PURPOSE: To prevent the generation of cracks by forming a polymer cement layer on an external surface of a skeleton by way of a building skeleton and coating the polymer cement layer with a mortar layer.

CONSTITUTION: A base sheet 2 is pasted on an outdoor side of a skeleton 1. A metal lath 3 is stretchingly installed by a staple 3a. A polymer cement layer 8, which includes about 8 to 50 parts by weight of a solid portion of organic polymer based on 100 parts by weight of cement, is formed. Then, the polymer layer 8 is coated with a mortar layer 4 where the external surface f the mortar layer 4 is spray-coated with a finishing layer, such as lysine. It is, therefore, possible to provide excellent durability without generating cracks on the outside wall.