A continually growing number of jurisdictions in Canada and the United States are placing restrictions on the use of engineered wood products manufactured with structural adhesives. Since vertical-use-only fingerjoined wood studs manufactured with a polyvinyl-acetate (PVA) adhesive are one of the products of concern, Forintek’s L. Richardson was appointed to chair a special task group of the American Wood Council (AWC) Subcommittee on Fire Performance of Wood to determine what if any fire testing should be carried out and then to oversee those fire tests. In 2005, three Canadian manufacturers of fingerjoined studs requested that Forintek develop a strategy for assessing the substitutability/inter-changeability of SPS-3 vertical-use-only fingerjoined studs manufactured with polyvinyl-acetate (PVA) adhesives for solid-sawn wood studs in the construction of wood-frame loadbearing walls. Therefore, Forintek concluded that it should focus its efforts in 2005-2006 on assessing the fire performance of vertical-use-only fingerjoined wood studs manufactured with PVA adhesives. This change in direction for the project was supported by the project’s technical liaisons and mid-year revisions were made to reflect the change.
In March 2006, a standard ASTM E 119 fire test was conducted on a wall assembly constructed with nominal 2x4 No. 2 (and better) SPF SPS-3 fingerjoined studs manufactured with a PVA adhesive, one layer of 15.9-mm Type X gypsum board on each face and 90-mm thick batts of mineral-fibre insulation filling the stud cavities. The load applied to the assembly during the test was 100% of the maximum load permitted according to the National Design Specification® for Wood Construction. An identical wall constructed with solid-sawn Douglas fir studs had exhibited 71 minutes of fire resistance during tests carried out for AWC several years earlier at the same facility.
This wall assembly constructed with fingerjoined studs was unable to support the applied structural load after 49 minutes of exposure during the fire test. Structural failure occurred rapidly and was total. An examination of the wall following the test determined that the nearest fingerjoints in each stud to a horizontal joint in the gypsum board on the unexposed face about 1.8-m above the bottom of the wall separated and acted as a hinge thereby permitting the studs to fold over. There was no evidence of wood failure in the fingerjoints after they separated and the studs “jack-knifed”. Tensile strength tests on one fingerjoint that did not separate during the fire test indicated that the average peak stress at failure for specimens obtained from that fingerjoint were about 70 percent of the average peak stress at failure for fingerjoined specimens obtained from a stud that was not fire-tested. Also, in the case of the specimens obtained from one fingerjoint that did not separate during the fire test, the failure occurred mostly along the bondline surfaces of the joint with little wood failure. In the case of the specimens from a fingerjoined stud that had not been fire tested, there was a great deal of wood failure (nearly 100 percent).
During a series of telephone conferences to discuss the results of this fire test, Robert Glowinski, Vice-president of the American Forest & Paper Association (AF&PA) and a lawyer, and prior to becoming Vice-president of AF&PA, the AWC staff member responsible for fire issues, stated that because building codes in the United States were specifically revised at the request of AF&PA to permit inter-changeability/substitutability of vertical-use-only fingerjoined studs for solid sawn studs, to do nothing as a consequence of the results of this test is not an option. AF&PA has legal obligations, as do each of the manufacturers of these products. AF&PA and all manufacturers of these products have a legal obligation to move continuously and directly to address the issues raised by the results of the fire test and/or to make the necessary notification.
A Task Group consisting of representatives from the Southern Forest Products Association, Western Wood Products Association, West Coast Lumber Inspection Bureau, Canada’s National Lumber Grades Authority (NLGA), CWC, Forintek and Weyerhaeuser was appointed to work with AWC staff to identify and contact stakeholders in the United States and Canada and provide them with background information about the test. The Task Group was also directed to develop a brief communication document to inform all United States and Canadian stakeholders (manufacturers) and lumber grading agencies of the results of the fire test, its implication for these products within the context of current building codes, and to invite them to a meeting to quickly develop one or more study plans on how to proceed. At the stakeholders’ meeting, both technical and legal issues will be considered. Once the stakeholders have identified the components of the study plan(s), they will prioritize each component of the plan and identify how each is to be funded. Forintek will work with the AWC Task Group, NLGA, CWC and Canadian manufacturers of vertical-use-only fingerjoined studs in development and implementation of those study plans.