STRUCTURAL

PLYWOOD

VOLUNTARY PRODUCT STANDARD PS 1-09

National Institute of Standards and Technology

U.S. Department of Commerce
Voluntary Product Standard PS 1-09

Structural Plywood

May 2010

U.S. Department of Commerce 

Gary Locke, Secretary

National Institute of Standards and Technology

Patrick D Gallagher, Director
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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 establish nationally recognized requirements for products and to provide all 

concerned interests with a basis for common understanding of the characteristics of the products. The National 

Institute of Standards and Technology (NIST) administers the Voluntary Product 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. 

Producers, 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.

It must be emphasized that the Department of Commerce has no regulatory authority or enforcement power to police 

the provisions of this or other Product Standards; but, inasmuch as the standard represents the consensus of the 

industry, its provisions are established by trade custom and are made effective through incorporation by reference in 

sales contracts, federal specifications, building codes, purchase invoices, advertising, and similar means.

USE OF VOLUNTARY PRODUCT STANDARDS

The use of DOC Voluntary Product Standards is voluntary. NIST has no regulatory power in the enforcement of 

their provisions; however, since the standards represent a consensus of all interested groups, their provisions are 

likely to become established as trade customs. In addition, when a DOC Voluntary Product Standard is made part of 

a legal document, such as a sales contract or code, compliance with the standard is enforceable.

The benefits derived from a DOC Voluntary Product Standard are in direct proportion to their general recognition 

and actual use. Producers 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.

For copies of DOC Voluntary Product Standards or more information concerning the development and use of these 

standards, contact the Standards Services Division, National Institute of Standards and Technology, 100 Bureau 

Drive, MS 2150, Gaithersburg, MD 20899-2150; http://ts.nist.gov/docvps.
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ABSTRACT

Voluntary Product Standard PS 1-09, reproduced in the following pages, provides expanded and updated 

requirements for producing, marketing, and specifying plywood for construction and industrial uses.

It covers the manufacture of such plywood from some 70 wood species and supersedes the Product Standard 

published in 2007.

The Standard establishes requirements, for those who choose to adhere to the standard, for the principal types and 

grades of structural plywood and provide a basis for common understanding among producers, distributors, and 

users of the product. This standard covers the wood species, veneer grading, adhesive bonds, panel construction and 

workmanship, dimensions and tolerances, marking, moisture content and packaging of structural plywood intended 

for construction and industrial uses.

Included in this standard are test methods to determine compliance and a glossary of trade terms and definitions. A 

quality certification program is provided whereby qualified testing agencies inspect, sample, and test products 

identified as complying with this standard. Information on species grouping is provided in Appendix A; information 

on reinspecting practices is provided in Appendix B; and information on the maintenance, history, and current 

edition of the standard is provided in Appendix C.

The Standard, a revision of Voluntary Product Standard PS 1-07, Construction and Industrial Plywood, was 

developed by the Standing Committee for Voluntary Product Standard PS1 in accordance with procedures of the 

U.S. Department of Commerce.

KEYWORDS

Certification, inspection, and grademarking of plywood, plywood classification, plywood product standard, plywood 

veneer, structural plywood, terminology. 
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TABLE OF CONTENTS

1. SCOPE.............................................................................................................................................................1

2. TERMINOLOGY............................................................................................................................................1

2.1 Back.................................................................................................................................................................1

2.2 Bond classifications.........................................................................................................................................1

2.3 Borer holes.......................................................................................................................................................1

2.4 Broken grain ....................................................................................................................................................2

2.5 Butt joint..........................................................................................................................................................2

2.6 Centers.............................................................................................................................................................2

2.7 Center gap........................................................................................................................................................2

2.8 Characteristics, growth.....................................................................................................................................2

2.9 Characteristics open .........................................................................................................................................2

2.10 Check...............................................................................................................................................................2

2.11 Class I, II..........................................................................................................................................................2

2.12 Construction (panel construction).....................................................................................................................2

2.13 Core.................................................................................................................................................................2

2.14 Critical section .................................................................................................................................................2

2.15 Crossband ........................................................................................................................................................2

2.16 Crossband gap and center gap ..........................................................................................................................2

2.17 Delamination....................................................................................................................................................2

2.17.1 Knotholes, pitch pockets, splits and gaps.......................................................................................3

2.17.2 Exposure 1.....................................................................................................................................3

2.17.3 Exterior .........................................................................................................................................3

2.18 Edge splits........................................................................................................................................................3

2.19 Exposure 1 bond classification.........................................................................................................................3

2.20 Exterior bond classification..............................................................................................................................3

2.21 Face .................................................................................................................................................................3

2.22 Finger joint.......................................................................................................................................................3

2.23 Group...............................................................................................................................................................3

2.24 Heartwood .......................................................................................................................................................4

2.25 Inner plies........................................................................................................................................................4

2.26 Jointed inner plies............................................................................................................................................4

2.27 Knot.................................................................................................................................................................4

2.28 Knotholes.........................................................................................................................................................5

2.29 Lap...................................................................................................................................................................5

2.30 Layer................................................................................................................................................................5

2.31 Lot ...................................................................................................................................................................5
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2.32 Major panel axis...............................................................................................................................................5

2.33 Mill specification .............................................................................................................................................5

2.34 Moisture content ..............................................................................................................................................5

2.35 Moisture resistant adhesive ..............................................................................................................................5

2.36 Panel thickness.................................................................................................................................................5

2.37 Patches.............................................................................................................................................................5

2.38 Performance category ......................................................................................................................................5

2.39 Performance testing..........................................................................................................................................5

2.40 Pitch pocket .....................................................................................................................................................5

2.41 Pitch streak.......................................................................................................................................................5

2.42 Plugs................................................................................................................................................................6

2.43 Plugged inner plies (also referred to as solid inner plies)..................................................................................6

2.44 Ply....................................................................................................................................................................6

2.45 Plywood...........................................................................................................................................................6

2.46 Plywood classification......................................................................................................................................6

2.47 Prescriptive specification..................................................................................................................................6

2.48 Reference value................................................................................................................................................6

2.49 Repair..............................................................................................................................................................6

2.50 Rough grain .....................................................................................................................................................6

2.51 Sapwood ..........................................................................................................................................................6

2.52 Scarfed joint.....................................................................................................................................................6

2.53 Shim ................................................................................................................................................................6

2.54 Shop-cutting panel ...........................................................................................................................................6

2.55 Span rating.......................................................................................................................................................7

2.56 Split .................................................................................................................................................................7

2.57 Sub-face (sub-back) .........................................................................................................................................7

2.58 Touch-sanding .................................................................................................................................................7

2.59 Veneer .............................................................................................................................................................7

2.60 Wane................................................................................................................................................................7

2.61 White pocket....................................................................................................................................................7

2.61.1 Light white pocket ........................................................................................................................7

2.61.2 Heavy white pocket ......................................................................................................................7

2.62 Wood failure (percent).....................................................................................................................................7

2.63 Working face ...................................................................................................................................................7

3 REFERENCE PUBLICATIONS ....................................................................................................................8

4 PLYWOOD CLASSIFICATION.....................................................................................................................8

4.1 General ............................................................................................................................................................8
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4.2 Bond classification...........................................................................................................................................8

4.2.1 Exposure 1 plywood .....................................................................................................................8

4.2.2 Exterior plywood ..........................................................................................................................8

4.3 Grade ...............................................................................................................................................................8

5 REQUIREMENTS...........................................................................................................................................9

5.1 General ............................................................................................................................................................9

5.2 Wood species...................................................................................................................................................9

5.2.1 Species groups..............................................................................................................................9

5.2.2 Species for faces and backs...........................................................................................................9

5.2.3 Species for inner plies...................................................................................................................9

5.2.4 Species classified by testing..........................................................................................................9

5.3 Synthetic repairs..............................................................................................................................................9

5.3.1 Synthetic fillers.............................................................................................................................9

5.3.2 Synthetic shims, patches, and plugs............................................................................................10

5.4 Grade description of veneers.........................................................................................................................10

5.4.1 Grade N veneer (intended for natural finish)..............................................................................10

5.4.2 Grade A veneer (suitable for painting)........................................................................................10

5.4.3 Grade B veneer ...........................................................................................................................11

5.4.4 Grade C veneer ...........................................................................................................................12

5.4.5 Grade C plugged veneer .............................................................................................................13

5.4.6 Grade D veneer...........................................................................................................................13

5.5 Veneers and layers.........................................................................................................................................14

5.5.1 Veneer thickness .........................................................................................................................14

5.5.2 Parallel laminated layers.............................................................................................................15

5.5.3 Scarfed veneers...........................................................................................................................15

5.6 Panel grades...................................................................................................................................................16

5.6.1 Marine.........................................................................................................................................16

5.6.2 Decorative panels........................................................................................................................17

5.6.3 Underlayment .............................................................................................................................17

5.6.4 Concrete form panels..................................................................................................................18

5.6.5 Structural I panels.......................................................................................................................18

5.6.6 Special exterior...........................................................................................................................18

5.6.7 Overlays......................................................................................................................................18

5.7 Adhesive bond requirements for a panel or a lot..............................................................................................19

5.7.1 Exposure 1 ..................................................................................................................................19

5.7.2 Exterior.......................................................................................................................................20

5.8 Panel constructions and workmanship ..........................................................................................................21
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5.8.1 Crossband gaps and center gaps .................................................................................................22

5.8.2 Veneer requirements ...................................................................................................................22

5.8.3 Sanded panels.............................................................................................................................23

5.8.4 Unsanded and touch-sanded panels............................................................................................24

5.8.5 Span ratings for unsanded and touch-sanded panels...................................................................24

5.8.6 Performance testing qualification requirements for span-rated panels .......................................25

5.8.7 Performance testing qualification requirements for other than span-rated panels ......................29

5.9 Scarf and finger jointed panels......................................................................................................................31

5.9.1 Strength requirements for scarf and finger jointed panels..........................................................32

5.9.2 Scarf joint bond performance for Exposure 1 and Exterior plywood .........................................32

5.9.3 Finger joint bond performance for Exposure 1 and Exterior plywood .......................................32

5.10 Dimensional tolerances and squareness of panels.........................................................................................32

5.10.1 Size tolerances............................................................................................................................33

5.10.2 Performance category and thickness tolerances..........................................................................33

5.10.3 Squareness and straightness........................................................................................................33

5.11 Moisture content............................................................................................................................................33

5.12 Loading or packing........................................................................................................................................33

6 SPECIMEN PREPARATION AND TESTING.............................................................................................34

6.1 Bond classification........................................................................................................................................34

