i 
  
 
 
Voluntary Product Standard PS 1- 22 
 
 
  
Structural Plywood 
 
 
 
 
  
 
  
 
 
  
 TBD 2023  
 
 
 
 
 
 
 
 
   
   
 
 
 
 
  
 
  
 
U.S. Department of Commerce  
Gina Rainmondo, Secretary  
 
National Institute of Standards and Technology  
Laurie E. Locascio, NIST Director and Undersecretary of Commerce for  
Standards and Technology  
 
 
 ii 
  
 
   
Certai n commercial  entities , equipment , or material s may be identified  in thi s 
document  in order  to describ e an experimental  procedur e or concept adequatel y. 
Such  identification  is not intended  to imply  recommendation  or endorsement  by the 
National  Institute  of Standards and Technology , nor is it intended  to imply that the 
entities , materials , or equipment  are necessaril y the bes t availabl e for the purpose.  
 
 
Additional information concerning the development and use of this standard can be 
obtained by contacting the Standards Coordination Office, National Institute of 
Standards and Technology, 100 Bureau Drive, MS 2100, Gaithersburg, MD 20899-2100 or visiting S tandards.G ov. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  iii 
 DEPARTMENT OF COMMERCE (DOC) VOLUNTARY PRODUCT STANDARDS  
 
 
DOC Voluntary Product Standards are developed under procedures published by the Department of 
Commerce in Title 15 Code of Federal Regulations Part 10, Procedures for the Development of Voluntary 
Product Standards.  The purpose of these standards is to est ablish nationally recognized requirements 
for products and to provide all concerned parties  with a basis for common understanding of the 
characteristics of the products.  The National Institute of Standards and Technology (NIST) administers 
the Voluntary P roduct Standards program on a reimbursable basis.  
 
ROLE OF NIST  
 
The role of NIST in the establishment of a DOC Voluntary Product Standard is to act as an unbiased 
coordinator in the development of the standard, provide editorial assistance in the preparation of the 
standard, supply such assistance and review as is required to assure the technical soundness of the 
standard, and seek satisfactory adjustment of valid points of disagreement.  NIST also determines 
compliance with the criteria of the Department’s procedures and publishes the standard as a public document.   
 Manufacturers , distributors, users, consumers, and other interested groups contribute to the 
establishment of Voluntary Product Standards.  These groups initiate and participate in the development of the standards, provide technical or other counsel as appropriate, promote the use of and support for 
the standards, and assist in keeping them current with respect to advancing technology and marketing practices.  
 
USE OF VOLUNTARY PRODUCT STANDARDS  
 
The use of DOC Voluntary Product Standards is voluntary.  N IST has no regulatory power in the 
enforcement of their provisions; however, since the standards represent a consensus of interested groups, their provisions are likely to become established as trade customs.  
 
The benefits derived from a DOC Voluntary Product Standard are in direct proportion to their general 
recognition and actual use.  Manufacturers  and distributors whose products meet the requirements of a 
DOC Voluntary Product Standard may refer to the standard in advertising and on labels to promote 
greater public understanding for confidence in their products.  At times, purchasers may order products 
conforming to the requirements of a DOC Voluntary Product Standard.   
 
Abstract  
 
This standard covers performance requirements, adhesive bond performance, grades, panel construction 
and workmanship, dimensions and tolerances, marking, and moisture content of structural plywood.  The 
standard classifies structural plywood by bond classification, span rating, performance category, and grade.  It provides test methods, a glossary of trade terms and definitions, and a quality certification 
program whereby agencies inspect, sample, and test products for conformance to this standard.  
Information regarding nonmandat ory industry practices for reinspection, history of the standard, labeling, 
and formaldehyde attributes are provided in the appendices.   
 
Keywords  
 
Adhesive bond classification; certification; construction sheathing; dimensions and tolerances; marking; 
moisture content; performance requirements; span rat ing; performance category; structural plywood; test 
methods; voluntary standard.   
 
 
 iv 
 Table of Contents  
1. SCOPE  .................................................................................................................................... 1 
2. TERMINOLOGY  ...................................................................................................................... 1 
3 REFERENCE PUBLICATIONS  ............................................................................................. 8 
4. PLYWOOD CLASSIFICATION  ............................................................................................... 9 
4.1 General  ........................................................................................................................... 9 
4.2 Bond classification  .......................................................................................................... 9 
4.3 Grade  .............................................................................................................................. 9 
5. REQUIREMENTS  .................................................................................................................... 9 
5.1 General  ........................................................................................................................... 9 
5.2 Wood species  ................................................................................................................. 9 
5.3 Synthetic repairs  ........................................................................................................... 11 
5.4 Grade desription of veneers  ......................................................................................... 11 
5.5 Veneers and layers  ....................................................................................................... 17 
5.6 Panel grades  ................................................................................................................. 19 
5.7 Adhesive bond requirements for a panel or a lot  .......................................................... 22 
5.8 Panel constructions and workmanship  ......................................................................... 24 
5.9 Scarf and finger jointed panels  ..................................................................................... 37 
5.10  Dimensional tolerances and squareness of panels  ...................................................... 39 
5.11  Moisture content  ........................................................................................................... 40 
5.12  Loading or packing  ....................................................................................................... 40 
6. SPECIMEN PREPARATION AND TESTING  ....................................................................... 40 
6.1 Bond classification  ........................................................................................................ 40 
6.2 Structural performance  .................................................................................................  45 
7 MARKING AND CERTIFICATION ........................................................................................ 50 
7.1 Certification  ................................................................................................................... 50 
7.2 Accredited Certification Agency  .................................................................................... 50 
7.3 Accredited Inspection Agency  ...................................................................................... 51 
7.4 Accredited Testing Laboratory  ...................................................................................... 51 
7.5 Panel marking  ............................................................................................................... 51 
7.6 Voiding marks  ............................................................................................................... 52 
 
8 QUALITY ASSURANCE REQUIREMENTS  ......................................................................... 53 
8.1 Manufacturing Quality Control  ...................................................................................... 53 v 
 8.2 Inspection and Test Program  ........................................................................................ 54 
8.3 Sampling  ....................................................................................................................... 54 
8.4 Corrective Action  .......................................................................................................... 55 
 
9 EFFECTIVE DATE  ................................................................................................................ 55 
 
10 STANDING COMMITTEE  ..................................................................................................... 55 
 
 
 
 
APPENDIX  
 
A Species Grouping (mandatory)  ............................................................................................ 56 
 
B Reinspection Practices (nonmandatory)  .............................................................................. 59 
 
C General Information and Comments on Current Edition (nonmandatory)  ........................... 61 
 
D Recommend thickness labels  (nonmandatory)  .................................................................... 63 
 
E Labeling Guidelines Based on the Uniform Packaging and Labeling Regulations of NIST  
 Handbook 130 and Handbook 133 (nonmandatory)  ............................................................ 65 
 F Formaldehyde (nonmandatory)  ............................................................................................ 66 
 
  
1 
  
 
VOLUNTARY PRODUCT STANDARD PS 1 -22 
STRUCTURAL PLYWOOD 
 
Effective TBD, 2023 
 (This Standard, which was initiated by APA - The Engineered Wood Association [formerly the 
American Plywood Association], has been developed under the Procedures for the Development  of Voluntary Product Standards  of the U.S. Department of Commerce as a 
revision of PS 1- 19, Structural  Plywood .) 
1. SCOPE 
 
1.1 This Voluntary Product Standard establishes requirements for the principal types and 
grades of structural plywood and provides a basis for common understanding among manufacturer s, distributors, and users of the product.  
 
1.2 This Standard covers the wood species, veneer grading, adhesive bonds, panel 
construction and workmanship, dimensions and tolerances, and moisture content of structural plywood intended for construction and industrial uses a s well as the certification and marking 
requiremen ts for panels determined to conform to the requirements herein. 
 1.3 Included in this Standard are test methods to determine compliance and a glossary of 
trade terms and definitions.  A quality certification program is specified whereby an Accredited 
Certification Ag ency  certifies the process used to manufacture  the product, an Accredited 
Inspection Agency inspects and samples the product and an Accredited Testing Laboratory tests the product following the requirements in  this Standard.  Information on species grouping 
is provided in Appendix A.  Information on re inspection practices is provided in Appendix B.  
Information on the maintenance, history, and current edition of the Standard is provided in Appendix C.  Recommended thickness labeling is provided in Appendix D .  Information on 
labeling regulations from NIST Handbook 130 and NIST Handbook 133 are provided in 
Appendix E.  Information  on formaldehyde emissions is provided in Appendix F. 
 1.4 This Voluntary Product Standard incorporates the International System of Unit s (SI) as 
well as U.S. customary units of measurement.  In conversion of U.S. customary units where 
exact placement is not an issue, such as nail spacing, approximate conversions to SI units are 
made to yield more easily recognizable numbers.  In critical matters, such as panel thickness, 
more precise conversions to SI units are made.  For nominal U.S. customary units, actual 
dimensions in SI units are given.  The values given in SI units are the standard.  The values in parentheses are for information only . 
 1.5 Advisory notes in this Standard and Appendices B through F are informational and shall 
not be considered mandatory.  
2. TERMINOLOGY  
2.1 Back  
Back of a plywood panel — The side of a panel that is of lower veneer quality on any panel 
whose outer plies (front and back) are of different veneer grades.  
 Back ply (back veneer)  — The outer veneer on the back of a plywood panel.   
2 
 2.2 Bond classifications  
Plywood is rated as Exposure 1 or Exterior bond classification.  (See Sections 2.20 and 2.21 .) 
2.3 Borer holes  
Voids made by wood- boring insects, such as grubs or worms.  
2.4 Broken grain  
A separation on the veneer surface between annual rings, such as leafing or shelling.  
2.5 Butt joint  
A straight joint in which the interface is perpendicular to the panel face.  An end butt joint is 
perpendicular to the grain.  
2.6 Centers  
Inner layers whose grain direction is oriented parallel to that of the outer plies.  Some centers 
consist of parallel laminated plies.  
2.7 Center gap  
See Section 2.16.  
2.8 Characteristics, growth  
Discolorations, pitch streaks , and knots that naturally occur in wood.  
2.9 Characteristics, open  
Irregularities such as splits, open joints, knotholes, loose knots, or wane.  
2.10 Check  
A lengthwise separation of wood fibers, usually extending across the rings of annual growth, 
caused chiefly by strains produced in seasoning.  
2.11 Class I, II  
Term used to identify different classifications of concrete form panels. (See Section 5.6.4.)  
2.12 Construction (panel construction)  
Term referring to the  detailed manner in which veneers are assembled and/or thickness of 
veneer used, e.g., "4 -ply 3 -layer construction," "2.5 mm (1/10 in) face and back," etc.  
2.13 Core  
See Section 2.15.  
2.14 Critical Section  
A rectangular area with a length  measuring 305 mm (12 in) parallel to  the grain of the face or 
back ply and a width equal to the full width  of the panel  that contains a knot or knothole 
requiring additional consideration.  For the purposes of determining conformance to the requirements specified in S ections 5.4.4.3, 5.4.6.2 and 5.4.6.3, the location of the c ritical section 
parallel to the grain of the face or back ply shall be determined by positioning the knot or 
knothole requiring additional consideration such that the maximum number of additional knots 
and knotholes is included in the aggregate evaluation.   
2.15 Crossband  
Inner, or core, plies whose grain direction is oriented perpendicular to that of the outer plies.  
Some crossbands consist of parallel -laminated plies.   
3 
 2.16 Crossband gap and center gap  
An open joint extending through,  or partially through,  a panel , which results when crossband or 
center veneers are not tightly butted.  
2.17 Delamination  
A visible separation between plies that normally receive adhesive at their interface and are 
firmly contacted in the pressing operation.  Wood characteristics such as checking, leafing, 
splitting , and broken grain are not to be construed as delamination.  
2.17.1  Knotholes, pitch pockets, splits , and gaps  
For the purpose of evaluating delamination, areas coinciding with open knotholes, pi tch pockets, 
splits, gaps , and other voids or characteristics permitted in the panel grade are not considered 
in evaluating ply separation.  
2.17.2  Delamination of Exposure 1 panels  
In evaluating Exposure 1 panels, delamination in any bond line is not to exceed 19.4 cm2 (3 in2) 
except where directly attributable to characteristics permitted in the grade as follows:  
 
Delamination associated with:  
 
(a) Knots and knotholes —  Not to exceed the size of the knot or knothole plus a 
surrounding band not wider than 19.1 mm (3/4  in). 
(b) All other forms of permissible characteristics —  Not to exceed the size of the 
characteristic.  
2.17.3  Delamination of Exterior  panels  
For the purpose of evaluating Exterior panels for ply separation, the area coinciding with the 
grade characteristics noted in Section 2.17.1 is considered, and a panel is considered 
delaminated if visible ply separation at a single bond line in such area exceeds 19.4 cm2 (3 in2). 
2.18 Depr ession  
A minor disruption of the panel surface with a smooth boundary.  
2.19 Edge splits  
Wedge- shaped openings in the inner plies caused by splitting of the veneer before pressing.  
2.20 Exposure 1  
Bond classification for panels  suitable for uses not permanently exposed to the weather.  Panels 
classified as Exposure 1 are intended to resist the effects of moisture on structural performance 
as may occur during construction, or other conditions of similar severity.   
2.21 Exterior  
Bond classification for panels  suitable for repeated wetting and redrying or long- term exposure 
to weather or other conditions of similar severity.   
2.22 Face 
Face of the plywood panel — The s ide of a panel that is of higher veneer quality on any panel 
whose outer plies (front and back) are of different veneer grades; either side of a panel where 
the grading rules draw no distinction between outer plies.  
Face ply (face veneer)  — The outer venee r on the face of a plywood panel.   
4 
 2.23 Finger joint  
Term indicating the method by which panels or sections of panels have been joined to create 
longer lengths or widths by means of a well -bonded series of sloped scarf cuts resembling 
fingers.  
2.24 Group  
Term used to classify wood  species or panels covered by this Standard.  Wood species covered 
by this Standard are classified as Groups 1, 2, 3, 4, and 5.  See Table 1 and Appendix A for a 
list of wood species in individual groups.   Section 5.8.7 provides p rocedures for grouping of 
other than span- rated  panels made  with species not listed in Table 1.  
2.25 Heartwood  
Nonactive core of a log generally distinguishable from the outer portion (sapwood) by its darker 
color.  
2.26 Indent  
A disruption of  the panel surface with sharp  or distinct  edges.  
2.27 Inner plies  
Plies other than face or back plies in a panel construction.  Sub- face, sub -back, crossband , and 
center are classed as inner plies.  
2.28 Jointed inner plies  
Crossband and center veneers with edges  that are  machine -squared to permit  the tightest 
possible layup.  
2.29 Knot  
Natural characteristic of wood that occurs where a branch base is embedded in the trunk of a tree.  Generally , the size of a knot is distinguishable by (1) a difference in color of limb wood and 
surrounding trunk wood; (2) an abrupt change in growth ring width between knot and bordering 
trunk wood; and (3) a diameter of circular or oval shape described by points where checks on 
the face of a knot that extend radially from its center to its side experi ence an abrupt change in 
direction.  
2.29.1  Knot, sound  
A knot that is solid across the face, as hard as the surrounding wood, and shows no indication 
of decay.  
2.29.2  Knot, tight 
A knot fixed by growth or position so as to retain its place in the veneer prior to panel layup.  
2.30 Knotholes  
Voids produced by the dropping of knots from the wood in which they were originally embedded.  
2.31 Lap 
A condition where the veneers in the same ply are so placed that one piece overlaps the other.  
2.32 Layer  
A single veneer ply or two or more plies laminated with grain direction parallel.  Two or more 
plies laminated with grain direction parallel is  referred to as  a "parallel laminated layer."  
2.33 Lot 
Any number of panels considered as a single group for evaluating conformance to this Standard.   
5 
 2.34 Major panel axis  
The direction parallel to the grain of the face and back plies.  
2.35 Mill specification  
A manufacturing specification based on the outcome of  product evaluation to be used for quality 
assurance purposes by the manufacturer , the Accredited Certification Agency , Accredited 
Inspection Agency  and the Accredited Testing Laboratory  as specified  in Section 7.  (See 
Sections 5.8.6. 4. and 5.8.7. 4.) 
2.36 Moisture content  
The weight of the water in wood expressed as a percent of the weight of t he oven- dry wood.  
(See Section 6.1.4.)  
2.37 Moisture- resistant adhesive  
Adhesive capable of bonding plywood in a manner to satisfy the bond classification 
requirements of this Standard.  
2.38 Patches 
Inserts of sound wood or synthetic material in veneers or panels f or replacing characteristics 
(open or growth).  "Boat" patches are oval -shaped with sides tapering in each direction to a 
point or to a small rounded end.  “Compound Boat” patches have multiple rounded or pointed 
ends. "Router" patches have parallel sides and rounded ends.  "Sled" patches are rectangular 
with feathered ends.  
2.39 Performance category  
A panel designation related to the panel thickness range that is linked to the nominal panel 
thickness designations used in the International Building Code (IBC) and International 
Residential Code (IRC).  For purposes of labeling, as specified  in Section 7. 5, abbreviations 
PERF CAT, CAT , or Category are permitted.  See Section 5.10.2 for thickness tolerances.  
ADVISORY NOTE:  The IRC and IBC specify a minimum 3/8 Performance Category for wall 
sheathing.  
2.40 Performance testing  
Tests that evaluate panel attributes typically required in the end -use applications as defined in 
this Standard.  
2.41 Pitch pocket  
A well- defined opening between rings of annual growth, usually containing, or which has 
contained, pitch, either solid or liquid.  
2.42 Pitch streak  
A localized accumulation of resin in coniferous woods that  permeates the cells forming resin 
soaks, patches, or streaks.  
2.43 Plugs  
Sound wood of various shapes  for replacing portions of veneers.  Also,  synthetic plugs used to 
fill openings and provide a smooth, level, durable surface.  Plugs usually are held in veneer by friction until veneers are bonded into plywood.  
2.44 Plugged inner plies (also referred to as sol id inner plies.)  
Refers to C Plugged crossband and centers and additional limitations, as given in Section 5.8.1.   
6 
 2.45 Ply  
A single veneer lamina in a bonded plywood panel.  (See also Section 2.32.) 
2.46 Plywood  
Plywood is a panel made  of sheets of veneer called pl ies, united under pressure by a bonding 
agent to create a panel with an adhesive bond between plies as strong as , or stronger than, the 
wood.  Plywood is constructed of an odd number of layers with grain direction  of adjacent layers 
oriented perpendicular.   Layers consist of a single ply,  or two or more plies laminated with 
parallel grain direction  (e.g., parallel -laminated layers) .  Outer layers and all odd- numbered 
layers generally have the grain direction oriented parallel to the long dimension of the panel.  
The layers with alternating grain direction equalize strains, reduce splitting, and minimize 
dimensional change and warping of the panel.  
2.47 Plywood classification  
Plywood is classified by bond classification and grade.  (See Section 4.)  
2.48 Prescriptive specification  
A panel  specification  that defines an approved product for a given end use and/or span rating 
that is  based upon the wood species, grade, bond type, thickness, construction, workmanship, 
and manufacturing parameters specified in this Standard without modification.  
2.49 Reference value  
The numerical value defined in the mill specification  that is established as an outcome of 
product evaluation (see Sections 5.8.6. 4 and 5.8.7. 4) for a given mechanical or physical 
property.  
2.50 Repair  
Any patch , plug, or shim.  
2.51 Rough grain  
Grain characteristics that  prevent sanding to a smooth surface.  
2.52 Sapwood  
The living wood of lighter color occurring in the outer portion of a log.  Sometimes referred to as "sap."  
2.53 Scarfed joint  
A term indicating the method by which panels or veneer, or sections of panels or veneer, have 
been joined to create longer lengths or widths by means of a well -bonded, sloped cut.  
2.54 Shim  
A long, narrow repair of wood,  or suitable synthetic  material , measuring not more than 4.8 mm 
(3/16  in) wide.  
2.55 Shop- cutting panel  
Panel that has been rejected as not conforming to a standard grade because of deficiencies, 
other than adhesive bond quality, which prevent it from meeting the requirements of this Standard.  Blistered panels are not permitted  within the category of “shop -cutting panel.”  
Localized delamination occurring as a result of a permiss ible characteristic  as specified in 
Section 2.17  is permitted.  Shop- cutting panels are suitable for cut -up use where cutting 
eliminates the deficiency in the portion of the panel salvaged.  The salvageable area shall be at 
least 85% of the original surface  area of the panel.  Such a panel shall  be identified with a 
separate mark as specified in Section 7. 6.  
7 
 2.56 Sized for spacing  
An optional panel mark indicating that the panel manufacturer has sized the panel to allow for 
industry -recommended panel installation spacing.  
2.57 Span rating  
An index number, based on customary inch units, that identifies the recommended maximum 
center -to-center support spacing, or “on-center” (o.c.) spacing,  for the specified end use under 
normal use conditions.  Spans are defined for end uses such as roof, subfloor, and single floor.  
As a matter of convention, spans are typically specified by a single index number for single floor 
(Floor 24 o.c.), while roof and subfloor are often combined in a fractional format.  For example, a 
span rating of 32/16 designates a roof span of 32 inches and a subfloor span of 16 inches.  As a 
matter of convention, a span rating of 20 is designated f or spans of 19.2 inch.  
2.58 Split  
Lengthwise separation of wood fibers completely through the veneer . 
2.59 Sub-face (sub- back)  
The ply adjacent to the exposed face (or back) of a parallel laminated outer layer.  
2.60 Touch- sanding  
A sizing operation consisting of a light surface sanding to thickness dimension.  Sander skips to any degree are admissible.  
2.61 Veneer  
Thin sheets of wood, usually not exceeding 6.4 mm (1/4 in) thick, that are  rotary cut, sliced, or 
sawed from a log, bolt, flitch, block , or culm  of which plywo od is made.  Also referred to as 
"plies" in the bonded panel.  
2.62 Void 
Open areas in veneer sheets , other than a knothole (see Section 2.30)  or wane (see Section 
2.63). 
2.63 Wane  
Thin to open areas in veneer sheets that result from outer log surface irregularities.  Some wane 
areas contain bark inclusions.  For grading, wane is classed as an open characteristic.  
2.64 White pocket  
A form of fungal decay ( Fomes pini ) that attacks most conifers but has never been known to 
develop in wood in service.  In plywood manufacture, routine drying of veneer effectively 
removes any possibility of the fungus surviving.  Also known as white speck.  
2.64.1  Light white pocket  
Fungal decay has advanced beyond incipient or stain stage to a point where pockets are present and plainly visible, mostly  small and filled with white cellulose; generally distributed with 
no heavy concentrations; pockets for the most part separate and distinct; few to no holes through the veneer.  
2.64.2  Heavy white pocket  
Contains a great number of pockets, in dense concentrations, running together and at times appearing continuous; holes extend through the veneer but wood between pockets appears 
firm.  At any cross section extending across the width of the affected area, sufficient wood fiber 
shall be present to develop not less than 40% of the strength of clear veneer.  Brown cubicle 
and similar forms of decay that  have caused the wood to crumble are prohibited.   
8 
 2.65 Wood failure (percent)  
The area of wood fiber remaining at the bond line following completion of the spec ified shear 
test.  Determination is by means of visual examination and expressed as a percent of the test 
area in accordance with ASTM D5266 and the requirements of this Standard.  
2.66 Working Face  
A face and/or back of a plywood panel that has an  overlay system that meets a defined Medium 
Density Overlay ( MDO ) or High Density Overlay ( HDO ) grade (see section 5.6.7).  
3 REFERENCE PUBLICATIONS  
ASTM E661 -22 Test Method for Performance of Wood and Wood -Based Floor and Roof 
Sheathing Under Concentrated Static and Impact Loads.  
 
