Abstract: A gypsum building material, characterised in that the gypsum building material comprises at least gypsum, H-siloxane and/or amorphous silicon dioxide and optionally further additives, wherein the H-siloxane is uniformly distributed in the gypsum building material and/or is applied to at least one surface of the gypsum building material, characterised in that the gypsum building material under the effect of temperatures of at least 80° C. has a longer expansion phase than a gypsum building material without H-siloxane and/or amorphous silicon dioxide, wherein the gypsum building material is otherwise of identical composition.