Voluntary Product Standard PS 2-18 

Performance Standard for Wood 

Structural Panels 

March 2019 

U.S. Department of Commerce 

Wilbur L. Ross, Jr., Secretary 

National Institute of Standards and Technology 

Walter Copan, NIST Director and Undersecretary of Commerce for 

Standards and Technology 
Certain commercial entities, equipment, or materials may be identified in this 

document in order to describe an experimental procedure or concept adequately. 

Such identification is not intended to imply recommendation or endorsement by the 

National Institute of Standards and Technology, nor is it intended to imply that the 

entities, materials, or equipment are necessarily the best available for the purpose. 

Additional information concerning the development and use of this standard can 

obtained by contacting the Standards Coordination Office, National Institute of 

Standards and Technology, 100 Bureau Drive, MS 2100, Gaithersburg, MD 20899-

2100 or visiting Standards.Gov. 

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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. 

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 interested groups, 

their provisions are likely to become established as trade customs. 

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

recognition and actual use. 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. 

Abstract 

This standard covers performance requirements, adhesive bond performance, panel construction and 

workmanship, dimensions and tolerances, marking, and moisture content of wood structural panels. Wood 

structural panels include structural plywood, oriented strand board (OSB), other mat-formed panels, and 

composite panels. The standard classifies panels by bond classification, span rating, performance 

category, and grade. It provides test methods, a glossary of trade terms and definitions, and a quality 

certification program whereby agencies inspect, sample, and test products for conformance to this 

standard. Information regarding industry practices for reinspection, a qualification flowchart, history of the 

standard, labeling, and environmental attributes are provided in nonmandatory appendices. 

Keywords 

Adhesive bond classification; certification; construction sheathing; wood structural panel; dimensions and 

tolerances; marking; moisture content; oriented strand board; OSB; panel construction; performance 

requirements; span rating; mat-formed panel; performance category; structural plywood; test methods; 

voluntary standard; wood-based panels. 

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CONTENTS 

SECTION PAGE 

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

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

3. REFERENCE PUBLICATIONS ........................................................................................................4 

4. CLASSIFICATION ............................................................................................................................4 

5. REQUIREMENTS..............................................................................................................................5 

6. QUALIFICATION TESTING AND MILL SPECIFICATION ............................................................13 

7. TEST METHODS ............................................................................................................................19 

8. TRADEMARKING AND CERTIFICATION .....................................................................................35 

9. EFFECTIVE DATE AND IDENTIFICATION ...................................................................................36 

10. STANDING COMMITTEE ...............................................................................................................37 

APPENDIX A. REINSPECTION PRACTICES ..........................................................................................38 

APPENDIX B. QUALIFICATION FLOWCHART........................................................................................41 

APPENDIX C. HISTORY OF CHANGES ..................................................................................................42 

APPENDIX D. RECOMMENDED THICKNESS LABELS .........................................................................45 

APPENDIX E. LABELING GUIDELINES ..................................................................................................46 

APPENDIX F. FORMALDEHYDE .............................................................................................................47 

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VOLUNTARY PRODUCT STANDARD PS 2-18 

PERFORMANCE STANDARD FOR WOOD STRUCTURAL PANELS 

Initially Approved as PS 2-92 August 27, 1992 (See Appendix C) 

This Revision Approved March 30, 2019 

(This standard, initiated by APA – The Engineered Wood Association, has been developed under the 

Procedures for the Development of Voluntary Product Standards for the U.S. Department of Commerce.) 

1 SCOPE 

1.1 This Voluntary Product Standard primarily establishes structural criteria for assessing the 

acceptability of wood structural panels for construction sheathing and single floor applications 

and provides a basis for common understanding among the producers, distributors, and the users 

of these products. The standard does not address non-structural issues such as resistance to 

biological agents. Applications other than construction sheathing and single floor may require 

additional engineering considerations that are not covered by this document. 

1.2 This standard covers the performance requirements, adhesive bond performance, panel 

construction and workmanship, dimensions and tolerances, marking, and moisture content of 

wood structural panels. 

1.3 This standard includes 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 for qualification under this standard. Information regarding industry 

practices for reinspection is provided in Appendix A. A flowchart depicting the qualification 

process is provided in Appendix B. Information on the maintenance, history, and current edition 

of the standard is provided in Appendix C. Recommended thickness labeling is provided in 

Appendix D. Information on labeling regulations from NIST Handbook 130 and Handbook 133 

are provided in Appendix E. Information on formaldehyde emissions is provided in Appendix F. 

1.4 This standard incorporates the International System of Units (SI) as well as customary units of 

measurement. The values given in SI units are the standard. The values given in parentheses 

are for information only. In conversion of 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, exact conversions to SI units 

are made. For nominal customary units, actual dimensions in SI units are given. 

1.5 Advisory notes in this standard shall not be considered mandatory. 

2 TERMINOLOGY 

2.1 Composite panel 

Any panel containing a combination of veneer and other wood-based material. 

2.2 Delamination 

For plywood or composite panels, delamination is a visible separation between plies or layers 

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. 

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2.3 Exposure 1 

A bond classification for structural panels suitable for uses not permanently exposed to the 

weather. Panels classified as Exposure 1 are intended to resist the effects of moisture on 

structural performance due to active construction. 

2.4 Exterior 

A bond classification for structural plywood suitable for repeated wetting and redrying or longterm exposure to weather or other conditions of similar severity. 

2.5 Furnish 

Wood-based material, such as flakes or strands, including applied resin, wax and other additives, 

as the primary constituent of mat-formed panels. 

2.6 Mat-formed panel 

Any wood-based panel that does not contain veneer, consistent with the definition of wood 

structural panels. 