ASTM D2555- 17 Test Methods for Establishing Clear Wood Strength Values.  
 
ASTM D2718- 18 Test Method for Structural Panels in Planar Shear (Rolling Shear).  
 ASTM D2719- 19 Test Methods for Structural Panels in Shear Through- the-Thickness.  
 
ASTM D2915- 17 Standard Practice for Evaluating Allowable Properties for Grades of Structural 
Lumber.  
 
ASTM D3043- 17 Methods of Testing Structural Panels in Flexure.  
 
ASTM D5266- 13 (2020)  Standard Practice for Estimating the Percentage of Wood Failure in 
Adhesive Bonded Joints . 
 
ASTM D906- 20 Standard Test Method for Strength Properties of Adhesives in Plywood Type 
Construction in Shear by Tension Loading.  
 
International Building Code (IBC) . International Code Council. Country Club Hills, IL.  
 
International Residential Code for One-  and Two -Family Dwellings  (IRC) . International Code 
Council. Country Club Hills, IL.  
 
PS 2 -18 Performance Standard for Wood Structural Panels.  
 
ISO/IEC 17020 -2012 Conformity Assessment –  Requirements for the Operation of Various 
Types of Bodies Performing Inspection.  
 
ISO/IEC 17025 -2017 General Requirements for the Competence of Testing and Calibration 
Laboratories . 
 ISO/IEC 17065 -2012 Conformity Assessment – Requirements for bodies certifying products, 
processes and services . 
 
 
4 PLYWOOD CLASSIFICATION  
4.1 General  
The plywood covered by this Standard is classified by bond classification and by grade.   
9 
 4.2 Bond classification  
The plywood covered by this Standard is classified as either Exposure 1 or Exterior.  Each 
classification is a function of veneer grade and adhesive performance. The bond classification is 
related to the moisture resistance of the adhesive bond under intended end -use conditions and 
does not relate to the physical (erosion, ultraviolet, etc.) or biological (mold, fungal decay, insect, etc.) resistance of the panel.  
4.2.1  Exposure 1 plywood  
Adhesive performance requirements for Exposure 1 plywood are provided in Section 5.7.1.  
4.2.2  Exterior plywood  
Adhesive performance requirements for Exterior plywood are provided in Section 5.7.2.  
4.3 Grade  
Within each bond classification, there are a number of panel grades based on the grade of the 
veneers and the panel construction.  (See Table 2 for Exposure 1 grades and Table 3 for 
Exterior grades.)  
5 REQUIREMENTS  
5.1 General  
All plywood panels represented as conforming to this Standard shall meet or exceed all 
applicable requirements set forth herein.  Test methods are given in Section 6.  All terms shall 
be as defined in Section 2.  Requirements for marking and certification shall be as specified in 
Section 7.  
5.2 Wood species  
5.2.1  Species groups  
For the purpose of this Standard, species shall be any softwood or hardwood species or trade groups listed in Table 1 and other species meeting the requirements of Sections 5.2.3 or 5.2.4.  
For species grouping purposes, species listed in Table 1 but grown in a different geographic 
region shall be evaluated in accordance with Appendix A.  For inclusion in Table 1, unlisted species shall be evaluated in accordance with Appendix A.  
5.2.1.1  Species segregation  
Species that cannot be distinguished in veneer form from similar species shall be classed as the 
largest numbered species group applicable (Group 4 is larger numbered than Group 1) unless 
the manufacturer provides valid evidence to the Accredited Certification Agency  that the species 
are properly segregated.  Such segregation shall be in the form of separation prior to peeling, 
mechanical testing for performance capability, or other means approved by the Accredited 
Certification Agency . 
5.2.2  Species for faces and backs 
Unless evaluated in accordance with Section 5.2.4, the species of face and back plies shall be from any group listed in Table 1.  When a face or back is made of more than one piece, the 
entire ply shall be of the same species.  When outer l ayers consist of two or more plies, the 
outer or exposed plies are classified as faces (face plies) or backs (back plies) and the 
unexposed plies (sub- faces and sub -backs) are classified as inner plies, in terms of species 
requirements as specified  in Sect ion 5.2.3.  Requirements for identification of all panels are 
given in Section 7. 5. 
 
   
10 
 TABLE 1.  CLASSIFICATION OF SPECIES(a) 
 
Group 1  Group 2  Group 3  Group 4  Group 5  
North American Species – Applicable to trees grown in North America   
Beech, American  Cedar, Port Orford  Pine Alder, Red  Aspen  Basswood  
Birch  Cypress   Pond  Birch, Paper   Bigtooth  Poplar, Balsam  
 Sweet  Douglas -fir (b)   Red Cedar, Alaska   Quaking   
 Yellow  Fir  Virginia  Fir, Subalpine  Cedar   
Douglas -fir (b)  Balsam   Western White  Hemlock, Eastern   Incense   
Larch, Western   California Red  Spruce  Maple, Bigleaf   Western Red   
Maple, Sugar   Grand   Black  Pine Cottonwood   
Pine, Southern   Noble   Red  Jack  Eastern   
 Loblolly   Pacific Silver   Sitka   Lodgepole   Black (W. Poplar)   
 Longleaf   White  Sweetgum   Ponderosa  Pine  
 Shortleaf  Hemlock, Western  Tamarack   Spruce   Eastern White   
 Slash  Maple, Black  Yellow Poplar  Redwood   Sugar   
Tanoak    Spruce    
    Engelmann    
    White    
Non North American Species   
Apitong(c)(d) Lauan  Mengkulang(c)   Cativo   
Kapur(c)  Almon  Meranti, Red(c)(e)     
Keruing(c)(d)  Bagtikan  Mersawa(c)    
Pine  Mayapis      
 Caribbean   Red Lauan      
 Ocote   Tangile      
  White Lauan      
(a) Table 1 species classified in accordance with ASTM D 2555 as discussed in Appendix A.  The species groupings are only 
valid for species grown in the regi ons referenced in Appendix A.  ( See Section 5.2.1 .) 
(b) Douglas -fir from trees grown in the states of Washington, Oregon, California, Idaho, Montana, Wyoming, and the 
Canadian Provinces of Alberta and British Columbia shall be classed as Group 1 Douglas -fir.  Douglas -fir from trees 
grown in the states of Nevada, Utah, Colorado, Arizona and New Mexico shall be  classed as Group 2 Douglas -fir. 
(c) Each of these names represents a trade group of woods consisting of a number of closely related species.  
(d) Species from the genus Dipterocarpus marketed collectively:  Apitong if originating in the Philippines, Keruing if 
originating in Malaysia or Indonesia.  
(e) Red Meranti shall be limited to species having a specific gravity of 0.41 or more based on green v olume and oven -dry 
weight.  
5.2.3  Species for inner plies  
5.2.3.1  Inner ply species group  
Unless otherwise permitted in Section 5.2.3.2 or 5.2.4, inner plies of Groups 1, 2, 3 or 4 panels 
shall be of any species listed in Groups 1, 2, 3,  or 4 in Table 1.  Inner plies of Group 5 panels 
are permitted to be any species listed in Table 1.  
5.2.3.2  Inner ply specific gravity 
Inner plies of all panels shall also be permitted to be of any softwood species or any hardwood 
species having a published average specific gravity value of 0.41 or more based on green 
volume and oven- dry weight.  The U.S. Forest Products Laboratory shall be considered as final 
evaluator of published specific gravity data.  
5.2.4  Species classified by testing  
Species not listed in Table 1 , species listed in Table 1 but grown in a different geographic 
region, and species  otherwise not covered by the provisions of Section 5.2 shall be qualified for 
use by panel performance testing in accordance with Section 5.8.6 for span- rated panels or with  
   
11 
 Section 5.8.7 for other -than span- rated  panels except that Concrete Form (see Section 5.6.4) , 
Marine (see Section 5.6.1)  and Structural  I (see Section 5.6.5)  grades  made using such species 
shall not be eligible for qualification by panel performance testing.   For panel marking purposes, 
re-classification of Group designation for species listed in Table 1  by panel performance testing 
in accordance with Section 5.8.7 i s permitted.  
5.3 Synthetic repairs  
5.3.1  Synthetic fillers  
Use of synthetic fillers shall be limited to the repair of minor characteristics as specified.  
Synthetic fillers shall be approved by the Accredited Certification Agency . 
5.3.2  Synthetic shims, patches, and plugs  
These repairs shall completely fill kerfs or voids; shall present a smooth, level surface; and shall 
not crack, shrink, or lose their bond.  Performance of synthetic shims, patches, and plugs under 
normal conditions of service shall be comparable to that of wood repairs.  The equivalency shall 
be established by the Accredited Certification Agency . 
5.4 Grade description of veneers  
All veneers in the finished plywood panel shall conform to one of the grade requirements listed 
in Sections 5.4.1 through 5.4.6.  U nless otherwise stated, these requirements apply to 1220 mm 
by 2440 mm (48 in x 96 in) panels and are proportionate for other sizes.  Grade N is the highest 
classification.  For grading purposes, depressions (see Section 2.18) shall be considered as 
rough g rain. 
5.4.1  Grade N veneer (intended for natural finish)  
5.4.1.1  General  
Grade N veneer shall be smoothly cut 100% heartwood or 100% sapwood, free from knots, 
knotholes, pitch pockets, open splits, other open characteristics, and stain.  The veneer shall 
consist of not more than two pieces in 1220 mm (48 in) widths and not more than three pieces 
in wider panels, and shall be well matched for color and grain.  When surface  sanding is required 
(see Tables 2 and 3) sander skips  shall not be permitted . 
 
Synthetic fillers shall be permitted to fill:  
 
(a) Small cracks or checks not more than 0.8 mm (1/32 in) wide.  
 
(b) Small splits or openings up to 1.6 mm (1/16 in) wide if not exceeding 50.8 mm 
(2 in) in length.  
 
(c) Small,  chipped areas or openings not more than 3.2 mm  (1/8 in)  wide by 6.4 mm 
(1/4 in) long.  
5.4.1.2  Growth characteristics  
Where pitch streaks occur, each shall average not more than 9.5 mm (3/8 in) in width and shall 
blend with the color of the wood.  
5.4.1.3  Repairs  
Repairs shall be of wood, neatly made, and parallel to grain.  They shall be limited to a total of 
six in number and be well matched for color and grain.  
 
   
12 
 Patches shall be limited to three "router" patches not exceeding 25.4 mm (1 in) in width and 
88.9 mm (3 -1/2 in) in length.  There shall be no overlapping.  
 
Shims shall not exceed 4.8 mm (3/16 in) in width or 305 mm (12 in) in length and shall occur 
only at the ends of the panel.  
5.4.2  Grade A veneer (suitable for painting)  
5.4.2.1  General  
Grade A veneer shall be firm, smoothly cut, and free of knots, pitch pockets, open splits, and other open characteristics and well joined when of more than one piece.  When surface  sanding 
is required (see Tables 2 and 3) sander skips  shall not be permitted.  
 
Synthetic fillers shall only be used to fill:  
 
(a)  In Exterior panels: small cr acks or checks not more than 0.8 mm (1/32 in) wide; 
small splits or openings up to 1.6 mm (1/16 in) wide, if not exceeding 50.8 mm 
(2 in) in length; and  small chipped areas or openings not more than 3.2 mm (1/8 
in) wide by 6.4 mm (1/4 in) long.  
 
(b) In Exposure 1 panels: small cracks or checks not more than 4.8 mm (3/16 in) 
wide; and openings or depressions up to 12.7 mm (1/2 in) wide by 50.8 mm (2 in) 
long or equivalent area.  
5.4.2.2  Growth characteristics  
Where pitch streaks occur, each shall average not more than 9.5 mm (3/8 in) in width and shall 
blend with the color of the wood.  Sapwood and discolorations to any degree shall be permitted.  
5.4.2.3  Repairs  
Repairs shall be of wood or synthetic patching material, neatly made, parallel to grain and 
limited to a total of 18 in number, excluding shims.  
5.4.2.4  Patches  
Patches, when of wood, shall be "boat,"  “compound boat,”  "router," or "sled" type.  The radius of 
ends of boat patches and compound boat patches shall not exceed 9.5 mm (3/8 in).  
 
A single wood patch shall be no larger than 57.2 mm x 114 mm (2 -1/4 in x 4- 1/2 in).  
 Multiple wood repairs shall consist of not more than two patches, neither of which shall exceed 
178 mm (7 in) in length if either is wider than 25.4 mm (1 in), except that one multiple repair 
consistin g of three die- cut veneer patches shall be permitted.  
 
For a multiple repair consisting of three patches across the width of the panel, the repaired area 
shall not exceed a width and length of 152 mm x 114 mm (6 in x 4 -1/2 in)  
 
For a multiple repair consisting of three patches along the length of the panel, the repaired area 
shall not exceed a width and length of 57.2 mm x 267 mm (2- 1/4 in x 10- 1/2 in)  
 
Synthetic repairs are limited to the same repair areas as wood patches and shall be counted as 
one, two, or three patches depending on the area repaired.  
 
The repair of a split having a width not greater than 31.8 mm (1- 1/4 in) and any length shall be 
considered one patch.  
  
13 
 Shims shall not be used over or around patches or as multiple repairs.  
5.4.3  Grade B veneer  
5.4.3.1  General  
Grade B veneer shall be solid and free from open characteristics and broken grain, except as 
permitted in Sections 5.4.3.1 through 5.4.3.4. Slightly rough grain shall be permitted.  
 
Minor sanding and patching characteristics, including sander skips, shall not exceed 5% of 
panel area.  See Tables 2 and 3 for sanding requirements.  
 Synthetic fillers shall only be used to fill:  
 
(a) In Exterior panels:  small splits or openings up to 1.6 mm (1/16 in) wide if not exceeding 50.8 mm (2 in) in length ; and small chipped areas or openings not 
more than 3.2 mm  (1/8 in)  wide by 6.4 mm  (1/4 in)  long.  
 
(b) In Exposure 1 panels:  small cracks or checks not more than 4.8 mm (3/16 in) 
wide; and openings or depressions up to 12.7 mm  (1/2 in) wide by 50.8 mm  (2 in) 
long or equivalent area.  
5.4.3.2  Growth characteristics  
Knots shall not exceed 25.4 mm (1 in) measured across the grain and shall be both sound and 
tight.  
 
Where pitch streaks occur, they shall average not more than 25.4 mm (1 in) in width.  
 Discolorations to any degree shall be permitted.  
5.4.3.3  Open characteristics  
Splits shall not be wider than 0.8 mm (1/32 in).  
 
Vertical borer holes shall not exceed 1.6 mm (1/16 in) in diameter and shall not exceed an 
average of one per 929 cm
2 (1 ft2) in number.  
 Horizontal or surface worm and borer holes shall be limited to 1.6 mm (1/16 in) across, 
25.4 mm (1 in) in length, and limited to 12 in number.  
5.4.3.4  Repairs  
Repairs shall be of wood or synthetic patching material and neatly made.  
 
Wood veneer repairs shall be die cut.  Wood panel repairs shall be "router" or "sled" type.  
 Wood repairs shall not exceed 76.2 mm (3 in) in width where occurring in multiple repairs, or 102 mm (4 in) in width where occurring singly.  
 Synthetic veneer repairs shall not exceed 102 mm ( 4 in) in width.  
 Synthetic panel repairs shall not exceed 57.2 mm (2- 1/4 in) in width by any length, except that 
repaired areas not exceeding 152 mm  (6 in)  in width by 114 mm  (4-1/2 in)  in length shall be 
allowed.  
 
Shims shall be permitted without limit.   
14 
 5.4.4  Grade C veneer  
5.4.4.1  General  
Sanding characteristics shall not impair the strength or serviceability of the panel.  See Tables 2 
and 3 for sanding requirements.  
5.4.4.2  Growth characteristics  
Knots shall be tight and not more than 38.1 mm (1- 1/2 in) when measured  across the grain.  
 
Discolorations to any degree shall be permitted.  
5.4.4.3   Open characteristics  
Any number of knotholes up to 25.4 mm (1 in) when measured across the grain shall be 
permitted.  However, an occasional knothole more than 25.4 mm (1 in) but not more than 38.1 mm (1 -1/2 in) measured across the grain shall be permitted subject to the following provision:  
 
(a) Determine the Critical Section containing the knothole.   (See Section 2.14.)  
 
(b) Determine the aggregate width of all knots and knotholes occurring wholly within 
the Critical Section.  Other open characteristics and growth characteristics are 
not included in this aggregate.  
 
(c) The knothole is permitted if the aggregate width of all knots and knotholes in the 
Critical Section does not exceed 152 mm (6 in) in a 1220 mm (48 in) wide panel 
and proportionately for other panel widths.  
 
Splits measured at a point located  203 mm (8 in) from the end of the panel shall not exceed :  
 
(a) 12.7 mm (1/2 in) in width by 1/2 panel length or   
(b) 9.5 mm (3/8 in) in width by any panel length p rovided the separation at one end 
does not exceed 1.6 mm (1/16 in) where the  split runs full panel length .  
 
In either case,  the maximum width  of the s plit within 203 mm (8 in) of the end of the panel (open 
end of split) shall not exceed the maximum width of knotholes permitted within the grade.  
 
Splits on panel faces and backs shall not exceed 6.4 mm (1/4 in) where located within 
25.4 mm (1 in) of  the parall el panel edge.  
 
Voids due to missing wood not otherwise specified above shall not exceed the maximum width 
of knotholes permitted in the grade and the length of such voids shall not exceed 152 mm (6 in).  
 Wane shall not exceed 203 mm (8 in) in length and t he width permitted for open characteristics  
providing that where wane occurs at edges of veneer sheets, panel ply separation due to wane 
shall not exceed the limit equivalent to that permitted for short and narrow inner plies in Section 
5.8.3 for sanded panels, or Section 5.8.4 for unsanded or touch -sanded panels.  
5.4.4.4  Repairs  
Repairs shall be wood or synthetic patching material, neatly made.  
 
Wood veneer repairs shall be die cut.  Wood panel repairs shall be "router" or "sled" type.  
 Wood repairs shall not exc eed 76.2 mm (3 in) in width where occurring in multiple repairs, or 
102 mm (4 in) in width where occurring singly.  
  
15 
 Synthetic veneer repairs shall not exceed 102 mm (4 in) in width.  
 
Synthetic panel repairs shall not exceed 57.2 mm (2- 1/4 in) in width.  
 
Shims shall be permitted without limit.  
5.4.5  Grade C P lugged veneer  
The following characteristics shall be permitted:  knotholes, worm and borer holes, and other 
open characteristics not larger than 6.4 mm  (1/4 in) by 12.7 mm (1/2 in); sound and tight knots 
up to 38.1 mm (1- 1/2 in) measured across the grain; splits up to 3.2 mm (1/8 in) wide; broken 
grain; pitch pockets, if solid and tight; plugs; patches ; and shims.  Synthetic repairs in veneer 
shall not exceed 102 mm (4 in) in width.  Synthetic panel repairs s hall not exceed 57.2 mm (2 -
1/4 in) in width by any length, except that repaired areas not exceeding 152 mm (6 in) in width by 114 mm (4- 1/2 in) in length shall be allowed.  See Tables 2 and 3 for sanding requirements. 
Where grades having C Plugged face veneer are identified as sanded, sanding characteristics 
shall be the same as admitted under B grade.  Sander skips to any degree shall be admissible 
in touch- sanded Grade  C Plugged veneer.  
5.4.6  Grade D veneer  
5.4.6.1  General  
Except as otherwise required in Sections 5.4.6.2 through 5.4.6.4, any number of plugs, patches, 
shims, worm or borer holes, sanding characteristics, and other characteristics shall be 
permitted, provided they do not seriously impair the strength or serviceability of the panels.  
5.4.6.2  Growth characteristics  
Tight knots in inner plies shall be permitted.  
 
In D grade faces or backs, any number of tight knots not larger than 63.5 mm (2 -1/2 in) 
measured  across the grain shall be permitted.  However, an occasional tight knot larger than 
63.5 mm  (2-1/2 in) but not larger than 76.2 mm (3 in) measured across the grain, shall be 
permitted subject to the following provision:   
(a) Determine the Critical Section containing the knot.   (See Section 2.14.)  
 (b) Determine the aggregate width of all knots and knotholes occurring wholly within 
the Critical Section.  Other open characteristics and growth characteristics are 
not included in this aggregate.  
 
(c) The knot is permitted if the aggregate width of all knots and knotholes in the 
Critical Section does not exceed 254 mm (10 i n) in a 1220 mm (48 in) wide panel 
and proportionately for other panel widths.  
5.4.6.3  Open characteristics  
Any number of knotholes up to 63.5 mm (2- 1/2 in) measured across the grain shall be 
permitted. However, an occasional knothole larger than 63.5 mm (2-1/2 in) but not larger than 
76.2 mm (3 in) measured across the grain shall be permitted subject to the following provision:  
   
16 
 (a) Determine the Critical Section containing the knothole.   (See Section 2.14)  
 
(b) Determine the aggregate width of all knots and  knotholes occurring wholly within 
the Critical Section.  Other open characteristics and growth characteristics are not included in this aggregate.  
 (c) The knothole is permitted if the aggregate width of all knots and knotholes in the Critical Section does not exceed 254 mm (10 in) in a 1220 mm (48 in) wide panel 
and proportionately for other panel widths.  
 Knotholes in sanded panels shall not exceed 63.5 mm (2- 1/2 in) across the grain in veneer 
thicker than 3.2 mm (1/8 in).  
 
