The feasibility of manufacturing cross-laminated timber (CLT) from southern yellow pine (United States grown) treated with micronized copper azole type C (MCA-C) preservative was evaluated. Lumber (2x6 visually graded no. 2 boards) was treated to two retention levels (1.0 and 2.4 kg/m3 ), planed to a thickness of 35 mm, and assembled along with an untreated control group using three adhesive systems following product specifications: melamine formaldehyde (MF), resorcinol formaldehyde (RF), and one-component polyurethane (PUR). Block shear and delamination tests were conducted to examine the bonding performance in accordance with ASTM D905 and ASTM D2559 Standards, respectively. One-way analysis of variance and Kruskal-Wallis H test were conducted to evaluate the effects of preservative retention and adhesive type on block shear strength (BSS) and wood failure percentage (WFP). Regardless of adhesive type, the 1.0 kg/m3 retention treatment significantly lowered BSS compared to the untreated control. CLT composed of the laminations treated at 2.4 kg/m3 maintained BSS when PUR and RF were used but not MF. The average WFP of each CLT configuration ranged from 89% to 99%. The untreated CLT specimens did not experience any delamination under accelerated weathering cycles. The delamination rates of the treated specimens assembled using MF and RF increased with the preservative retention level, while PUR provided delamination rates less than 1% to the laminations treated at both levels. These combined data suggest that, under the conditions tested, PUR provided overall better bonding performance than MF and RF for MCA-C treated wood.
Mass timber construction in Canada is in the spotlight and emerging as a sustainable building system that offers an opportunity to optimize the value of every tree harvested and to revitalize a declining forest industry, while providing climate mitigation solutions. Little research has been conducted, however, to identify the mass timber research priorities of end users, barriers to adoption and engineering, procurement and construction challenges in Canada. This study helps bridge these gaps. The study also created an interactive, three-dimensional GIS map displaying mass timber projects across North America, as an attempt to offer a helpful tool to practitioners, researchers and students, and fill a gap in existing knowledge sharing. The study findings, based on a web-based survey of mass timber end users, suggest the need for more research on (a) total project cost comparisons with concrete and steel, (b) hybrid systems and (c) mass timber building construction methods and guidelines. The most important barriers for successful adoption are (a) misconceptions about mass timber with respect to fire and building longevity, (b) high and uncertain insurance premiums, (c) higher cost of mass timber products compared to concrete and steel, and (d) resistance to changing from concrete and steel. In terms of challenges: (a) building code compliance and regulations, (b) design permits and approvals, and (c) insufficient design experts in the market are rated by study participants as the most pressing “engineering” challenge. The top procurement challenges are (a) too few manufactures and suppliers, (b) long distance transportation, and (c) supply and demand gaps. The most important construction challenges are (a) inadequate skilled workforce, (b) inadequate specialized subcontractors, and (c) excessive moisture exposure during construction.
This monitoring study aims to generate field performance data from a highly energy efficient building in the west coast climate as part of FPInnovations’ efforts to assist the building sector in developing durable and energy efficient wood-based buildings. A six-storey mixed-use building, with five storeys of wood-frame residential construction on top of concrete commercial space was completed in early 2018 in the City of Vancouver. It was designed to meet the Passive House standard. The instrumentation aimed to gather field data related to the indoor environment, building envelope moisture performance, and vertical movement to address the most critical concerns among practitioners for such buildings.