2.7 Mill specification 

A document that defines product characteristics that affect (or may affect) the classification 

(Section 4) and/or the performance of the product relative to the requirements of this standard. 

The mill specification is unique to each qualified product of a given grade. The specification is 

used in the mill quality program as audited under third-party inspection. 

2.8 Moisture resistant adhesive 

Adhesive capable of bonding structural panels in a manner to satisfy the bond classification 

requirements of this standard. 

2.9 OSB 

An abbreviation for oriented strand board, a multi-layered board made from strands of wood, 

together with a binder, by the application of heat and pressure, with the strands in the external 

layers primarily oriented along the panel’s strength axis. 

2.10 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 5.2.1.2, abbreviations 

PERF CAT, CAT, or Category are permitted. 

Advisory Note: The IBC and IRC specify a minimum 3/8 Performance Category for wall 

sheathing. 

2.11 Performance standard 

A standard for trademarked products based on performance. Performance is measured by tests 

that approximate intended end-use conditions. 

2.12 Plywood 

A conventional all-veneer panel with alternate layers of veneer running perpendicular to one 

another. For all-veneer panels, a layer is a single veneer ply or two or more adjacent plies with 

grain direction parallel. 

2.13 PS 1 

Voluntary Product Standard PS 1-09 “Structural Plywood.” Later issues of Voluntary Product

Standard PS 1 shall be permitted providing the requirements are applicable and consistent with 

the issue designated. 

2.14 Reference value 

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

property. 

2.15 Sample 

A set of specimens analyzed together. 

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2.16 Sample average 

The average test value, obtained by summing the observations and dividing by the number of 

tests. 

2.17 Sample standard deviation 

A measure of test variation. Calculated as: 

1 - n

n

)x(

x

 S

2

2 

−

=

where: 

S = sample standard deviation 

x = test observation 

n = number of observations. 

2.18 Shop-cutting panel 

A panel that has been rejected as not conforming to a panel grade because of deficiencies, other 

than adhesive bond quality, which prevent it from meeting the requirements of this standard. 

Such a panel shall be identified with a separate mark as specified in Section 8.3.1. 

2.19 Sized for Spacing 

An optional panel mark indicating that the panel manufacturer has sized the panel to allow for 

industry recommended panel installation spacing. 

2.20 Specimen 

The individual test piece. 

2.21 Strength axis 

The axis parallel to the face and back orientation of the flakes or the grain (veneer), which is 

generally the long panel direction, unless otherwise marked. 

2.22 Wood Structural Panel 

A panel product composed primarily of wood that, in its commodity end use, is essentially 

dependent upon certain mechanical and/or physical properties for successful end-use 

performance. Such a product carrying the trademark of a qualified inspection and testing agency 

shall conform to performance requirements of one or more of the end-uses contained herein and, 

where applicable, approved by one or more national regulatory agencies for single-layer floors 

or for sheathing with respect to roofs, subfloors, and walls. Such a panel shall be identified in a 

manner clearly conveying its intended end use. The International Building Code and International 

Residential Code (see Section 3.2) use the term “wood structural panel” to refer to panels that

comply with PS 2 and PS 1. 

2.23 Test exposure condition 

The exposure condition to which a panel is subjected prior to test. The following terms apply to 

the panel moisture conditioning used during performance testing: 

Dry test condition – Panel moisture content is within +/- 3% of the as-shipped moisture 

content. 

Wet test condition – Panel moisture content upon three days of one-sided wetting. 

Wet/redry test condition – After three days of one-sided wetting, the panel is dried until 

the panel moisture content is within +/- 3% of the as-shipped moisture content. 

As-shipped moisture content – The expected panel moisture content when the panels 

are shipped from the panel manufacturer’s production facility.

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3 REFERENCE PUBLICATIONS 

3.1 ASTM standards1 

• E 72-15 Standard Test Methods for Conducting Strength Tests of Panels for Building 

Construction 

• E 661-03 Standard Test Method for Performance of Wood and Wood-Based Floor and Roof 

Sheathing Under Concentrated Static and Impact Loads 

• D 1037-12 Standard Test Methods for Evaluating Properties of Wood-Base Fiber and 

Particle Panel Materials 

• D 1761-12 Standard Test Methods for Mechanical Fasteners in Wood 

• D 3043-17 Standard Test Methods for Structural Panels in Flexure 

• D 4442-16 Standard Test Methods for Direct Moisture Content Measurement of Wood and 

Wood-Base Materials 

• D 2915-17 Standard Practice for Evaluating Allowable Properties for Grades of Structural 

Lumber 

3.2 Other documents 

• Voluntary Product Standard PS 1-09 – Structural Plywood2 

• CSA-O325.0-2016 Construction Sheathing3 

• 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. 

• ISO/IEC 17020, Conformity Assessment – Requirements for the Operation of Various 

Types of Bodies Performing Inspection 

• ISO/IEC 17025, General Requirements for the Competence of Testing and Calibration 

Laboratories 

• ISO/IEC 17065, Conformity Assessment – Requirements for bodies certifying products, 

processes and services 

4 CLASSIFICATION 

4.1 General 

The wood structural panels covered by this standard are specified by bond classification, span 

rating, performance category, and grade. 

4.1.1 Bond classification 

The bond classification is related to the moisture resistance of the glue bond under intended enduse conditions and does not relate to the physical (erosion, ultraviolet, etc.) or biological (mold, 

fungal decay, insect, etc.) resistance of the panel. This standard covers structural panels with 

Exterior (see section 2.4) and Exposure 1 (see section 2.3) bond classifications. 

