Technical service

Clay plasters do not dry chemically like lime or lime-cement plasters, for example; they dry physically, i.e. by releasing water. Delayed drying and prolonged moisture content increase the risk of mould growth, which decreases as drying progresses. Factors that determine the final drying speed are temperature, air movement and humidity. There are two types of drying: natural and mechanical. With natural drying, sufficient cross ventilation must be ensured, as large amounts of air are required to dry plaster surfaces. This means that all windows and doors must remain open around the clock. Openings in opposite exterior walls are particularly effective for this purpose. With this cross ventilation, a complete air exchange takes place after only approx. 1-5 minutes, whereas with one-sided tilt ventilation it takes approx. 30-60 minutes (source: Moisture and mould formation, Verbraucherzentrale Bundesverband e.V., 2007).

In order to ensure the best possible drying in advance, a drying log must be kept for plaster thicknesses of 15 mm or more. (Source: Dachverband Clay e.V.). Under good conditions, a drying potential of 1-2 mm plaster thickness per day can be assumed.

This type of drying has the advantage that it can be controlled. Various methods are suitable for mechanical building drying, with the use of condensation dryers and blowers having proven effective. The drying equipment must not be oversized, as otherwise the clay plaster will dry too quickly in the outer layer, which can lead to increased cracking. If slight mould growth has occurred due to poor drying, the drying process must be accelerated immediately. The use of drying equipment is essential in this case. To assess the damage and the subsequent treatment of the area, please contact our technical department, who will discuss everything else with you.