Development of patterned stains on building façades: investigation of the phenomenon and its prevention

Title: Development of patterned stains on building façades: investigation of the phenomenon and its prevention
Author(s): M. Puterman, R. Becker
Paper category : conference
Book title: First International RILEM Workshop on Microbial Impact on Building Materials
Editor(s): M. Ribas Silva
Print-ISBN: None
e-ISBN: 2351580133
Publisher: RILEM Publications SARL
Publication year: 2000
Pages: 22 - 27
Total Pages: 6
Nb references: 4
Language: English

Abstract: A strange and bothersome phenomenon is observed on many facades of newly built buildings in various areas in Israel: formation of non-aesthetic, dark and large stains of geometric shapes. The stains appear mainly on buildings that were coated with polymeric-based rendering materials, and “reflect” the wall substrates: they form mainly on the masonry parts and do not form on the cast concrete elements.
The purpose of the work, which is still being carried out, is to investigate and analyze the phenomenon and its reasons, and to recommend preventive measures to avoid their formation.
Microscopic and biological investigations of the surface of the stained facades have suggested that the dark stains might be, indeed, mold that is growing on organic rendering materials. In a further step of the work the susceptibility of various rendering materials to mold growth was investigated using standard laboratory methods of fungi growth on a substrate. The tests have shown that polymeric rendering materials, which did not contain fungicide additives, had supported mold growth on their surfaces.
Likewise, the materials containing fungicide but which were exposed to (artificial) UV radiation were also problematic. Only those renderings containing a sufficient concentration of the biocide were resistant from the development of mold on them.
At the next stage of the work experimental walls built of concrete blocks, aerated concrete and cast concrete (with and without expended PS boards on it), and coated with different rendering and finish materials will be tested regarding the effect of the different substrates on the growth of the micro-organisms. This experimental step will be done in a closed laboratory as well as under external conditions.

Online publication: 2000-06-30
Publication type : full_text
Public price (Euros): 0.00
doi: 10.1617/2351580133.003