4.1.2 Grade 

This standard covers grades of wood structural panels designed and manufactured for 

Sheathing, Structural I Sheathing, Single Floor and Structural I Single Floor. 

4.1.2.1 Sheathing 

A wood structural panel intended for use in construction applications as covering material for 

roofs, subfloors, and walls when fastened to supports spaced in accordance with the span rating. 

1 Copies of these publications are available from ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, 

PA 19428-2959, www.astm.org. 

2 Copies of the current standard are available from the Superintendent of Documents, U.S. Government Printing Office, Washington, 

DC 20402 and the Standards Services Division, National Institute of Standards and Technology, 100 Bureau Drive, Stop 2100, 

Gaithersburg, MD 20899-2100, web site: standards.gov. 

3 Copies of this publication are available from the Canadian Standards Association, 5060 Spectrum Way, Mississauga, ON, Canada 

L4W 5N6, www.csa.ca. 

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4.1.2.2 Structural I Sheathing 

A wood structural panel consistent with that described in Section 4.1.2.1, except that Structural I 

panels meet additional requirements in this standard for cross-panel strength and stiffness and 

for racking load performance. 

4.1.2.3 Single Floor 

A wood structural panel intended for use as combination subfloor and underlayment when 

fastened to supports spaced in accordance with the span rating. 

4.1.2.4 Structural I Single Floor 

A wood structural panel consistent with that described in Section 4.1.2.3 that also meets the 

additional requirements in this standard for cross-panel strength and stiffness and racking load 

performance. 

4.1.3 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, wall, subfloor, and single floor. As a matter of convention, 

spans are typically specified singly for wall (Wall 24) and 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. 

4.1.4 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 5.2.1.2, abbreviations 

PERF CAT, CAT or Category are permitted. 

ADVISORY NOTE: The IRC and IBC specify a minimum 3/8 Performance Category for wall 

sheathing. 

5 REQUIREMENTS 

5.1 General 

Wood structural panels represented as conforming to this standard shall meet all applicable 

requirements set forth herein. 

5.2 General Requirements 

5.2.1 Dimensional tolerances and squareness of panels 

5.2.1.1 Size 

A length and a width measurement shall be made at a location 50 mm to 75 mm (2 in. to 3 in.) 

from the panel edge. A tolerance of plus or minus 1.6 mm (1/16 in.) shall be allowed on 

manufacturer’s stated length and/or width. 

5.2.1.2 Performance Category and Thickness Tolerance 

A tolerance of plus or minus 0.8 mm (for metric basis) or 1/32 in. (for English basis) shall be 

allowed on the trademark-specified Performance Category of 20.5 mm (13/16 in.) and less, and 

+/- 5% of the trademark-specified Performance Category for panels thicker than 20.5 mm (13/16 

in.), unless a closer tolerance is determined through qualification testing. 

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) with the anvil center at 19 to 25 mm 

(3/4 to 1 in.) from the panel edge. The location of the measurements shall be representative of 

panel thickness mid-length, +/- 50 mm (2 in.) along each edge of the panel and the average of 

the four measurements shall be taken as the thickness of that panel. If a measurement point 

contains a permissible grade characteristic that affects panel thickness, then the measurement 

point shall be shifted from that point. 

The panel thickness shall conform to Table 1. 

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TABLE 1. PANEL THICKNESS REQUIREMENTS 

Thickness Requirements1 

PERFORMANCE 

CATEGORY2 

Minimum Thickness, 

mm (in.) 

Maximum Thickness, 

mm (in.) 

1/4 PERF CAT 5.56 (0.219) 7.14 (0.281) 

5/16 PERF CAT 7.14 (0.281) 8.73 (0.344) 

11/32 PERF CAT 7.94 (0.313) 9.53 (0.375) 

3/8 PERF CAT 8.73 (0.344) 10.32 (0.406) 

7/16 PERF CAT 10.32 (0.406) 11.91 (0.469) 

15/32 PERF CAT 11.11 (0.438) 12.70 (0.500) 

1/2 PERF CAT 11.91 (0.469) 13.49 (0.531) 

9/16 PERF CAT 13.49 (0.531) 15.08 (0.594) 

19/32 PERF CAT 14.29 (0.563) 15.88 (0.625) 

5/8 PERF CAT 15.08 (0.594) 16.67 (0.656) 

23/32 PERF CAT 17.46 (0.688) 19.05 (0.750) 

3/4 PERF CAT 18.26 (0.719) 19.84 (0.781) 

13/16 PERF CAT 19.84 (0.781) 21.43 (0.844) 

7/8 PERF CAT 21.11 (0.831) 23.34 (0.919) 

1 PERF CAT 24.13 (0.950) 26.67 (1.050) 

1-1/8 PERF CAT 27.15 (1.069) 30.00 (1.181) 

1-1/4 PERF CAT 30.16 (1.188) 33.34 (1.313) 

1Thickness requirements 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. 

2 For labeling purposes, abbreviation of “Performance Category” by PERF CAT, CAT or Category is permitted.

Performance Categories for other thicknesses are permitted provided the product complies with Section 5.2.1.2. 

5.2.1.3 Squareness and straightness 

Panels shall be square within 1.3 mm per lineal meter (1/64 in. per lineal foot) of the longest edge 

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. 

5.2.2 Wood materials 

5.2.2.1 Veneer 

Any wood veneer used as a component of a panel shall be in accordance with the applicable 

veneer grade and workmanship requirements of Voluntary Product Standard PS 1. 

ADVISORY NOTE: Canadian Standard CAN/CSA-O325.0, which is the Canadian counterpart to 

PS 2, limits maximum size of knots and knotholes to 76 mm (3 in.) as measured across the grain. 

