This report describes a full-scale exterior wall fire test conducted on December 16, 2014 on a Nordic cross-laminated timber (CLT) wall system. The test was conducted in accordance with CAN/ULC-S134-13, Standard Method of Fire Test of Exterior Wall Assemblies. The test was conducted using the exterior wall fire test facility located in the Burn Hall of the NRC Fire Laboratory, Mississippi Mills, Ontario. The CLT wall system was assembled to represent a continuous solid wood wall covered by a water barrier membrane and insulation. The pilot burners were lit prior to the commencement of the test. Gas flow to the burners was manually adjusted to follow the prescribed heat input required by the standard.
In general for both wall constructions simulation results tended to point to the exterior of the stud
in the Lightweight Wood Frame (LWF) and Cross Laminated Timber (CLT) construction cases to
be the area most at risk, specifically toward the exterior surface of the stud. Generally the total
Moisture Content (MC) of the stud decreased to an acceptable level within the simulation period
however the exterior surface appeared to remain at relatively high of moisture content level for
significant periods of time. The presence of wood strapping covering the exterior face of the stud
seemed to exacerbate the situation. If a support system for the cladding can be designed that does
not rely on wood strapping or covers a minimum area of the stud the performance of this critical
area could be improved. If the initial moisture content of the wood materials could be reduced
before close up the performance would also be improved for all locations that did not show an
increase in moisture content and the RHT index in the second year, at least with respect to
computer modelling. This work however was not in scope of the work.
Solutions for Mid-Rise Wood Construction: Full-Scale Standard Fire Test for Exterior Wall Assembly Using a Simulated Cross-Laminated Timber Wall Assembly with Interior Fire-Retardant-Treated Plywood Sheathing