C037 -- Experience and Evaluation of Moisture Protection Strategies for Mass Timber Buildings

Interest in mass timber, and awareness of its advantages, have exploded in recent years. But with any new construction technique comes new challenges. For mass timber, a particular concern is sufficient moisture protection during construction: many examples exist of floor and roof panels of all mass timber types left exposed to precipitation, resulting in significant increases in wood moisture content and the potential for slow and limited drying ability depending on the assembly. Wetting of mass timber during construction often leads to schedule delays and staining of finished surfaces that requires sanding and refinishing. In more severe cases, the wetted wood elements expand in constrained areas and become damaged, or fungal growth occurs on the wood or within concealed assemblies, leading to the possibility of fungal decay over time. Fortunately, many solutions exist, but choosing between them can be daunting; the cost-benefit assessment is often questioned and becomes a budget and risk management choice. This paper offers a simple moisture management process and guidance for designers and contractors that was created from firsthand and shared experiences on mass timber projects constructed across Canada and the US over the past decade. This process will help inform risk management decisions about mass timber moisture protection and the selection of appropriate protection for the anticipated exposure to wetting.