6.1.1 General........................................................................................................................................34

6.1.2 Specimen preparation (see appendix B for sampling for reinspection) ......................................34

6.1.3 Tests for Exposure 1 and Exterior plywood................................................................................34

6.1.4 Test for determination of moisture content (oven-drying method) .............................................36

6.1.5 Scarf and finger-joint tests..........................................................................................................36

6.2 Structural performance ..................................................................................................................................38

6.2.1 Tests for performance under concentrated static and impact loads.............................................38

6.2.2 Test for performance under uniform loads..................................................................................39

6.2.3 Test for panel bending.................................................................................................................40

6.2.4 Test for planar shear strength......................................................................................................40

6.2.5 Test for shear-through-the-thickness strength .............................................................................41

7 GRADEMARKING AND CERTIFICATION...............................................................................................41

7.1 Certification...................................................................................................................................................41

7.2 Qualified inspection and testing agency........................................................................................................41

7.3 Panel marking................................................................................................................................................41

7.4 Voiding marks................................................................................................................................................42

8 EFFECTIVE DATE.......................................................................................................................................42

9 STANDING COMMITTEE...........................................................................................................................42
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APPENDIX A: SPECIES GROUPING (MANDATORY)...................................................................................43

A1 General ..........................................................................................................................................................43

A2 Grouping in practice......................................................................................................................................43

A3 Species grouping ...........................................................................................................................................43

APPENDIX B: REINSPECTION PRACTICES (NON MANDATORY)............................................................46

B1 General ..........................................................................................................................................................46

B2 Request for reinspection................................................................................................................................46

B3 Responsibility of the buyer............................................................................................................................46

B4 Responsibility of the seller............................................................................................................................46

B5 Responsibility of the qualified inspection agency conducting the reinspection ............................................46

B6 Cost and assistance........................................................................................................................................46

B7 Resinspection procedures and settlement ......................................................................................................46

APPENDIX C: GENERAL INFORMATION AND COMMENTS ON CURRENT EDITION 

(NON MANDATORY)...............................................................................................................48

C1 Current edition, PS 1-09 that became May 1, 2010.......................................................................................48

C2 History of the project.....................................................................................................................................48

APPENDIX D: (NON MANDATORY)...............................................................................................................50

D1 Recommended thickness labels.....................................................................................................................50

D2 Regulations on labeling.................................................................................................................................51

APPENDIX E: LABELING GUIDELINES BASED ON THE UNIFORM PACKAGING AND LABELING 

REGULATIONS OF NIST HANDBOOK 130 V2009 (NON MANDATORY) ........................52

E1 Summary .......................................................................................................................................................52

E2 Background ...................................................................................................................................................52

E3 Scope and definitions....................................................................................................................................52

E4 Declaration of identity and responsibility .....................................................................................................53

E5 Declaration of quantity..................................................................................................................................53

E6 Prominence and placement............................................................................................................................55

APPENDIX F: WOOD STRUCTURAL PANELS AS GREEN BUILDING MATERIALS 

(NON MANDATORY) .................................................................................................................................57

F1 Overview .......................................................................................................................................................57

F2 Green attributes of wood................................................................................................................................57

F3 Sustainable Forest Management Programs.....................................................................................................57

F4 Major Green Building Rating Systems...........................................................................................................58
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APPENDIX G – FORMALDEHYDE (NON MANDATORY) ...................................................................................59

G1 General ..........................................................................................................................................................59

G2 Formaldehyde Regulations ............................................................................................................................59

G3 Formaldehyde Emission from PS 1 Plywood .................................................................................................59

TABLES

TABLE 1: Classification of species....................................................................................................................4

TABLE 2: Exposure 1 plywood grades ............................................................................................................15

TABLE 3: Exterior plywood grades.................................................................................................................17

TABLE 4: Panel constructions (minimum number of plies and layers) ...........................................................21

TABLE 5: Characteristics prohibited or restricted in certain panel grades.......................................................23

TABLE 6: Span ratings for sheathing and single-floor panels based on 

prescriptive specifications...............................................................................................................25

TABLE 7: Concentrated static and impact test performance criteria for panel testing 

according to Section 6.2.1...............................................................................................................27

TABLE 8: Uniform load performance criteria for panels tested according to Section 6.2.2............................28

TABLE 9: Species group classification test criteria for other than span-rated panels............................................30

TABLE 10: Plywood thickness requirements.....................................................................................................33

TABLE A1: Clear wood property assignments...................................................................................................43

TABLE A2: Source of data used to classify foreign species in Plywood Product Standard PS 1.......................44

TABLE D1: Recommended thickness labeling for unsanded, touch sanded and overlaid panels.......................50

TABLE D2: Recommended thickness labeling for sanded panels ......................................................................51

FIGURE 1: Finger-joints – location of scarfed portion of joints........................................................................32

FIGURES

FIGURE 2: Shear test specimens .......................................................................................................................34

FIGURE 3: Apparatus for heat durability test....................................................................................................36

FIGURE 4: Tension specimen for scarfed jointed panels...................................................................................37

FIGURE 5: Specimen preparation......................................................................................................................37

FIGURE 6: Cleavage test, typical test specimen................................................................................................38

FIGURE 7: Wedge or chisel used for cleavage test............................................................................................38

FIGURE 8: Vacuum chamber test equipment.....................................................................................................39

FIGURE 9: Uniform-load test specimens...........................................................................................................40
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VOLUNTARY PRODUCT STANDARD PS 1-09

STRUCTURAL PLYWOOD

Effective May 1, 2010

(This standard, which was initiated by the 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 1-07, 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 producers, 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, marking, moisture content, and packaging of structural plywood 

intended for construction and industrial uses. 

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 provided whereby qualified testing agencies inspect, sample, 

and test products identified as complying with this standard. Information on species grouping is provided in 

Appendix A. Information on reinspecting 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 is provided in Appendix E. Information on environmental attributes of structural plywood is provided 

in Appendix F and information on formaldehyde emissions is provided in Appendix G.

1.4 This Voluntary Product Standard incorporates the International System of Units (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 G 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 of a plywood panel – The outer veneer on the back side of a panel.

2.2 Bond classifications 

Plywood is rated as Exposure 1 or Exterior bond classification. (See Section 4.2)

2.3 Borer holes 

Voids made by wood-boring insects, such as grubs or worms.
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2.4 Broken grain 

A separation on 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 runs 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 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 measuring 305 mm (12 in) along the grain by full panel width that contains a knot or 

knothole requiring additional consideration. (See Sections 5.4.4.3, 5.4.6.2 and 5.4.6.3)

2.15 Crossband 

Inner, or core, plies whose grain direction runs perpendicular to that of the outer plies. Some crossbands 

consist of parallel laminated plies.

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 purpose of evaluation of delamination, areas coinciding with open knotholes, pitch pockets, splits, and 

gaps and other voids or characteristics permitted in the panel grade are not considered in evaluating ply 

separation.
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2.17.2 Exposure 1

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 Exterior

For purposes of evaluation of 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 Edge splits 

Wedge-shaped openings in the inner plies caused by splitting of the veneer before pressing.

2.19 Exposure 1 bond classification

See Section 4.2.1.

2.20 Exterior bond classification 

See Section 4.2.2.

2.21 Face

Face of the plywood panel – The side 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 of a panel – The outer veneer on the face of a panel.

2.22 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.

2.23 Group

Term used to classify species or panels covered by this standard. Species covered by this standard are 

classified as Groups 1, 2, 3, 4, and 5. See Table 1 and Appendix A for listing of species in individual groups. 

Section 5.8.7 provides procedures for grouping of panels with species not listed in Table 1.
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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

Birch

Sweet

Yellow

Douglas-fir(b)

Larch, Western

Maple, Sugar

Pine, Southern

Loblolly

Longleaf

Shortleaf

Slash

Tanoak

Cedar,

Port Orford

Cypress

Douglas-fir(b)

Fir

Balsam

California 

Red

Grand

Noble

Pacific 

Silver

White

Hemlock, Western

Maple, Black

Pine

Pond

Red

Virginia

Western 

White

Spruce

Black

Red

Sitka

Sweetgum

Tamarack

Yellow Poplar

Alder, Red

Birch, Paper

Cedar, Alaska

Fir, Subalpine

Hemlock, Eastern

Maple, Bigleaf

Pine

Jack

Lodgepole

Ponderosa

Spruce 

Redwood

Spruce

Engelmann

White

Aspen

Bigtooth

Quaking

Cedar

Incense

Western Red

Cottonwood

Eastern

Black (W. Poplar)

Pine

Eastern White 

Sugar

Basswood

Poplar, 

Balsam

Non North American Species

Apitong(c)(d)

Kapur(c)

Keruing(c)(d)

Pine

Caribbean

Ocote

Lauan

Almon

Bagtikan

Mayapis

Red Lauan

Tangile

White Lauan

Mengkulang(c)

Meranti, 

Red(c)(e)

Mersawa(c)

Cativo

(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 regions 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 volume and oven dry weight.

2.24 Heartwood

Nonactive core of a log generally distinguishable from the outer portion (sapwood) by its darker color.

2.25 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.

2.26 Jointed inner plies

Crossband and center veneers with edges machine-squared to permit tightest possible layup.

2.27 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 
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side experience an abrupt change in direction.

2.28 Knotholes

Voids produced by the dropping of knots from the wood in which they were originally embedded.

2.29 Lap

A condition where the veneers are so placed that one piece overlaps the other.

2.30 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 a “parallel laminated layer.”

2.31 Lot

Any number of panels considered as a single group for evaluating conformance to this standard.

2.32 Major panel axis 

The direction parallel to the grain of the face and back plies.

2.33 Mill specification

A manufacturing specification based on product evaluation to be used for quality assurance purposes by the 

manufacturer and the qualified testing agency as defined in Section 7.2. (See Sections 5.8.6.5 and 5.8.7.3.)

2.34 Moisture content 

The weight of the water in wood expressed as a percent of the weight of the oven-dry wood. (See Section 

6.1.4.)

2.35 Moisture resistant adhesive

Adhesive capable of bonding plywood in a manner to satisfy the bond classification requirements of this 

standard.

2.36 Panel thickness

Designated thickness subject to tolerances specified in this standard. See Section 5.10.2 for thickness 

tolerances. See Section 2.38 for definition of Performance Category.

2.37 Patches

Inserts of sound wood or synthetic material in veneers or panels for 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. 

“Router” patches have parallel sides and rounded ends. “Sled” patches are rectangular with feathered ends.

2.38 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 defined in Section 7.3, abbreviations PERF CAT, CAT or Category are permitted.

