The fire resistance of cross-laminated timber (CLT) could be improved by treating the lamina with fire retardants. The major issues with this technology are the reduced bondability of the treated lamina with commercial adhesives. This study assessed several surface preparation methods that could improve the bondability and bond durability of fire-retardant treated wood with two commercial adhesives. Four surface preparation methods, including moisture/heat/pressure, surface planing, surface chemical treatment, and surface plasma treatment were assessed for their impact on the bondability and bond durability of lodgepole pine lamina. The block shear test results indicated that all surface preparation methods were somewhat effective in improving bond performance of fire-retardant treated wood compared to the untreated control wood samples, depending on the types of fire retardants and wood adhesives applied in the treatment process and bonding process. The selection of surface preparation, fire retardant, and wood adhesive should be considered interactively to obtain the best bond properties and fire performance. It may be possible to effectively bond the treated lamina with PUR adhesive without any additional surface preparation for the fire retardant used in the treatment at FPInnovations.
Currently, mass timber building designs commonly incorporate a concrete floor topping. This can improve building accoustics by increasing the mass of the assembly, reduce floor vibration and create a smooth flat surface to install finish flooring on. The installation of concrete requires formwork, pouring and finishing the concrete and time to cure which adds to project schedules. One way to address this is to use mass timber elements that are prefabricated with concrete toppings preinstalled. Replaceing the concrete floor toppings wiht dry alternatives, such as cement board, may also reduce construction timelines, while still ensuring adequate acoustic and vibration performance. Cement board needs only to be screwed in place and can be walked on immediately after installation; this reduction in construction time may reduce overall project costs and help make wood buildings more cost competitive than other types of construction.
These concealed or void space cases require installation of elements which represent additional material cost and labour. For wood buildings that rely heavily on prefabrication, these steps can have a significant impact on scheduling. Removing dependence on concrete and gypsum board in certain applications could make wood buildings more cost competitive to similar buildings of steel and concrete and could further enhance the benefits of prefabricated construction.