5.2.2.2 Other material 

Other materials used in panel manufacture shall include particles or fiber produced by breaking 

down solid wood. 

5.2.3 Design and construction 

Panels qualifying for a span rating are identified in three classes: plywood panels, composite 

panels, or mat-formed panels. See Section 2 for definitions of terms. Panels shall qualify on an 

individual panel construction basis for the grade and span rating upon demonstrated conformance to the appropriate requirements of Section 5.3. 

5.3 Performance requirements 

Wood structural panels to be trademarked in accordance with this standard shall pass 

performance criteria established in three areas: structural performance, physical properties, and 

adhesive bond performance. Performance requirements listed in Sections 5.3.1, 5.3.2, and 5.3.3 

are for all grades of wood structural panels except where noted otherwise. 

5.3.1 Structural performance 

Panels shall meet the performance requirements of Sections 5.3.1.1 through 5.3.1.4 when tested 

for each structural condition in accordance with the referenced test procedure. Section 6 details 

specimen requirements and additional test set procedures. 

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5.3.1.1 Concentrated loads 

Panels shall be tested according to the procedures of Section 7.1 for concentrated static and 

impact loads. Panels shall conform to the criteria of Table 2 for the grade and span shown on 

the trademark. 

Panels to be identified as Structural I Sheathing and with a Performance Category of 7/16 or 

thicker shall also be tested according to the procedures of Section 7.1, with the framing members 

parallel to the strength axis direction, except the load shall be applied at panel mid-length. 

Minimum test panel size shall be 1,220 mm x 2,440 mm (48 in. x 96 in.). The framing shall be 

spaced 610 mm (24 in.) on center (o.c.). The panel ends shall not be supported by framing. 

Panels shall conform to the criteria of Table 2 for Roof - 24. See Section 6.2.4.2 for additional 

testing requirements associated with knots and knotholes. 

5.3.1.2 Uniform loads 

Panels shall be tested according to the procedures of Section 7.2 for uniform loads. Panels shall 

conform to the criteria of Table 3 for the grade and span shown on the trademark. 

Panels to be identified as Structural I Sheathing and Structural I Single Floor shall also be tested 

according to procedures of Section 7.2 with the framing members parallel to the strength axis 

direction. Minimum test panel size shall be 1,220 mm x 1,220 mm (48 in. x 48 in.). The framing 

shall be spaced 610 mm (24 in.) o.c. The panel ends shall not be supported by framing. Panels 

shall conform to the criteria of Table 4 for the grade and span rating shown on the trademark. 

5.3.1.3 Wall racking 

Sheathing panels that are rated for wall span 16 or 24 and for roof span 16, 20, or 24 shall be 

tested according to the procedures of Section 7.3 for wall racking. Panels shall conform to the 

criteria of Table 5 for the Performance Category shown on the trademark. 

Panels to be identified as Structural I Sheathing and Structural I Single Floor shall meet the 

Structural I requirements of Table 5 for the Performance Category shown on the trademark, when 

tested according to the procedures of Section 7.3. 

5.3.1.4 Fastener holding 

Panels shall be tested according to the procedures of Section 7.4 for fastener holding under 

lateral and withdrawal loads. Panels shall conform to the criteria of Table 6 for the grade and 

Performance Category shown on the trademark. 

5.3.2 Physical properties 

Panels shall meet the performance requirements of Section 5.3.2.1 when tested in accordance 

with the referenced test method. Section 6.2.3 details specimen requirements and additional test 

set procedures. 

5.3.2.1 Dimensional Stability 

Panels shall be tested and meet requirements of one of the sections below: 

a. Exposure to 50% (+/-5%) relative humidity; 21°C +/-6°C (70°F +/-10°F) and vacuumpressure soak – Panels shall be tested along and across the strength axis according to the 

procedures of Section 7.8 for linear expansion from 50% relative humidity to vacuumpressure soak. The average linear expansion shall be no more than 0.50% as measured 

according to the test method. 

b. One-sided wetting and relative humidity – Panels shall be tested according to the 

procedures of Section 7.9 for linear expansion as measured by one-sided wetting and 

Section 7.10 for linear expansion as measured by relative humidity exposures. The free 

panel linear expansion shall be no more than 0.30% along the panel strength axis and 0.35% 

across the panel strength axis. 

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Table 2. Concentrated static and impact test performance criteria for panels tested according to 

Section 7.1. (See Section 6.2.2.1 for pass/fail criteria) 

End Use –

Span Rating 

Test 

Exposure 

Conditions(a) 

Performance Criteria 

Ultimate Load Deflection 

Under 0.89 kN (200 lbf) 

Static Load 

Following 

Impact(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. Wet 

conditioning shall be exposure to three days of continuous wetting, then tested wet. Dry shall be within 

+/- 3% 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 rating designation is intended for end-use spans of 19.2 inch. 

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Table 3. Uniform load performance criteria for panels tested according to Section 7.2. (See 

Section 6.2.2.2 for pass/fail criteria) 

End Use -

Span Rating 

Test 

Exposure 

Conditions(b) 

