EWPAA Structural Plywood and LVL Design Manual - Engineered ...

11.2 MaterialsPlywoodPlywood used in the construction of stressed skin panels designed to the specifications stated herein, shall beEWPAA product certified structural plywood, manufactured to AS/NZS 2269-2004 : Plywood - Structural.Plywood panels can be joined by scarf jointing provided: the scarf is;• not steeper than 1 in 8 in the tension skin;• not steeper than 1 in 5 in the compression skin.Butt joints in the plywood skins shall be backed with plywood splice plates centred over the joint and gluedover the full contact area. The width of splice plates shall be 25 x thickness of the plywood skin.At the time of gluing the plywood moisture content must be within the limits specified by the gluemanufacturer.StringersStringers of LVL must be EWPAA stamped with a stress grade or an identification mark associated with adefined mechanical property.At the time of gluing the moisture content of the stringers must be within the limits specified by the gluemanufacturer. Stringer surfaces to be glued must be clean and free from oil and other foreign matter likelyto inhibit the gluing process.GlueStress skin plywood systems in which the components have been interconnected using thermo-settingresins, the shear resistance is fully dependent upon the adhesive, the nail contribution being discounted.The reason for this is attributed to the greater rigidity of the adhesive compared to the nails whose mainfunction is to apply the necessary pressure to effect curing.Adhesives used in this application must be room temperature setting with a modicum of gap fillingproperties in the event mating surfaces are not smooth and even. The preferred adhesive for this applicationwill therefore be of the resorcinol family, unless otherwise specified by the designer. Because nailingapplies permanent pressure to the glueline curing time is not critical.NailsNails should be minimum of 2.8mm diameter for all thicknesses of plywood with a depth of penetration intothe stringers of not less than 2.5 x plywood thickness or 20mm. Nail spacing should be:• not greater than 100mm along the framing members,• a single row on stringers up to 50mm thick and two rows on stringers greater than 50mm wide up to100mm wide.Nailing may commence at any point but must progress to an end or ends.Unless otherwise stated panel edge straightness, squareness, width and length shall not vary outside thelimits set for these parameters for a plywood panel.Insulation and/or Vapour-Barrier MaterialInsulation and vapour-barrier material must be securely fastened to the structural assembly in such amanner as to not interfere with the gluing of the plywood skins to the stringers. Ventilation requirementsshould be incorporated as seen necessary by the designer.11.3 ApplicationAlthough only the design of flat panels will be considered in this Manual curved panels for roof constructionare also a viable proposition. Uses for plywood stressed skin panels can be found in:143