Gypsum consists of calcium sulphate, which crystallizes under the influence of water. Gypsum plaster can be carried out with a particularly high-quality, smooth and even surface. In the event of permanent moisture penetration, plasters containing gypsum lose their strength, which is why they are excluded in accordance with DIN 18550-2 for damp rooms, with the exception of domestic kitchens and bathrooms. However, in the case of temporary moisture, e.g. in domestic bathrooms and kitchens, gypsum can absorb the moisture well and release it again with a time delay without being damaged. In the splash-affected area, waterproofing is required in accordance with the ZDB leaflet "Instructions for the execution of composite waterproofing with cladding and coverings made of tiles and slabs for indoor and outdoor use".
Gypsum lime plasters have an evenly grained surface and are more resistant to mould and fungal infestation due to the alkaline effect of the lime. Plaster containing gypsum cannot be applied outdoors.
Source: bauwion