2.39 Performance testing 

Tests that evaluate panel attributes typically required in the end-use applications as defined in this standard. 

2.40 Pitch pocket 

A well-defined opening between rings of annual growth, usually containing, or which has contained, pitch, 

either solid or liquid.

2.41 Pitch streak

A localized accumulation of resin in coniferous woods which permeates the cells forming resin soaks, 

patches, or streaks.
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2.42 Plugs

Sound wood of various shapes, including among others, circular and dog-bone, 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.

2.43 Plugged inner plies (also referred to as solid inner plies)

Refers to C Plugged crossband and centers and additional limitations, as given in Section 5.8.1.

2.44 Ply 

A single veneer lamina in a bonded plywood panel. (See also 2.30.)

2.45 Plywood

Plywood is a panel built up of sheets of veneer called plies, 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 of adjacent layers perpendicular. Layers consist of a single ply or two or 

more plies laminated with parallel grain direction. 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.

2.46 Plywood classification

Plywood is classified by bond classification and grade. (See Section 4.)

2.47 Prescriptive specification 

A specification based upon manufacturing parameters that define the approved product.

2.48 Reference value

The numerical value established for the mill specification for a given mechanical or physical property.

2.49 Repair

Any patch, plug, or shim.

2.50 Rough grain

Grain characteristics which prevent sanding to a smooth surface.

2.51 Sapwood 

The living wood of lighter color occurring in the outer portion of a log. Sometimes referred to as “sap.”

2.52 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.

2.53 Shim

A long, narrow repair of wood or suitable synthetic not more than 4.8 mm (3/16 in) wide.

2.54 Shop-cutting panel

Panel which 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 

deficiency 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 area of the panel. Such a 

panel must be identified with a separate mark as specified in Section 7.4.
7

2.55 Span rating

An index number, based on customary inch units, that identifies the recommended maximum center-to-center 

support 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 for spans of 19.2 inches.

2.56 Split 

Lengthwise separation of wood fibers completely through the veneer, caused chiefly by the manufacturing 

process or handling.

2.57 Sub-face (sub-back)

The ply adjacent to the exposed face (or back) of a parallel laminated outer layer.

2.58 Touch-sanding

A sizing operation consisting of a light surface sanding to thickness dimension in a sander. Sander skips to 

any degree are admissible.

2.59 Veneer

Thin sheets of wood of which plywood is made. Also referred to as “plies” in the bonded panel.

2.60 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.

2.61 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.

2.61.1 Light white pocket

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.

2.61.2 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 which have caused the wood to 

crumble are prohibited.

2.62 Wood failure (percent) 

The area of wood fiber remaining at the bond line following completion of the specified shear test. 

Determination is by means of visual examination and expressed as a percent of the test area.

2.63 Working Face

A face and/or back of a plywood panel that has an overlay system that meets a defined MDO or HDO grade 

(see Section 5.6.7).
8

3 REFERENCE PUBLICATIONS (1)

- ASTM E 661-03 Test Method for Performance of Wood and Wood-Based Floor and Roof Sheathing Under 

Concentrated Static and Impact Loads.

- ASTM D 2555-06 Test Methods for Establishing Clear Wood Strength Values.

- ASTM D 2718-00 (2006) Test Method for Structural Panels in Planar Shear (Rolling Shear).

- ASTM D 2719-89 (2007) Test Methods for Structural Panels in Shear Through-the-Thickness.

- ASTM D 2915-03 Standard Practice for Evaluating Allowable Properties for Grades of Structural Lumber.

- ASTM D 3043-00 (2006) Methods of Testing Structural Panels in Flexure.

- ASTM D 5266-99 (2005) Standard Practice for Estimating the Percentage of Wood Failure in Adhesive 

Bonded Joints.

- International Building Code®. International Code Council. Country Club Hills, IL.

- International Residential Code® for One- and Two-Family Dwellings. International Code Council. Country 

Club Hills, IL. 

- PS 2-04 Performance Standard for Wood-Based Structural-Use Panels.

4 PLYWOOD CLASSIFICATION

4.1 General

The plywood covered by this standard is classified by bond classification and by grade.

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 

Plywood 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 due to construction delays, or 

other conditions of similar severity. Adhesive performance requirements are provided in Section 5.7.1.

Note: Exposure 1 was formerly identified as Interior with Exterior Glue. 

4.2.2 Exterior plywood

Plywood suitable for repeated wetting and redrying or long-term exposure to weather or other conditions of 

similar severity. Adhesive performance requirements 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.)
9

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 trademarking and certification shall be as provided 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 which 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 qualified inspection and testing 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 qualified inspection and testing 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 layers 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 provided in Section 5.2.3. Requirements for identification of all panels are 

given in Section 7.3.

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 or 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 Section 5.8.7 

for other panels except concrete form, Marine and Structural I grades. For panel marking purposes, reclassification of Group designation for species listed in Table 1 by panel performance testing in accordance 

with Section 5.8.7 is 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 qualified testing and inspection agency.
10

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 qualified 

testing and inspection 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. Unless otherwise stated, these requirements apply to 1220 mm by 2440 mm (48 x 96 in) 

panels and are proportionate for other sizes. Grade N is the highest classification.

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 sanding is required (see Tables 2 and 3) panels shall be sanded and shall permit no sander 

skips.

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 wide by 6.4 mm long (1/8 in x 1/4 in).

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.

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 sanding is required (see Tables 2 and 3) 

panels shall be sanded and shall permit no sander skips.

Synthetic fillers shall only be used to fill:

a. In Exterior panels: small cracks 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; 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; openings or 
11

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,” “router,” or “sled” type. The radius of ends of boat patches shall not 

exceed 3.2 mm (1/8 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 consisting 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.

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; small chipped areas or openings not more than 3.2 mm wide by 6.4 mm long (1/8 in x 1/4 in).

b. In Exposure 1 panels: small cracks or checks not more than 4.8 mm (3/16 in) wide; openings or 

depressions up to 12.7 mm wide by 50.8 mm long (1/2 in x 2 in) 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.
12

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 cm2 (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 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 in width by 114 mm in length (6 in x 4-1/2 in) shall be allowed.

Shims shall be permitted without limit.

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) 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) 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 203 mm (8 in) from the end of the panel shall not exceed 12.7 mm (1/2 in) in width 

by 1/2 panel length or 9.5 mm (3/8 in) in width by any panel length, provided separation at one end does not 

exceed 1.6 mm (1/16 in) where split runs full panel length; however, the maximum width 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.
13

Splits on panel faces and backs shall not exceed 6.4 mm (1/4 in) where located within 25.4 mm (1 in) of 

parallel panel edge.

Voids due to missing wood on panel faces and backs 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 not exceeding 203 mm (8 in) in length and the width permitted for open characteristics shall be 

allowed, 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 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.

Shims shall be permitted without limit.

5.4.5 Grade C Plugged veneer

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 shall be permitted. Synthetic 

repairs in veneer 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. See Tables 2 and 3 for sanding requirements. Where grades having C 

Plugged face veneer are identified as fully sanded, sanding characteristics shall be the same as admitted under 

B grade. Sander skips to any degree shall be admissible in touch-sanded 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) 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 
14

exceed 254 mm (10 in) 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) 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:

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 at least two plies removed from the 

face or back plies of C-D, D-D and C-D Plugged grades having five or more plies.

Splits measured at a point 203 mm (8 in) from the end of the panel shall not exceed 25.4 mm (1 in) in width, 

tapering to not more than 1.6 mm (1/16 in) where split runs full panel length; however, the maximum width 

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) in width where located within 25.4 mm (1 in) 

of parallel panel edge.

Voids due to missing wood on panel backs not otherwise specified in Section 5.4.6.3 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 not exceeding 203 mm (8 in) in length and the width permitted for open characteristics is allowed, 

providing that where occurring 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 610 mm (24 in) wide across the grain and 305 mm (12 in) long, in which light or heavy white pocket 

occurs, shall contain not 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, 38.1 mm (1-1/2 in) to 63.5 mm (2-1/2 in), or two knots or knotholes, 25.4 mm (1 in) 

to 38.1 mm (1-1/2 in). Knots or knotholes less than 25.4 mm (1 in) shall not be considered. Sizes of any 

knot or knothole shall be measured across the grain. Any repair in a white pocket area shall be considered

for grading purposes as a knothole.
15

TABLE 2

EXPOSURE 1 PLYWOOD GRADES (PERMITS D GRADE VENEER)

Panel Grade Designations

Minimum Veneer Quality

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 2-04) or 

PS 2-04.

5.5 Veneers and layers

5.5.1 Veneer thickness

Except as provided for in the following paragraphs, veneer shall be 2.5 mm (1/10 in) or thicker in panels with 

Performance Category of 3/8 rough (unsanded) thickness or over; 2.1 mm (1/12 in) or thicker in panels with 

Performance Category of less than 3/8 rough (unsanded) thickness. 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) 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 provided for in Section 5.5.2.

Veneer of 1.6 mm (1/16 in) 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 

provided for 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, 5/8, 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 provided 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 
16

5.8 and performance testing in accordance with Section 5.8.6 shall be permitted.

5.5.2 Parallel laminated layers

Parallel-laminated outer layers shall only be used in C-C, C-D, D-D and Structural I C-C and C-D grades. 

Such layers shall consist of veneers 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 or exposed plies of outer layers shall conform to the 

species group and grade requirements for faces and backs, respectively, of the panel grade. The unexposed 

plies of outer layers, or 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 Section 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 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.

Parallel-laminated inner layers in any grade shall consist of veneers 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 shall be permitted.

5.5.3 Scarfed veneers

Scarfed veneers shall be permitted for any face, back, or inner ply except as provided in Section 5.9. Scarfed 

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 provided in Tables 2 and 3, with the additional requirements provided 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.

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.

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 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.
17

There shall be no filling of crossband gaps and edge splits.

TABLE 3

EXTERIOR PLYWOOD GRADES(a) (DOES NOT PERMIT D GRADE VENEER)

Panel Grade Designations

Minimum Veneer Quality

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, 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 provided 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) (e) For more clarification on concrete form grades, see Section 5.6.4.

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. All 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 in) 

and shall be limited to one panel face. Where butt joints 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 produced with touch sanded faces is appropriate for floor applications using carpet and pad.

5.6.3.1 Exposure 1 underlayment

Face veneer shall be C plugged grade 2.5 mm (1/10 in) or thicker before sanding. 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. 
18

5.6.3.2 Exterior underlayment (C-C plugged or better) 

Face veneer shall be C plugged grade or better 2.5 mm (1/10 in) or thicker before sanding. 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 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 trademark. 

