Re-Drying Behavior of Plywood-based Single Surface Splines as a CLT In-plane Connector

Moisture management is essential for Cross-Laminated Timber (CLT) structure, as repetitive wetting and re-drying cycles lead to moisture related issues of dimensional instability, distortion, and delamination of the CLT panels. In addition, concerns about indoor air quality may arise because of fungus growth when the structure is closed in at a continual wet condition. Special attention is given to single surface splines, one of the inplane connections for CLT floors that typically comprise a strip of plywood installed into the profiled edges of two CLT panels adjacent to each other. The industry has reported its tendency to absorb a much larger amount of water than the CLT panels they connect and can be more difficult to dry out when severely wetted. It is critical to study the re-drying potential of the single surface spline as one of the "hot spots" in terms of water uptake. The aim of this project is to develop an understanding of the re-drying potential of wetted plywood-based single surface spline connections under two case scenarios, i.e., with and without a water-resistive barrier (WRB) between the spline-to-CLT wood-to-wood connections. Through this experimental study, time-dependent curves to reflect the redrying rate of wetted plywood-based single surface spline were developed. The experimental results revealed that it took as little as eight (8) days for saturated plywood-based splines to dry below the recommended moisture content level if the proper air-dry solution was in place. At least a month is needed to facilitate such drying for single surface splines installed with and without a water-resistive barrier (WRB) between the spline-to-CLT wood-to-wood connections, which might cause conflict with the construction schedule. It was recommended for the construction team to come up with alternative solutions for issues with the wetted splines on-site, for instance, replacing the wetted plywood-based splines with the new/reused air-dried splines after overarching structural evaluation could be one of the solutions that would not become a burden to the construction cost and schedule. Solutions to facilitate air-drying of the single surface splines, as well as the CLT floors, should be explored in future research.