2001 ASD Supplements - unprotected PDF - American Wood Council

ASD WOOD STRUCTURAL PANELS SUPPLEMENTSP-5this reason, wall sheathing panels may be applied witheither the strength (primary) or secondary axis acrosssupports.• Single Floor: The Single Floor span rating is an indexnumber that provides the maximum recommended supportspacing with the strength axis across two or moresupports. Typical Single Floor span ratings are 20 ocand 24 oc, although 16 oc, 32 oc, and 48 oc Single Floorpanels are also available.Panel Constructions• Plywood: Plywood is comprised of alternating layersof veneer (plies). Each layer consists of one or moreplies. Wood structural plywood panels are assembledwith waterproof adhesive applied between plies. Theadhesive cures upon application of heat and pressure.Plywood has been manufactured since the early 1930sand was the original wood structural panel. Plywoodpanels were originally manufactured from Douglas-firlogs. Presently a variety of domestic species are usedin plywood manufacture. Due to continued strong demandfor forest products, along with artificialconstraints on wood supply, imported species are becominga factor in domestic plywood production.• Veneer Classifications: Veneer is divided into five levelsas follows:N, A: Highest grade level. No knots, restricted patches.N is intended for natural finish while A is intended fora paintable surface. Check local suppliers for availabilityof N grade before specifying.B: Solid surface - Small round knots. Patches and roundplugs are allowed.C Plugged: Special improved C grade. Used in SingleFloor, Underlayment, C-C Plugged, and C-D Plugged.in a minimum of three cross-aligned layers and bondedunder heat and pressure with a waterproof and boilproofadhesive. OSB’s predecessor product waswaferboard, a wood panel product that was first commerciallyproduced in the mid-1960s. Waferboardmanufacture involved a mat-formed panel product withrandom distribution of rectangular wafers. Orientedstrand board, a significantly improved structural panelcompared to waferboard, was first produced in the early1980s.Oriented strand board is manufactured from hardwoodspecies, softwood species, and mixed species. The hardwoodspecies used are selectively harvested from foreststhat naturally regenerate. The softwood resource is derivedfrom fast-maturing species from managed forests.Much of the softwood resource represents selective harvestingfrom these managed forests.• COM-PLY®: COM-PLY panels are composite panelsof wood veneer and other wood-based material. COM-PLY panels are typically manufactured with five layers.The outer layers and the center layer are wood veneer,and the two remaining core layers are comprised of reconstitutedwood fiber sandwiched between the veneerlayers. COM-PLY panels are manufactured with waterproofadhesives.COM-PLY was developed as a cooperative effort ofthe U.S. Forest Service and APA to more efficientlyutilize the wood resource.Bond ClassificationThe following bond classifications are based on productcomposition and adhesive bond durability.• Exterior: Exterior panels may be used in applicationsthat are subject to long-term exposure to the weather orto moisture or other conditions of similar severity.2INTRODUCTION TO WOOD STRUCTURAL PANELSC: Small knots, knotholes, patches. Lowest grade allowedin Exterior plywood. For sheathing faces andinner plies in Exterior panels.D: Larger knots, knotholes, some limited white pocketin sheathing grades. This grade not permitted in Exteriorpanels.• Oriented Strand Board: Oriented strand board (OSB)is comprised of thin rectangular wood strands arranged• Exposure 1: Exposure 1 panels may be used in applicationsthat are not subject to long-term exposure toweather or moisture, but where resistance to moistureeffects due to exposure during construction or otherconditions of similar severity is required.• Interior: Interior panels may be used for permanentlyprotected interior applications.APA – The Engineered Wood Association