSTITUTION: A heat-insulating material 51b is disposed in tension in the surface direction while interposing first rafters 50b for ventilation arranged on the outside of a board 46 mounted on the outdoor side of a roof framework 25 assembled by stretching a plurality of rafters 42 between a ridge piece 40 and a fasica board 41 consisting of a base material at intervals, thus an internal permeable layer 52b is formed. Plywood for a roof backing, an asphalt roofing and a roof material 55b are arranged in tension in the surface direction while interposing second rafters 54b for ventilation disposed outside the heat-insulating material 51b at intervals, thus an external permeable layer 56b is formed.