Knotholes shall not exceed 88. 9 mm (3 -1/2 in) across the grain in veneers  located at least two 
plies removed from the face or back plies of C -D, D-D and C -D Plugged panel  grades having 
five or more plies.  
 
Splits measured at a point 203 mm (8 in) from the end of the panel shall not exc eed 
25.4 mm (1 in) in width, tapering to not more than 1.6 mm (1/16 in) where the split runs full 
panel length; however, the maximum width of the split  within 203 mm (8 in) of the end of the 
panel (open end of split) shall not exceed the maximum width of k notholes permitted within the 
grade.  
 
Splits on panel faces and backs shall not exceed 6.4 mm (1/4 in) in width where located within 
25.4 mm (1 in) of the  parallel panel edge.  
 Voids due to missing wood not otherwise specified above shall not exceed the maximum width 
of knotholes permitted in the grade and the length of such voids shall not exceed 152 mm (6 in).  
 Wane shall not exceed 203 mm (8 in) in length and the width permitted for open characteristics  
providing that where  wane  occur s at edges of veneer sheets, panel ply separation due to wane 
shall not exceed the limit equivalent to that permitted for short and narrow inner plies in Section 
5.8.3 for sanded panels, or Section 5.8.4 for unsanded or touch -sanded panels.  
5.4.6.4  White pocket  
Any area  measuring 610 mm (24 in) wide across the grain and 305 mm (12 in) long, in which 
light or heavy white pocket occurs shall not  contain more than three of the following 
characteristics, in any combination:  
 
(a) A 152 mm (6 in) width of heavy white pocket.  
 
(b) A 305 mm (12 in) width of light white pocket  
 
(c) One knot or knothole measuring 38.1 mm (1 -1/2 in) to 63.5 mm (2 -1/2 in)  across  
the grain, or two knots or knotholes  measuring 25.4 mm (1 in) to 38.1 mm (1- 1/2 
in) across the grain. Knots or knotholes less than 25.4 mm (1  in) shall not be 
considered.  Any repair in a white pocket area shall be considered for grading 
purposes as a knothole.  
 
5.5 Veneers and layers  
   
17 
 5.5.1  Veneer thickness  
Except as specified  in the following paragraphs, veneer shall be  either :  
 
(a) 2.5 mm (1/10 in) or thicker in panels with Performance Category of equal to or 
greater than 3/8 or  
 
(b) 2.1 mm (1/12 in) or thicker in panels with Performance Category of less than 3/8.  
In no case shall veneers used in face or back layers be thicker than 6.4 mm (1/4 
in), or veneers used in inner layers be thicker than 7.9 mm (5/16 in).  
 Veneer of 2.1 mm (1/12 in) in thickness  shall be permitted as crossbands in 5- ply, 5 -layer 
panels with Performance Category of 15/32 and 1/2  and in parallel -laminated layers as specified  
in Section 5.5.2.  
 
Veneer of 1.6 mm (1/16 in)  in thickness  shall be permitted for any ply in 5 -ply Exterior type 
panels with Performance Category of less than 15/32; as the center only in other 5 -ply panels; 
and in a parallel laminated layer as specified in Section 5.5.2.  
 
Face and back veneers shall be a minimum thickness of 3.2 mm (1/8 in) for panels with 
Performance Category of 19/32 or 5/8, where constructed as either  3, 4, and 5 -ply, 3 -layer 
panels of C -D, C-D Plugged, C -C, C-C Plugged and Underlayment grades.  
 Further limitations on panel layup are specified in Section 5.8, Panel Constructions and 
Workmanship.  
 
The average veneer thickness shall conform to the limitations given in this Standard within a 
tolerance of ± 5% of the specified nominal thickness measured dry before layup.  
 
In lieu of veneer thickness requirements above, panels qualifying under workmanship provisions 
of Section 5.8 and performance testing in accordance with Section 5.8.6 or 5.8 .7 shall be 
permitted.  A thickness  tolerance of ± 5% also applies to the normal dry veneer thicknesses used 
in panels qualified by performance testing.  
5.5.2  Parallel laminated layers 
Parallel -laminated outer layers shall only be used in C -C, C-D, D-D, Structural I C -C and 
Structural I  C-D grades.  Such layers shall consist of veneers  measuring  2.5 mm (1/10 in) or 
thicker in any combination not exceeding 6.4 mm (1/4 in) total layer thickness.  The face and back plies shall conform to the s pecies group and grade requirements for faces and backs, 
respectively, of the panel grade.  The sub -face and sub- back plies  shall conform to the species 
group and grade requirements for inner plies of the panel grade as specified in Tables 2 and 3 
and Sect ion 5.6.5.  The maximum split or gap in sub- faces and sub- backs shall be 6.4 mm (1/4 
in) under the faces of Structural I C -C and Structural I  C-D panels; 12.7 mm (1/2 in) under the 
faces of C -C, C-D and D -D grades, and 12.7 mm (1/2 in) under D backs.  
 
Para llel-laminated inner layers in any grade shall consist of veneers  measuring 1.6 mm (1/16 in) 
or thicker in any thickness combination not exceeding 11.1 mm (7/16 in) total layer thickness.  Individual plies in such layers shall conform to the species group and grade requirements for 
inner plies of the panel grade.  
 
In lieu of veneer thickness requirements above, panels qualifying under workmanship provisions 
of Section 5.8 and performance testing in accordance with Section 5.8.6 or Section 5.8.7 shall 
be per mitted.  
  
18 
 TABLE 2.  EXPOSURE 1 PLYWOOD GRADES (PERMITS D GRADE VENEER)  
 
 Minimum Veneer Quality   
Panel Grade Designations  Face  Back  Inner Plies  Surface  
N-N N N C Sanded 2 sides  
N-A N A C Sanded 2 sides  
N-B N B C Sanded 2 sides  
N-D N D D Sanded 2 sides  
A-A A A D Sanded 2 sides  
A-B A B D Sanded 2 sides  
A-D A D D Sanded 2 sides  
B-B B B D Sanded 2 sides  
B-D B D D Sanded 2 sides  
Underlayment(a) C Plugged  D C & D  Touch -sanded  
C-D Plugged  C Plugged  D D Touch -sanded  
Structural I C -D  See 5.6.5   Unsanded(b) 
Structural I C -D Plugged, Underlayment   See 5.6.5   Touch -sanded  
C-D C D D Unsanded(b) 
D-D(c) D D D Unsanded(b) 
(a) See Section 5.6.3 and Table 5 for special limitations.  
(b) See Section 5.8.4 for requirements.  
(c) Applicable only to panels qualified through performance testing per Section 5.8.6 (plus Section 6.2.2.3 of PS 2 -
18) or PS 2 -18. 
5.5.3  Scarfed veneers  
Scarfed veneers shall be permitted for any face, back, or inner ply except as specified in 
Section 5.9.  Scarfe d joints shall not have a slope steeper than 1 to 8.  Veneer in the scarf area 
shall not contain characteristics which reduce its effective cross section by more than 20%.  
Veneer scarfed joints shall be bonded with a moisture resistant adhesive.  
5.6 Panel grades  
The standard combination of the veneers described in Section 5.4 assembled into the various panel grades shall be as  specified in Tables 2 and 3, with the additional requirements  specified 
in Sections 5.6.1 through 5.6.7.  The grain direction of the outer layers shall be either parallel or 
perpendicular to the long dimension of the panel.  
   
19 
 TABLE 3.  EXTERIOR PLYWOOD GRADES(a) (DOES NOT PERMIT D GRADE VENEER)  
 
 Minimum Veneer Quality   
Panel Grade Designations  Face  Back  Inner 
Plies  Surface  
Marine (A -A, A-B, B-B, HDO, MDO)   See 5.6.1   See regular grades  
Special Exterior (A -A, A-B, B-B, HDO, MDO)   See 5.6.6   See regular grades  
A-A A A C Sanded 2 sides  
A-B A B C Sanded 2 sides  
A-C A C C Sanded 2 sides  
B-B (concrete form)  B B C See 5.6.4  
B-C (concrete form)  B C C See 5.6.4  
B-B B B C Sanded 2 sides  
B-C B C C Sanded 2 sides  
C-C Plugged(b) C Plugged  C C Touch -sanded  
C-C C C C Unsanded(c) 
HDO -Industrial A -A, B-B, B-C       C (d)  
HDO -Concrete Form(e)  A-A, B-B, B-C   C  
MDO -General B -B, B-C   C  
MDO -Concrete Form(e) B-B, B-C   C  
Special Overlays  C C C — 
(a) Available also in Structural I classification as  specified  in Section 5.6.5.  
(b) See Section 5.6.3 and Table 5 for special limitations.  
(c) See Section 5.8.4 for requirements.  
(d) C Plugged for HDO -Industrial when intended for sign applications  
(e) For more clarification on concrete form grades, see Section 5.6.4.  
5.6.1  Marine  
Marine grades shall meet the requirements of Exterior plywood and shall be of one of the 
following grades:  A -A, A- B, B-B, High Density Overlay, or Medium Density Overlay, all as 
modified in Sections 5.6.1.1 through 5.6.1.3.  
5.6.1.1  Species 
Only Group 1 Douglas -fir and Western Larch veneers shall be used.  The restrictions on 
qualification of panels by performance testing referenced in Section 5.2.4 shall apply . 
5.6.1.2  Veneers  
Grade A faces shall be limited to a total of nine single wood repairs in a 1220 mm by 2440  mm 
(48 in x 96 in) sheet, or to a proportionate number in any other size as manufactured.  
 
All inner plies shall be B grade or better and shall be full length and width.  
 All wood repairs shall be bonded with an adhesive meeting the Exterior performance 
requirements of Section 5.7.2 and, in addition, shall be set in the panel using a technique 
involving both heat and pressure.  
 
When the inner plies consist of two or more pieces  of veneer, the edges shall be straight and 
square, and shall not overlap.  
5.6.1.3  Crossband gaps and edge splits  
Neither edge of a panel shall have any crossband gap or edge split in excess of 3.2 mm (1/8 in) 
wide.  Crossband gaps and edge splits per 2440 mm (96 in) of crossband ply shall not exceed 
four in number.  End splits and gaps on either end of a panel shall not exceed 3.2  mm (1/8 in) in 
aggregate width.  
 
There shall be no filling of crossband gaps and edge splits.   
20 
 5.6.2  Decorative panels  
Specialty panels with decorative face and veneer treatments which, except for the special face 
treatment, meet all of the requirements of this Standard, including veneer qualities, adhesive 
bond performance,  and workmanship, shall be considered as conforming to this Standard.  A ll 
grades in Tables 2 and 3 shall be permitted to be manufactured as decorative grades.  
 
An occasional butt joint used for decorative effect in veneer shall have a maximum width of 
152 mm (6 inches) and shall be limited to one panel face.  Where butt joint s occur, the 
aggregate width of all knots and knotholes and two- thirds the aggregate width of all repairs, 
including butt joints, shall not exceed 152 mm (6 in) in any area 305 mm (12 in) along the grain 
by 1220 mm (48 in) wide or proportionately for other  widths.  
5.6.3  Underlayment  
Underlayment is plywood produced with touch sanded or sanded faces to the following 
requirements : 
 5.6.3.1 Exposure 1 u nderlayment  (C-D plugged or better) .   
Face veneer shall be C -plugged grade or better  2.5 mm (1/10 in) or thicker before sanding. 
Finished face veneers after sanding shall each have a minimum net thickness equal to 90% of the nominal veneer thickness.   The veneer immediately adjacent to the face ply shall be C 
grade or better with no open characteristics over 25.4 mm (1 in) across the grain except that veneer immediately adjacent to the face ply shall be permitted to be D grade with open 
characteristics up to 63.5 mm (2- 1/2 in) across the grain,  provided the face veneer is of Group 1 
or 2 species of 4.2 mm (1/6 in) minimum thickness before sanding.  Also see Table 5 
requirements.  
 5.6.3.2 Exterior u nderlayment (C-C plugged or better) .   
Face veneer shall be C -plugged grade or better 2.5 mm (1/10 in) or thicker before sanding. 
Finished face veneers after sanding shall each have a minimum net thickness equal to 90% of 
the nominal veneer thickness.   The veneer immediately adjacent to the fac e ply shall be C 
grade or better with no open characteristics over 25.4 mm (1  in) across the grain except that 
veneer immediately adjacent to the face ply shall be permitted to be C grade with open characteristics up to 38.1 mm (1- 1/2 in) across the grain,  provided the face veneer is of Group 1 
or 2 species of 4.2 mm (1/6 in) minimum thickness before sanding.  Also see Table 5 requirements.  
5.6.4  Concrete form panels  
Face veneers shall not be less than B grade , and back veneers shall not be less than C grade.  
The face and back veneers shall be of the same species group.  The face and back veneers 
shall be designated in the mark.  Inner plies shall be not less than C grade.  This grade of 
plywood is produced in two classes, and panels of each class shall be ident ified accordingly.  
Non-overlaid panels shall be sanded on two sides and have a mill -applied release agent unless 
otherwise agreed upon between buyer and seller.  For non -overlaid panels, Western Larch shall 
be excluded from use in the face plies of concre te form plywood due to the excessive wood 
sugars that prohibit proper curing of concrete.  Species shall be further limited as follows and are applicable also to High Density Overlaid Exterior and Medium Density Overlaid Exterior 
concrete form panels . The restrictions on qualification of panels by performance testing 
referenced in Section 5.2.4 shall apply : 
 
(a) Class I — Faces of Group 1 species, crossband of Group 1 or Group 2 species, 
and centers of Group 1, 2, 3, or 4 species.  
 
(b) Class II —  Faces of Group 1 or Group 2 species, and crossband and centers of 
Group  1, 2, 3, or 4 species; or, faces of Group 3 species of 3.2 mm (1/8 in)  
21 
 minimum thickness before sanding, crossband of Group 1, 2, or 3 species, and 
centers of Group 1, 2, 3, or 4 species.  
5.6.5  Struc tural I panels  
These panels are designed for engineered applications such as structural components where 
design properties, including tension, compression, shear, cross -panel flexural properties , and 
nail bearing are of significant importance.  Structural I shall be produced as C -D, C-D Plugged, 
Underlayment or any Exterior grade (see Table 3). Structural  I panels shall meet all other 
requirements in this Standard for the applicable types and grades and the additional 
requirements below:  
 
(a) All face, back , and inner plies shall be Group 1 species as listed in Table 1 . The 
restrictions on qualification of panels by performance testing referenced in 
Section 5.2.4 shall apply . 
 
(b) Special limitations applying to Structural I (C -D, C-D Plugged, Underlayment) 
grade panels are:  
 
• In D grade veneers, white pocket in any area larger than the size of the 
largest knothole,  pitch pocket or split specifically permitted in D grade shall 
not be permitted in any ply . 
• Sound tight knots in D grade shall not exceed 63.5 mm (2- 1/2 in) measured 
across the grain, except as specified in Table 5.  
• Plugs, including multiple repairs, shall not exceed 102 mm (4 in) in width.  
5.6.6  Special Exterior  
An Exterior panel that is produced from any species covered by this Standard.  Except in regard to species, it shall meet all of the requirements for Marine panels (see Section 5.6.1) and be 
produced in one of the following grades:  A -A, A-B, B-B, High Density Overlay, or Medium 
Density Overlay.  
5.6.7  Overlays  
For overlaid plywood, the grade designation for f ace and back, as given in Table 3, refers to the 
veneer directly beneath the overlay.  All overlaid plywood shall be overlaid on two sides unless  
identified as having one working face as specified in S ection 7. 5.(c).  When only one side is 
overlaid (or when a backer sheet is applied), the back shall be C or better.  The surface of overlaid plywood shall be smooth, or uniformly textured, although some evidence of underlying 
grain shall be permitted.  
5.6.7.1  High Density Overlay – Concrete Form  
HDO Concrete Form plywood shall be manufactured with thermosetting phenolic resin 
impregnated cellulose- fiber sheet or sheets bonded to the working face.  The overlay layer shall 
consist of a sheet or sheets, containing not less than 52% phenolic resin content, based on the volatile -free weight of fiber and resin.  The thickness of resin- impregnated materials for each 
working face shall be not less than 0.30 mm (0.012 in) thick before pressing and shall weigh not 
less than 290 g per m
2 (60 pounds per 1000 ft2) in the ready -to-use condition.  When the 
overlay layer is composed of MDO cushion sheet and HDO cap sheet (or sheets), the MDO sheet shall be not less than 34% phenolic resin content based on the volatile- free weight of 
resin and fiber, exclusive of bond line.  
5.6.7.2  High Density Overlay – Industrial  
HDO Industrial plywood is typically used for highway signs or industrial applications.  HDO -
Industrial plywood shall be manufactured with thermosetting phenolic resin impregnated 
cellulose -fiber sheet or sheets bonded to the working face.  The overlay layer shall consist of a  
22 
 sheet or sheets, containing not less than 45% phenolic resin content based on the volatile- free 
weight of fiber and resin.  The thickness of resin- impregnated materials for each working face 
shall be not less than 0.30 mm (0.012 in) thick before pressing and shall weigh not less than 
290 g per m2 (60 pounds per 1000 ft2) in the ready -to-use condition.  When the overlay layer is 
composed of MDO cushion sheet and HDO cap sheet ( or sheets), the MDO sheet shall be not 
less than 34% resin content based on the volatile- free weight of resin and fiber, exclusive of 
bond line.  
5.6.7.3  Medium Density Overlay –  Concrete Form  
MDO Concrete Form plywood shall be manufactured with thermosetting phenolic resin 
impregnated cellulose- fiber sheet or sheets bonded to the working face.  The overlay layer shall 
consist of a sheet or sheets, containing not less than 34% phenolic resin content based on the 
volatile -free weight of fiber and resin, but exclusiv e of bond line.  The thickness of resin-
impregnated materials for each working face shall be not less than 0.30 mm (0.012 in) thick 
after pressing and shall weigh not less than 280 g per m2 (58 pounds per 1000 ft2) including 
both resin and fiber, but exclusive of bond line.  Unless otherwise agreed upon between buyer 
and seller, MDO Concrete Form plywood shall be treated with a release agent.  
5.6.7.4  Medium Density Overlay –  General  
MDO General plywood shall be manufactured with thermosetting phenolic resin impregnated cellulose -fiber sheet or sheets bonded to the working face.  The overlay layer shall consist of a 
sheet or sheets, containing not less than 27% phenolic resin content based on the volatile- free 
weight of fiber and resin, but exclusive of bond line.  The thickness of resin -impregnated 
materials for each working face shall be not less than 0.30 mm (0.012 in) thick after pressing 
and shall weigh not less than 280 g per m
2 (58 pounds per 1000 ft2) including both resin and 
fiber, but exclusive of bond line.   The resin -treated facing on the finished product s hall be 
suitable for painting.  
5.6.7.5  Special overlays  
These are surfacing materials having resin systems, resin- treated fiber materials, or special 
characteristics that do not fit the particular description of High Density or Medium Density overlays as given in Sections 5.6.7.1, 5.6.7.2, 5.6.7.3, or 5.6.7.4.  Special Overlays shall meet 
the adhesive bond requirements for overlaid plywood.  (See 5.7.2.2 .)  Although designed for a 
wide variety of uses, this overlaid plywood shall be Exterior, including the base panel, bond of 
overlay to the panel, and the overlay itself.  Panels shall be identified as "Special Overlay"  as 
part of the panel mark (see Section 7.5) . 
5.7 Adhesive bond requirements for a panel or a lot  
The adhesive bond shall meet the requirements below.  
5.7.1  Exposure 1  
Plywood  shall be considered as meeting Exposure 1 adhesive bond requirements of this 
Standard if all test specimens taken from all individual panels average 80% wood failure or 
greater when tested in accordance with Section 6.1.3. For qualification purposes, specimens 
from at least 20 panels shall be sampled. For other purposes, specimens from less than 20 
panels shall be permitted.  
 Lots represented by test panels shall be considered as meeting the requirements of this 
Standard if the following  requirements are met:  
 
1. When at least 20 panels are tested, at least 95% of the individual panels represented by the test pieces shall have 30% wood failure or better, and at least 
90% of the individual panels represented by the test pieces shall have 60% wood 
failure or better.   In addition, the average wood failure of all test specimens taken  
23 
 from all individual panels shall be not less than  80%.  
 
NOTE:  Wood failure is defined as the rupturing of wood fibers on bonded 
specimens  and is expressed as the percentage of wood fiber area to the total 
area involved which shows failure.  A successful adhesive bond is stronger than 
the wood, forcing the failure in the wood . 
 
2. When at least 10 but less than 20 panels are tested, at least 90% of the individual panels represented by the test pieces shall have 60% wood failure or better.   In 
addition, the average wood failure of all test specimens taken from  all individual 
panels shall be not less than 80%.  
 
3. When fewer than 10 panels are tested, all individual panels represented by the 
test pieces shall have 60% wood failure or better.   In addition, the average wood 
failure of all test specimens taken from al l individual panels shall be not less than 
80%.  
 
The requirements of Section 5.7.1 are applicable separately and independently to the results obtained from the vacuum -pressure test (Section 6.1.3.2) and the boiling test (Section 6.1.3.3).  
Specimens cut through localized characteristics permitted in the grade shall be discarded.  Test specimens showing delamination in excess of 3.2 mm (1/8 in) deep and 25.4 mm (1 in) long 
shall be rated as zero (0)% wood failure.  
5.7.1.1  Heat performance  
Panels shall meet the heat performance requirements for Exterior adhesives.  (See Section 
5.7.2.1.)  
5.7.2  Exterior  
Exterior Plywood shall be considered as meeting the adhesive bond requirements of this 
Standard if all test specimens taken from all individual panels average 85% wood failur e or 
greater when tested in accordance with Section 6.1.3. For qualification purposes, specimens 
from at least 20 panels shall be sampled. For other purposes, specimens from less than 20 
panels shall be permitted.  
 