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 identified accordingly. Non-overlaid panels shall be sanded two sides and have a millapplied 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 concrete 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:

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) 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 Structural I panels

These panels are especially 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. In addition to the special species, grade, and adhesive bond requirements set 

forth in the tabulation below, Structural I panels shall meet all other requirements in this standard for the 

applicable types and grades.

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 face 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 Section 7.3.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 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% 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 
19

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 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 

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 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 m2 (58 pounds per 1000 ft2

) including both 

resin and fiber, but exclusive of bond line. The resin-treated facing on the finished product shall 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 Section 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.”

5.7 Adhesive bond requirements for a panel or a lot

The adhesive bond shall meet the requirements below.

Grade Bond Performance Species

Structural I(a)

C-D

C-D Plugged

Underlayment

Shall meet the requirements of 

5.7.1 for Exposure 1

Face, back and all inner plies 

limited to Group 1 species

Structural I

All Exterior grades (See Table 3) Shall meet the requirements of 

5.7.2 for Exterior

Face, back and all inner plies 

limited to Group 1 species

(a) 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 provided in Table 5.

• Plugs, including multiple repairs, shall not exceed 102 mm (4 in) in width.

• Panel construction shall be as specified in Section 5.8. 

5.7.1 Exposure 1

A panel shall be considered as meeting Exposure 1 adhesive bond requirements of this standard if the test 

specimens taken from a panel average 80% wood failure or greater when tested in accordance with Section 
20

6.1.3. For qualification purposes, specimens from at least 20 panels shall be sampled.

Lots represented by test panels shall be considered as meeting the requirements of this standard if the 

requirements of (a) and (b) are met:

a. The average wood failure of all test specimens, regardless of the number of panels tested, shall be not less 

than 80%,

b. And:

1. When at least 10 panels are tested, at least 90% of the panels represented by the test pieces shall have 

60% wood failure or better, and

2. When at least 20 panels are tested, at least 95% of the panels represented by the test pieces shall have 

30% wood failure or better.

3. When fewer than 10 panels are tested, all panels represented by the test pieces shall have 60% wood 

failure or better. 

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

When tested in accordance with Section 6.1.3, Exterior plywood shall be considered as meeting the adhesive 

bond requirements of this standard if the test specimens taken from a panel average 85% wood failure or 

greater. For qualification purposes, specimens from at least 20 panels shall be sampled.

Lots represented by test panels shall be considered as meeting the requirements of this standard if the 

minimum requirements of (a) and (b) are met:

a. The average wood failure of all test specimens, regardless of the number of panels tested, shall be not less 

than 85%,

b. And:

1. When at least 4 panels are tested, at least 75% of the panels represented by the test pieces shall have 

80% wood failure or better; and

2. When at least 10 panels are tested, at least 90% of the panels represented by the test pieces shall have 

60% wood failure or better; and

3. When at least 20 panels are tested, at least 95% of the panels represented by the test pieces shall have 

30% wood failure or better.

4. When fewer than 4 panels are tested, all panels represented by the test pieces shall have 80% wood 

failure or better. 

The requirements of Section 5.7.2 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.
21

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 specimen, 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 described 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 proportion of wood with grain perpendicular to panel face grain shall be not less than 33% or 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.

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 form

B-C Concrete form

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

Through 5/8

Over 5/8 through 3/4

Over 3/4

3

4

5

3

3

5
22

Exterior

C-C

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. 

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 provided 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 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 7.3.

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. The average of all gaps 

occurring in a panel shall not exceed 12.7 mm (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). 

5.8.2 Veneer requirements

The veneers used in each ply of each panel and the completed panel shall conform with the applicable veneer 
23

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.

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 (See 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. Plies 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 only, 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.
24

5.8.4 Unsanded and touch-sanded panels

Grade C or D veneers 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 in) 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 in 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 cm2 (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 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 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 sanded, touchsanded, surface textured, or thickness sized by any mechanical means. However, sanded or touch-sanded 

panels which do not meet the grades for which they were intended shall not be reclassified and marked as CC, C-D or D-D, unless the panels meet all applicable requirements for C-C, C-D or D-D and the finished face 

and back veneers after sanding each have a minimum net thickness equal to 90% of the applicable thickness in 

Table 6 or in the mill specification. (See Section 5.8.7.3.)

5.8.5 Span ratings for unsanded and touch-sanded panels

Grade-trademarking of C-C, C-D, D-D, Structural I C-C, Structural I C-D, and of C-C Plugged and 

Underlayment to be used as combination subfloor-underlayment (single floor) shall include a span rating. The 

numbers are presented as a fraction in the marking of sheathing grades of plywood, and as a single number for 

C-C Plugged and Underlayment. They describe the maximum spans in inches under normal use conditions 

and are in accordance with commonly accepted criteria. Panels for which there is no span rating shall be 

identified by largest species group number of the face and back, or by the span rating of the next thinner 

comparable panel. 

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 Underlayment and C-C Plugged refers to spacing 

of the floor framing in single floor applications. Actual maximum spans are established by local building 

codes.

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 specification as detailed in Table 6, or

b. By performance testing to satisfy the strength, stiffness and bond criteria as detailed in Section 5.8.6. Such 

performance testing shall be performed by a qualified testing agency, as described in Section 7.2.
25

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.) 

Span

Rating (a)

Panel

Performance 

Category

Minimum 

Number

of PliesLayers

Minimum Face & Back Veneer Thickness 

Before Pressing, for Species Group(b)

Inner Ply

Species

1 2 3 4 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)

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 Section 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 spans of 19.2 inches.

5.8.6 Performance testing qualification requirements for span-rated panels

5.8.6.1 General

Acceptance of performance tested plywood under this standard is based upon testing of panel strength, 

stiffness and bond performance. Panels selected for testing shall be of near minimum grade and near 

minimum thickness. Panel average thickness shall be established in accordance with Section 5.10.2. All 

provisions of veneer grade and panel workmanship are applicable. 
26

5.8.6.2 Performance testing

Panels qualified by performance testing shall satisfy the criteria called for in Section 5.8.6 when tested in 

accordance with Sections 5.8.6.3 and 5.8.6.4. 

5.8.6.3 Structural performance

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 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.

Concentrated loads

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 ten additional specimens are tested, the combined passing rate shall be at least 85%.

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%.

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.

Uniform loads
27

TABLE 7

CONCENTRATED STATIC AND IMPACT TEST PERFORMANCE CRITERIA FOR PANELS TESTED 

ACCORDING TO SECTION 6.2.1 (See Section 5.8.6.3 for Pass/Fail Criteria)

End Use –Span 

Rating

Test Exposure

Conditions(a)

Performance Criteria

Ultimate Load Deflection

Under 0.89 kN 

Static Following Impact (200 lbf) Load (b)

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 wetting, followed by testing dry. Dry shall be within  3 percent of the 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 spans of 19.2 inches.
28

TABLE 8

UNIFORM LOAD PERFORMANCE CRITERIA FOR PANELS TESTED ACCORDING TO SECTION 6.2.2 (See 

Section 5.8.6.3 for Pass/Fail Criteria)

End Use –

Span Rating

Test Exposure

Conditions(a)

Performance Criteria(b)

Ultimate 

Uniform Load(b)

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(c) 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 in at 100 lbf/ft2

) 15.8 330

Single Floor – 20(c) Dry

Wet/Redry 1.3 mm at 4.79 kPa (0.053 in 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 wetting, followed by testing dry. Dry shall be as received or conditioned in 

accordance with ASTM E 661.

(b) The panel strength axis shall be placed along the supports for testing, unless otherwise specified.

(c) The “20” span designation is intended for spans of 19.2 inches.

Deflection – The average deflection shall not be greater than that specified.

The initial test consists of 10 specimens.

 Ifthe 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 load – 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%
29

5.8.6.4 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 specified 

in Section 5.7.2.

5.8.6.5 Product evaluation

Mill specification – Upon conformance with the appropriate requirements of Sections 5.8.6.3 and 5.8.6.4, a 

manufacturing specification unique to the product and mill shall be written based on product evaluation. This 

specification shall be used for quality assurance purposes by the manufacturer and the qualified testing agency, 

according to Section 5.8.7.3. 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 twenty panels as sampled under Section 5.8.6.1.

Mechanical properties 

Bending stiffness – Twenty 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.

Bending strength – Ten tests (specimens taken from ten different panels) shall be tested 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 provided 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. Results of testing shall establish a 

Group classification for use as required in Section 7.3.a. Group classification established by panel testing shall 

be determined by the largest Group number obtained from all performance tests. 

5.8.7.2 Performance testing

Bending stiffness – A minimum of twenty 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 Performance Category tested.
30

TABLE 9

SPECIES GROUP CLASSIFICATION TEST CRITERIA FOR OTHER THAN SPAN-RATED PANELS

Performance

Category Group

Shear 

Through

Thickness

Strength

kN/m (lbf/in)

Stress Along (Parallel to Face)

Bending 

Stiffness

kN•m2/m 

(lbf•in2/ft)

Bending 

Strength

kN•m/m 

(lbf•in/ft)

Planar Shear 

Strength

kN/m (lbf/ft)

1/4

1

2

3

4

21.0 (120)

15.8 (90)

15.8 (90)

14.5 (83)

0.15 (16 000)

0.12 (13 000)

0.10 (10 500)

0.08 (8 800)

0.087 (235)

0.063 (170)

0.063 (170)

0.057 (155)

3.7 (255)

3.7 (255)

3.7 (255)

3.7 (255)

11/32

1

2

3

4

22.8 (130)

16.6 (95)

16.6 (95)

15.6 (89)

0.35 (37 500)

0.30 (31 500)

0.24 (25 000)

0.20 (21 000)

0.137 (370)

0.100 (270)

0.100 (270)

0.093 (250)

5.1 (350)

5.1 (350)

5.1 (350)

5.1 (350)

3/8

1

2

3

4

22.8 (130)

17.0 (97)

17.0 (97)

15.8 (90)

0.50 (53 500)

0.42 (44 500)

0.33 (35 500)

0.28 (29 500)

0.183 (495)

0.133 (360)

0.133 (360)

0.124 (335)

5.8 (395)

5.8 (395)

5.8 (395)

5.8 (395)

15/32

1

2

3

4

33.3 (190)

24.5 (140)

24.5 (140)

22.8 (130)

1.22 (130 000)

1.04 (110 000)

0.82 (87 000)

0.68 (72 500)

0.313 (845)

0.228 (615)

0.228 (615)

0.211 (570)

7.7 (525)

7.7 (525)

7.7 (525)

7.7 (525)

1/2

1

2

3

4

34.1 (195)