Performance Criteria 

Average 

Deflection 

Under Load 

Ultimate 

Uniform Load 

kPa lbf/ft2 

Wall - 16(c) Dry 6.8 mm at 1.20 kPa (0.267 in. at 25 lbf/ft2) 3.6 75 

Wall - 24(c) Dry 10.2 mm at 1.20 kPa (0.400 in. at 25 lbf/ft2) 3.6 75 

Roof - 16(a) Dry 1.7 mm at 1.68 kPa (0.067 in. at 35 lbf/ft2) 7.2 150 

Roof - 20(a)(d) Dry 2.0 mm at 1.68 kPa (0.080 in. at 35 lbf/ft2) 7.2 150 

Roof - 24(a) Dry 2.5 mm at 1.68 kPa (0.100 in. at 35 lbf/ft2) 7.2 150 

Roof - 32 Dry 3.4 mm at 1.68 kPa (0.133 in. at 35 lbf/ft2) 7.2 150 

Roof - 40 Dry 4.2 mm at 1.68 kPa (0.167 in. at 35 lbf/ft2) 7.2 150 

Roof - 48 Dry 5.1 mm at 1.68 kPa (0.200 in. at 35 lbf/ft2) 7.2 150 

Roof - 54 Dry 5.7 mm at 1.68 kPa (0.225 in. at 35 lbf/ft2) 7.2 150 

Roof - 60 Dry 6.4 mm at 1.68 kPa (0.250 in. at 35 lbf/ft2) 7.2 150 

Subfloor - 16 Dry 

Wet/Redry 

1.1 mm at 4.79 kPa (0.044 in. at 100 lbf/ft2) 15.8 330 

Subfloor - 20(d) Dry 

Wet/Redry 

1.3 mm at 4.79 kPa (0.053 in. at 100 lbf/ft2) 15.8 330 

Subfloor - 24 Dry 

Wet/Redry 

1.7 mm at 4.79 kPa (0.067 in. at 100 lbf/ft2) 15.8 330 

Subfloor - 32 Dry 

Wet/Redry 

2.2 mm at 4.79 kPa (0.088 in. at 100 lbf/ft2) 15.8 330 

Subfloor - 48 Dry 

Wet/Redry 

3.4 mm at 3.83 kPa (0.133 in. at 80 lbf/ft2) 10.8 225 

Single Floor - 16 Dry 

Wet/Redry 

1.1 mm at 4.79 kPa (0.044 in. at 100 lbf/ft2) 15.8 330 

Single Floor - 20(d) 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) Panels with Roof - 16 and Roof - 20 rating shall also meet performance requirements for Wall - 16 

rating. Panels with Roof - 24 rating shall also meet requirements for Wall - 24 rating. (b) Wet/Redry shall be exposure to three days of continuous wetting, followed by testing dry. Dry shall be 

within +/- 3% of the as-shipped moisture content. 

(c) The panel strength axis shall be placed along the supports for testing, unless otherwise specified. (d) The “20“ span rating designation is intended for end-use spans of 19.2 inch. 

Table 4. Uniform load performance criteria for Structural I Sheathing and Single Floor panels tested 

according to Section 7.2. (Also see Section 5.3.1.2 and Section 6.2.2.2 for pass/fail criteria) 

Performance Category and 

Span Rating 

Test 

Exposure 

Conditions(a) 

Performance Criteria 

Average Deflection Under Load 

Ultimate 

Uniform Load 

kPa lbf/ft2 

Structural I Sheathing 

7/16 Category 24/16 Dry 2.5 mm at 0.96 kPa (0.100 in. at 20 lbf/ft2) 4.3 90 

15/32 Category 32/16 Dry 2.5 mm at 1.68 kPa (0.100 in. at 35 lbf/ft2) 6.5 135 

1/2 Category 32/16 Dry 2.5 mm at 1.92 kPa (0.100 in. at 40 lbf/ft2) 7.2 150 

19/32 & 5/8 Category 40/20 Dry 2.5 mm at 3.35 kPa (0.100 in. at 70 lbf/ft2) 11.5 240 

23/32 & 3⁄4 Category 48/24 Dry 2.5 mm at 4.31 kPa (0.100 in. at 90 lbf/ft2) 14.4 300 

Structural I Single Floor 

19/32 & 5/8 Category 20 o.c. Dry 2.5 mm at 2.40 kPa (0.100 in. at 50 lbf/ft2) 8.6 180 

23/32 & 3⁄4 Category 24 o.c. Dry 2.5 mm at 3.84 kPa (0.100 in. at 80 lbf/ft2) 13.0 270 

(a) Dry shall be within +/- 3% of the as-shipped moisture content. 

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Table 5. Racking load performance criteria for panels tested according to Section 7.3. (See Section 6.2.2.3 for pass/fail criteria) 

Performance 

Category 

Test 

Exposure 

Condition(b) 

Nail 

Size 

(dia. x length) 

Nail Spacing Test Load 

Performance Criteria(a) 

Deflection 

@ Test 

Load 

Ultimate Load 

Panel 

Edge 

Intermediate 

Studs(c) 

Sheathing 

Structural I 

Sheathing 

and Structural 

I Single Floor Sheathing 

Structural I 

Sheathing 

and 

Structural I 

Single Floor 

mm in. mm in. mm in. kN/m lbf/ft kN/m lbf/ft mm in. kN/m lbf/ft kN/m lbf/ft 

Less than 5/16 Dry 2.9 x 

51 

0.113 

x 2.0 150 6 300 12 2.2 150 --- --- 5.1 0.2 9.5 650 --- --- 4.4 300 --- --- 15.2 0.6 

5/16 Dry 2.9 x 

51 

0.113 

x 2.0 75 3 300 12 5.1 350 --- --- 5.1 0.2 14.3 980 --- ---

3/8 Dry 3.3 x 

64 

0.131 

x 2.5 75 3 300 12 6.0 410 6.7 460 5.1 0.2 16.8 1150 18.8 1290 

7/16 Dry 3.3 x 

64 

0.131 

x 2.5 75 3 300 12 6.6 450 7.4 505 5.1 0.2 18.4 1260 20.7 1415 

15/32 Dry 3.8 x 

76 

0.148 

x 3.0 75 3 300 12 8.8 600 9.7 665 5.1 0.2 24.5 1680 27.1 1860 

19/32 and 

greater Dry 3.8 x 76 

0.148 

x 3.0 75 3 300 12 9.7 665 9.7 665 5.1 0.2 27.1 1860 27.1 1860 

(a) Stud spacing – 405 mm (16 in.) o.c. for Wall-16, Roof-16, and Roof-20; 610 mm (24 in.) o.c. for all other span ratings and all Structural I Sheathing and 

Structural I Single Floor panels. 