Lots represented by test panels shall be considered as meeting the requirements of this 
Standard if the following  requirements are met:  
 
1. When at least 20 panels are tested, at least 95% of the individual panels 
represented by the test pieces shall have 30% wood failure or better, and at least 
90% of the individual panels represented by the test pieces shall have 60% wood 
failure or better, and at least 75% of the panels represented by the test pieces 
shall have 80% wood failure or better.   In addition, the average wood failure of all 
test specimen s taken from all individual panels shall be not less than 85%.  
 
2. When at least 10 but less than 20 panels are tested, at least 90% of the 
individual panels represented by the test pieces shall have 60% wood failure or 
better, and at least 75% of the panels represented by the test pieces shall have 
80% wood failure or better.   In addition, the average wood failure of all test 
specimens taken from all individual panels shall be not less than 85%.  
 
3. When at least 4 but fewer than 10 panels are tested, at least 75% of the panels 
represented by the test pieces shall have 80% wood failure or better.   In addition, 
the average wood failure of all test specimens taken from all individual panels shall be not less than 85%.   
24 
  
4. When fewer than 4 panels are tested, al l individual panels represented by the 
test pieces shall have 80% wood failure or better. In addition, the average wood 
failure of all test specimens taken from all individual panels shall be not less than 
85%.  
 
The requirements of Section 5.7.2 are applic able separately and independently to the results 
obtained from the vacuum -pressure test (Section 6.1.3.2) and the boiling test (Section 6.1.3.3).  
Specimens cut through localized characteristics permitted in the grade shall be discarded.  Test specimens showing delamination in excess of 3.2 mm (1/8 in) deep and 25.4 mm (1 in) long 
shall be rated as zero (0)% wood failure.  
5.7.2.1  Heat performance  
Exterior plywood shall be considered as meeting the requirements of this section if there is no 
delamination in any spec imen, except when occurring at a localized characteristic permitted in 
the grade when tested in accordance with Section 6.1.3.4.  When testing overlaid plywood, 
blisters or bubbles in the surface caused by combustion shall not be considered as 
delamination.  
5.7.2.2  Overlaid plywood  
The bond between veneers of overlaid plywood as well as the bond between the overlay and the base panel shall meet the wood failure requirements specified  in Section 5.7.2 for Exterior 
plywood.  In evaluating specimens for separation of  the resin- treated face from the plywood, 
fiber failure shall be considered the same as wood failure.  
5.8 Panel constructions and workmanship  
Constructions for all panels shall conform to the minimum number of plies and layers as set 
forth in Table 4.  The pr oportion of wood with grain perpendicular to panel face grain shall be 
not less than 33% nor more than 70% of the total panel thickness.  The combined thickness of inner layers in panels having 4 or more plies shall be not less than 45% of the total panel 
thickness.  For application of these requirements, the panel thickness shall be the actual 
finished panel thickness and the veneer thickness shall be the dry veneer thickness before layup.   
 The grain of all layers shall be perpendicular to the grain of adjacent layers and to the ends or 
edges of the panel.  The entire area of each contacting surface of the adjacent plies, including 
repairs, shall be bonded with an adhesive in a manner to assure compliance with the performance requirements for its type as set forth in the test described in Section 6.   
 For the purpose of veneer repairing or edge joining, strings, ribbons, or tapes up to 9.5 mm 
(3/8 in) maximum width can occur in a bond line and shall be considered as allowable localized 
characteristics in the evaluation of bond line test specimens.  Wider strings, ribbons, or tapes 
shall not be used for veneer repairing or joining unless they are pre -qualified to show bonding 
equal to the required bonding for the panel.  Bond line test specimens cut to include the strings, 
ribbons, or tapes wider than 9.5  mm (3/8 in) shall not be discarded because of the presence of 
these materials.   
Veneer strips shall not be joined by string stitching unless the punch for making holes prior to 
stitching has a dimension across the grain of 2.4 mm (0.095 inch) or less and the holes are 
spaced 12.7 mm (1/2 inch) center to center or greater.  All veneer used for inner plies shall be 
permitted to be stitched.  Stitched veneer used for outer plies is limited to panels with C or D 
grade faces or backs, except stitched C veneer shall not be used for faces in Decorative panels. 
Stitched veneer shall not be used for both the face and the back ply .  
  
25 
 Rough or unsanded plywood shall be permitted to have paper tape on either face or back, or 
both; except that, in C -C Exterior, no tape  used for veneer splicing shall be permitted.  
 
Shims or strips of veneer shall not be used to repair panel edge voids.  However, filling of 
permissible edge voids with synthetic fillers neatly applied shall be allowed, except as prohibited 
in Marine grades.  (See Section 5.6.1.)  Staples or pins of metal or synthetic material shall be 
prohibited.  
 Where face or back plies consist of more than one piece of edge joined veneer, gaps between 
adjacent pieces shall be graded as splits.  
 End butt joints shall only be used under the following conditions:  
 
(a) Decorative grades as specified  in Section 5.6.2.  
 
(b) Butt joints having a total aggregate width not exceeding the width of the panel 
shall occur in the center ply of 5 -ply, 5 -layer panels.  The butt joints  shall be 
perpendicular to the grain of the panel face and back plies.  The use of butt -
jointed centers shall be allowed in Exposure 1 sanded grades in panels with Performance Category up to and including 1/2, and in D -D, C-D and C -D 
Plugged panels with Performance Category up to and including 3/4 .  End butt 
joints shall not be used in Structural I panels.  Panels with butt joints in center plies shall be marked "butt -jointed center" as specified in Section 7. 5. 
 Plywood shall be free from blisters, laps and other characteristics, except as expressly 
permitted in Section 5.8 and its subsections.  Panels shall have no continuous holes or through 
openings from face to back.  
5.8.1  Crossband gaps and center gaps  
Crossband gaps or center gaps, except as noted for plugged crossband and jointed crossband, shall not exceed 25.4 mm (1 in) in width for a depth of 203 mm (8 in) measured from panel 
edge.  When two (2) or more gaps are present t he average width  of all gaps , measured on the 
panel edge,   shall not exceed 12.7 m m (1/2 in).  Where inner layers are thicker than 6.4 mm 
(1/4 in), gaps in the laminated plies shall be offset 25.4 mm (1 in) if over 6.4 mm (1/4 in) wide.  
 
Where plugged inner plies are specified, inner plies shall be of C Plugged veneer, and gaps 
between adjacent pieces of inner plies shall not exceed 12.7 mm (1/2 in).  
 Where jointed inner plies are specified, gaps between pieces of inner plies shall not exceed 
9.5 mm (3/8 in), and the average of all gaps occurring in a panel shall not exceed 4.8  mm 
(3/16  in).  
    
26 
 TABLE 4.  PANEL CONSTRUCTIONS (MINIMUM NUMBER OF PLIES AND LAYERS)  
 
 
 
Panel Grades  Finished Panel  
Performance Category Range  Minimum  
Number  
of Plies  Minimum  
Number  
of Layers  
 
Exterior 
 Marine 
 Special Exterior (See 5.6.6 )  
 B-B Concrete F orm 
 B-C Concrete F orm 
 HDO Industrial A -A, B -B, B-C 
 HDO Concrete Form A -A, B -B, B -C 
 MDO Concrete Form B -B, B-C 
  
  
 
Through 3/8  
Over 3/8 , through 3/4  
Over 3/4   
  
 
3 
5 
7  
 
 
 
3 
5 
7 
 
Exposure 1  
 N-N, N-A, N -B, N -D, A -A, A-B, 
  A-D, B-B, B-D 
 Structural I (C -D, C-D Plugged  
  and Underlayment)  
 
Exterior  A-A, A-B, A-C, B -B, B-C 
 Structural I (C -C and  
  C-C Plugged) (See 5.6.5)  
 MDO General B -B, B -C 
 Special Overlays  
  
   
 
Through 3/8  
Over 3/8 , through 1/2  
Over 1/2 , through 7/8  
Over 7/8   
   
 
3 
4 
5 
6  
 
  
 
3 
3 
5 
5 
 
Exposure 1  
 Underlayment  
  
Exterior  C-C Plugged  
 
  
 
Through 1/2  
Over 1/2 , through 3/4  
Over 3/4   
 
3 
4 
5  
 
3 
3 
5 
 
Exposure 1  
 C-D 
 C-D Plugged  
 D-D 
 
Exterior  C-C 
  
  Through 5/8  
Over 5/8 , through 3/4  
Over 3/4   
  
3 
4 
5  
  
3 
3 
5 
5.8.2  Veneer requirements  
The veneers used in each ply of each panel and the completed panel shall conform with the 
applicable veneer grade and with the construction and workmanship requirements given herein.  
Additionally, in recognition of the requirements of selected end uses, the type and frequency of 
specific characteristics shall be further limited for grades in Table 5.  
    
27 
 TABLE 5.  CHARACTERISTICS PROHIBITED OR RESTRICTED IN CERTAIN PANEL GRADES  
 
Panel Grade 
Designation   
Description and Number of Characteristics Per Panel  
N-N, N-A No crossband laps adjacent to faces and backs  
N-B No crossband laps adjacent to N faces  
No more than 2 crossband laps adjacent to B grade side (Section 5.8.3)  
Laps are limited to 4.8 mm (3/16 in)  
N-D No crossband laps adjacent to faces  
No more than a total of 2 of any combination of the following:  
 — Knothole in D veneer over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
  — Split in D veneer over 12.7 mm (1/2 in) but not over 25.4 mm (1 in)  
 — Crossband lap adjacent to backs  
Underlayment 
and C -C 
Plugged  No knotholes in veneer adjacent to face over 25.4 mm (1 in) across the grain where C grade is required per 
Tables 2 and 3  
No knotholes in veneer adjacent to face over 63.5 mm (2-1/2 in) where D grade is permitted or over 38.1 mm 
(1-1/2 in) where C grade is permitted per 5.6.3  
No laps adjacent to face  
Structural I C -D No splits in faces over 6.4 mm (1/4 in)  
No splits in backs over 12.7 mm (1/2 in)  
No more than a total of 2 of any combination of the following:  
 — Knothole in C veneer over 25.4 mm (1 in) but not over 38.1 mm (1-1/2 in)  
 — Knot in D backs over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
 — Knothole in D veneer over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
 — Crossband lap adjacent to faces (See Section 5.8.4)  
 — Crossband lap adjacent to backs (See Section 5.8.4)  
Structural I C -D 
Plugged  No splits in backs over 12.7 mm (1/2 in)  
No more than a total of 2 of any combination of the following:  
 — Knot in D backs over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
 — Knothole in D veneer over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
 — Crossband lap adjacent to faces (See Section 5.8.4)  
 — Crossband lap adjacent to backs (See Section 5.8.4)  
Structural I 
Underlayment  No knotholes in core veneer next to face over 25.4 mm (1 in)  
No crossband laps adjacent to faces  
No splits in backs over 12.7 mm (1/2 in)  
No more than a total of 2 of any combination of the following:  
 — Knot in D backs over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
 — Knothole in D veneer over 63.5 mm (2-1/2 in) but not over 76.2 mm (3 in)  
 — Crossband lap adjacent to backs (See Sections 5.8.3, 5.8.4)  
5.8.3  Sanded panels  
Unless otherwise specified, sanded plywood shall be sanded on two sides.  Sanding 
characteristics for N, A, B, and C Plugged faces shall be as given in Section 5.4.  Exposed N, A, 
and B veneer surfaces of panels shall have the bark or tight surface out.  P lies directly under the 
surface of overlaid panels are not considered exposed veneers.  Faces and backs of panels shall be full width and full length; except that C grade and D grade backs shall be permitted to 
be narrow on one edge or short on one end onl y, but by not more than  3.2 mm (1/8 in) for half 
the panel length or width.  Inner plies shall be full width and length; except that panels other 
than Marine shall be permitted to have one edge or end void not exceeding 3.2 mm (1/8 in) in 
depth and 203 mm (8 in) in length per panel.  Except as otherwise specified in Table 5 for 
specific panel grade designations, crossband veneers not exceeding 3.2 mm (1/8 in) in 
thickness shall be permitted to be lapped but by not more than  4.8 mm (3/16 in) when adjacent 
to faces, or 12.7 mm (1/2 in) when adjacent to backs, and provided such laps create no 
adjacent visible openings.  Sanding characteristics resulting from crossband laps shall not be 
permitted in panel faces.  
   
28 
 5.8.4  Unsanded and touch -sanded panels  
Grade C or D v eneers shall be permitted to be lapped by not more than 12.7 mm (1/2 in) 
provided such laps shall create no adjacent visible opening.  Additional limitations on laps 
adjacent to panel faces and backs are included in Table 5. All plies of C -D and D -D panels  shall 
be full length and full width except that no more than half the length of one edge nor half the width of one end shall be permitted to contain short or narrow plies, provided:  
 
(a) Such plies shall not be short or narrow by more than 4.8 mm (3/16 i n) except that 
crossbands shall be permitted to be short by 12.7 mm (1/2 in) and centers shall 
be permitted to be narrow by 12.7 mm (1/2 in) provided they taper to within 
4.8 mm (3/16  in) or less of the panel edge over a span of  203 mm (8 in).  
 
(b) When short or narrow by more than 4.8 mm (3/16 in), the aggregate area in the 
plane of the plies of such edge characteristics shall not exceed 39 cm
2 (6 in2) in 
the entire panel.  
 
(c) Such edge characteristics shall not occur in more than one ply at any panel cross 
section.  
 In grades other than C -D and D -D, backs shall be permitted to be narrow on one edge or short 
on one end only, but by less than or equal to 3.2 mm (1/8 in) for half the panel length or width; inner plies shall be full width and length except that one edge or end void not exceeding 3.2  mm 
(1/8 in) in depth and 203 mm (8 in) in length per panel, shall be acceptable.  
 Panels manufactured as C -C, C-D, D- D, Structural I C -C and Structural I C -D shall not be 
surface textured.  Panels manufactured as C -C, C- D, D-D, Structural I C -C and Structural I C -D 
that are sanded or touch -sanded shall meet all applicable requirements for C -C, C-D or D -D and 
the finished face and back veneers after sanding shall each have a minimum net thickness 
equal to 90% of the applicable thickness in Table 6 or in the mill specification.  (See Sections 
5.8.6.4 and  5.8.7. 4) 
 For touch sanded panels, indents (see Section 2.26) shall be considered as an open 
characteristic.  
   
29 
 TABLE 6.  SPAN RATINGS FOR SHEATHING AND SINGLE -FLOOR PANELS BASED ON PRESCRIPTIVE 
SPECIFICATIONS (FOR SPECIAL PLY-LAYER AND SPECIES REQUIREMENTS APPLICABLE TO STRUCTURAL I 
PANELS, SEE SECTION 5.6.5 AND TABLE 4.  FOR CROSSBAND AND TOTAL INNER PLY THICKNESS PROPORTION 
REQUIREMENTS, SEE SECTION 5.8.)  
 
   Minimum Face & Back Veneer Thickness  
Before Pressing, for Species Group(b)  
Span  
Rating 
(a)  
 
Panel  
Performance Category  Minimum 
Number  
of Plies - 
Layers   
 
 
1  
  
2  
  
3  
  
4  
Inner Ply  
Species  
Group  
Sheathing Panels (C -D, C-C) 
12/0 5/16  3-3 2.1 mm (1/12 in)  2.1 mm (1/12 in)  2.1 mm (1/12 in)  2.1 mm (1/12 in)  1, 2, 3 or 4  
16/0 5/16 
11/32  3-3 
3-3 2.1 mm (1/12 in)  
2.1 mm (1/12 in)  2.1 mm (1/12 in) 
2.1 mm (1/12 in)  2.1 mm (1/12 in)  
2.1 mm (1/12 in)  (c) 
2.1 mm (1/12 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
20/0(e) 5/16  
11/32  
3/8  3-3 
3-3 
3-3 2.1 mm (1/12 in)  
2.1 mm (1/12 in)  
2.5 mm(1/10 in)  (c) 
2.1 mm (1/12 in)  
2.5 mm (1/10 in)  (c) 
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
(c) 
2.5 mm (1/10 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
24/0 3/8 
13/32 
1/2  3-3 
3-3 
3-3 2.5 mm (1/10 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
(c) 
2.5 mm (1/10 in)  (c) 
(c) 
2.5 mm (1/10 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
32/16  1/2  
17/32  
5/8  3-3 
3-3 
3-3 2.5 mm (1/10 in)  
2.5 mm (1/10 in)  
(d) 4.2 mm (1/6 in)  
2.5 mm (1/10 in)  
(d) (c) 
4.2 mm (1/6 in)  
(d) (c) 
(c) 
(d) 1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
40/20(e) 5/8  
21/32  
3/4  
25/32  3-3 
3-3 
4-3 
4-3 (d) 
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  4.2 mm (1/6 in)  
3.2 mm (1/8 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
4.2 mm (1/6 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
(c) 
3.2 mm (1/8 in)  
2.5 mm (1/10 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
48/24  3/4  
25/32  
7/8  
29/32  4-3 
4-3 
5-5 
5-5 2.5 mm (1/10 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  4.2 mm (1/6 in)  
3.2 mm (1/8 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
4.2 mm (1/6 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
(c) (c) 
3.2 mm (1/8 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
Single -Floor Panels (UNDERLAYMENT, C -C Plugged)  
16 o.c.  1/2  
19/32  
5/8  3-3 
4-3 
4-3 2.5 mm (1/10 in)  
(d) 
(d) (c) 
(d) 
(d) (c) 
(d) 
(d) (c) 
4.2 mm (1/6 in)  
(d) 1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
20 o.c.(e) 19/32  
5/8  
23/32 
 3/4 4-3 
4-3 
4-3 
4-3 (d) 
(d) 
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  4.2 mm (1/6 in)  
3.2 mm (1/8 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
4.2 mm (1/6 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  (c) 
(c) 
3.2 mm (1/8 in)  
2.5 mm (1/10 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
24 o.c.  23/32  
3/4  
7/8  4-3 
4-3 
5-5 2.5 mm (1/10 in)  
2.5 mm (1/10 in)  
2.5 mm (1/10 in)  4.2 mm (1/6 in)  
3.2 mm (1/8 in)  
2.5 mm (1/10 in)  4.8 mm (3/16 in)  
4.2 mm (1/6 in)  
2.5 mm (1/10 in)  (c) 
(c) 
3.2 mm (1/8 in)  1, 2, 3 or 4  
1, 2, 3 or 4  
1, 2, 3 or 4  
48 o.c.  1-1/8  
1-1/8  
1-1/8 
1-1/8  7-5 
7-5 
7-7 
7-7 3.2 mm (1/8 in)  
3.6 mm (1/7 in)  
2.5 mm (1/10 in)  
3.2 mm (1/8 in)  4.2 mm (1/6 in)  
4.2 mm (1/6 in)  
4.2 mm (1/6 in)  
4.2 mm (1/6 in)  (c) 
(c) 
4.8 mm (3/16 in)  
4.8 mm (3/16 in)  (c) 
(c) (c) 
(c) 1 or 2  
1, 2 or 3  
1 
1, 2 or 3  
(a) See Section 5.8.5 for description.  
(b) Intermixing between species groups and/or thicknesses in the faces and backs of panels is permitted.  Use the lowest applicable span rating 
to identify the panel.  Also see Section 5.5.1.  
(c) Not permitted.  
(d) A minimum of 3.2 mm (1/8 in) for 3, 4 and 5- ply 3 -layer panels per 5.5.1. A minimum of 2.5 mm (1/10 in) for 5- ply 5 -layer panels.  
(e) The “20” span  designation is intended for span s of 19.2 inch.  
5.8.5  Span ratings for panels  
The panel mark (see Section 7.5)  of C-C, C-D, D-D, Structural I C -C, Structural I C -D, and 
single -floor panels  shall include a span rating (see Section 2.57 ).  The numbers are presented 
as a fraction in the marking of sheathing grades of plywood, and as a single number for  single -
floor panels .  Panels for which there is no span rating shall be identified by  the largest species 
group number of the face and back.    
 
For sheathing, the left -hand number shall refer to spacing of roof framing, and the right -hand 
number shall relate to spacing of the floor framing. The single number for single -floor panels  
refers to spacing of the floor framing in single floor applications.  Actual maximum spans are 
established by local building codes.   
30 
  
When used as single floor, panels shall also meet the grade requirements of Section 5.6.3.  
 
The span rating number is related to species and thickness of the panel face and back veneers , 
and panel Performance Category . It shall be established by either procedure (a) or (b):  
 
(a) By meeting prescriptive requirements  as specified  in Table 6, or  
 
(b) By performance testing to satisfy the strength, stiffness and bond criteria as 
specified in Section 5.8.6.  Such performance testing shall be performed by a n 
Accredited Testing Laboratory , as specified  in Section 7. 4. 
5.8.6  Performance testing qualification requirements for span -rated panels 
5.8.6.1  General  
Span- rated panels qualified by performance testing shall satisfy the criteria specified in Section 
5.8.6 when tested in accordance with  Sections 5.8.6.2 and 5.8.6.3.  
Panels selected for qualification testing shall be representative of the grade  and applicable 
panel workmanship requirements . Face and back veneers shall not be  a higher grade than 
specified.  No panel selected for testing shall have a thickness exceeding the average of the 
minimum and maximum thicknesses for the performance category as established in accordance with Table 10 . Panel thickness shall be measured  in accordance with Section 5.10.2.  
5.8.6.2  Structural performance  
 
Concentrated loads  
Test a maximum of 20 specimens taken from at least 10 panels.  Ten specimens (taken from at least five panels) for each test exposure conditi on shall be evaluated for both concentrated 
static and impact loads according to Section 6.2.1.  Requirements are found in Table 7.  If 
additional tests are needed, they shall also consist of 10 specimens, and the results of the two 
10-specimen sets shall be combined.  Only one additional test set is allowed.  If the combined 
results meet or exceed the minimum passing rate, the sample passes.  
Deflection – The initial test set consists of 10 specimens.  
The average deflection shall not be greater than the appropriate requirement in Table 7. 
• If no more than one value is above the requirement, the sample passes.  
• If two or three values are above the requirement, test an additional set.  
• If four or more values are above the requirement, the sample fails.  
• If 10 additional specimens are tested, the combined passing rate shall be at least 85%.   
31 
 Ultimate load  – The initial test set consists of 10 specimens.  
The average load shall not be less than the appropriate requirement in Table 7.  
• If all of the values meet or exceed the requirement, the sample passes.  
• If one of the values is below the requirement, test an additional set.  
• If two or more values are below the requirement, the sample fails.  
• If ten additional specimens are tested, the combined passing rate shall be at least 95%.  
Uniform loads  
Test a maximum of 20 specimens taken from at least 10 panels.  Ten specimens (taken from at 
least five panels) for each test exposure condition shall be evaluated for uniform load capacity 
according to Section 6.2.2.  Test requirements are found in Table 8.  If additional tests are 
needed, they shall also consist of 10 specimens, and the results of the two 10- specimen sets 
shall be combined.  Only one additional test set is allowed.  If the combined results meet or 
exceed the minimum passing rate, the sample passes.  
Deflection – The average deflection shall not be greater than that specified.  The initial test 
consists of 10 specimens.  
• If the average value is below the requirement, the sample passes.  
• If the average value is above the requirement, test an additional set.  
• If the average value based on combined results is above the requirement, the sample fails. 
Ultimate lo ad – The initial test consists of 10 specimens.  The average load shall not be less 
than the appropriate requirement in Table 8.  
• If all of the values meet or exceed the requirement, the sample passes.  
• If one of the values is below the requirement, test an additional set.  
• If two or more values are below the requirement, the sample fails.  
• If ten additional specimens are tested, the combined passing rate shall be at least 95%.  
  
