Overview
ISO 21265:2021 - "Building and civil engineering sealants - Assessment of the fungal growth on sealant surfaces" specifies a laboratory method to evaluate fungal growth on sealants used in building joints. The standard defines test specimens, microbial strains, apparatus, inoculation and incubation procedures, and assessment/reporting requirements so manufacturers, test laboratories and specifiers can determine a sealant’s resistance to fungal colonization under controlled conditions.
Key Topics and Technical Requirements
- Scope: Method for evaluation of fungal growth on sealant surfaces used in building construction (ISO 21265:2021).
- Test fungi: Intended to evaluate the five common strains found on sealants - Fusarium oxysporum, Aspergillus niger, Phoma herbarum, Exophiala jeanselmei and Penicillium chrysogenum (national collection strains such as ATCC identifiers are cited).
- Apparatus & environmental control:
- Incubators capable of 20–35 °C (±1 °C) and ≥90% relative humidity.
- Oven, water bath (50 ±1 °C), autoclave (120 ±2 °C, 2 bar), analytical balance, centrifuge and stereoscopic microscope.
- Specimen preparation:
- Sealant extruded onto anti‑adherent (PE/PTFE) to form sheets ~2 ±0.5 mm thick; specimens cut to ~50 × 50 × 2 mm.
- Preconditioning: 28 days at (23 ±2) °C and (50 ±10) % RH.
- Optional water‑immersion protocol: immersion cycles in deionized water (document specifies immersion handling and conditioning).
- Culture media & inoculum:
- Defined mineral‑salt and glucose media; complete agar medium for solid‑medium tests.
- Procedures for stock strains, spore harvesting, centrifugation/washing and viability checks.
- Assessment:
- Visual scoring of fungal growth on specimens, measurement of inhibition zones where applicable, and standardized test reporting and expression of results.
Applications and Who Uses It
- Sealant manufacturers: product development, quality control and claims substantiation for fungal resistance.
- Independent test laboratories: routine conformity testing and certification.
- Architects, façade engineers and specifiers: selecting sealants for high‑humidity or sanitary applications where mould and mildew resistance is critical.
- Facility managers and contractors: validating maintenance and performance expectations in wet environments (bathrooms, kitchens, façades, underground works).
Related Standards
- ISO 846 - Plastics: evaluation of the action of microorganisms (referenced for related methods).
- ISO 6927 - Vocabulary for building and civil engineering sealants (terminology).
Keywords: ISO 21265:2021, building sealants, civil engineering sealants, fungal growth testing, sealant fungal resistance, test fungi strains, mould resistance testing.
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