25.4 (145)

25.4 (145)

23.6 (135)

1.41 (150 000)

1.18 (125 000)

0.94 (100 000)

0.80 (84 500)

0.347 (935)

0.252 (680)

0.252 (680)

0.234 (630)

8.3 (570)

8.3 (570)

8.3 (570)

8.3 (570)

19/32

1

2

3

4

43.8 (250)

32.4 (185)

32.4 (185)

29.8 (170)

2.17 (230 000)

1.79 (190 000)

1.41 (150 000)

1.18 (125 000)

0.463 (1250)

0.335 (905)

0.335 (905)

0.311 (840)

10.1 (695)

10.1 (695)

10.1 (695)

10.1 (695)

5/8

1

2

3

4

43.8 (250)

32.4 (185)

32.4 (185)

29.8 (170)

2.40 (255 000)

2.02 (215 000)

1.60 (170 000)

1.32 (140 000)

0.500 (1350)

0.361 (975)

0.361 (975)

0.335 (905)

10.8 (740)

10.8 (740)

10.8 (740)

10.8 (740)

23/32

1

2

3

4

44.7 (255)

33.3 (190)

33.3 (190)

30.6 (175)

3.34 (355 000)

2.78 (295 000)

2.21 (235 000)

1.84 (195 000)

0.575 (1550)

0.408 (1100)

0.408 (1100)

0.389 (1050)

12.2 (835)

12.2 (835)

12.2 (835)

12.2 (835)

3/4

1

2

3

4

45.5 (260)

33.3 (190)

33.3 (190)

30.6 (175)

3.67 (390 000)

3.06 (325 000)

2.45 (260 000)

2.02 (215 000)

0.612 (1650)

0.445 (1200)

0.445 (1200)

0.408 (1100)

12.6 (860)

12.6 (860)

12.6 (860)

12.6 (860)

7/8

1

2

3

4

46.4 (265)

34.1 (195)

34.1 (195)

32.4 (185)

5.18 (550 000)

4.33 (460 000)

3.44 (365 000)

2.87 (305 000)

0.760 (2050)

0.556 (1500)

0.556 (1500)

0.500 (1350)

14.6 (1000)

14.6 (1000)

14.6 (1000)

14.6 (1000)

1

1

2

3

4

65.7 (375)

48.2 (275)

48.2 (275)

44.7 (255)

7.91 (840 000)

6.59 (700 000)

5.27 (560 000)

4.38 (465 000)

0.982 (2650)

0.704 (1900)

0.704 (1900)

0.649 (1750)

16.8 (1150)

16.8 (1150)

16.8 (1150)

16.8 (1150)

1-1/8

1

2

3

4

66.5 (380)

49.0 (280)

49.0 (280)

45.5 (260)

10.36 (1 100 000)

8.52 (905 000)

6.83 (725 000)

5.70 (605 000)

1.205 (3250)

0.871 (2350)

0.871 (2350)

0.816 (2200)

18.3 (1250)

18.3 (1250)

18.3 (1250)

18.3 (1250)
31

Bending strength – A minimum of ten tests (specimens taken from ten different panels) shall be tested 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 shear strength value along the major axis given in Table 9 for the 

Performance Category tested.

Shear-through-the-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 Mill specification

Upon conformance with the requirements of Section 5.8.7.2, a manufacturing specification unique to the 

product and mill shall be written. This specification shall be used for quality assurance purposes by the 

manufacturer and the qualified testing agency defined in Section 7.2. The manufacturing specification shall 

define veneer species and panel construction and shall include the following reference values:

Thickness – The reference value shall be the average panel thickness less 1.932 standard deviations (the 95% 

lower tolerance limit at 75% confidence) for twenty panels tested under Section 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 (see ASTM D 2915) established on the mean for each panel direction.

Bending strength – The reference values for each panel direction shall be the minimum observed value, or 

the sample mean less 1.8 times the sample standard deviation, whichever is the higher value for each panel 

direction.

Planar shear strength – The reference value shall be the minimum observed value, or the sample mean less 

1.8 times the sample standard deviation whichever is the higher value.

Shear-through-the-thickness strength – The reference value shall be the minimum observed value, or the 

sample mean less 1.8 times the sample standard deviation, whichever is the higher value.

As an alternative to the mechanical properties, the performance tests of Section 5.8.7.2 may also be used for 

quality assurance purposes.

5.9 Scarf and finger jointed panels

Neither panels with N faces, nor the faces 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.
32

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 species, 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%.

FIGURE1

FINGER JOINTS – LOCATION OF SCARFED PORTION OF JOINTS

End Finger Joint

(Joint perpendicular to face grain)

End Finger Joint

(Joint parallel to face grain)

NOTES:

(a) Arrows ( ) indicate vertical shoulder in scarfed plies with grain perpendicular to joint. Maximum vertical shoulder in these plies is 0.8 mm

(1/ 32 in.).

(b) Arrows ( ) illustrate point with no shoulder in plies with grain perpendicular to joint.

(c) The number of fingers and panel constructions shown are illustrative only.
33

5.10.1 Size tolerances

A tolerance of plus zero (0) mm, minus 1.6 mm (1/16 in) shall be allowed on the specified length and width.

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. Measurements 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 shall be representative of general panel 

thickness at approximate mid-length 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 from that point.

The panel thickness shall conform to Table 10.

TABLE 10

PLYWOOD THICKNESS REQUIREMENTS

PERFORMANCE 

CATEGORY(c)

Thickness Requirements for Unsanded, 

Touch Sanded and Overlaid Grades(a)

Thickness Requirements for 

Sanded Grades(b)

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)

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)

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)

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 (0.837)

7/8 PERF CAT 21.11 (0.831) 23.34 (0.919) 21.56 (0.849) 22.89 (0.901)

1 PERF CAT 24.13 (0.950) 26.67 (1.050) 24.64 (0.970) 26.16 (1.030)

1-1/8 PERF CAT 27.15 (1.069) 30.00 (1.181) 27.72 (1.091) 29.43 (1.159)

1-1/4 PERF CAT 30.16 (1.188) 33.34 (1.313) 30.80 (1.213) 32.70 (1.288)

(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 than 13/16 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.

5.10.3 Squareness and straightness

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 
34

condition.

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. Unless otherwise specified by the qualified testing 

agency, 10 test specimens shall be cut as described in Section 6.1.3.1 for panels bonded with moistureresistant adhesive. Of the 10 specimens cut from each test piece for panels bonded with moisture resistant 

adhesive, 5 shall be for the vacuum-pressure test and 5 shall be for the boil test. In addition, from each panel 

selected, a specimen 140 mm by 203 mm (5-1/2 x 8 in) shall be cut and tested as described in Section 6.1.3.4.

6.1.3 Tests for Exposure 1 and Exterior plywood

6.1.3.1 Preparation of test specimens

Test specimens taken as described in Section 6.1.2 shall be cut 82.6 mm long by 25.4 mm wide (3-1/4 in x 1 

in), 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 runs at a 90° angle to the length 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 described 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.

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 of the retaining jaws 

on the testing device. When required to accommodate thicker plywood, 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 qualified 

inspection and testing agency, but at least one-half of the tests shall 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 to 

98.5 kPa or 24.7 to 29.0 inches of mercury shall be drawn and maintained for 30 minutes, followed 

immediately with application of 450 kPa to 480 kPa (65 psi to 70 psi) of pressure for 30 minutes duration. 

3.2 mm

(1/8 in.)

25.4 mm

(1 in.)

25.4 mm

(1 in.)

25.4 mm

(1 in.)

3.2 mm

(1/8 in.)

3.2 mm

(1/8 in.)

25.4 mm

(1 in.)

25.4 mm

(1 in.)

25.4 mm

(1 in.)

25.4 m

m

(1 in.)

3.2 mm

(1/8 in.)

FIGURE2

SHEAR TEST SPECIMENS

82.6 mm (3-1/ 4 in.) 82.6 mm (3-1/ 4 in.)
35

Specimens shall then be removed from the vessel and tested while wet by tension loading to failure in a shear 

testing machine operated at a maximum head travel of 406 mm (16 in) per minute. The jaws of the machine 

shall securely grip the specimens so there is no slippage. The percentage of wood failure of the specimens 

shall be determined in a dry condition and evaluated as described in Sections 5.7.1 and 5.7.2.

The bond between veneers in overlaid plywood shall be tested in an identical manner and evaluated as 

described in Section 5.7.2. 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 estimated with specimens in a dry 

condition and evaluated as described in Section 5.7.2. The value for each specimen shall be the average of the 

test areas on each face.

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 ± 3°C 

(145 ± 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 406 mm (16 in) per minute. 

Jaws of the machine shall securely grip the specimens so there is no slippage. The percentage of wood failure 

of the specimens shall be determined with specimens in a dry condition and evaluated as described in Sections 

5.7.1 and 5.7.2.

The bond between veneers in overlaid plywood shall be tested in an identical manner and evaluated as 

described in Section 5.7.2. Specimens to test the bond between the overlay and the base panels shall be 

subjected to the same test cycle described 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. 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 estimated with 

specimens in a dry condition and evaluated as described in Section 5.7.2. The value for each specimen shall be 

the average of the test areas on each face.

6.1.3.4 Heat performance test

A specimen cut as described in Section 6.1.2 shall be placed on a stand as illustrated in Figure 3. A specimen 

shall then be subjected to a 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, chisellike instrument. Specimens shall be evaluated in accordance with the requirements of Section 5.7.2.1.
36

6.1.4 Test for determination 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 cm2 (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 100°C to 105°C (212°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 weight. The moisture content shall be calculated as follows:

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.

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%.

100 mm 75 mm

20

mm

90° 45°

150°

355 mm

80 m

m

100 m

m

4.8 mm x 20 mm 

Strap iron frame

Plywood sample

30

mm

20

mm

30

mm

20

mm 100 mm

200 mm

180 mm

2

m

0

m

3

m

0

m

250

mm

200

mm

FIGURE3

APPARATUS FOR HEAT DURABILITY TEST
37

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 described in Section 6.1.3.1 and shall 

be cut so that the joint runs through the test specimens as shown in Figure 5.

Five specimens shall be subjected to the vacuum-pressure test described in Section 6.1.3.2, and five to the 

boiling test of Section 6.1.3.3. The panels shall be evaluated as described in Sections 5.7.1 and 5.7.2.

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.

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 

described in Section 5.9.3.

FIGURE4

TENSION SPECIMEN FOR SCARFED JOINTED PANELS

203 mm (8 in.) Joint 203 mm (8 in.) varies

50.8 m

m

(2 in.)

