A material-specific speciality is responsible for the pronounced fire protection effect of gypsum plasters. Although the plaster layers are absolutely dry, they nevertheless contain a high share of H2O.
It originates from the mixing water, which with admixture, is intercalated into the molecular structure and remains there as so-called constitutional water. With pure gypsum plaster with a thickness of 10 mm one is concerned with ca. two litres of water per square metre. In a case of fire this water evaporates and protects the rendered building unit. The gypsum, which is classified in accordance with DIN 4102 in Building Material Class A1, is therefore not only incombustible in itself but it even contributes actively against the spread of fire. This property can be utilised both for rendered surfaces on walls and ceilings but also for the strengthening of supports and similar.