Methods of Nailing and Adhesive Consistency Affect the Strength of Nailed-Glued Construction Joints

The shear strengths of plywood-to-lumber joints, nail-glued with two elastomeric construction adhesives of high quality, were affected to varying degrees by methods of nailing, depending upon consistencies of the adhesives. However, both adhesives produced joints with shear strengths that exceeded minimum requirements of the American Plywood Association’s interim specification AFG-01 for field-glued plywood floor systems. Hand nailed joints, bonded with an elastomeric adhesive of low viscosity, proved superior in strength to power nailed and power stapled joints. With an elastomeric adhesive of high viscosity, hand and power nailed joints were comparable in strength, but both were of significantly higher strength than power stapled joints. The shear strength of joints made with a high-strength, gap-filling phenol-resorcinol resin adhesive of intermediate viscosity was not affected by any of the three methods of nailing. Nail spacings of 6, 12, and 24 inches had no important effects on the strength of these joints, regardless of methods of nailing or adhesive consistenies. However, it should be recognized that nail spacings closer than 24 inches will be required whenever warped or misaligned framing lumber, or warped plywood, do not make a close fitting joint. In view of results from this experiment, it seems advisable that adhesive users cooperate with suppliers in selecting an adhesive of a consistency that will be compatible with the method of nailing. Such a selection process, coupled with limited testing and existing performance standards for construction adhesives, should result in more efficient utilization of the potential strength of any construction adhesive in a given application.

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