To solve the problem of soaring disassembly cost, tight waste disposal sites, and vain cost increase which may consequently affect construction cost in treatment of gypsum board materials used in a large quantity for ceiling and wall parts when a building is disassembled because a method for the treatment is obliged recently to carry out separation of used construction materials according to the material types and thereafter to dispose of the wastes.

In the disassembly and recovery work of waste gypsum board materials, the materials are carbonized to make the gypsum of the materials be anhydrous gypsum and simultaneously producing carbides of paper materials and cloths contained in or covering the surface and organic substances attached to or contained in the gypsum board materials such as corn starch working as a bond in the gypsum. The carbides and the anhydrous gypsum produced simultaneously are utilized for moisture adjustment agents owing to their mixing ratio and for sandbags excellent in water containment and solidification for countermeasure against floods or prevention of water immersion of housings.