(b) Dry shall be within +/- 3% of the as-shipped moisture content. 

(c) For studs spaced 610 mm (24 in.) o.c., nail spacing on intermediate studs shall be 150 mm (6 in.) o.c. for panels with a Performance Category of 7/16 and less. 

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Table 6. Fastener performance criteria under lateral and withdrawal loads for panels tested 

according to Section 7.4. (See Section 6.2.2.4 for pass/fail criteria) 

Performance 

Criteria for 

Ultimate Load(c) 

Grade 

End 

Use 

Performance 

Category 

Nail 

Size(a) 

(dia. x length) 

Test 

Exposure 

Condition(b) 

Lateral 

Nail 

holding 

Withdrawal 

mm in. N lbf N lbf 

Sheathing 

Wall 

Through 1/2 

Greater than 1/2 

2.9 x 

51 

3.3 x 

64 

0.113 x 

2.0 

0.131 x 

2.5 

Dry 778 175 (d) (d) 

Wet/Redry 600 135 (d) (d) 

Roof 

Through 1/2 

Greater than 1/2 

2.9 x 

51 

3.3 x 

64 

0.113 x 

2.0 

0.131 x 

2.5 

Dry 778 175 89 20 

Wet/Redry 600 135 67 15 

Subfloor 

Through 1/2 

Greater than 1/2 

2.9 x 

51 

3.3 x 

64 

0.113 x 

2.0 

0.131 x 

2.5 

Dry 934 210 89 20 

Wet/Redry 712 160 67 15 

Single 

Floor Floor 

Through 1/2 

Greater than 1/2 

2.9 x 

51 

3.3 x 

64 

0.113 x 

2.0 

0.131 x 

2.5 

Dry 934 210 89 20 

Wet/Redry 712 160 67 15 

(a) Common smooth-shank nail. 

(b) Wet/redry shall be exposure to three days of continuous wetting, followed by testing dry. Dry shall be 

within +/- 3% of the as-shipped moisture content. 

(c) Tabulated values represent the 10th percentile with 75% confidence from 20 specimens. 

(d) Not applicable. 

Table 7. Exposure 1 Criteria for OSB Tested Along the Strength Axis According to Section 7.6, 

Cycled According to Section 7.16a (See Section 6.2.4.1(d) for pass/fail criteria) 

Performance Category End Use - Span Rating 

Bending Capacity 

(Required Moment) 

N-mm/mm lbf-in./ft 

3/8 Roof - 24 310 830 

7/16 Roof - 24/Subfloor - 16 350 950 

15/32 & 1/2 Roof - 32/Subfloor - 16 380 1,030 

19/32 & 5/8 Roof - 40/Subfloor - 20 450 1,210 

23/32 & 3/4 Roof - 48/Subfloor - 24 640 1,720 

9/16 Single Floor - 16 390 1,060 

19/32 & 5/8 Single Floor - 20 420 1,130 

23/32 & 3/4 Single Floor - 24 610 1,650 

7/8 & 1 Single Floor - 32 1,000 2,690 

1-1/8 Single Floor - 48 1,140 3,060 

a Bond performance may also be established using procedures defined in Section 6.2.4.1.e. 

5.3.3 Bond performance 

Panels shall meet the performance requirements of Sections 5.3.3.1 through 5.3.4.3 for 

properties that affect the adhesive bonding system when tested in accordance with the 

referenced test method. Section 6.2.4 details specimen requirements and additional test set 

procedures. 

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5.3.3.1 Bond classification 

Wood structural panels shall meet the bond requirements listed below for their respective 

exposure bond classification. 

a. Exterior Plywood – Plywood rated as Exterior shall meet PS 1 bond requirements for Exterior 

panels. Exterior delamination in plywood is a visible separation at a single glueline that 

exceeds 19.4 cm2 (3 in.2) in an area coinciding with open knotholes, pitch pockets, splits, gaps 

and other voids or characteristics permitted in the panel grade. 

b. Exposure 1 Plywood – Plywood rated as Exposure 1 shall meet PS 1 bond requirements for 

Exposure 1. Exposure 1 delamination in plywood is a visible separation in any glueline that 

exceeds 19.4 cm2 (3 in.2) except where directly attributable to characteristics permitted in the 

grade as follows: 

• Knots and knotholes – not to exceed the size permitted in the grade plus a 

surrounding band not wider than 19.1 mm (3/4 in.). 

• Other permissible grade characteristics – not to exceed the size permitted in the 

grade. 

c. Exposure 1 Composite panels - Composite panels rated as Exposure 1 shall satisfy the 

delamination requirements of Section 6.2.4.1.c when tested in accordance with Section 7.13, 

following moisture cycling according to Section 7.17. Exposure 1 delamination in composites 

is a visible separation along a test specimen edge and/or end, between veneer-to-veneer or 

veneer-to-wood-based material gluelines, not to exceed 6.4 mm (1/4 in.) depth for a 

continuous length of 25 mm (1 in.). 

d. Exposure 1 OSB – OSB panels rated as Exposure 1 shall meet or exceed the criteria in Table 

7 when tested in accordance with method Section 7.6 following moisture cycling according to 

Section 7.16 or the procedures of Section 5.3.3.1.e. 

