Abstract Cross-laminated timber (CLT) is increasingly used in carbon neutral -structures but it can be susceptible to fungal and insect attack when wetted for prolonged periods. Moisture intrusion can be especially important during construction, when the timber can be exposed to prolonged periods of rainfall. Understanding how rainfall impacts CLT is important for managing mass timber construction to minimise dimensional changes and limit the potential for fungal attack. To expand this understanding, two different tests were conducted on CLT involving moisture ingress. First, the effect of repeated rainfall exposure on moisture intrusion into CLT was assessed on 300 mm square three-ply Douglas-fir CLT exposed outdoors for one month and subsequently examined for moisture distribution using Computerized Axial Tomography (CT). Overall moisture contents increased markedly, but moisture intrusion was concentrated in the non-edge-glued joints. Second, small-scale tests of Douglas-fir and southern pine CLT showed similar water absorption patterns while applying a water repellent markedly reduced water uptake. The overall results showed that CLT of both species readily absorbed moisture and illustrate the need to consider water management during construction as well as the benefits of water repellents as a part of this process.
Ramirez et al. (2026) studied this question.