25.4 m

m

(1 in. )

25.4 mm

(1 in.)

82.6 mm (3-1/4 in.) 82.6 mm (3-1/4 in.)

3.2 mm

(1/8 in.)

25.4 mm

(1 in.)

25.4 mm

(1 in.)

3.2 mm

(1/8 in.)

25.4 mm

(1 in.)

3.2 mm

(1/8 in.)

25.4 mm

(1 in.)

25.4 mm

(1 in.)

3.2 mm

(1/8 in.)

FIGURE5

SPECIMEN PREPARATION
38

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 E 661 shall be followed except as modified in these sections. 

The test span shall be 19.2 inches for the span rating of 20. 

The dry test condition shall be within +/- 3% of the as-shipped moisture content. The wet test condition shall 

be exposure to three days of continuous wetting, then tested wet. The wet/redry condition shall be exposure to 

three days of continuous wetting, followed by testing within 3% of the as-shipped moisture content.

6.2.1.2 Specimen preparation

Test specimens shall be prepared as specified in ASTM E 661. The number of specimens required is given in 

Section 5.8.6.3. Specimens shall also be moisture cycled as required.

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 which 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 which 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.

127 mm (5 in.)

25.4 mm

(1 in.)

Area of wedging

Test area

Test area

Area of wedging

FIGURE 6

CLEAVAGE TEST, TYPICAL TEST SPECIMEN

12.7 mm to

25.4 mm

(1/2 in. to 

1 in.) wide

Attach to press as required Taper starts

12.7 mm (1/2 in.) dia.

50.8 mm (2 in.)

FIGURE7

WEDGE OR CHISEL USED FOR CLEAVAGE TEST
39

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.

Joist supports – The framing members shall be spaced at the intended span rating, except that 20 span rating 

shall have framing spaced 19.2 in 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.

Length – The specimen length perpendicular to the framing member shall be equal to twice the center-tocenter 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.

To vacuum pump To pressure gage or manometer

Test panel

Framing member

Polyethylene sheet taped to top of chamber

Tape

Framing member, supported to 

resist rotation and deflection

Vacuum chamber

Test panel

FIGURE8

VACUUM CHAMBER TEST EQUIPMENT
40

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 the gages positioned to 

read deflection at the point of maximum 

deflection(2) of the two outer spans (Figure 9).

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

Specimens shall be prepared according to ASTM D 3043 Method C.

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 distortion 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

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. 

Framing member 

supported to resist

rotation and vertical

movement

d

S

W

W/2

FIGURE9

UNIFORM-LOAD TEST SPECIMENS
41

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

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-thickness strength shall 

be measured and reported as a capacity, Fvtv.

7 GRADEMARKING AND CERTIFICATION 

7.1 Certification

Plywood represented as being in conformance with this standard shall bear the stamp of a qualified inspection 

and testing agency which (1) either inspects the manufacture (with adequate sampling, testing of bond line, 

and examination for quality of all veneers) or (2) has tested a random sampling of the finished panels in the 

shipment being certified for conformance with this standard.

7.2 Qualified inspection and testing agency 

A qualified inspection and testing agency is defined to be one that:

a. has the facilities and trained technical personnel to verify that the grading, measuring, species, 

construction, sanding, bonding, workmanship, and other characteristics of the products as determined by 

inspection, sampling and testing conform to all of the applicable requirements specified herein;

b. has developed procedures to be followed by agency personnel in performance of the inspection and testing;

c. has no financial interest in, or is not financially dependent upon, any single company manufacturing the 

product being inspected or tested; and

d. is not owned, operated or controlled by any such company.

7.3 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 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 manufactured 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 in) or thicker before sanding. A class number as provided in Section 

5.6.4 shall be used in lieu of a species group number to identify concrete form panels and a span rating 

shall be used for unsanded and touch-sanded grades as provided for in Section 5.8.5.

b. Either “Exposure 1” or “Exterior” – Panels not fully satisfying Exterior requirements shall be identified 

as “Exposure 1.” 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, 
42

shall be separated from the grademarks or trademarks of the testing agency by not less than 152 mm (6 in).

c. The grade name or the grade of face and back veneers or a mark of a qualified inspection and testing 

agency. If identified by such a mark, the product specification shall be available from the qualified 

inspection and testing 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 include “Two Working Faces” or “2S” within the grade declaration.

d. The symbol “PS 1-09” 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 labels.

f. The designation “Butt-Jointed Center” for those panels manufactured with butt joints in center plies in 

accordance with Section 5.8.

7.4 Voiding marks 

Panels originally marked as conforming to this standard but subsequently rejected as not conforming thereto 

shall have any reference to the standard obliterated or voided by the manufacturer as follows:

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 2.53.)

No reference shall be made to this standard in the certification or grade trademarking of panels not 

conforming to all of the applicable provisions of this standard.

8. EFFECTIVE DATE

The effective date of this standard is May 1, 2010. As of the effective date, reference to PS 1-09 shall be 

permitted in contracts, codes, advertising, invoices, product labels, and the like, but no product shall be 

advertised or represented in any manner which 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.

9. STANDING COMMITTEE

A Standing Committee for PS 1-09 will be appointed to be responsible for interpretation and for consideration 

of future proposals for amendments and revisions to the standard. The names of the 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 http://ts.nist.gov/ssd.

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. 
43

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 CS 45-60 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, Methods 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 properties. 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 provided in Table A1 are reduced by the addition.

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

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, straightgrained solid wood of all species in each group in the green and dry condition. The five properties are 

bending modulus of elasticity (MOE), bending modulus 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 laboratory. 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.
44

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 laevisA. 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

S. hemslevana

S. leprosula

S. macroptera

S. pauciflora

S. platyclados

S. rugosa

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

Malayan Forest Service Trade Leaflet #34

Malayan Forest Service Trade Leaflet #34

Malayan Forest Service Trade Leaflet #34

Malayan Forest Service Trade Leaflet #34

Malayan Forest Service Trade Leaflet #34

Malayan Forest Service Trade Leaflet #34

Group 4

Cativo Prioria copaifera FPL 125

Yale Bulletin #98 Tropical Woods (bearing only)
45

b. The maximum assignable MOE value is either the species average increased by 10% if volume data is 

available in ASTM D 2555 or the species average if no volume data exists or if it is a foreign species. 

c. The strength properties are calculated in one of the following three methods:

Method A species in ASTM D 2555

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 property values listed in Table C1 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.) 
46

APPENDIX B – REINSPECTION PRACTICES (non mandatory)

B1 GENERAL

Based on industry practice, the following information is offered 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 qualified inspection agency 

whose grademark 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, deterioration and 

from direct exposure to moisture which 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 QUALIFIED 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 provided 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 complying 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.
47

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 grademarks obliterated and shall be remarked with appropriate designation with 

a special inspection mark registered by the qualified agency conducting the reinspection and applied by that 

agency’s authorized representative.

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 the 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, twenty 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 provided for in 5.7, testing and evaluation shall apply separately to 

each category. Sampling of Exposure 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 less 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 described 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.
48

APPENDIX C – GENERAL INFORMATION AND COMMENTS ON CURRENT EDITION 

(non mandatory)

C1 CURRENT EDITION, PS 1-09 THAT BECAME EFFECTIVE MAY 1, 2010

The Standing Committee for PS 1 initiated a thorough review of PS 1-07 in early 2009 due in part to 

consumer complaints that indicated that panels were out of compliance to provisions of NIST Handbook 130 

and 133 dealing with packaging and labeling. 

The consensus review process, which allowed for discussions and resolution of points of difference, moved at 

a steady pace. This resulted in some noteworthy changes to the standard some of which are highlighted as 

follows:

C1.1 Labeling of panel thickness

In response to consumer complaints regarding thickness labeling being out of compliance with NIST 

Handbook 130 and 133, the standard was revised to create a Performance Category based on customary 

thickness notations used in U.S. model building codes. In addition, panel labeling requirements were changed 

to require the Performance Category and decimal thickness representation.

C1.2 Formaldehyde appendix

In response to national and international regulations of formaldehyde emissions from some wood products, an 

appendix was added to review those regulations with respect to PS 1 plywood.

C1.3 Environmental attributes and green building rating systems

An appendix was added to review environmental attributes of PS 1 plywood with respect to various green 

building rating systems.

C1.4 Technical revisions

A review of technical provisions and terminology led to various changes to reflect industry practice. 

C2 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 Department procedures, issued on November 16, 1965, for development of Voluntary 

Product Standards.

Since 1966, there have been five revisions to the standard: 

C2.1 PS 1-74 Construction and Industrial Plywood became effective August 1, 1974 

Among other revisions, this version added over 20 species, primarily Southeast Asian hardwoods, to Table 1.

C2.2 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.

C2.3 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 because 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.

C2.4 PS 1-07 Structural Plywood became effective February 26, 2007

This version revised several sections of the standard to better represent the production and trade specifications 
49

for the products. These included a change to the title of the standard, elimination 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. 
50

Appendix D (non-mandatory)

D1 RECOMMENDED THICKNESS LABELS 

Section 5.10.2 specifies thickness tolerances and Performance Categories for plywood grades. Section 7.3.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 thickness specification for that Performance Category. Table D1 

and Table D2 present recommended thickness labels.

TABLE D1

RECOMMENDED THICKNESS LABELING FOR UNSANDED, TOUCH SANDED AND OVERLAID PANELS

Performance

Category(b)

Thickness Requirements for Unsanded, 

Touch Sanded and Overlaid Grades(a)

Minimum Thickness

in (mm)

Maximum Thickness

in (mm)

Recommended

Thickness Label(c)

1/4 PERF CAT 0.219 (5.56) 0.281 (7.14) Thickness 0.225 in

11/32 PERF CAT 0.313 (7.94) 0.375 (9.53) Thickness 0.322 in

3/8 PERF CAT 0.344 (8.73) 0.406 (10.32) Thickness 0.354 in

7/16 PERF CAT 0.406 (10.32) 0.469 (11.91) Thickness 0.418 in

15/32 PERF CAT 0.438 (11.11) 0.500 (12.70) Thickness 0.451 in

1/2 PERF CAT 0.469 (11.91) 0.531 (13.49) Thickness 0.483 in

19/32 PERF CAT 0.563 (14.29) 0.625 (15.88) Thickness 0.578 in

5/8 PERF CAT 0.594 (15.08) 0.656 (16.67) Thickness 0.609 in

23/32 PERF CAT 0.688 (17.46) 0.750 (19.05) Thickness 0.703 in

3/4 PERF CAT 0.719 (18.26) 0.781 (19.84) Thickness 0.734 in

13/16 PERF CAT 0.781 (19.84) 0.844 (21.43) Thickness 0.788 in

7/8 PERF CAT 0.831 (21.11) 0.919 (23.34) Thickness 0.849 in

1 PERF CAT 0.950 (24.13) 1.050 (26.67) Thickness 0.970 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

(a) Thickness requirements for unsanded panels, 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 ± 5.0% 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.