 
   
32 
  
TABLE 7.  CONCENTRATED STATIC AND IMPACT TEST PERFORMANCE CRITERIA  
FOR PANELS TESTED ACCORDING TO SECTION 6.2.1 (SEE SECTION 5.8.6. 2  
FOR PASS/FAIL CRITERIA)  
 
  Performance Criteria  
  Ultimate Load   
End Use – Span 
Rating  Test Exposure  
Conditions(a) Static  Following Impact(b) Deflection  
Under 0.89 kN (200 lbf) Load  
kN lbf kN lbf mm in 
Roof – 16 Dry 
Wet 1.78 400 1.33 300 11.1(c)(d)  0.438(c)(d) 
Roof – 20(f) Dry 
Wet 1.78 400 1.33 300 11.9(c)(d) 0.469(c)(d) 
Roof – 24 Dry 
Wet 1.78 400 1.33 300 12.7(c)(d) 0.500(c)(d) 
Roof – 32 Dry 
Wet 1.78 400 1.33 300 12.7(c)(d) 0.500(c)(d) 
Roof – 40 Dry 
Wet 1.78 400 1.33 300 12.7(c)(d) 0.500(c)(d) 
Roof – 48 Dry 
Wet 1.78 400 1.33 300 12.7(c)(d) 0.500(c)(d) 
Roof – 54 Dry 
Wet 1.78 400 1.33 300 12.7(c)(d) 0.500(c)(d) 
Roof – 60 Dry 
Wet 1.78 400 1.33 300 12.7(c)(d) 0.500(c)(d) 
Subfloor – 16 Dry 
Wet/Redry  1.78 400 1.78 400 4.8(c) 0.188(c) 
Subfloor – 20(f) Dry 
Wet/Redry  1.78 400 1.78 400 5.6(c) 0.219(c) 
Subfloor – 24 Dry 
Wet/Redry  1.78 400 1.78 400 6.4(c) 0.250(c) 
Subfloor – 32 Dry 
Wet/Redry  2.45 550 1.78 400 5.3(c) 0.207(c) 
Subfloor – 48 Dry 
Wet/Redry  2.45 550 1.78 400 8.0(c) 0.313(c) 
Single Floor - 16 Dry 
Wet/Redry  2.45 550 1.78 400 2.0(e) 0.078(e) 
Single Floor - 
20(f) Dry 
Wet/Redry  2.45 550 1.78 400 2.4(e) 0.094(e) 
Single Floor - 24 Dry 
Wet/Redry  2.45 550 1.78 400 2.7(e) 0.108(e) 
Single Floor - 32 Dry 
Wet/Redry  3.11 700 1.78 400 2.2(e) 0.088(e) 
Single Floor - 48 Dry 
Wet/Redry  3.11 700 1.78 400 3.4(e) 0.133(e) 
(a) Wet/redry shall be exposure to three days of continuous  one-sided  wetting  on the panel face , followed 
by testing dry. Wet conditioning shall be exposure to three days of continuous  one-sided  wetting  on the 
panel face, then tested wet. Dry shall be within +/ - 3% of the manufacturer’s  as-shipped moisture 
content.  
(b) Impact shall be 102 N•m (75 lbf•ft) for span ratings up to 24 ; 122 N•m (90 lbf•ft) for 32;  163 N•m 
(120 lbf•ft) for 40 ; and 203 N•m (150 lbf•ft) for 48 and greater.  
(c) Criteria apply under static concentrated load. They do not apply following impact.  
(d) Deflection after wet conditioning not applicable.  
(e) Criteria apply under static concentrated load and following impact.  
(f) The “20” span  designation is intended for span s of 19.2 in.  
 
   
33 
  
TABLE 8.  UNIFORM LOAD PERFORMANCE CRITERIA FOR PANELS TESTED  
ACCORDING TO SECTION 6.2.2  
(SEE SECTION 5.8.6. 2 FOR PA SS/FAIL CRITERIA)  
 
 Performance Criteria(b) 
 Ultimate  
Uniform Load  
End Use - 
Span Rating  Test Exposure  
Conditions(a) Average Deflection Under Load  
kPa  
lbf/ft2 
Roof - 16 Dry 1.7 mm at 1.68 kPa  (0.067 in at 35 lbf/ft2) 7.2 150 
Roof - 20 (c) Dry 2.0 mm at 1.68 kPa  (0.080 in at 35 lbf/ft2) 7.2 150 
Roof - 24 Dry 2.5 mm at 1.68 kPa  (0.100 in at 35 lbf/ft2) 7.2 150 
Roof – 32 Dry 3.4 mm at 1.68 kPa  (0.133 in at 35 lbf/ft2) 7.2 150 
Roof – 40 Dry 4.2 mm at 1.68 kPa  (0.167 in at 35 lbf/ft2) 7.2 150 
Roof – 48 Dry 5.1 mm at 1.68 kPa  (0.200 in at 35 lbf/ft2) 7.2 150 
Roof – 54 Dry 5.7 mm at 1.68 kPa  (0.225 in at 35 lbf/ft2) 7.2 150 
Roof – 60 Dry 6.4 mm at 1.68 kPa  (0.250 in at 35 lbf/ft2) 7.2 150 
Subfloor – 16 Dry 
Wet/Redry  1.1 mm at 4.79 kPa  (0.044 in at 100 lbf/ft2) 15.8 330 
Subfloor – 20(d) Dry 
Wet/Redry  1.3 mm at 4.79 kPa  (0.053 in at 100 lbf/ft2) 15.8 330 
Subfloor – 24 Dry 
Wet/Redry  1.7 mm at 4.79 kPa  (0.067 in at 100 lbf/ft2) 15.8 330 
Subfloor – 32 Dry 
Wet/Redry  2.2 mm at 4.79 kPa  (0.088 in at 100 lbf/ft2) 15.8 330 
Subfloor – 48 Dry 
Wet/Redry  3.4 mm at 3.83 kPa  (0.133 in at 80 lbf/ft2) 10.8 225 
Single Floor – 16 Dry 
Wet/Redry  1.1 mm at 4.79 kPa  (0.044 i n at 100 lbf/ft2) 15.8 330 
Single Floor – 20(c) Dry 
Wet/Redry  1.3 mm at 4.79 kPa  (0.053 i n at 100 lbf/ft2) 15.8 330 
Single Floor – 24 Dry 
Wet/Redry  1.7 mm at 4.79 kPa  (0.067 in at 100 lbf/ft2) 15.8 330 
Single Floor – 32 Dry 
Wet/Redry  2.2 mm at 4.79 kPa  (0.088 in at 100 lbf/ft2) 15.8 330 
Single Floor – 48 Dry 
Wet/Redry  3.4 mm at 3.83 kPa  (0.133 in at 80 lbf/ft2) 10.8 225 
(a) Wet/Redry shall be exposure to three days of continuous  one-sided  wetting  on the panel face , followed by testing 
dry. Dry shall be within 3% of the manuf acturer’s  as shipped moisture content.  
(b) The panel strength axis shall be across supports, unless otherwise specified.  
(c) The “20” span designation is intended for spans of 19.2 in.  
 
 
5.8.6.3  Bond performance  
Panels shall be classed as “Exposure 1” or “Exterior” . 
 
Exposure 1 — Panels rated as “Exposure 1” shall be so identified and shall satisfy the bond 
requirements as specified in Section 5.7.1.  
 
Exterior — Panels rated as “Exterior” shall be so identified and shall satisfy the bond 
requirements speci fied in Section 5.7.2.  
   
34 
 5.8.6.4  Product evaluation  
 
Mill specification  — Upon conformance with the  requirements specified in Sections 5.8.6. 2 
and 5.8.6. 3, a mill specification (see Section 2.35)  unique to the product and mill shall be written 
based on the outcome of product evaluation. This specification shall be used for quality 
assurance purposes by the manufacturer , the Accredited Certification Agency, the Accredited 
Inspection Agency,  and the Accredited Testing Laboratory,  according to Section 7 .  Product 
evaluation will be accomplished on the same lot supplied by the manufacturer for qualification 
testing.  Reference values shall be established during product evaluation or from applicable 
performance requirements in this Standard.  The mill specification shall contain the following 
information:  
 
Panel construction — Panels shall be defined as to veneer species and construction.  
 Thickness — The reference value shall be the average panel thickness less 1.932 standard 
deviations (the 95% lower tolerance limit at 75% confidence) for 20 panels as sampled under 
Section 5.8.6.1.  
 
Mechanical properties   
 Bending stiffness — Results from 20 tests  (specimens taken from at least ten panels) shall be 
evaluated for bending stiffness both along and across the major panel axis according to the 
procedures of Section 6.2.3.  The reference value for each panel direction shall be the lower value of a 90% confidence interval established on the mean  (see ASTM D2915 ). 
 Bending strength —  Results from 10 tests  (specimens taken from ten different panels) shall be 
evaluated for maximum bending moment both along and across the major panel axis according 
to the procedures of Section 6.2.3. The reference values for each panel direction will be the 
minimum observed value, or the sample mean less 1.8 times the sample standard deviation, whichever is the higher value.  
5.8.7  Performance testing qualification requirements for other than span- rated panels  
5.8.7.1  General  
Panels using species as  specified in Section 5.2.4 shall be qualified for use under this Standard 
based upon testing of panel strength and stiffness in accordance with Section 5.8.7.2 and bond 
performance with Section 5.8.7.3 .  Results of testing shall establish a Group classification for 
use as required in Section 7. 5 (a).  Group classification established by panel testing shall be 
determined by the largest Group number obtained from all performance tests. Panels selected 
for qualification testing shall be representati ve of the grade and applicable panel workmanship 
requirements.  Face and back veneers shall not be  a higher grade than specified.  No panel 
selected for testing shall have a thickness exceeding the average of the minimum and maximum 
thicknesses for the perf ormance category as established in accordance with Table 10.  Panel 
thickness shall be measured in accordance with Section 5.10.2.   
5.8.7.2  Performance testing  
 
Bending stiffness — A minimum of 20 tests (specimens taken from at least ten panels) shall 
be evaluated for bending stiffness both along and across the major panel axis according to the procedures of Section 6.2.3.  At least 90% of specimens tested along the major axis shall meet 
the minimum stiffness value along the major axis given in Table 9 for the Perfo rmance Category 
tested.  
  
35 
 TABLE 9.  SPECIES GROUP CLASSIFICATION TEST CRITERIA FOR OTHER  
THAN SPAN- RATED PANELS  
 
  Shear Through  Stress Along (Parallel to Face)  
Performance 
Category   
Group  Thickness 
Strength   
Bending Stiffness   
Bending Strength  Planar Shear  
Strength 
  kN/m (lbf/in)  kN•m2/m (lbf•in2/ft) kN•m/m (lbf•in/ft)  kN/m (lbf/ft)  
 ¼ 1 21.0 (120)  0.15 (  16 000)  0.087 (  235)  3.7 (  255)  
 2 15.8 (  90)  0.12 (  13 000)  0.063 (  170)  3.7 (  255)  
 3 15.8 (  90)  0.10 (  10 500)  0.063 (  170) 3.7 (  255)  
 4 14.5 (  83)  0.08 (    8 800)  0.057 (  155)  3.7 (  255)  
 11/32  1 22.8 (130)  0.35 (  37 500)  0.137 (  370)  5.1 (  350)  
 2 16.6 (  95)  0.30 (  31 500)  0.100 (  270)  5.1 (  350)  
 3 16.6 (  95)  0.24 (  25 000)  0.100 (  270)  5.1 (  350) 
 4 15.6 (  89)  0.20 (  21 000)  0.093 (  250)  5.1 (  350)  
 3/8 1 22.8 (130)  0.50 (  53 500)  0.183 (  495)  5.8 (  395)  
 2 17.0 (  97)  0.42 (  44 500)  0.133 (  360)  5.8 (  395)  
 3 17.0 (  97)  0.33 (  35 500)  0.133 (  360)  5.8 (  395)  
 4 15.8 (  90) 0.28 (  29 500)  0.124 (  335)  5.8 (  395)  
15/32  1 33.3 (190)  1.22 (130 000)  0.313 (  845)  7.7 (  525)  
 2 24.5 (140)  1.04 (110 000)  0.228 (  615)  7.7 (  525)  
 3 24.5 (140)  0.82 (  87 000)  0.228 (  615)  7.7 (  525)  
 4 22.8 (130)  0.68 (  72 500)  0.211 (  570)  7.7 (  525)  
 1/2 1 34.1 (195)  1.41 (150 000)  0.347 (  935)  8.3 (  570)  
 2 25.4 (145)  1.18 (125 000)  0.252 (  680)  8.3 (  570)  
 3 25.4 (145)  0.94 (100 000)  0.252 (  680)  8.3 (  570)  
 4 23.6 (135)  0.80 (  84 500)  0.234 (  630)  8.3 (  570) 
 19/32  1 43.8 (250)  2.17 (230 000)  0.463 (1250)  10.1 (  695)  
 2 32.4 (185)  1.79 (190 000)  0.335 (  905)  10.1 (  695)  
 3 32.4 (185)  1.41 (150 000)  0.335 (  905)  10.1 (  695)  
 4 29.8 (170)  1.18 (125 000)  0.311 (  840)  10.1 (  695)  
 5/8 1 43.8 (250)  2.40 (255 000)  0.500 (1350)  10.8 (  740)  
 2 32.4 (185)  2.02 (215 000)  0.361 (  975)  10.8 (  740)  
 3 32.4 (185)  1.60 (170 000)  0.361 (  975)  10.8 (  740)  
 4 29.8 (170)  1.32 (140 000)  0.335 (  905)  10.8 (  740)  
 23/32  1 44.7 (255)  3.34 (355 000) 0.575 (1550)  12.2 (  835)  
 2 33.3 (190)  2.78 (295 000)  0.408 (1100)  12.2 (  835)  
 3 33.3 (190)  2.21 (235 000)  0.408 (1100)  12.2 (  835)  
 4 30.6 (175)  1.84 (195 000)  0.389 (1050)  12.2 (  835)  
 3/4 1 45.5 (260)  3.67 (390 000)  0.612 (1650)  12.6 (  860) 
 2 33.3 (190)  3.06 (325 000)  0.445 (1200)  12.6 (  860)  
 3 33.3 (190)  2.45 (260 000)  0.445 (1200)  12.6 (  860)  
 4 30.6 (175)  2.02 (215 000)  0.408 (1100)  12.6 (  860)  
 7/8 1 46.4 (265)  5.18 (550 000)  0.760 (2050)  14.6 (1000)  
  2 34.1 (195)  4.33 (460 000)  0.556 (1500)  14.6 (1000)  
 3 34.1 (195)  3.44 (365 000)  0.556 (1500)  14.6 (1000)  
 4 32.4 (185)  2.87 (305 000)  0.500 (1350)  14.6 (1000)  
 1 1 65.7 (375)  7.91 (840 000)  0.982 (2650)  16.8 (1150)  
  2 48.2 (275)  6.59 (700 000)  0.704 (1900)  16.8 (1150)  
 3 48.2 (275)  5.27 (560 000)  0.704 (1900)  16.8 (1150)  
 4 44.7 (255)  4.38 (465 000)  0.649 (1750)  16.8 (1150)  
 1-1/8 1 66.5 (380)  10.36 (1 100 000)  1.205 (3250)  18.3 (1250)  
 2 49.0 (280)  8.52 (905 000)  0.871 (2350)  18.3 (1250)  
 3 49.0 (280)  6.83 (725 000)  0.871 (2350)  18.3 (1250)  
 4 45.5 (260)  5.70 (605 000)  0.816 (2200)  18.3 (1250)  
  
36 
 Bending strength  — A minimum of 10 tests (specimens taken from ten different panels) shall 
be evaluated  for bending strength both along and across the major panel axis according to the 
procedures of Section 6.2.3.  At least 95% of the specimens tested along the major axis 
direction shall meet the value given in Table 9 for the Performance Category tested.  
 Planar shear strength  — A minimum of ten tests (specimens taken from ten different panels) 
shall be tested for planar shear strength along the major panel axis according to the procedures 
of Section 6.2.4.  At least 95% of the tests shall meet the planar s hear strength value along the 
major axis given in Table 9 for the Performance Category  tested.  
 
Shear  Through  Thickness Strength — A minimum of ten tests (specimens taken from ten 
different panels) shall be tested for shear strength through the thickness according to the 
procedures of Section 6.2.5.  At least 95% of tests shall meet the shear -through- the-thickness 
strength value given in Table 9 for the Performance Category  tested.  
5.8.7.3  Bond Performance  
Panels shall  be classified as “Exposure 1” or “Exterior”.  
 Exposure 1 — Panels rated as “Exposure 1” shall be so identified and shall satisfy the bond 
requirements as specified in Section 5.7 .1. 
 
Exterior  — Panels rated as “Exterior” shall be so identified and shall satisfy the bond 
requirements as specified in Section 5.7. 2. 
5.8.7.4  Product evaluation  
 
Mill specification  
Upon conformance with the requirements specified in Sections  5.8.7.2  and 5.8.7.3  a mill 
speci fication (see Section 2.35)  unique to the product and mill shall be written  based on the 
outcome of product eval uation.   The mill  specification shall be used for quality assurance 
purposes by the manufacturer , the Accredited Certification Agency, the Accredited Ins pection 
Agency and the Accredited Testing Laboratory  specified  in Section 7. 
 
Reference values shall be established during product evaluation or from applicable performance 
requirements in this Standard. The mill specification shall contain t he following information:  
 
Panel construction — Panels shall be defined as to veneer species and construction.  
 
Thickness — The reference value shall be the average panel thickness minus  1.932 standard 
deviations (the 95% lower tolerance limit at 75% confi dence) for 20 panels  as sampled under 
Section 5.8.7.1  and tested under S ection 5.8.7.2.  
 
Mechanical Properties  
 Bending stiffness — The reference values for each panel direction shall be the lower value of 
a 90% confidence interval established on the mean for each panel direction (see ASTM D 
2915) . 
 
Bending strength —  The reference values for each panel direction shall be the minimum 
observed value, or the sample mean minus  1.8 times the sample standard deviation, whichever 
is the higher value for each panel direction.  
 
Planar shear strength — The reference value shal l be the minimum observed value, or the 
sample mean less 1.8 times the sample standard deviation whichever is the higher value   
37 
  
Shear -through -the-thickness strength — The reference value shall be the minimum observed 
value, or the sample mean less 1.8 tim es the sample standard deviation, whichever is the 
higher value.  
 
As an alternative to establish ing reference values for  mechanical properties  based on the 
outcome of performance evaluation,  the performance tests and acceptance criteria specified in 
Section 5.8.7.2 may also be used for quality assurance purposes  by the manufacturer, 
Accredited Certification Agency, and Accredited Testing Agency.  When  this is the case, it shall 
be clearly stated in the mill specification.  
5.9 Scarf and finger  jointed panels  
Neither panels with N faces, nor the face veneers  of such panels, unless longer than 3 m (10 ft), 
shall be scarf or finger jointed unless otherwise agreed to by buyer and seller.  Panels of other 
grades shall be permitted to be scarf or finger jointed unless otherwise agreed to by buyer and 
seller, and panels longer than 3.7 m (12 ft) are necessarily scarf or finger -jointed.  Plain scarfed 
joints and the scarfed portion of finger  joints shall not have a slope greater than 1 to 8.  All plies 
with grain perpendicular to the finger joint shall be included in the scarfed portions of the joint, except that such plies shall be permitted to include up to 0.8 mm (1/32 in) of vertical shoulder in 
the scarf (see Figure 1).  Joints shall be bonded with a moisture- resistant adhesive and shall 
meet the test requirements set forth in Sections 5.9.1, 5.9.2, and 5.9.3 as applicable.  In addition, the adhesive shall not show creep or flow characteristics greater than unjointed wood 
when subject to load under any conditions of temperature and moisture.  
 
 
Figure 1.  Finger joints –  Location of scarfed portion of joints.  
 
38 
 5.9.1  Strength requirements for scarf and finger jointed panels  
If the average ultimate stress of the three test specimens of any one panel is less than 
27.6 MPa (4000 psi) for panels of Group 1 species, or less than 19.3 MPa (2800 psi) for panels 
of Group 2 or Group 3 species, or less than 16.5 MPa (2400 psi) for panels of Group 4 species, 
or less than 13.8 MPa (2000 psi) for panels of Group 5 s pecies, when tested in accordance with 
Section 6.1.5.1, then that panel shall fail.  The jointed panels represented by a sampling of ten 
panels shall be acceptable if not more than one of the panels fails and the average ultimate 
stress of the failing panel is at least 80% of that specified for the applicable species group.  If 
the average ultimate stress of the failing panel is at least 75% of that specified for the applicable 
species group, another series of ten panels shall be tested.  If none of the panels in this series 
fails, the jointed panels shall be accepted; otherwise they shall be rejected.  
5.9.2  Scarf joint bond performance for Exposure 1 and Exterior plywood  
Panels shall be tested in accordance with Section 6.1.5.2.  The material represented by the 
sampling shall be evaluated in accordance with Sections 5.7.1 and 5.7.2, as applicable.  
5.9.3  Finger joint bond performance for Exposure 1 and Exterior plywood  
Panels shall be tested in accordance with Section 6.1.5.3.  The joints shall meet all of the 
following minimum conditions:  
 
(a) The average wood failure rating of all specimens from each panel when tested in accordance with Section 6.1.5.3 shall be not less than 85%.  
 (b) No single specimen from a panel (average of face and back bond lines) shall rate 
less than 60% wood failure.  
 (c) No single face or back bond line in any specimen shall rate less than 30% wood 
failure.  
5.10 Dimensional tolerances and squareness of panels  
Panel measurements shall be based on a moisture content of 9%.  
 
