Bioreceptivity of different painting systems to mould growth on "tabique" walls and plasterboards

Mould growth on the inner surfaces of building elements is a common pathology found in buildings, resulting not only in the early degradation of the materials but also in the deterioration of the indoor environment. On the other hand, building renovation provides an exceptional opportunity to improve the quality of life of its users. Within this scope it is therefore relevant to understand the effect that different painting solutions may have on mould growth. This work evaluated the mould growth in four kinds of substrates, with different painting systems. The selected case studies were: two "tabique" walls (constructive solution with strong implantation in the built heritage), one with lime mortar and another with lime and cement mortar; and two gypsum plasterboards (a constructive solution that is widely applied in building renovation), a normal and a water repellent. To evaluate the mould growth, two methodologies were adopted: counting the number of colony forming units (CFU) in six sampling periods; and visual inspection through photographic recording, including the quantification of the percentage of "dark pixels". At the end of the test it was established that plasterboard was more favourable to mould growth when compared to "tabique" walls. Moreover, the roughness of the substrates and the sampling location had also significant impact on the results.