FIELD: building practice. SUBSTANCE: to produce composite material, method uses diluted slurry formed by mixture of gypsum and filler, latter being reinforcing particulate material such as wood fibres. Slurry thus-prepared is subjected to heating under pressure to convert gypsum to calcium sulfate alpha-semihydrate, followed by significantly dewatering hot slurry before re-hydrating semihydrate to re-convert it to gypsum. Resulting material is homogeneous and comprises, embedded into it, gypsum crystals forming physical aggregates with surrounding individual particles. According to an other alternative embodiment, said of hydrating composite mass is preceded by step of treating this mass under pressure until it is fully settled. EFFECT: wall plaster made of proposed composition possesses improved properties, viz it is fire-resistant, preserves dimensional stability and has excellent strength parameters. 30 cl, 14 dwg , 2 tbl