NOTE : The moisture content of 9% is consistent with NIST Handbook 133 –  Checking the Net 
Contents of Packaged Goods.  
5.10.1  Size tolerances  
A length and a width measurement shall be made at a location 50 mm to 75 mm (2 in to 3 in) from 
the panel edge. A tolerance of plus zero (0) mm , minus 1.6 mm (1/16 in) shall be allowed on the 
manufacturer’s stated  length and /or width . Where panels are marked "sized for spacing” a 
tolerance of plus zero (0) mm, minus 3.2 mm (1/8 in) shall be allowed on the manufacturer's stated 
length and/or width .  (See Section 2.56). 
ADVISORY NOTE : For tongue- and-groove and ship- lapped panels, the width and squareness 
measurements should be made on the net panel face.  
 
5.10.2  Performance category and thickness tolerances 
 
Panel thickness shall be measured with a micrometer having 19.1 mm (3/4 in) (minus 0, plus 
1.3 mm [0 .050 in]) diameter anvils. Measurement s shall be taken at an applied anvil pressure of 
not less than 34 kPa (5 psi) or more than 69 kPa (10 psi). The location of the measurements  
   
39 
 shall be representative of panel thickness mid- length, ± 50 mm (2 in) along each edge of the 
panel and the average of the four measurements shall be taken as the thickness of that panel.   
If a measurement point contains a permissible grade characteristic that affects panel  thickness, 
then the measurement point shall be shifted f rom that point.  
 
The panel thickness shall conform to Table 10. 
 
TABLE 10.  PLYWOOD THICKNESS REQUIREMENTS  
 
 Thickness Requirements for  
Unsanded, Touch Sanded and 
Overlaid Grades(a)  
Thickness Requirements for  
Sanded Grades(b) 
PERFORMANCE 
CATEGORY(c) Minimum 
Thickness, mm (in)  Maximum 
Thickness, mm (in)  Minimum 
Thickness, mm (in)  Maximum 
Thickness, mm  (in) 
1/4 PERF CAT  5.56 (0.219)  7.14 (0.281)  5.95 (0.234)  6.75 (0.266)  
5/16 PERF CAT  7.14 (0.281)  8.73 (0.344)  7.54 (0.297)  8.33 (0.328)  
11/32 PERF CAT  7.94 (0.313)  9.53 (0.375)  8.33 (0.328)  9.13 (0.359)  
3/8 PERF CAT  8.73 (0.344)  10.32 (0.406)  9.13 (0.359)  9.92 (0.391)  
 7/16 PERF CAT  10.32 (0.406)  11.91 (0.469)  10.72 (0.422)  11.51 (0.453)  
15/32 PERF CAT  11.11 (0.438)  12.70 (0.500)  11.51 (0.453)  12.30 (0.484)  
 1/2 PERF CAT  11.91 (0.469)  13.49 (0.531)  12.30 (0.484)  13.10 (0.516)  
9/16 PERF CAT  13.49 (0.531)  15.08 (0.594)  13.89 (0.547)  14.68 (0.578)  
19/32 PERF CAT  14.29 (0.563)  15.88 (0.625)  14.68 (0.578)  15.48 (0.609)  
5/8 PERF CAT  15.08 (0.594)  16.67 (0.656)  15.48 (0.609)  16.27 (0.641)  
11/16 PERF CAT  16.67 (0.656)  18.26 (0.719)  17.07 (0.672)  17.86 (0.703)  
23/32 PERF CAT  17.46 (0.688)  19.05 (0.750)  17.86 (0.703)  18.65 (0.734)  
3/4 PERF CAT  18.26 (0.719)  19.84 (0.781)  18.65 (0.734)  19.45 (0.766)  
13/16 PERF CAT  19.84 (0.781)  21.43 (0.844)  20.02 (0.788)  21.26 (0.8 37)  
7/8 PERF CAT  21.11 (0.831)  23.34 (0.9 16) 21.56 (0.849)  22.89 (0. 901)  
1 PERF CAT  24.13 (0.950)  26.67 (1.0 50) 24.64 (0.970)  26.16 (1.0 30)  
1-1/8 PERF CAT  27.15 (1.069)  30.00 (1.1 81) 27.72 (1.091)  29.43 (1.1 59)  
1-1/4 PERF CAT  30.16 (1.188)  33.34 (1. 313) 30.80 (1.213)  32.70 (1.2 88)  
(a) Thickness requirements for unsanded, touch sanded, and overlaid panels are based on a tolerance of ± 0.8 mm (1/32 in) 
for panels with Performance Categories of 13/16 and less and ±  5% for panels with Performance Categories greater 
than13/16 unless a closer  tolerance is determined through qualification testing.  
(b) Thickness requirements for sanded panels is based on a tolerance of ±  0.4 mm (1/64 in) for panels with Performance 
Categories of 3/4  and less and ±  3.0% for panels with Performance Categories greater than 3/4  unless a closer tolerance 
is determined through qualification testing.  
(c) For labeling purposes, abbreviation of “Performance Category” by PERF CAT, CAT or Category is permitted. 
Performance Categories for other panel thicknesses are permitted.  
5.10.3  Squareness and straightness  
Panels shall be square within 1.3 mm per lineal meter of the longest edge (1/64 in per lineal 
foot) measured along the diagonals.  All panels shall be manufactured so that a straight line 
drawn from one corner to the adjacent corner is within 1.6 mm (1/16 in) of the panel edge.  
5.11 Moisture content  
Moisture content of panels at time of shipment shall not exceed 18% when tested in accordance with Section 6.1.4.  
5.12 Loading or packing  
The plywood shall be securely loaded or packaged to ensure delivery to destination in a clean and serviceable condition.  
40 
 6. SPECIMEN PREPARATION AND TESTING  
6.1 Bond classification  
6.1.1  General  
The tests set forth in this section shall be used to determine the adhesive bond quality of 
plywood produced under this Standard.  
6.1.2  Specimen preparation (see appendix B for sampling for reinspection)  
One test piece shall be cut from each panel selected.  From each test piece,  10 test specimens 
shall be cut as specified in Section 6.1.3.1.   Additional speci mens may be cut and tested at the 
discretion of the Accredited Cer tification Agency or the Accredited Testing Laboratory. Of the 10 
specimens cut from each test piece, 5  specimens shall be for the vacuum -pressure test (see 
Section 6.1.3.2) and 5 specimens shall be for the boil test  (see Section 6.1.3.3) .  In addition, 
from each panel selected, one specimen  measuring 140 mm  (5-1/2 in)  by 203 mm (8 in) shall 
be cut and tested as specified  in Section 6.1.3.4.  
6.1.3  Tests for Exposure 1 and Exterior plywood  
Specimen preparation shall follow the general principles of the procedures specifically 
prescribed herein.  
6.1.3.1  Preparation of test specimens  
Test specimens taken as specified in Section 6.1.2 shall be cut 82.6 mm (3-1/4 in) long by 
25.4 mm (1 in)  wide, and kerfed one -third of the length of the specimen from each end, as 
illustrated in Figure 2 , to provide a 25.4 mm (1 in) square test area in the center.  Specimens 
shall be oriented so that the grain direction of the ply under test is orient ed at a 90° angle to the 
lengt h of the specimen.  Kerfing shall extend two- thirds of the way through the ply under test, 
and shall not penetrate the next bond line.  For overlaid plywood, the additional 10 specimens 
for testing of bond between veneers shall be cut as specified in this section for Exterior 
specimens except that they shall be cut 25.4 mm (1 in) wide and 76.2 mm (3 in) long, and kerfed just through the overlay 25.4 mm (1 in) from the end, on each overlay face.  
 
Figure 2.  Shear test specimens.  
 If the number of plies exceeds three, the cuts shall be made so as to test any two of the joints, 
but the additional plies need not be stripped except as demanded by the limitations of the width  
  
 
41 
 of the retaining jaws on the testing device.  When required to accommodate thicker pl ywood, 
special jaws shall be constructed.  If the number of plies exceeds three, the choice of joints to 
be tested shall be left to the discretion of the Accredited Certification Agency or Accredited 
Testing Laboratory , but at least one- half of the tests s hall include the innermost joints.  
6.1.3.2  Vacuum -pressure test  
The test specimen shall be placed in a pressure vessel and submerged in cold tap water.  A 
vacuum of 83.5 kPa to 98.5 kPa (24.7 inches  to 29.0 inches of mercury ) shall be drawn and 
maintained for 30 m inutes, followed immediately with application of 450 kPa to 480 kPa (65 psi 
to 70 psi) of pressure for 30 minutes duration.  Specimens shall then be removed from the 
vessel and tested while wet by tension loading to failure in a shear testing machine opera ted at 
a maximum head travel of 762 mm (30 in)  per minute.  The jaws of the machine shall securely 
grip the specimens so there is no slippage.  The percentage of wood failure of each  specimen 
shall be visually  determined in the  dry condition  to the nearest 5%  in accordance with ASTM 
D5266.   For the purposes of evaluating product conformance to the requirements  specified in 
Sections 5.7.1 and 5.7.2 , the average wood failure for each panel and for the lot, regardless of 
the number of panels tes ted, shall be calculated to the nearest 1% . 
 
The bond between veneers in overlaid plywood shall be tested in an identical manner and 
evaluated as specified in Section 5.7.2. 2.  Specimens for testing the bond between the overlay 
and the base panel shall be subjected to the same test  cycle just described.  The bond between 
the overlay and the base panel shall be tested by inserting a sharp, thin blade of adequate 
stiffness into the corner of the 25.4 mm (1 in) test area at the overlay -veneer interface, taking 
care not to cut into the overlay, and attempting to peel the overlay off.  Reinsertion of the blade 
several times shall be permitted if necessary,  to remove the overlay from the 6.5 cm2 (1 in2) 
area.  The percentage of wood and/or fiber failure shall then  be visually determined with 
specimens in the  dry condition in accordance with ASTM . For the purpose of evaluating product 
conformance to the requirements specified in Section 5.7.2.2, the average wood and/or fiber 
failure for each panel and for the lot, regardless of the number of panels tested, shall be 
calculated to the nearest 1% . 
6.1.3.3  Boiling test  
Test specimens shall be boiled in water for 4 hours and then dried for 20 hours at a temperature 
of 63  °C ± 3 °C (145 °F ± 5 °F) with sufficient air circulation to lower moisture content of the 
specimens to a maximum of 8%.  The specimens shall be boiled again for a period of 4 hours, 
cooled in water, and tested while wet by tension loading to failure in a shear testing machine 
operated at a maximum head travel of 762 mm (30 in) per minute.  Jaws of the machine shall 
securely grip the specimens so there is no slippage.  The percentage of wood failure of each 
specimen shall be visually determined in the  dry condition to the nearest 5%  in accordance with 
ASTM D5266.  For the purposes of evaluating product conformance to the requirements  
specified in Sections 5.7.1 and 5.7.2 , the average wood failure for each panel and for the lot, 
regardless of the number of panels tested, shall be calculated to the nearest 1% . 
 
The bond between veneers in overlaid plywood shall be tested in an identical manner and 
evaluated as  specified in Section 5.7.2. 2.  Specimens  to test the bond between the overlay and 
the base panels shall be subjected to the same test cycle specified  in the previous paragraph.  
The bond between the overlay and the base panel shall be tested by inserting a sharp, thin 
blade of adequate stiffness  into the corner of the 25.4 mm (1 in) test area at the overlay -veneer 
interface, taking care not to cut into the overlay, and attempting to peel the overlay off.   
   
42 
 Reinsertion of the blade several times shall be permitted if necessary,  to remove the overlay 
from the 6.5 cm2 (1 in2) area.  The percentage of wood and/or fiber failure shall then be visually 
determined with specimens in the dry condition in accordance with ASTM D5266.  For the 
purpose of evaluating product conformance to the requirements specified in Section 5.7.2.2, the 
average wood and/or fiber failure for each panel and for the lot, regardless of the number of 
panels tested, shall be calculated to the nearest 1%.  
6.1.3.4  Heat performance test  
A specimen cut as specified in Section 6.1.2 shall be placed on a stand as illustrated in 
Figure 3. The specimen s hall then be subjected to an 800 °C to 900  °C (1472 °F to 1652 °F) 
flame from a Bunsen -type burner for a period of 10 minutes, or until a brown charred area 
appears on the back side, whichever occurs first.  The burner shall be equipped with a wing top 
to envelop the entire width of the specimen in flame.  The top of the burner shall be 25.4 mm (1 
in) from the specimen face and the flame 38.1 mm (1- 1/2 in) high.  The flame shall impinge on 
the face of the specimen 50.8 mm (2 in) from the bottom end.  After the test, the sample shall be 
removed from the stand and the bond lines examined for delamination by separating the 
charred plies with a sharp, chisel -like instrument.  Specimens shall be evaluated according to 
the requirements specified in Section 5.7.2.1.  
 
 
Figure 3.  Apparatus for heat durability test.  
6.1.4  Test for de termination of moisture content (oven- drying method)  
The moisture content of the plywood shall be determined as follows:  A small test specimen shall be cut from each sample panel; the test specimen shall measure not less than 58 cm
2 
(9 in2) in area and shall weigh not less than 20 grams (approximately 3/4 ounce).  All loose 
splinters shall be removed from the specimen.  The specimen shall be immediately weighed on 
a scale that is accurate to ±0.5%, and the weight shall be recorded as  the “original” weight.  The 
specimen shall then be dried in an oven at 101 ° C to 105°  C (21 4° F to 221°  F) until constant 
weight is attained.  After drying, the specimen shall be reweighed immediately, and this weight 
shall be recorded as the “oven- dry” w eight.  The moisture content shall be calculated as follows:  
 
 
43 
 (%) content Moisture  100  ) dry weight (Oven) dry weight (Oven  -    weight) (Original= ×  
6.1.5  Scarf and finger -joint tests  
6.1.5.1  Scarf and finger -joint strength  
Three test specimens shall be cut at random along each joint from each panel selected.  Type, 
grade and species of the panels shall be recorded.  The specimens shall be cut so as to include 
the joint and shall be prepared as illustrated in Figure 4. 
 
 
Figure 4.  Tension specimen for scarf jointed panels.  
 
Insofar as possible, the joint test area shall contain no localized natural characteristics permitted 
within the grade.  At the joint, the maximum thickness and width of plies parallel with the load shall be recorded.  Each specimen shall then be placed in the tension grips of a testing machine 
and loaded continuously at a rate of cross -head travel of from 0.8 mm to 1.0 mm (0.030 in to 
0.040 in) per minute until failure, and the ultimate load shall be recorded.  The ultimate stress in MPa (psi) shall be computed using the ultimate load and area of those  plies whose grain is 
parallel with direction of load.  Moisture content of the specimens at the time of testing shall not 
exceed 16%  as determined in accordance with the procedures specified in Section 6.1.4 . 
6.1.5.2  Scarf joint bond performance of Exterior and Exposure 1 plywood  
Ten test specimens shall be cut at random along each joint from each panel selected according 
to Section 6.1.2.  The specimens shall be prepared following the general procedure specified in 
Section 6.1.3.1 and shall be cut so that the joint runs through the test specimens as shown in 
Figure 5.  
 
Figure 5.  Specimen preparation.  
 
 
44 
  
Five specimens shall be subjected to the vacuum -pressure test specified in Section 6.1.3.2, and 
five to the boiling test of Section 6.1.3.3.  The percentage of wood failure of each specimen shall 
be visually determined in the dry condition to the nearest 5% in accordance with ASTM D5266.  
For the purposes of evaluating product conformance to the requirements specified in Sections 
5.7.1 and 5.7.2, the average wood failure for each panel and for the lot, regardless of the 
number of panels tested, shall be calculated to the nearest 1%.  
6.1.5.3  Finger -joint bond performance of Exterior and Exposure 1  
Ten specimens shall be cut at random along the finger joint from  each panel selected according 
to Section 6.1.2.  These specimens shall be cut so as to include the joint and shall be prepared 
as illustrated in Figure 6.  
 
 
Figure 6.  Cleavage test, typical test specimen.  
 Five of the specimens shall be subjected to the  vacuum -pressure test of Section 6.1.3.2 and five 
to the boiling test of Section 6.1.3.3.  
 
Upon completion of the applicable moisture cycle(s), a wedge or chisel (see Figure 7) shall be 
inserted in locations shown in Figure 6 in such a manner as to pry apart the scarfed portions of 
the joint without directly contacting the bonded area.  Test specimens shall be dried and percent 
wood failure in the test area estimated and applied separately for both the boil and vacuum -
pressure treatments.  The panels shall be evaluated as specified  in Section 5.9.3.  
 
 
Figure 7.  Wedge or chisel used for cleavage test.  
6.2 Structural performance  
6.2.1  Tests for performance under concentrated static and impact loads  
6.2.1.1  General  
The general provisions of ASTM E661 shall be followed as modified herein .  
 
6.2.1.2  Specimen preparation  
The required number of test specimens shall be as specified in Section 5.8.6. 2.  The test span 
 
45 
 shall be 19.2 inch for the span rating of 20.  
Test specimens shall be prepared and conditioned as specified in ASTM E 661 and Table 7 as 
applicable to the intended end use/span rating. The dry test condition shall be within ±  3% of the 
manufacturer’s as -shipped moisture content.  The wet test condition shall be exposure to three 
days of continuous one -sided wetting on the panel face, then tested wet.   
 
The wet/redry condition shall be exposure to three days of continuous one -sided wetting on the 
panel face, followed by drying at 20 °C ± 3 °C (65  °F ± 5 °F). The panel moisture content at the 
time of testing for the wet/redry condition shall be within ±  3% of the manufacturer’s as -shipped 
moisture content.  
6.2.1.3  Test procedure  
 
Concentrated static —  Procedures of ASTM E 661 shall be followed, except the test frame 
shall be constructed of lumber with nails or of steel using fasteners that simulate nails.  The 
loading rate shall be 445 N (100 lbf) per 30 seconds to yield failure within 5 minutes if a hand -
pumped hydraulic loading system is used.  
 
Concentrated impact  — Procedures of ASTM E 661 Method A shall be followed, except:  
 
(a) The test frame shall be constructed of lumber with nails or of steel using 
fasteners that simulate nails.  
 
(b) For span ratings greater than 24 o.c., the shot bag shall weigh 27 kg (60 
pounds).  
 
The width of individual pieces in assembling a test shall be 610 mm (24 in) or greater for span ratings up to 24 o.c., and 1220 mm (48 in) for greater span ratings.  
6.2.2  Test for performance under uniform loads  
6.2.2.1  General  
This method shall determine the performance of structural -use panels under uniform loads such 
as snow, wind,  and occupancy loads.  The uniform load is applied by atmospheric pressure as a 
vacuum is drawn under the test specimen, which is mounted on fully -supported framing 
members in a vacuum chamber.  
6.2.2.2  Equipment  
 Vacuum chamber  — The vacuum chamber (see Figure 8) shall consist of a sealed box with 
the panel to be tested forming the top.  A 0.15 mm  (6 mil or 0.006 in) polyethylene sheet or 
equivalent, the perimeter of which is attached securely with tape, shall seal the top surface of 
the vacuum chamber.  The chamber shall be strong and rigid to resist the applied load without 
failure or excessive deformation.  A vacuum pump shall be used to reduce the air pressure 
under the specimen.  The load shall be measured with absolute pressure gages for electronic 
data readout, but manometers or vacuum gages shall also be permitted.  
  
46 
  
Figure 8.  Vacuum chamber test equipment.  
 
Joist supports —  The framing members shall be spaced at the intended span rating, except 
that the 20 span rating shall have framing spaced 19.2 inch es on center . Framing shall be 
supported so as to resist deflection or rotation under applied load.  
 
Deflection gages  — The deflection gages shall be mounted to rigid tripods whose legs rest 
above the joists.  Deflection shall be measured to the nearest 0.03 mm (0.001 in).  
6.2.2.3  Specimen preparation  
Samples shall be selected that are representative of the product being tested.  The required 
number of test specimens shall be as specified in Section 5.8.6. 2. 
 
Length — The specimen length perpendicular to the framing member shall be equal to twice 
the center -to-center spacing.  
 
Width  — The specimen width shall be at least 597 mm (23- 1/2 in).  
 
Thickness — The specimen thickness shall be measured after conditioning and recorded.  
 
Test specimens shall be conditioned according to the intended end use/span rating as specified 
in Table 8. The dry  test condition shall be within ± 3% of the manufacturer’s as -shipped 
moisture content. The wet/redry condition shall be exposure to three days of continuous one-sided wetting on the panel face, followed by drying at 20 ℃ ± 3 ℃ (65 ℉ ± 5 ℉). The panel 
mois ture content at the time of testing for the wet/redry condition shall be within ±  3% of the 
manufacturer’s as -shipped moisture content.  
  
 
47 
 6.2.2.4  Test procedure  
After conditioning, the specimen to be tested shall be mounted on the framing members in the 
vacuum chamber in accordance with the anticipated joist spacing and the recommended nail 
size and spacing.  The top of the vacuum chamber shall then be sealed with the polyethylene 
sheet, and the tripod holding the deflection gages set in its proper position with t he gages 
positioned to read deflection at the point of maximum deflection1 of the two outer spans 
(Figure 9). 
 
 
Figure 9.  Uniform -load test specimens.  
 
The panel shall be loaded at a uniform rate of 2.4 kPa (50 lbf/ft2) per minute and deflections 
recorded at 1.2 kPa (25 lbf/ft2) increments until maximum load is achieved or until the desired 
proof load is achieved, as required.  Deflection data shall be required only in sufficient numbers to develop the straight -line portion of the load- deflection curve.  In no case shall the number of 
data points be less than six.  Deflection at a given load shall be determined by translating the slope to pass through the origin, thereby correcting for any settling of the system.  
6.2.3  Test for panel bending  
6.2.3.1  General  
This test procedure shall provide the basic data regarding full panel bending strength and 
stiffness.  The general provisions of ASTM D 3043 Method C shall be followed.  
6.2.3.2  Specimen preparation  
The required number of test specimens shall be as specified in Sections 5.8.6. 4 or 5.8.7.2, as 
applicable to the panel type and test objectives.  Specimens shall be prepared according to 
ASTM D 3043 Method C.  
 
