Installation on gypsum plaster (mortar group PIV to DIN 18550)
All plaster beneath ceramic tiles or natural stone are to be struck off tightly with a straight edge. The surface must remain rough and may not be smoothened or felt boarded. To enable an orderly tile installation, increased requirements for flatness of the plaster should be contractually stipulated. Gypsum plaster is only suitable as a substrate for exposure class A0, i.e. for moderately wet wall areas (e.g. domestic bathrooms).