Mould resistance of five different treatments were tested using two methods, a recently developed method for the determination of critical moisture levels of building materials (RHcrit), and ASTM D3273-94. The critical moisture level method exposed samples at 22 °C and 98, 92, 86 and 82% relative humidity (RH) for 12 weeks. ASTM D3273-94 was performed at 29 °C and about 95% RH. Treatments containing fungicide had better efficacy against mould growth than treatments/materials without fungicide. Whilst the ASTM method is relatively simple to perform and provides quick results, the critical moisture level method provides valuable information for different treatments and contributes to a more nuanced evaluation of the treatments' mould resistance. The results from the (RHcrit) test and ASTM after 28 days were compared and there was good correlation between the test methods with respect to mould resistance.

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