Mould and phototroph growth on masonry façades after repainting

• Published in: Materials and structures Vol. 37; no. 271; pp. 472 - 479
• Main Authors: SHIRAKAWA, M. A, JOHN, V. M, GAYLARDE, C. C, GAYLARDE, P, GAMBALE, W
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.08.2004
• Subjects: Applied sciences; Building structure; Buildings; Buildings. Public works; Construction (buildings and works); Durability of constructions; Durability. Pathology. Repairing. Maintenance; Exact sciences and technology; External envelopes; Masonry structure; Materials; Paints and renderings. Protection products; Wall. Partition; South America; Brazil; America; Microbial activity; Phototropism; Durability; Disinfection; Washing; Front wall; Masonry; Paint; Biodiversity; Outdoor study; Fungi; Microscopy; Microorganism; Biocide; Thallophyta
• ISSN: 1359-5997; 1871-6873
• DOI: 10.1617/13914

The appearance and durability of paint films are affected by microbial growth and fungi and phototrophs are considered to be especially important, degrading the films mechanically, by the production of metabolites, chiefly acids, and by enzymatic activity. In this study, fungi and phototrophs were identified before and throughout one year after painting two building facades in Sao Paulo. Disinfection with hypochlorite and high-pressure water jet cleaning of the facades caused reduction of at least 85% in the microbial population. Paint was applied with or without a biocide formulation (0.25% w/w) - carbendazin, N-octyl2H-isothiazolin-3-one and N-(3,4-dichlorophenyl)N,Ndimethyl urea. The biocide reduced fungal colonization up to 10 months after painting on one building. However after 12 months biocide made no statistically significant difference. The major fungal contaminant was the genus Cladosporium. After 10 months Aureobasidium was also associated with black discoloration. On both the re-painted facades, fungi were detected before phototrophs, contrary to the citations from the literature. SEM showed that fungal contamination was present not only on the surface, but between the old and new paint films and between old paint and rendering mortar. Under these conditions building facade details and micro-environment seem to be more important than biocide in controlling fungal growth.