1 The point of maximum deflection for a uniformly loaded two- span system shall occur at 0.4215 (S) 
measured from the centerline of the outer joist, where S equals the center -to-center joist spacing.  
 
48 
 6.2.3.3  Test procedure  
The procedures of ASTM D 3043 Method C shall be followed except specimens shall be tested 
for stiffness both along and across the major panel axis, and the maximum bending moment 
shall be taken as required.  
6.2.4  Test for planar shear strength  
6.2.4.1  General  
This test procedure shall determine the shear strength of plywood panels associated with shear 
disto rtion of the planes parallel to the edge planes of the panel.  The general provisions of 
ASTM D 2718 shall be followed.  
6.2.4.2  Specimen preparation  
The required number of test specimens shall be as specified in Sections 5.8.7.2.  Specimens 
shall be prepared in accordance with ASTM D 2718.  Specimens shall be prepared to evaluate planar shear with the face grain direction parallel to the long dimension  
6.2.4.3  Test procedure  
The procedures of ASTM D 2718 (Method A or Method B) shall be followed.  Lumber side 
plates may be used in lieu of steel plates in Method A.  The planar shear strength shall be 
measured parallel to the face grain direction. The planar shear strength shall be reported as a 
planar shear capacit y, F
s (Ib/Q), calculated in accordance with equation [1]. 
 
Equation [1]      𝐹𝐹𝑠𝑠� 𝐼𝐼 𝑏𝑏
𝑄𝑄 �=  �2
3� 𝑘𝑘1 𝑓𝑓𝑣𝑣 𝑡𝑡𝑠𝑠 
 
Where:  
𝐹𝐹𝑠𝑠� 𝐼𝐼 𝑏𝑏
𝑄𝑄 � = Planar shear capacity, N/mm of panel width (lbf/ft of panel width),  
k1 = a conversion factor = 1 mm/mm for SI units or 12 in/ft for imperial units,  
ƒv = Planar shear strength determined from ASTM D2718 Method A or B, N/mm2 (psi), and  
ts = Planar shear specimen thickness, mm (in)  
6.2.5  Test for shear -through- the-thickness strength  
6.2.5.1  General  
This test procedure shall determine the shear strength when loads are developed along 
opposite edges of panels.  The general provisions of ASTM D 2719 Method C shall be followed.  
6.2.5.2  Specimen preparation  
The required number of test specimens shall be as specified in Sections 5.8.7.2.  Specimens 
shall be prepared in accordance with ASTM D 2719 Method C – Two Rail Test.   
6.2.5.3  Test procedure  
The procedures of ASTM D 2719 Method C shall be followed.  The shear -through- the-thicknes s 
strength shall be reported as a through- the-thicknes s shear capacity, F vtv as calculated in 
accordance with E quation [2] : 
 
Equation [2]    Fvtv =  T × t v 
 
   
49 
 Where:  
Fvtv = Shear -through- the-thickness capacity, N/mm of panel thickness (lbf/in of panel 
thickness),  
T = Maximum shear -through -the-thickness stress determined from ASTM D2719 Method C, 
N/mm2 (psi), and  
 tv = Shear -through -the-thickness specimen thickness, mm (in)  
7. MARKING AND CERTIFICATION  
7.1 Certification  
Plywood represented as being in conformance with this Standard shall bear the mark of an 
Accredited Certification Agency  (see Section 7.2).  The mark shall retain legibility after weather 
exposure during construction.  
 
Plywood that bears the mark of an Accredited Certification Agency requires an initial and 
ongoing periodic inspections of the manufacturing and quality processes used to produce the product, by an Accredited Inspection Agency and periodic testing by an Accredited Testing 
Laboratory using specific methods and performance criteria to verify initial and ongoing product 
conformity to this Standard.  
 The Accredited Inspection Agency and Accredited Testing Laboratory shall be approved by the 
Accred ited Certification Agency.  
 
Testing by a manufacturer’s testing laboratory shall be permitted if approved by the Accredited 
Certification Agency.  
7.1.1  Marks indicating conformance with this Standard shall be applied to plywood products 
when certified by the Acc redited Certification Agency based on either 7.1.1.1 or 7.1.1.2.   
7.1.1.1  Plywood shall meet the prescriptive requirements of this Standard, specified in Sections 
5.1 through 5.8.5, including adhesive bond tests.  
7.1.1.2  Plywood shall meet the performance requirements of this Standard, specified in Section 
5.8.6 or 5.8.7.  
7.2 Accredited Certification Agency  
7.2.1  To qualify as an Accredited Certification  Agency  in accordance with this Standard, a 
Certification Agency shall  be accredited in accordance with ISO/IEC 17065, Conformity 
assessment – Requirements for bodies certifying products, processes and services  by an 
accreditation body that is a signatory to the International Accreditation Forum (IAF) Multilateral Recognition Agreement (MRA).  The Certification Agency’s scope of accreditation or the 
corresponding list of standards provided to the Accreditation Body  shall include a reference to 
this PS 1 Standard.   
7.2.2  Outsourcing ( subcontracting )  
7.2.2.1  If an Accredited Certification Agency subcontracts any part of the evaluation, to include 
inspection or testing, it shall comply with the requirements of ISO/IEC  17065 Section 6.2.2 .  
 
   
50 
 NOTE:  Consistent with ISO/IEC 17065, use of external personnel under contract is not 
considered outsourcing provided such persons are formally contracted to operate under the 
Certification Agency’s accredited management system .  In doing so, the Certification A gency  
shall take responsibility for the competence, awareness, and training for such individuals as 
specified in ISO/IEC 17065 and, for the purposes of persons contracted to perform inspections, 
the requirements specified in ISO/IEC 17020 as required by I SO/IEC 17065 Section 6.2.1.  
7.2.2.2  Whenever  subcontractors carry out work that forms part of an inspection or test, the 
responsibility for any determination of conformity of the inspected or tested item  to the 
requirements defined or referenced in this Standard s hall remain with the Accredited 
Certification Agency .  
7.2.2.3  The Accredited Certification Agency  shall record the details of its investigation of the 
competence of its subcontractors  and of their con formance to the requirements specified  or 
referenced in ISO/IEC 17065 and the requirements specified in this Standard.  The A ccredited 
Certification Agency  shall maintain a register of approved subcontractors .  
7.3 Accredited Inspection Agency  
7.3.1  To qualify as an Accredited Inspection Agency in accordance with this Standard, an 
Inspection Agency shall “be accredited in accordance with ISO/IEC 17020, Conformity 
assessment – Requirements for the operations of various types of bodies performing inspec tion 
by an accreditation body that is a signatory to the International Accreditation Forum (IAF) 
Multilateral Recognition Agreement (MRA) and shall:  
7.3.1.1  Have trained personnel capable of conducting inspections of structural plywood products 
and the manufacturi ng and quality processes used to produce such products according to the 
requirements of ISO/IEC 17020 and this Standard.  
7.3.1.2  Have trained personnel able to conduct or oversee sampling for testing as specified in 
this Standard.  
7.4 Accredited Testing Laboratory  
7.4.1  To qualify as an Accredited Testing Laboratory in accordance with this standard, a 
Testing Laboratory shall be accredited in accordance with ISO/IEC 17025 General requirements 
for the competence of testing and calibration laboratories;  by an accreditation body who is a 
signatory to the International Laboratory Accreditation Cooperation (ILAC) Mutual Recognition 
Agreement (MRA). An Accredited Testing Laboratory that conducts testing to meet the 
requirements of this Standard must have those tests under their scope of accreditation and 
shall: 
7.4.1.1  Have access to the facilities, equipment , and competent technical personnel to test 
structural plywood products according to the requirements and test methods specified in this Standard.  
7.4.1.2  Have procedures to be followed by its personnel in the performance of the testing.  
7.5 Panel marking  
All panels represented as conforming to this Standard shall be identified with marks giving the 
following information:  
 
(a) Species group number, span rating and  class — Unless otherwise provided, 
panels which are produced with face and back veneers of the same species  
51 
 group shall be identified as being of that species group.  Touch -sanded panels 
without span ratings that are manufactured with face and back plies of different 
species groups shall be identified by the larger numbered species group (i.e., 
Group 4 is larger numbered than Group 1).  Sanded panels with Performance 
Category of 3/8 or less, and Decorative panels of any Performance Category , 
that are manuf actured with face and back plies of different species groups shall 
be identified by the face species group number.  Sanded panels with Performance Category greater than 3/8 that are manufactured with face and 
back plies of different species groups shall be identified by the larger numbered 
species group, except that sanded panels with C or D grade backs shall be 
permitted to be identified by the face species group number if backs are no more 
than one species group larger in number than the face and are 3.2 mm (1/8  inch) 
or thicker before sanding.  A class number as specified  in Section 5.6.4 shall be 
used in lieu of a species group number to identify concrete form panels . A span 
rating shall be used for grades as specified  in Section 5.8.5.  Other than span 
rated panels qualified through performance testing in accordance with Section 5.8.7, panels shall be identified with the Group classification determined in 
accordance with Section 5.8.7.1.  
 
(b) Bond Classification  — The panel mark shall include the Exterior or Exposure 1 
bond classification.   Any further reference to adhesive bond, including those 
which imply premium performance or special warranty by the manufacturer, as well as manufacturer's proprietary designations, shall be separated from the 
mark of the  Accredited Certification Agency  per the Accredited Certification 
Agency’s policy . 
 
(c) The grade name or the grade of face and back veneers or a mark of an 
Accredited Certification Agency .  If identified by such a mark, the product 
specification shall be available from the  Accredited Certification Agency  whose 
mark appears on the panel.   MDO and HDO panels with one working face shall 
include “One Working Face” or “1S” within the grade declaration. MDO and HDO 
panels with two working faces may incl ude “Two Working Faces” or “2S” within 
the grade declaration.  
 
(d) The symbol “PS 1 -22” signifying conformance with this Standard.  
 
(e) The panel fractional Performance Category  (see section 5.10.2) and term 
“Performance Category” or abbreviation ( i.e., PERF CAT, CAT or Category)  shall 
be labeled on the panel. In addition, the thickness in 1000ths  of an inch within the 
permitted tolerance for the Performance Category shall be labeled on the panel. 
See Appendix D  for a table of recommended  Thickness  label s. 
 
(f) The designation “Butt -Jointed Center” for those panels manufactured with butt 
joints in center plies in accordance with Section 5.8.  
7.6 Voiding marks  
Panels originally marked as conforming to this Standard but subsequently rejected as not 
conforming t hereto shall have any reference to the Standard obliterated or voided by the 
manufacturer as follows:  
 
   
52 
 Shop panels shall be plainly marked by means of a 102 mm by 127 mm (4 in x 5 in) minimum 
size mark carrying the legend "Shop- cutting panel — all other agency marks void."  (See 
Section 2. 56.) 
Other panels rejected as not conforming shall be plainly identified by a mark placed next to, and be no less prominent than the original mark, carrying the legend, “REJECT –  All other agency 
marks void”.  
No referenc e shall be made to this Standard in the certification or  marking of panels not 
conforming to all of the applicable provisions of this Standard.  
8 QUALITY ASSURANCE REQUIREMENTS  
 
The Accredited Certification Agency shall implement an inspection and test program as 
specified in Section 8.2.  
 
The production process and quality system of each facility producing plywood in accordance 
with this standard shall be subject to on- site audits by the Accredited Inspection Agency at a 
minimum frequency (approximately  quarterly) of four times per year when certified panels are 
manufactured.  In the event that a manufacturer goes more than three months without producing certified panels, once production restarts an audit shall be conducted in accordance 
with the Accredi ted Certification Agency’s program.  
 NOTE: In situations where travel is unsafe due to pandemic, social unrest, etc. virtual audits can 
be used in place of on -site audits.  
8.1 Manufacturing Quality Program  
To consistently meet the requirements of this standard, manufacturers shall  implement a 
manufacturing quality program.  The extent of this program is determined by the manufacturer 
but shall include at a minimum, but not be limited to, the following:  
 
• Roles and Responsibilities for Quality Personnel  
• Document and Data Control  
• Procurement  
• Production  
• Specifications  
• Inspection and Product Testing  
• Control of Measuring Equipment  
• Control of Nonconforming Materials  
• Product Marking 
• Internal Audits  
• Product Performance Feedback  
• Records Retention  
The manufactur er’s quality program shall be documented in a Quality Manual that is reviewed 
and approved by the Accredited Certification Agency.  The Quality Manual is evaluated as part 
of the Accredited Inspection Agency’s periodic audits and the results of that evaluation  are 
reported to the Accredited Certification Agency . 
   
53 
 8.2 Inspection and Test Program  
The Accredited Certification Agency shall establish and implement an Inspection and Test 
Program to verify ongoing manufacturer and product conformity to the mill specification and the 
requirements of this Standard.  At a minimum, the Inspection and Test Program shall include the 
following:  
8.2.1  At least annually (approximately  every 12 calendar months):  
8.2.1.1  Assessment that the mill specifications for each mill are appropriat e for the product 
being certified.  
8.2.1.2  A review of manufacturer’s Quality Manual.  Updates to the Quality Manual shall be 
prepared by the manufacturer and submitted to the Accredited Certification Agency for review and approval.  If the manufacturer made no updates to the Quality Manual in that year the 
manufacturer needs to notify the Accredited Certification Agency that no updates were done.  
8.2.2  At least semi annually (approximately every 6 calendar months):  
8.2.2.1  Inspection of species, construction, panel grade , and thickness conformity with this 
Standard.  
8.2.3  At least quarterly (approximately every 3  calendar months):  
8.2.3.1  The production and quality system of each production facility producing plywood in 
accordance with this Standard shall undergo on -site audits by the A ccredited Inspection Agency 
at a minimum frequency of four (4) times per year.  Quarterly audits shall include, at a minimum:  
8.2.3.1.1  Verification of the appropriate use and legibility of panel marks to include, if 
applicable, the appropriate use of panel voiding marks as specified in Section 7.6.  
8.2.3.1.2  Review of the manufacturer’s in- plant quality inspection and test data to verify on -
going product conformity to the mill specification and the requirements of this Standard.  
8.2.3.2  Verification sampling and inspection shall be c onducted by the Accredited Inspection 
Agency at least (4) times per year, either in conjunction with or independent from the quarterly 
audits specified in Section 8.2.3.1.  The sampling requirements in Section 8.3 shall apply.  
Verification testing of the sampling identified above shall be performed by the Accredited 
Testing Laboratory  or by the manufacturer’s testing laboratory if it has been approved by the 
Accredited Certification Agency.  
8.3 Sampling  
8.3.1  Samples collected for inspection and/or testing as part of the Accredited Certification 
Agency’s Inspection and Test program shall be randomly sampled and shall be representative 
of the population being inspected or tested. Samples shall not be selected fr om lots/batches 
produced specially for sampling and inspection/testing.  
8.3.2  The sampling for the Inspection and Test program shall be performed by the Accredited 
Inspection Agency or the Accredited Inspection Agency shall witness the sampling being 
performed and ensure that the samples are properly identified and traceable back to witnessing 
documentation.  
   
54 
 8.3.3  If the manufacturer does not produce a given product type within the scope of 
certification during the period between regularly scheduled sampling, the Acc redited 
Certification Agency shall work with the manufacturer to ensure that sampling is conducted at 
the time of the next regular production for that product type.  
8.4 Corrective Action  
8.4.1  When the inspection and test program reveal noncompliance with the manufacturer’s 
quality system, the mill specification, the Accredited Certification Agency’s policies and 
procedures, and/or the requirements of this Standard, the Accredited Certification Agency shall 
notify the manufacturer of all nonconformities it identifies. The manufacturer is required to take 
corrective action according to the Accredited Certification Agency’s program requirements. The 
manufacturer shall  document the measures taken (or to be taken) to correct the identified 
nonconformities and to prevent them from recurring. The Accredited Certification Agency and/or 
Accredited Inspection Agency shall conduct appropriate follow -up to verify that the actions taken 
were effective in correcting the problem and preventing it from recurring.  
9 EFFECTIVE DATE  
 
The effective date of this Standard is TBD , 2023 .  As of the effective date, reference to PS 1- 22 
shall be permitted in contracts, codes, advertising, invoices, product labels, and the like, but no 
product shall be advertised or represented in any manner that  would imply or tend to imply 
approval or endorsement of that product by the National Institute of Standards and Technology, the Department of Commerce, or by the Federal Government.  
 
10 STANDING COMMITTEE  
 
The Standing Committee for PS 1 -22 is responsible for interpretation and for consideration of 
future proposals for amendments and revisions to the Standard.  The Standard Review 
Committee is responsible for drafting proposed changes to t he Standard for review and 
approval by the Standing Committee.   The names of the Standing Committee members are 
available from the Committee’s Secretariat:  Standards Coordination and Conformity Group, Standards Services Division, National Institute of Standards and Technology, 100 Bureau Drive, 
MS 2100, Gaithersburg, MD  20899- 2100.  Comments regarding the Standard and suggestions 
for its amendment or revision may also be sent to this address or contact NIST at https://www.standards.gov . 
 Issues regarding interpretation or implementation of the Standard and third -party quality 
assurance policies and procedures shall be considered by a Standard Implementation Review 
Subcommittee as appointed by the Standing Committee.  A request to consider such issues 
shall be made  in writing to the Secretariat of the Standing Committee (NIST), who will bring it to 
the attention of  the Standing Committee.  Formal operating procedures developed for the 
Subcommittee shall be subject to approval by NIST.  Any recommended actions by the 
Subcommittee will be reported to the Standing Committee for their consideration and action.  
   
55 
 Appendix A.  Species Grouping (mandatory)  
A1 General  
Product Standard PS 1  has included provisions for species grouping since the inception of PS  1 
in 1966.  Prior to PS 1 -66, U.S. plywood was manufactured in accordance with three regional 
plywood standards, Commercial Standard CS45- 60 for Douglas -fir Plywood, Commercial 
Standard CS 122- 60 for Western Softwood Plywood,  and Commercial Standard CS 269 -63 for 
Southern Pine Plywood.  Grouping of wood species on the basis of similar mechanical 
properties in order to provide needed simplification in product manufacture, design,  and 
specification became possible with the advent of ASTM D 2555, Me thods for Establishing Clear 
Wood Strength Values .  
A2 Grouping in practice  
Under the provisions of PS 1, it is possible to manufacture span rated plywood Sheathing and Single -Floor on the basis of the species group and plywood construction.  Similarly, the plywood 
group rating or plywood classification of non- span rated plywood may be determined by the 
species group and plywood construction.  PS 1 -83 introduced the provisions of determining 
span ratings on the basis of performance testing.  PS 1- 95 included a performance -based 
method for evaluating new species not listed in Table 1, made desirable because of the 
changing available timber resource for plywood production.  
A3 Species grouping  
Wood species in Table 1 are grouped on the basis of mechanical prope rties.  Because bending 
stiffness and bending strength are the most important properties for many plywood uses, 
species groups were initially set up first on the basis of bending stiffness and second on the 
basis of bending strength.  Past practice of the PS 1 Standing Committee has been to add new 
species to the highest existing group so long as none of the existing group properties 
assignments specified  in Table A1 are reduced by the addition.  
A3.1  Assignment of a species group shall be as follows:  
 
(a) Obtain average and standard deviation data of the five important mechanical 
properties of clear, straight -grained solid wood of all species in each group in the 
green and dry condition.  The five properties are bending modulus of elasticity 
(MOE), bending m odulus of rupture, compression parallel to grain, shear parallel 
to grain,  and compression perpendicular to grain.  Property data for North 
American woods must be included in ASTM D 2555 or must be developed by the 
U.S. Forest Service or by a recognized Canadian government l aboratory.  In 
addition, new data must be obtained using recognized statistical sampling of the entire growth range of the species.  Foreign species are classified using data 
from the government laboratory in the respective country.  Table A2 provides the 
source of data used to classify non -North American species listed in PS  1.  For 
each of the five properties, the limiting property value that can be assigned to any 
group that includes that species is determined at the dry (12% for MOE, 15% for 
all other properties) and green moisture content.  
 (b) The maximum assignable MOE value is either the species average increased by 
10% if volume data is available in ASTM D2555 or the species average if no 
volume data exists or if it is a foreign s pecies.  
 
(c) The strength properties are calculated in one of the following three methods:  
 
Method A species in ASTM D 2555  
  
56 
 Max. Assignable = (species average/variability index) –  1.18 x species standard 
deviation 
 
Method B species in ASTM D 2555  
 Max. Assignable = species average –  1.48 x species standard deviation 
 
Domestic species with no volume data and foreign species  
Max. Assignable = species average –  1.645 x species standard deviation 
 
The maximum assignable property must meet or exceed all prope rty values listed 
in Table A1 for the species group in order to be assigned that group.  
 
(d) Assignment of a species group to Table 1 shall be approved by the Standing 
Committee.   (See Section 5.2.)  
 