ADVISORY NOTE: Values in Table 7 are based on properties from representative industry 

panels that met requirements for structural performance when tested in accordance with 

Section 6.2.2.1 and bond performance when tested in accordance with Section 7.7 following 

moisture cycling according to Section 7.17. 

e. Exposure 1 mat-formed panels - Mat-formed panels and wood-based material for composite 

panels rated as Exposure 1 shall exhibit a minimum average strength retention of 50% with 

no individual panel retained strength less than 40% when tested in accordance with Section 

7.7 following moisture cycling according to Section 7.17. 

5.3.3.2 Bond performance associated with knots and knotholes 

Structural plywood rated as Exposure 1 shall satisfy the requirements of Section 6.3.4.4 when 

tested in accordance with Sections 7.18 and 7.19. 

5.3.4 Adhesive performance 

5.3.4.1 Adhesive mold resistance 

Panel adhesive bonds shall satisfy the mold resistance test according to the procedures of 

Section 7.14 as defined in Section 6.2.5.1. Phenolic and isocyanate-based adhesives have 

demonstrated resistance to attack from mold and shall be considered as meeting this 

requirement. 

5.3.4.2 Adhesive resistance to elevated temperature 

Panel adhesive bonds shall be considered to satisfy sufficient elevated-temperature resistance 

(71°C [160°F]) when they meet the requirements of Section 5.3.3.1. 

5.3.4.3 Adhesive bacteria resistance 

Panel adhesive bonds shall satisfy the bacteria test according to the procedures of Section 7.15 

as defined in Section 6.2.5.3. Phenolic and isocyanate-based adhesives have demonstrated 

resistance to attack from bacteria and shall be considered as meeting this requirement. 

5.4 Moisture content 

Moisture content of panels at time of shipment from the manufacturer and at the time of testing 

shall be less than 16% as determined by Section 7.11. 

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6 QUALIFICATION TESTING AND MILL SPECIFICATION 

6.1 General 

This section details test specimen requirements, conformance criteria, additional test set options, 

and mill specifications. See Appendix B for a flowchart. 

6.2 Qualification testing 

6.2.1 General 

Qualification tests are a function of the panel grade. Required tests and performance criteria are 

detailed in Section 5. Conformance criteria and additional test set requirements are given by test 

in this section. 

Panels for qualification testing shall be representative of minimum performance. 

Tests shall be conducted according to the application specifications of the manufacturer and the 

use for which the panel is being qualified, at the support spacing to be shown on the trademark. 

Any special product modification that affects performance (e.g., moisturizing or water repellent 

treatment) shall be noted per Section 6.3. Upon failure of qualification tests, provisions shall be 

followed for one additional series of tests provided no change has been made in the 

manufacturing process. If a product satisfies the provisions of the additional testing, it shall pass 

the performance qualification test in question. If it does not, the product shall fail the performance 

qualification test. If a change in panel configuration or processing has been made, additional 

qualification tests shall be performed when required by the qualified testing agency. 

6.2.2 Structural performance 

6.2.2.1 Concentrated loads 

Test a maximum of 20 specimens taken from at least 10 panels. Ten specimens (taken from at 

least five panels) for each test exposure condition shall be evaluated for both concentrated static 

and impact loads according to Section 7.1. Requirements are found in Table 2. 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. 

a. Deflection – The initial test set consists of 10 specimens. 

• The average deflection shall not be greater than the appropriate requirement in Table 2. 

• If no more than one value is above the requirement, the sample passes. 

• If two or three values are above the requirement, test an additional set. 

• If four or more values are above the requirement, the sample fails. 

• If 10 additional specimens are tested, the combined passing rate shall be at least 85%. 

b. Ultimate load – The initial test set consists of 10 specimens. 

• The average load shall not be less than the appropriate requirement in Table 2. 

• 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 10 additional specimens are tested, the combined passing rate shall be at least 95%. 

6.2.2.2 Uniform loads 

Test a maximum of 20 specimens taken from at least 10 panels. Ten specimens (taken from at 

least five panels) for each test exposure condition shall be evaluated for uniform-load capacity 

according to Section 7.2. Test requirements are found in Table 3 and Table 4 (Structural I 

Sheathing and Structural I Single Floor). 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. 

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

consists of 10 specimens. 

• If the average value is below the requirement, the sample passes. 

• If the average value is above the requirement, test an additional set. 

• If the average value based on combined results is above the requirement, the sample fails. 

b. Ultimate load – The initial test consists of 10 specimens. 

• The average load shall not be less than the appropriate requirement. 

• 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 10 additional specimens are tested, the combined passing rate shall be at least 95%. 

6.2.2.3 Wall racking 

Two wall assemblies shall be evaluated for wall racking according to Section 7.3. Requirements 

are found in Table 5. If an additional test is needed, it shall consist of one wall assembly, and the 

results of the three tests shall be combined. Only one additional test is allowed. 

a. Deflection – The average deflection shall not be greater than that specified (Table 5). The 

initial test shall consist of two samples. 

• If the average value is below the requirement, the sample passes. 

• If the average value is above the requirement, test one additional wall assembly. 

• If the average value based on combined results is above the requirement, the wall 

evaluation fails. 

b. Ultimate load – The minimum passing rate shall be 100%. The initial test shall consist of two 

samples. If only two walls are tested, the ultimate loads shall be within 10% of each other. 

• If either of the two test values is below the requirement, the sample fails. 

• If the two test values meet the requirement but do not agree within 10%, test one additional 

wall assembly. The lower of the two test values shall be used to calculate the 10% 

allowance. 

• If the lowest value of the three walls tested exceeds the specified minimum ultimate load, 

the wall evaluation passes. 

