Cross-laminated timber (CLT) products are used as load-carrying slab and wall elements in structural systems, thus load duration and creep behaviour are critical characteristics that should be taken into account in design. Given the nature of CLT with orthogonal arrangement of layers and either mechanically fastened with nails or wood dowels, or bonded with structural adhesive, CLT is more prone to time-dependent deformations under load (creep) than other engineered wood products such as glued-laminated timber.
Time-dependent behaviour of structural wood products is accounted for in design standards by providing load duration factors to adjust specified strengths. Since the Canadian Standard on Engineering Design in Wood (CSA O86-09) does not deal with CLT, it does not provide load duration and service condition factors. Until this can be rectified, two options are proposed for adopters of CLT systems in Canada. These include not only load duration and service factors, but also an approach to accounting for creep in CLT structural elements. The proposed recommendations are in line with the specifications in CSA O86-09 and Canadian National Building Code.