TABLE A1.  CLEAR WOOD PROPERTY ASSIGNMENTS  
 
 
Species  
Group  MOE  
(million psi)  Strength Property (psi)  
Bending  Comp Par  Shear  Comp Perp  
Wet Dry Wet Dry Wet Dry Wet Dry Wet Dry 
1 1.483  1.857  5300  8064  2425  4123  665 855 193 354 
2 1.249  1.588  3662  6297  1833  3163  532 692 124 221 
3 1.047  1.310  3681  5985  1548  2662  524 652 123 212 
4 0.924  1.146  3483  5389  1570  2630  476 633 97 152 
5 0.748  1.100  2843  4345  1190  2187  387 542 73 132 
  
57 
 TABLE A2.  SOURCE OF DATA USED TO CLASSIFY FOREIGN SPECIES IN PLYWOOD  
PRODUCT STANDARD PS 1  
 
Common Name or  
Trade Group  Scientific Name  Source of Data  
Group 1    
Apitong  Dipterocarpus spp.  FPL 125  
FPL 2242 (bearing only)  
Kapur  Dryobalanops aromatica  
D. lanceolata  
D. oblongifolia  Malayan Forest Service Trade Leaflet #34  
FPL 125  
Malayan Forest Service Trade Leaflet #34  
Keruing  Dipterocarpus spp.  
D. baudii  
D. caudiferus  
D. cornutus  
D. crinitus  
D. lowii  FPL 2242  
Malayan Forest Service Trade Leaflet #34  
FPL 2242  
Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
Caribbean Pine  Pinus caribaea  FPL 125  
Ocote Pine  Pinus oocarpa  FPL 125  
Group 2    
Red Lauan  Shorea negrosensis  FPL 125  
FPL 2242 (bearing only)  
Tangile  Shorea polysperma  FPL 125  
FPL 2242 (bearing only)  
White Lauan  Pentacme contorta  FPL 125  
FPL 2242 (bearing only)  
Almon  Shorea almon  FPL 125  
FPL 2242 (bearing only)  
Bagtikan  Parashorea plicata  FPL 125 
FPL 2242 (bearing only)  
Mersawa  Anisoptera laevis  
A. marginata  Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
Mayapis  Shorea squamata  FPL 125  
Meranti  Parashorea lucida  
Shorea acuminata  
S. singkawang  
S. curtisii  
S. dasyphylla  Malayan Forest Service Trade Leaflet #5  
Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
FPL 125  
 S. hemslevana  Malayan Forest Service Trade Leaflet #34  
 S. leprosula  
S. macroptera  Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
 S. pauciflora  
S. platyclados  Malayan Forest Service Trade Leaflet #34  
Malayan Forest Service Trade Leaflet #34  
 S. rugosa  Malayan Forest  Service Trade Leaflet #34  
Group 4    
Cativo  Prioria copaifera  FPL 125  
Yale Bulletin #98 Tropical Woods (bearing only)  
 
   
58 
 Appendix B.  Reinspection Practices (nonmandatory)  
B1 General  
Based on industry practice, the following information is offered  to plywood purchasers:  
B2 Request for reinspection  
Any request by the buyer for the reinspection of any item or lot of plywood certified as 
conforming to this Standard shall be directed to the seller.  Lacking agreement of the buyer and 
seller as to the settlement of a complaint, the purchase, sale, or shipment of plywood certified 
as conforming to this Standard shall be construed as involving agreement to submit such 
plywood to reinspection by the Accredited Inspection Agency as directed  by the Ac credited 
Certification Agency  whose  mark was used.  
B3 Responsibility of the buyer  
A request for reinspection shall be made to the seller:  
 
For panel grade — within 30 days after arrival at the first point of receipt from the mill, if the 
grade of any item, as invoiced, is in doubt;  
 
For adhesive bond quality of Exterior panels —  when delamination is visibly evident;  
 
For adhesive bond quality of Exposure 1 — within 6 months after arrival at first point of receipt 
from the mill if delamination is visibly evident;  
 
All plywood of disputed grade shall be kept intact and properly protected from damage and 
deterioration and from direct exposure to moisture that could interfere with a fair reinspection.  
All plywood in question shall be held for a period not to exceed 30 days after the date of request 
for reinspection.  Use by the buyer of any or all of the disputed stock within the 30- day period 
shall constitute an acceptance of the used portion.  
B4 Responsibility of the seller  
A request for reinspection shall be promptly acknowledged by the seller following receipt of the request.  
B5 Responsibility of the Accredited Inspection Agency conducting the reinspection  
Should either the buyer or the seller wish to have a representative present at the reinspection, 
the agency conducting the reinspection will provide all reasonable accommodation to facilitate 
that request. Any party wishing to witness the reinspection shall inform the agency of that desire 
at the time of the initial request for reinspection, and shall be responsible for any costs they 
incur in order to attend. Costs incurred by the agency performing the reinspection shall be 
assessed as noted in Section B6.  
B6 Cost and assistance  
The expense of reinspection shall be borne by the seller if the item, lot, or shipment in dispute fails to pass the reinspection as  specified for in Section B7.  If the plywood passes the 
reinspection, said expenses shall be borne by the buyer.  The buyer shall lend all reasonable assistance to facilitate the reinspection.  
B7 Reinspection procedures and settlement  
B7.1  Condition of plywood  
All plywood designated as conforming with this Standard shall be subject to reinspection in the 
white (unfinished) only, except that concrete -form material is permitted to have a priming coat of 
a release agent.  This requirement does not apply to Exposure 1 or Exterior plywood when 
tested for adhesive bond quality.   
59 
 B7.2  Sampling for panel grade, size,  and thickness reinspections  
At buyer's or seller's option, grade, size, and thickness reinspections shall include all panels of 
an item whose conformance to this Standard is in dispute; however, agreement between the 
buyer and seller on a reduced basis for sampling is permitted provided at least 20% or 300 
panels, whichever is smaller and which represents only those items as invoiced which are in 
dispute, are reinspected for conformance.  For reduced sampling, the quantity of panels 
selected from each disputed item shall be prorated according to the number of panels included 
in each item as invoiced.  Panels found to be below grade or out of tolerance for size and thickness shall have improper marks obliterated and shall be remarked with appropriate 
designation with a special inspection mark registered by the Accredited Certification Agency .  
B7.3 Plywood panel grade, size,  and thickness reinspections  
If reinspection establishes that a disputed item is more than 5% below grade or out of dimensional tolerance for the product description as invoiced, that product fails to pass the 
reinspection and t he nonconforming panels need not be accepted.  If a disputed product is 5% 
or less below grade or out of dimensional tolerance, it shall pass the reinspection and the disposition of the nonconforming panels shall be as agreed upon between buyer and seller.   In 
addition to the above 5% grade and dimensional tolerance, a 5% tolerance shall apply separately to the inner ply gap limitations, including the limitations applicable to the plugged 
crossband and jointed crossband, as set forth in section 5.8.1.  
B7.4  Sampling for adhesive bond quality reinspections 
For test purposes, 20 panels, or 5% of the panels, whichever is less, shall be selected at 
random from the item, lot, or shipment which is in dispute.  The number of panels required is 
calculated by applying the "percent panels" to the lot size and converting part panels to whole panels by using a rounding procedure where 0.01 to 0.49 parts are considered to be the smaller 
whole number, while 0.50 to 0.99 parts are considered to be the larger whole number.  These 
panels shall be selected from locations distributed as widely as practicable throughout the 
material being sampled.  When an item, lot, or shipment involves panels with different adhesive bond requirements as specified  for in  Section 5.7, testing and evaluation shall apply separately 
to each category.  Sampling of Expos ure 1 plywood or Exterior plywood shall be prorated on the 
basis of ratio of their volume to total volume (i.e., for shipment containing 50% Exterior, 10 Exterior panels shall be selected), but in no case shall fewer  than 10 panels of each type or 
adhesive quality be selected.  Shipments of Exposure 1 plywood shall be sampled in the same 
manner as Exterior plywood.  
 
From each of five of the panels selected, a specimen 140 mm by 203 mm (5- 1/2 in x 8  in) shall 
be cut and tested as specified  in Section 6.1.3.4 . 
B7.5  Plywood adhesive bond quality reinspections  
Reinspection of the unused panels in the disputed item, lot, or shipment shall be carried out 
following the procedures set forth in Section 6, "Specimen Preparation and Testing," and 
Section B7.4.  If the reinspection tests establish that the adhesive bond quality of the panels 
does not meet the requirements of Section 5.7, as applicable, the item, lot, or shipment shall fail 
to pass the reinspection and is not required to be accepted by the buyer.  If the adhesive bond 
quality requirements are met, the item, lot, or shipment shall pass the reinspection and the 
buyer shall accept the item, lot, or shipment as invoiced, except that the buyer is not required to 
accept any delaminated Exterior plywood or overlaid panels.  
  
60 
 Appendix C.  General Information and Comments On Current Edition (nonmandatory)  
C1 History of the project  
On October 1, 1965, the American Plywood Association (now APA –  The Engineered Wood 
Association) submitted to the National Bureau of Standards (now the National Institute of 
Standards and Technology) a draft of a proposed Commercial Standard on softwood plywood, 
with a request that it be processed as a revision and consolidation of Commercial Standards 
CS 45-60 Douglas Fir Plywood, CS 122 -60 Western Softwood Plywood, and CS 259- 63 
Southern Pine Plywood. On November 1, 1966, Product Standard PS 1 -66 Softwood Plywood, 
Construction and Industrial  became effective.  It was the first Voluntary Product Standard 
developed under new Depart ment procedures, issued on November 16, 1965, for development 
of Voluntary Product Standards.  
 
Since 1966, there have been six revisions to the Standard:  
C1.1 PS 1 -74 Construction and Industrial Plywood became effective August 1, 1974   
Among other revisi ons, this version added over 20 species, primarily Southeast Asian 
hardwoods, to Table 1.  
C1.2 PS 1 -83 Construction and Industrial Plywood became effective December 30, 1983   
This version added performance -based test methods and criteria for span rated applications.  
C1.3 PS 1 -95 Construction and Industrial Plywood became effective September 7, 1995  
This version included the incorporation of a performance- based method for evaluating plywood 
manufactured with species not listed in Table 1, made desirable bec ause of the changing 
available timber resource for plywood production.  The revisions included the elimination of 
Structural II panel grades from the Standard because this product had rarely been 
manufactured since it was first introduced in PS 1 -66. 
C1.4 PS 1 -07 Structural Plywood beca me effective February 26, 2007  
This version revised several sections of the S tandard to better represent the production and 
trade specifications for the products. These included a change to the title of the S tandard, 
eliminat ion of the interior and intermediate bond types, revisions to the overlaid plywood 
designations and addition of an appendix to detail the process for species grouping.  
 
C1.5 PS 1 -09 Structural Plywood became effective May 2010  
In response to consumer complaints regarding thickness labeling being out of compliance with NIST Handbook 130 and 133, the S tandard was revised to create a Performance Category 
based on customary thickness notations used in U.S. model building codes. In addition, panel 
labeling requirements was changed to require the Performance Category and decimal thickness 
representation. Nonmandatory Appendices were added to provide recommended labeling and 
to provide guidance on quantity representations on bundles.  
 
In addition, nonmandatory Appendices were added to describe formaldehyde emission 
characteristics of PS 1 panels and how PS 1 panels align with various green building 
specifications.  
C1.6 PS 1 -19 that became effective  December 1, 2019  
After considerable t echnical review by members of the PS 1  Standing Committee, the S tandard 
was revised to address the following technical and informational aspects. Additional details were 
added regarding measurement of dimensions. The term “sized for spacing” was added to denote 
panels that are sized for compatibility to recommended application for construction uses.  
   
61 
 Other technical and editorial revisions were made to reflect industry practices, including:  
• Simplification of the Appendix on labeling 
• Deletion of the Appendix on Green Building Provisions  
• Revised definition of qualified testing and inspection agency  
• Added abbreviations commonly used for labeling 
 
C1.7 Current edition, PS 1- 22 that became effective Month Date , 2023  
In response to complaints regarding the lack  of quality assurance requirements, the Standard 
was revised and addressed the following:  
• Updated definitions to address Critical Section, Sound Knot, and Tight Knot 
• For species classified by testing Section 5.2.4 c larified that species listed in 
Table 1 but grown in a different geographic region shall be qualified for use  by 
performance testing  
• Clarified the requirements under  Section  5.7.1 Exposure 1 and 5.7.2 Exterior  
• Added calculations for planar shear strength Section 6.2.4  and shear -through -
the-thickness strength  Section 6.2.5  
• Added Categories 5/16 and 11/16 to Table 10, Table D1, and Table D2  
• Updated Section 7 Marking and Certification.  This includes : 
o Added Section on  Accredited Certification Agency  
o Revised Qualified Inspection and Testing Agency Section and added 
Section on Accredited Inspection Agency  and Section on Accredited 
Testing Laboratory  
o Added a Subsection on Subcontract ing 
• Added Section 8 on Quality Assurance Requirements that includ ed adding  
the following subsections:  
o Manufacturing Quality Program  
o Inspection and Test Program  
o Sampling 
o Corrective Action  
   
62 
 Appendix D .  (nonmandatory)  
D1 Recommend t hickness labels   
Section 5.10.2 specifies thickness tolerances and Performance  Categories for plywood grades . 
Section 7.5.(e) specifies that the panels shall be labeled with a thickness label in 1000ths of an 
inch and that labeled quantity shall be within the minimum and maximum thicknes s specification 
for that Performance Category. T able D1 and Table D2 present recommended thickness labels.  
D2 Regulations on labeling  
See Appendix E for discussion of regulations dealing with labeling.  
 
TABLE  D1.  RECOMMENDED THICKNESS LABELING FOR UNSANDED,  
TOUCH SANDED AND OVERLAID PANELS  
 
 Thickness Requirements for  
Unsanded, Touch Sanded and Overlaid Grades1 
Performance  
Category2 Minimum Thickness  
in (mm) Maximum Thickness  
in (mm)  Recommended  
Thickness  Label(3) 
1/4 PERF CAT  0.219 (5.56)  0.281 (7.14)  Thickness .225 in 
5/16 PERF CAT  0.281  (7.14) 0.344 (8.73) Thickness .29 0 in 
11/32 PERF CAT  0.313 (7.94)  0.375 (9.53)  Thickness .322 in 
3/8 PERF CAT  0.344 (8.73)  0.406 (10.32)  Thickness .354 in 
 7/16 PERF CAT  0.406 (10.32)  0.469 (11.91)  Thickness .418 in 
15/32 PERF CAT  0.438 (11.11)  0.500 (12.70)  Thickness .451 in 
 1/2 PERF CAT  0.469 (11.91)  0.531 (13.49)  Thickness .483 in 
9/16 PERF CAT  0.531 (13.49)  0.594 (15.08)  Thickness . 547 in 
19/32 PERF CAT  0.563 (14.29)  0.625 (15.88)  Thickness .578 in 
5/8 PERF CAT  0.594 (15.08)  0.656 (16.67)  Thickness .609 in 
11/16 PERF CAT  0.656 (16.67) 0.719 (18.26) Thickness .672 in  
23/32 PERF CAT  0.688 (17.46)  0.750 (19.05)  Thickness .703 in 
3/4 PERF CAT  0.719 (18.26)  0.781 (19.84)  Thickness .734 in 
13/16 PERF CAT  0.781 (19.84)  0.844 (21.43)  Thickness .788 in 
7/8 PERF CAT  0.831 (21.11)  0.919 (23.34)  Thickness .849 in 
1 PERF CAT  0.950 (24.13)  1.050 (26.67)  Thickness .970 in 
1-1/8 PERF CAT  1.069 (27.15)  1.181 (30.00)  Thickness 1.091 in 
1-1/4 PERF CAT  1.188 (30.16)  1.313 (33.34)  Thickness 1.213 in 
1 1Thickness requirements for unsanded, touch sanded,  and overlaid panels are based on a tolerance of +/ - 0.8 
mm (1/32 in) for panels with Performance Categories of 13/16 and less and ± 5% for panels with Performance 
Categories greater than 13/16 unless a closer tolerance is determined through qualification testing.  Inch units 
are presented as primary units due to customary practice in the United States.  
2 Acceptable abbreviations are PERF CAT, CAT or Category.   
3 The recommended thickness label for categories less than 9/16 is 3% above the minimum.   The recommended 
thickness label for categories greater than or equal to 9/16 are the minimum values for sanded panels.  
 
   
63 
  
TABLE D2.  RECOMMENDED THICKNESS LABELING FOR SANDED PANELS  
 
 Thickness Requirements for  
Sanded Panels1 
Performance  
Category2 Minimum Thickness  
in (mm)  Maximum Thickness  
in (mm)  Recommended  
Thickness  Label3 
1/4 PERF CAT  0.234 (5.95)  0.266 (6.75)  Thickness .234 in 
5/16 PERF CAT  0.297 (7.54)  0.328 (8.33)  Thickness .297 in  
11/32 PERF CAT  0.328 (8.33)  0.359 (9.139  Thickness .328 in 
3/8 PERF CAT  0.359 (9.13)  0.391 (9.92)  Thickness .359 in 
 7/16 PERF CAT  0.422 (10.72)  0.453 (11.51)  Thickness .422 in 
15/32 PERF CAT  0.453 (11.51)  0.484 (12.30)  Thickness .453 in 
 1/2 PERF CAT  0.484 (12.30)  0.516 (13.10)  Thickness .484 in 
9/16 PERF CAT  0.547  (13.8 9) 0.578 (1 4.68) Thickness .547 in 
5/8 PERF CAT  0.609 (15.48)  0.641 (16.27)  Thickness .609 in 
11/16 PERF CAT  0.672 (17.07)  0.703 (17.86)  Thickness .672 in  
23/32 PERF CAT  0.703 (17.86)  0.734 (18.65)  Thickness .703 in 
3/4 PERF CAT  0.734 (18.65)  0.766 (19.45)  Thickness .734 in 
13/16 PERF CAT  0.788 (20.02)  0.837 (21.26)  Thickness .788 in 
7/8 PERF CAT  0.849 (21.56)  0.901 (22.89)  Thickness .849 in 
1 PERF CAT  0.970 (24.64)  1.030 (26.16)  Thickness .970 in 
1-1/8 PERF CAT  1.091 (27.72)  1.159 (29.43)  Thickness 1.091 in 
1-1/4 PERF CAT  1.213 (30.80)  1.288 (32.70) Thickness 1.213 in 
1 Thickness requirements for sanded panels are based on a tolerance of ± 0.4 mm (1/64 in) for specified 
performance categories of 3/ 4 and less and ± 3.0% for panels with a performance category greater than 3/4 unless 
a closer tolerance is determined through qualification testing.  Inch units are presented as primary units due to 
customary practice in the United States.  
2 Acceptable abbreviations are PERF CAT, CAT or Category.  
3 Recommended thickness labels for performance categories are based on the minimum permissible thickness for 
that category . 
   
64 
  
Appendix E.  Labeling Guidelines Based on the Uniform Packaging and Labeling 
Regulations of NIST Handbook 130 and Handbook 133 (nonmandatory)  
E1 Summary  
E1.1 When intended for sale or distribution, the labeling of the panels should meet the 
requirements of the Uniform Packaging and Labeling Regulation. This section provides 
references to standards applicable to labeling and packaging.  
E2 Background 
E2.1 The Nat ional Institute of Standards and Technology  (NIST)  of the U.S. Department of 
Commerce promotes the development of standards to be applied across industry and supports 
the publishing of NIST Handbook 130, Uniform Laws and Regulations in the A reas of L egal 
Metrology and E ngine Fuel Quality . NIST Handbook 130 is a compilation of the latest uniform 
laws and regulations regarding packaging and labeling requirements adopted by the National Conference on Weights and Measures, Inc. (NCWM) and is intended to represent standards to 
be adopted into law by the weights and measures jurisdictions of the United States.   
E2.2 Procedures used by Weights and Measures inspectors are included in NIST Handbook 
133, Checking the Net Contents of Packaged Goods  
E2.3 For information, a complete copy of the most recent version of NI ST Handbook 130 and 
133 are  available at :  https://www.nist.gov/publications/  
   
65 
 Appendix F.  Formaldehyde ( nonmandatory ) 
F1 General  
Formaldehyde is a simple naturally occurring chemical made of carbon, oxygen,  and hydrogen. 
It is produced by the human body and animals and plants. It is also formed by combustion and 
is an industrial chemical widely used in the manufacture of many consumer products.  
Background information on formaldehyde and health concerns relat ed to elevated levels in 
indoor air can be found at www.epa.gov/iaq/formaldehyde.html. 
F2 Formaldehyde regulations  
F2.1  
There are no national or state regulations of formaldehyde emissions expressly stated for PS 1 
Structural Plywood. This is mainly due to the very low emission rates demonstrated by PS 1 
Structural Plywood.  
F2.2  
U.S. Department of Housing and Urban Development Rules and Regulations 24 CFR 3280 for 
manufactured housing includes § 3280.308 “Formaldehyde emission controls for certain wood 
products” that deals with formaldehyde emissions from particleboard and plywood. The 
regulations establish limits for formaldehyde emission levels and ongoing evaluation requirements . 
 
PS 1 Structural Plywood is made  predominantly  with phenol -formaldehyde adhesives . When 
made as such, it  is exempt  from the HUD requirements.  
F2.3 California Air Resources Board (CARB) air toxic control measure for c omposite 
wood products (see : http://www.arb.ca.gov/research/indoor/formaldehyde.htm ) 
The CARB ATCM for Composite Wood was approved for implementation on January 1, 2009. 
The scope of the standard is particleboard, medium Density Fiberboard (MDF) and hardwood 
plywood. Section § 93120.1 “ Definitions” explicitly excludes PS 1 Structural Plywood and other 
structural wood products from the scope of the standard as follows (underlined emphasis 
added):  
 
(8) “Composite wood products” means hardwood plywood, particleboard,  and medium density 
fiberboard. “Composite wood products ” does not  include hardboard, structural plywood as 
specified in the Voluntary  Product Standard -  Structural Plywood (PS 1 -07), structural panels as  
specified in the Voluntary Product Standard –  Performance Standard for Wood- Based 
Structural -Use Panels  (PS 2 -04), structural  composite lumber as specified in Standard 
Specification for  Evaluation of Structural Composite Lumber Produc ts (ASTM D 5456- 06), 
oriented strand board, glued laminated timber as specified in Structural Glued Laminated 
Timber  (ANSI A190.1 -2002),  prefabricated wood I -joists as specified in Standard Specification 
for Establishing and Monitoring Structural Capacities of Prefabricated  Wood I -Joists  (ASTM 
D 5055- 05), finger -jointed lumber, or “composite  wood products” used inside of new vehicles as 
defined in section 430  of the California Vehicle Code (excluding recreational vehicles), railcars, 
boats, aerospace craft,  or aircraft.  
   
66 
 F2.4 National “Formaldehyde Standards for Composite Wood Products Act”  
The Formaldehyde Standards for Composite Wood Products Act was signed into law on July 7, 2010.   
With respect to PS 1 panels, this law is identical to the CARB ATCM for Composite Wood (see Section 
F2.3). PS 1 panels are exempt from the scope of the Formaldehyde Standards for Composite Wood Act. 
For further information see: https://www.epa.gov/ formaldehyde/formaldehyde- emission- standards -
composite- wood- products  
F3 Formaldehyde emission from PS 1 Plywood  
F3.1 Information on formaldehyde emission from PS 1  panels is available from APA in 
Technical Note J330, Formaldehyde and Engineered Wood Products  (see: www.apawood.org).