The study contains a field study in which several facades of buildings were studied, as well as a survey where real estate managers have shared their experiences.

On 28% of the total of 268 facades studied in the field study, discoloration was found to such an extent that it was judged to affect the aesthetic impression. Both mould fungi and algae could be identified in the samples taken on discoloured facades. Most of the facade materials studied consisted of rendering or sheet metal. On buildings with façade of sheet metal, the north side was more susceptible to discoloration than other parts of the buildings. No impact on the point of the compass could be observed on buildings with other facade materials. No regional difference in the extent of discoloration could be found in the study. The survey confirms these observations.

The survey shows that many property managers consider that discolouration generally constitutes a problem in their property portfolio, due to costs for maintenance or cleaning, complaints from residents or a reduced general impression of the property portfolio. Although some managers did not consider it to be a general problem, some specific façade types in the property stock may be discoloured and cause problems. Most property managers considered that a façade should not receive an unacceptable discoloration until after at least 10 years. Their experience was that several buildings received such growth already within 10 years after construction of the building.

Respondents of the survey were asked to evaluate discolouration of some example facades, by looking at pictures. It was found that the extent of a discolouration to be regarded as unacceptable varies between different people and different types of buildings. In the survey, real estate owners' experiences of different remediation methods of discoloured facades were surveyed, and it was found that the experiences differ. The property managers believe that a cleaned facade should last at least 5 years before the extent of discoloration becomes unacceptable.

Results from the study will be used as questions and hypotheses in future studies, e.g. to investigate the effectiveness of remediation agents and to develop tools and guidelines for preventing new discoloration.