(b) Acceptable abbreviations are PERF CAT, CAT or Category.

(c) The recommended thickness label for Performance Categories less than 9/16 is 3% above the minimum. The recommended thickness label for 

Performance Categories greater than or equal to 9/16 are the minimum values for sanded panels.
51

TABLE D2

RECOMMENDED THICKNESS LABELING FOR SANDED PANELS

Performance

Category(b)

Thickness Requirements for Sanded Panels(a)

Minimum Thickness

in (mm)

Maximum Thickness

in (mm)

Recommended

Thickness Label(c)

1/4 PERF CAT 0.234 (5.95) 0.266 (6.75) Thickness 0.234 in

11/32 PERF CAT 0.328 (8.33) 0.359 (9.13) Thickness 0.328 in

3/8 PERF CAT 0.359 (9.13) 0.391 (9.92) Thickness 0.359 in

7/16 PERF CAT 0.422 (10.72) 0.453 (11.51) Thickness 0.422 in

15/32 PERF CAT 0.453 (11.51) 0.484 (12.30) Thickness 0.453 in

1/2 PERF CAT 0.484 (12.30) 0.516 (13.10) Thickness 0.484 in

19/32 PERF CAT 0.578 (14.68) 0.609 (15.48) Thickness 0.578 in

5/8 PERF CAT 0.609 (15.48) 0.641 (16.27) Thickness 0.609 in

23/32 PERF CAT 0.703 (17.86) 0.734 (18.65) Thickness 0.703 in

3/4 PERF CAT 0.734 (18.65) 0.766 (19.45) Thickness 0.734 in

13/16 PERF CAT 0.788 (20.02) 0.837 (21.26) Thickness 0.788 in

7/8 PERF CAT 0.849 (21.56) 0.901 (22.89) Thickness 0.849 in

1 PERF CAT 0.970 (24.64) 1.030 (26.16) Thickness 0.970 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

(a) 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.

(b) Acceptable abbreviations are PERF CAT, CAT or Category.

(c) Recommended thickness labels for Performance Categories are based on the minimum permissible thickness for that category.

D2 REGULATIONS ON LABELING

See Appendix E for discussion of regulations dealing with labeling.
52

APPENDIX E – LABELING GUIDELINES BASED ON THE UNIFORM PACKAGING AND 

LABELING REGULATIONS OF NIST HANDBOOK 130 V2009 (non mandatory)

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 guidance on the requirements 

applicable to wood panels. 

E2 BACKGROUND

E2.1 The National Institute of Standards and Technology of the U.S. Department of Commerce (NIST) promotes 

the development of standards to be applied across industry and supports the publishing of NIST Handbook 

130, Uniform Laws and Regulations in the areas of legal metrology and engine 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 Of the weights and measures jurisdictions of the United States (including the 50 states, Washington DC, 

Puerto Rico and the Virgin Islands) with respect to the Uniform Packaging and Labeling Regulation, (i) 19 

have adopted the most current version of NIST Handbook 130, (ii) 29 have adopted a prior version of NIST 

Handbook 130, (iii) four have laws and regulations in place that are not based on NIST Handbook 130 and 

(iv) one has no specific laws or regulations in this regard.

E2.3 This appendix provides a summary of NIST Handbook 130 provisions relevant to wood panels, with 

specific references to sections of the 2009 version. This summary is not intended to be comprehensive, but 

is offered as guidance. For additional information, a complete copy of the most recent version of NIST 

Handbook 130 is available at http://ts.nist.gov/WeightsAndMeasures/Publications.

E3 SCOPE AND DEFINITIONS

E3.1 Except for packages intended for export, the Uniform Packaging and Labeling Regulation of NIST 

Handbook 130 applies to consumer and non-consumer packages.

E3.1.1 Consumer package

“[A] package that is customarily produced or distributed for sale through retail sales agencies or 

instrumentalities for consumption or use by individuals for the purposes of personal care or in the 

performance of services ordinarily rendered in or about the household or in connection with personal 

possessions.” (See Section 2.2 of the Uniform Packaging and Labeling Regulation).

E3.1.2 Non-consumer package

“Any package other than a consumer package, and particularly a package intended solely for industrial or 

institutional use or for wholesale distribution.” (See Section 2.3 of the Uniform Packaging and Labeling 

Regulation).

E3.2 The requirements of the Uniform Packaging and Labeling Regulation set forth in NIST Handbook 130 are 

to be set forth generally on labels and/or principal display panels.

E3.2.1 Label 

“Any written, printed, or graphic matter affixed to, applied to, attached to, blown into, formed, molded into, 

embossed on, or appearing upon or adjacent to a consumer commodity or a package containing any consumer 

commodity, for purposes of branding, identifying, or giving any information with respect to the commodity or 

to the contents of the package, except that an inspector’s tag or other nonpromotional matter affixed to or 

appearing upon a consumer commodity shall not be considered a label requiring the repetition of label 
53

information required by this regulation.” (See Section 2.5 of the Uniform Packaging and Labeling 

Regulation).

Note: For the purpose of structural wood panels, the “label” encompasses information that is attached to or 

affixed to the panel or to the panel bundle prior to shipping from the mill. At the retail level, the label may 

encompass information that is adjacent to the panels. 

E3.2.2 Principal display panel

“[t]hat part, or those parts, of a label that is, or are, so designed as to most likely be displayed, presented, 

shown, or examined under normal and customary conditions of display and purchase. Wherever a principal 

display panel appears more than once on a package, all requirements pertaining to the ‘principal display panel’ 

shall pertain to all such ‘principal display panels.” (See Section 2.7 of the Uniform Packaging and Labeling 

Regulation).

E4 DECLARATION OF IDENTITY AND RESPONSIBILITY

E4.1 The package of wood panels must be labeled with the product identity and with the panel producer. 

E4.2 Product identity

The name of the panel product should be included on the principal display panel for consumer packages and 

on the outside of the package for non-consumer packages. (See Sections 3.1 (consumer) and 4 (nonconsumer) of the Uniform Packaging and Labeling Regulation.) The product identity for consumer packages 

should be parallel to the base on which the package rests as it is designed to be displayed. (See Section 3.1.1 

of the Uniform Packaging and Labeling Regulation.)

E4.3 Product responsibility

The company name should be included on the label of the package. (See Section 5 of the Uniform Packaging 

and Labeling Regulation.) 

E4.3.1 The company identification on the label should include city, state and zip code of the company. (See 

Section 5 of the Uniform Packaging and Labeling Regulation.) 

E5 DECLARATION OF QUANTITY

E5.1 The following guidance on Declaration of Quantity is based on the requirements for “Consumer Packages.” 

Deviations based on “Non-Consumer Packages” are provided in [brackets].

E5.2 Quantity should be expressed in terms of count combined with appropriate declarations of the weight, 

measure and/or size of the individual units unless a declaration of count alone is fully informative but, if 

there exists a firmly established general consumer usage and trade custom with respect to the terms used in 

expressing a declaration of quantity of a particular commodity, such declaration of quantity may be 

expressed in its traditional terms if such traditional declaration gives accurate and adequate information as 

to the quantity of the commodity. (See Sections 6.4 and 6.4.1 of the Uniform Packaging and Labeling 

Regulation.) [There is no stated requirement regarding additional measurements other than count for nonconsumer packaging. In other words, count or established trade custom is the requirements for nonconsumer packages. (See Section 7.3 of the Uniform Packaging and Labeling Regulation)].

E5.3 General Rules

E5.3.1 The size quantity declaration must be expressed in metric system units (meter (m), centimeter (cm) or 

millimeter (mm)) and in inch-pound system units (yard (yd), foot (ft), inch (in)). (See Sections 6.1 (Note 

3), 6.5, 6.5.1, 6.7 and 6.7.1 of the Uniform Packaging and Labeling Regulation). [The same rules apply to 

non-consumer packages except that either or both the metric system units and the inch-pound system units 

may be used. (See Sections 7.1 (Note 6), 7.4, 7.4.1, 7.5 and 7.5.1 of the Uniform Packaging and Labeling 

Regulation.)]
54

X5.3.2 The size quantity should be expressed in terms of the largest whole unit. (See Section 6.2 of the 

Uniform Packaging and Labeling Regulation.) [The same rules apply to non-consumer packages. See Section 

7.2 of the Uniform Packaging and Labeling Regulation.]

• Remainders for the metric system units should be expressed as decimals. (See Section 6.2 of the Uniform 

Packaging and Labeling Regulation.) [The same rules apply to non-consumer packages. See Section 7.2 of 

the Uniform Packaging and Labeling Regulation.]

• If less than 1 m, then length measure is expressed in terms of cm or mm. See Section 6.6.1(a) of the 

Uniform Packaging and Labeling Regulation. [No comparable rules for non-consumer.]

• If greater than 1 m, then length is expressed in m with decimal fractions. See Section 6.6.2(a) of the 

Uniform Packaging and Labeling Regulation. [No comparable rules for non-consumer.]

• Metric system measurements should go 3 digits out except where the quantity is below 100 mm or cm, 

where it may be shown in 2 digits. In any case, any final zero appearing to the right of the decimal point 

need not be shown. See Section 6.5(g) of the Uniform Packaging and Labeling Regulation. [Same rules 

for non-consumer packages. See Section 7.4 of the Uniform Packaging and Labeling Regulation.]

• Remainders for the inch-pound system units should be expressed in common fractions or decimal fractions 

of the largest whole unit or in the next smaller whole unit with any further remainder in terms of common 

or decimal fractions of the smallest unit present. See Section 6.2 of the Uniform Packaging and Labeling 

Regulation. [Same rules for non-consumer packages. See Section 7.2 of the Uniform Packaging and 

Labeling Regulation.]

• If less than 1 ft, then length is expressed in terms of in. See Section 6.8.1(a) of the Uniform Packaging and 

Labeling Regulation. [No comparable rules for non-consumer.]

• If greater than 1 ft, then length is expressed in terms of the largest whole unit (yd or ft) with any remainder 

expressed in inches and fractions of the inch or in fractions of the ft or yd, except that it shall be optional 

to include a statement of length in terms of inches. See Section 6.8.2(a) of the Uniform Packaging and 

Labeling Regulation. [No comparable rules for non-consumer.]

