Standard fire endurance tests were performed on a full-scale floor assembly and a full-scale wall assembly constructed with cross-laminated timber (CLT) as the main structural element. The full-scale floor assembly consisted of CLT panels encapsulated with fiberglass wool and a single layer of 15.9 mm thick Type X gypsum board on the exposed side and with two layers of 12.7 mm thick cement board on the unexposed side. The full-scale wall assembly was constructed from CLT panels encapsulated with two layers of 15.9 mm thick Type X gypsum board on both faces. Nine thermocouples were installed on the unexposed face of both assemblies to monitor the temperature rise throughout the test and nine deflection gauges were installed on each assembly to monitor deformations. The superimposed load applied on the floor assembly was 9.4 kN/m² and the load imposed on the wall assembly was 449 kN/m. The fire endurance period of the full-scale floor assembly was 128 minutes and that of the full-scale wall assembly 219 minutes. Both the full-scale floor assembly and the full-scale wall assembly failed structurally afterwards under the applied loading. No hose stream tests were carried out on the fullscale floor and wall assemblies.
A research project, Wood and Wood-Hybrid Midrise Buildings, was undertaken to develop information to be used as the basis for alternative/acceptable solutions for mid-rise construction using wood structural elements. As one approach, encapsulation materials could be used to protect the combustible (wood) structural materials for a period of time in order to delay the effects of the fire on the combustible structural elements, including delay of ignition. In delaying ignition, any effects of the combustion of the combustible structural elements on the fire severity can be delayed. In some cases, and depending upon the amount of encapsulating material used (e.g. number of layers), ignition of the elements might be avoided completely. This scenario would primarily depend upon the fire event and the actual fire performance of the encapsulating materials used. The effectiveness of the encapsulation approach in limiting the involvement of wood structural materials in fires was demonstrated in the research project through bench-, intermediate- and full-scale fire experiments.
A research project, Wood and Wood-Hybrid Midrise Buildings, was undertaken to develop information to be used as the basis for alternative/acceptable solutions for mid-rise construction using wood structural elements. The effectiveness of the encapsulation approach in limiting the involvement of wood structural materials in fires was demonstrated in this research project through bench-, intermediate- and full-scale fire experiments. These results for encapsulated lightweight wood-frame (LWF) systems and encapsulated cross-laminated timber (CLT) systems are documented in a series of reports [3, 4, 5, 6].
In addition to developing the encapsulation approach for protecting the wood structural materials to meet the above code intent, research was undertaken to examine standard fire resistance of encapsulated wood structural assemblies for use in mid-rise wood/timber buildings. One of the major differences between structural LWF assemblies used in mid-rise wood buildings (5-6 storeys) and low-rise wood buildings (= 4 stories) is the wall assemblies for the lower storeys. For mid-rise wood buildings, loadbearing wall assemblies on the lower storeys have to be designed to resist higher axial loads due to the self-weight of the upper storeys, which often result in the need for larger-size stud members and/or a greater number of studs, and higher lateral loads in case of seismic events or wind loads, which often requires the use of wood shear panels within the wall assembly. These wall assemblies very often will need to meet standard fire resistance requirements, and therefore, information regarding their standard fire-resistance ratings should be developed. This report documents the results of fullscale furnace tests conducted to develop standard fire-resistance ratings of encapsulated LWF assemblies for use in mid-rise applications.
The acceptable solutions provided in the 2010 National Building Code (NBC) Division B [1] limits the use of combustible (wood) construction based on building height. For example, for Group C (Residential), Group D (Business and Personal Services) and Group E (Mercantile) occupancies, combustible construction can be used up to 4 storeys, and up to 2 storeys for Group A – Division 2 (Assembly) occupancies. In addition to the building height limitation, there are also building area limitations in the 2010 NBC for the use of combustible construction for these occupancies. For buildings that exceed the height and area requirements for combustible construction, the prescriptive requirements in the 2010 NBC require that noncombustible construction be used for the primary structural elements.
Three materials were selected for investigation as encapsulation materials for combustible structural elements: Type X gypsum board (12.7 mm thick and 15.9 mm thick), cement board (12.7 mm thick) and gypsum-concrete (25 mm thick and 39 mm thick). This report documents the results of intermediate-scale furnace tests conducted to investigate the performance of the three encapsulation materials.
