The Tallwood House project was intended to advance the design and
manufacture of mass timber products in Canada and demonstrate
that mass timber is a viable structural option for mid-rise and
high-rise buildings. The use of mass timber and engineered wood
products in high-rise construction is becoming more common
around the world leading to a growing interest in the performance of
mass timber over time.
This report describes the performance of the mass timber structure
in Tallwood House, between September 2017 and August 2019,
based on measurements of the moisture content in the prefabricated
CLT floor panels and the displacement of the vertical structural
system. It is intended to initiate discussions on the performance of
mass timber structure elements during building occupancy and lead
to further research that can explore the influential factors.
Cross-laminated timber (CLT) may require preservative treatment in markets with severe termite hazards. Given the size of CLT panels, conventional pressure treatment would not be feasible. We therefore assessed the treatability of CLT panels with an alternative low moisture uptake surface-applied penetrating process for applying termiticides. Hem-fir panels were selected for the initial tests on the grounds that western hemlock and amabilis fir are relatively treatable. Nine test panels were dip treated and stored for 7, 14, or 21 day activation periods. Borate retention ranged from 1.2 to 6.5 kg/m3 and penetration ranged from 3 to 9 mm. Longer activation periods did not result in improved penetration. Greater penetration would likely be needed to meet performance-based standards.