• A common fraction is reduced to its lowest term. A decimal fraction shall not be carried out more than 3 

decimal places. See Section 6.11 of the Uniform Packaging and Labeling Regulation. [No comparable 

rules for non-consumer.]

E5.3.2 Rules specific to bi-dimensional commodities [No comparable rules for non-consumer.]

• Must be expressed in both metric and inch-pound units. No declaration of area is required for commodities 

for which the length and width measurements are critical in terms of end use if such commodities clearly 

present the length and width measurements on the label. (See Section 6.9 of the Uniform Packaging and 

Labeling Regulation.) 

• If the area is 37.1 dm2 (4 ft2

) or more, in terms of the length and width, in terms of the largest whole unit, 

provided bi-dimensional commodities with a width of 10 cm (4 in) or less, the inch-pound statement of 

width shall be expressed in terms of linear inches and fractions thereof, and length shall be expressed in 

the largest whole unit (yard or foot) with any remainder in terms of fractions of the yard or foot, except 

that it shall be optional to express the length in the largest whole unit followed by a statement of length in 

inches or to express the length in inches followed by a statement of length in the largest whole unit. An 

inch-pound dimension of less than 2 ft may be stated in inches. (See Section 6.9(c) of the Uniform 

Packaging and Labeling Regulation.)

Examples: 5 cm x 9.14 m (2 in x 10 yd), or 5 cm x 9.14 m (2 in x 10 yd) (360 in), or 5 cm x 9.14 m (2 in x 

360 in) (10 yd),

E5.3.3 The required quantity declaration may be supplemented by one or more declarations of weight, measure, or 
55

count, such declaration appearing other than on a principal display panel. Such supplemental statement of 

quantity of contents shall not include any term qualifying a unit of weight, measure, or count that tends to 

exaggerate the amount of commodity contained in the package (e.g., “giant” quart, “larger” liter, “full” 

gallon, “when packed,” “minimum,” or words of similar import). (See Section 6.12 of the Uniform 

Packaging and Labeling Regulation.) [No such provision applies to non-consumer packages.]

E5.3.4 In no event, may any declaration of quantity be qualified by the addition of the words “when packed,” 

“minimum,” or “not less than” or any words of similar import (e.g., “approximately”), nor shall any unit of 

weight, measure, or count be qualified by any term (such as “jumbo,” “giant,” “full,” or the like) that tends 

to exaggerate the amount of commodity. (See Section 6.14 of the Uniform Packaging and Labeling 

Regulation.) [No such provision applies to non-consumer packages.]

E6 PROMINENCE AND PLACEMENT

E6.1 General

All information required to appear on a consumer package shall appear thereon in the English language and 

shall be prominent, definite, plain, and conspicuous as to size and style of letters and numbers and as to color 

of letters and numbers in contrast to color of background. Any required information that is either in hand 

lettering or hand script shall be entirely clear and equal to printing in legibility. (See Section 8.11 of the 

Uniform Packaging and Labeling Regulation.) [All information required to appear on a non-consumer 

package shall be definitely and clearly stated thereon in the English language. Any required information that is 

either in hand lettering or hand script shall be entirely clear and equal to printing in legibility. (See Section 9.1 

of the Uniform Packaging and Labeling Regulation.)] 

E6.2 Location

The declaration or declarations of quantity of the contents of a package shall appear in the bottom 30 percent 

of the principal display panel or panels. (See Section 8.1.1 of the Uniform Packaging and Labeling 

Regulation.) 

E6.3 Style of type and lettering

The declaration or declarations of quantity shall be in such a style of type or lettering as to be boldly, clearly, 

and conspicuously presented with respect to other type, lettering, or graphic material on the package. (See 

Section 8.1.2 of the Uniform Packaging and Labeling Regulation.) 

E6.4 Color contrast

The declaration or declarations of quantity shall be in a color that contrasts conspicuously with its 

background. (See Section 8.1.3 of the Uniform Packaging and Labeling Regulation.) 

E6.5 Free area

The area surrounding the quantity declaration shall be free of printed information: (a) above and below, by a 

space equal to at least the height of the lettering in the declaration, and (b) to the left and right, by a space 

equal to twice the width of the letter “N” of the style and size of type used in the declaration. (See Section 

8.1.4 of the Uniform Packaging and Labeling Regulation.)

E6.6 Parallel quantity declaration

The quantity declaration shall be presented in such a manner as to be generally parallel to the declaration of 

identity and to the base on which the package rests as it is designed to be displayed. (See Section 8.1.5 of the 

Uniform Packaging and Labeling Regulation.) 

E6.7 Height and proportion of numbers and letters

A Table 1 sets forth minimum heights of numbers and letters based upon the area of the principal display 

panel. The minimum height of numbers and letters for an area of 400 in2 or greater is 1/2 in The height of each 

number of a common fraction must meet 1⁄2 the minimum height standard. No number or letter may be more 

than 3X as high as it is wide. (See Sections 8.2.1 and 8.2.2 of the Uniform Packaging and Labeling 
56

Regulation.)
57

Appendix F – Wood Structural Panels as Green Building Materials (non-mandatory)

F1 OVERVIEW

There is a growing emphasis in North America to recognize the importance of protecting the environment. 

This is commonly referred to as being “green” and has resulted in a need to increase the awareness of wood as 

an environmentally friendly or green building material. Wood structural panels, as members of the broader 

wood products “family,” have numerous green attributes and are considered to be environmentally friendly.

F2 GREEN ATTRIBUTES OF WOOD

Solar energy: powered by solar energy collected by the tree’s leaves, carbon dioxide extracted from the 

atmosphere is combined with water and nutrients absorbed through the tree’s roots to form a composite of 

hollow cellulose fibers bound in a matrix of lignin by photosynthesis. 

Renewable: as mature trees are harvested they are replaced by younger trees and the wood resource is 

renewed. This natural renewal can continue indefinitely as long as there is an ample source of water, carbon 

dioxide and sunlight.

Sustainable: through responsible forest management the forest resource can be sustained at levels far 

exceeding their harvesting. Responsible forest management is the key to minimizing adverse environmental 

impacts associated with the extraction of timber from forests. (Society of American Foresters (SAF), 

www.safnet.org)

Embodied Energy: studies have shown that wood has low embodied energy compared to most other 

structural materials. The energy consumed in managing forests, harvesting trees, milling timber into various 

end products and transporting the finished wood products to job sites is relatively small. (CORRIM, 

www.corrim.org)

Carbon Sequestration: scientific evidence suggests that increasing levels of carbon dioxide in the atmosphere 

is one cause of accelerated climate change. Trees absorb CO2 from the atmosphere through photosynthesis, 

storing it as carbon in their organic matter and releasing the remaining oxygen back into the atmosphere. On 

average a typical tree absorbs, through photosynthesis, the equivalent of 56 pounds of carbon dioxide for 

every cubic foot of growth, while producing the equivalent of 45 pounds of oxygen. (Adapted from 

Edinburgh Centre for Carbon Management.)

Life Cycle Assessment: Life Cycle Assessment (LCA) is important because it quantifies how a building 

product or system affects the environment during each phase of its life: extraction, production, installation, use 

and disposal or re-use. (International Organization for Standardization, ISO 14040, 14042 and 14043) 

Several CORRIM reports address many of these attributes and provide extensive scientific data supporting the 

relatively minimal impact that producing wood products has on the environment.

F3 SUSTAINABLE FOREST MANAGEMENT PROGRAMS

There are four generally recognized sustainable forest management programs with the approximate amount of 

acres covered in North America for each shown in parentheses: 

The Forest Stewardship Council (FSC), (82 million acres) www.fscus.org

The Sustainable Forestry Initiative® (SFI), (143 million acres) www.sfiprogram.org

The Canadian Standards Association (CAN/CSA-Z809), (192 million acres) www.csainternational.org/product_areas/forest_products_marking 

The American Tree Farm System (ATFS) (27 million acres) www.treefarmsystem.org 

All of these sustainable forest management programs are intended to ensure that forestry is practiced in an 
58

environmentally responsible, socially beneficial, and economically viable way.

The CSA, FSC, and SFI programs currently have criteria for on-product labeling of certified wood products. 

Each has a system for manufacturing facilities to track the percentage of fiber that originates from certified 

forests.

F4 MAJOR GREEN BUILDING RATING SYSTEMS

To account for and quantify the effects of building construction on the environment, three major green 

building rating systems have evolved. These are the:

Green Building Initiative (GBI) Green Globes: this is a rating system for new commercial building 

construction and has been approved as an ANSI standard. www.thegbi.org

Green Building Standard: this is a program to rate residential construction and has been approved as an ANSI 

standard with ICC and NAHB jointly sponsoring the standard. www.nahbgreen.org

USGBC LEEDTM which has four distinct rating programs including, LEEDTM for New Construction; LEEDTM 

for Existing Buildings (Remodeling); LEEDTM for Commercial Interiors and LEEDTM for Homes. 

www.usgbc.org/LEED

Each of these programs considers the impact of various environmental considerations and assigns points 

accordingly to achieve a green rating threshold. 

While there are similarities in these rating systems there are also differences that can impact the wood 

products industry. The GBI Green Globes and NAHB Green Building Standard both award points for wood 

being a renewable resource, for wood products harvested from any of the four forest certification programs 

and for using LCA to compare building materials and systems. The USGBC LEEDTM program only awards 

points for products that are renewed within a 10 year harvest cycle thus excluding most structural wood 

products, only awards points for wood products manufactured from FSC certified forests and does not 

consider LCA as a science based evaluation tool.
59

Appendix G – Formaldehyde (NON MANDATORY)

G1 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 related to elevated levels in indoor air can be found at:

www.epa.gov/iaq/formalde.html.

G2 FORMALDEHYDE REGULATIONS 

G2.1 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. 

G2.2 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 as follows (emphasis added):

(b) Product certification and continuing qualification. All plywood and particleboard materials to be installed 

in manufactured homes which are bonded with a resin system or coated with a surface finish containing 

formaldehyde, other than an exclusively phenol-formaldehyde resin system or finish, shall be certified by 

a nationally recognized testing laboratory as complying with paragraph (a) of this section.

PS 1 Structural Plywood is made predominantly with phenol-formaldehyde adhesives. When made as such, it 

is exempt from the HUD requirements.

G2.3 California Air Resources Board (CARB) Air Toxic Control Measure for Composite 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 (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 Products” (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.

G3 FORMALDEHYDE EMISSION FROM PS 1 PLYWOOD

G3.1 Information on formaldehyde emission from PS 1 plywood is available from APA in report SPE-1040, 

Structural Wood Panels and Formaldehyde.