The recent growth of mass timber buildings (MTB) in number, height, and architectural complexity represents a major opportunity for the timber construction sector, but it also introduces significant challenges to overcome, particularly regarding moisture management and long-term performance in diverse climatic conditions. In this context, this study presents 240 days of hygrothermal monitoring data of a MTB during construction, focusing on the moisture behaviour of cross-laminated timber (CLT) elements and the influence of construction practices on moisture safety. Monitoring was carried out in high-risk zones, including wall–floor joints on north and south façades and interior moisture-prone rooms. Moisture content (MC) was continuously recorded alongside daily precipitation and key construction events. During the first 100 days, characterised by mild temperatures and limited rainfall, MC values remained mostly below 20%. However, short and intense rainfall events caused rapid increases above 30%, demonstrating the high sensitivity of CLT to water exposure. As precipitation increased and temperatures decreased, drying was limited, and MC remained above 20% for prolonged periods. The premature installation of gypsum boards and bituminous membranes before roof and façade waterproofing trapped moisture, resulting in visible mould growth. The construction schedule and lack of temporary protection significantly extended water exposure, while alternative strategies, such as early roof waterproofing, temporary shelters, or targeted end-grain protection were not adopted. These results demonstrate that the growing complexity of MTBs requires an integrated moisture management plan developed prior to construction and applied throughout the construction phase. Such a plan should consider local climate, construction sequencing, protective measures, and continuous monitoring to ensure moisture-safe building practices and support the long-term performance of timber structures.
Lima et al. (Tue,) studied this question.