6.2.2.4 Fastener holding 

Test a maximum of 40 specimens taken from at least 20 panels. Twenty specimens (taken from 

at least 10 panels) for each test exposure condition and property shall be tested for lateral and 

withdrawal loads according to Section 7.4. Requirements are found in Table 6. If additional tests 

are needed, they shall also consist of 20 specimens, and the results of the two 20-specimen sets 

shall be combined. Only one additional test set is allowed. 

Ultimate load – The initial test consists of 20 specimens. 

• If no more than two values are below the requirement, the sample passes. 

• If three or four values are below the requirement, test an additional set. 

• If five or more values are below the requirement, the sample fails. 

• If 20 additional panels are tested, the combined passing rate shall be at least 90%. 

6.2.3 Dimensional stability 

One of the following linear expansion test methods and associated criteria shall be satisfied as 

noted for the grade in Section 5.3.2.1. Any special feature included by the manufacturer, such 

as coatings or moisture conditioning, shall be stated for Section 6.3. 

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a. Exposure to 50% (±5%) relative humidity; 21°C ±6°C (70°F ±10°F) and vacuum-pressure 

soak – A minimum of 10 specimens (taken from at least five panels) both along and across 

the panel strength axis shall be conducted according to Section 7.8 for linear expansion 

measured from 50% relative humidity to vacuum-pressure soak. 

The average linear expansion from each panel axis, as measured according to the test method 

from 50% relative humidity to vacuum-pressure soak, shall be no greater than specified. 

Additional tests – If the average linear expansion exceeds 0.55%, the test fails. If the 

average linear expansion fails to meet the linear expansion requirement and is no greater than 

0.55%, another lot of 10 specimens for a given panel axis shall be permitted. If the combined 

average of all the specimens meets the specified criteria, the requirement shall be considered 

satisfied. 

b. Exposure to one-sided wetting and relative humidity – Test a maximum of 20 specimens 

taken from at least 10 panels. Ten specimens (taken from at least five panels) for both along 

and across the panel strength axis shall be evaluated for linear and/or thickness expansion 

measured from as-received to wet-one-side exposure according to Section 7.9. Ten 

specimens (taken from at least five panels) for both along and across the panel strength axis 

shall be evaluated for linear and/or thickness expansion measured when exposed to relative 

humidity change according to Section 7.10. 

Each panel axis is evaluated separately. The initial test consists of 10 specimens. If additional 

test sets 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. 

• If no more than three values are above the requirement, the sample passes. 

• If four, five or six values are above the requirement, test an additional set. 

• If seven or more samples are above the requirement, the sample fails. 

• If 10 additional specimens are tested, the minimum passing rate is 70%. 

6.2.4 Bond performance 

6.2.4.1 Bond classification 

Bond classification performance tests shall be conducted as follows: 

a. Exterior Plywood – Plywood rated as Exterior shall satisfy PS 1 bond requirements for 

Exterior panels. 

b. Exposure 1 Plywood – Plywood rated as Exposure 1 shall satisfy PS 1 bond requirements 

for Exposure 1. 

c. Exposure 1 Composite panels – Composite panels rated as Exposure 1 shall have one 

sample (of at least five specimens) from each of at least 20 panels tested according to 

Section 7.17 and evaluated for delamination according to Section 7.13 following the fourth 

and sixth moisture cycles. At least 95% of the samples shall pass four moisture cycles, and 

90% shall pass six moisture cycles. If more than 85% but fewer than 90% of the samples 

pass delamination requirements following the six-cycle test of Section 7.17 and evaluated 

according to Section 7.13, one additional test set of 20 samples shall be permitted. If the 

additional test results meet the requirements, bond performance requirements shall be 

considered satisfied. 

d. Exposure 1 OSB – OSB shall satisfy the requirements of this section or the requirements of 

Section 6.2.4.1.e. To satisfy the requirements of this section, OSB rated as Exposure 1 shall 

have one sample (of at least two specimens) from each of at least 20 panels tested for 

parallel strength according to Section 7.6 after cycling according to Section 7.16. If no more 

than one of the samples is below the minimum criterion in Table 7, the 20-panel test set shall 

be considered passing. If four or more samples fall below the minimum requirement, the test 

set shall be considered failing. If two or three of the samples are below the minimum criterion, 

an additional test set of 20 samples from the same lot shall be allowed. The combined 

passing rate of the 40-panel test set shall be 92.5% or greater. 

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e. Exposure 1 mat-formed panels – Mat-formed panels rated as Exposure 1 shall have one 

sample (of at least five specimens) from each of at least 20 panels cycled according to 

Section 7.17 and tested for strength retention according to Section 7.7. Strength retention is 

calculated by the following method: 

100 

P

 %RS 

t =

Pc

where % RS = Percent retained strength of sample. 

Pt = Average of five-specimen breaking load after cycling. 

Pc* = Average unexposed sample (five-specimen) breaking load. 

*Unexposed (control) specimens are broken in the as-received condition. 

Samples tested shall exhibit the specified minimum strength retention following six moisture 

cycles.4 

Additional tests - If the 20-sample average strength retention meets the requirements, but 

no more than one sample fails to meet the minimum individual strength retention specified, an 

additional test of 20 samples (one sample from each of 20 panels) shall be permitted. The 

combined passing rate of the 40-panel test set shall be 97.5% or greater. 

6.2.4.2 Bond performance of plywood with knots and knotholes 

Structural plywood rated as Exposure 1 shall be tested according to Sections 7.18 and 7.19. 

Knots and/or knotholes in the samples tested shall be greater than 51 mm (2 in.) but not 

exceeding 76 mm (3 in.) in width measured across the grain. Twenty samples with knots and/or 

knotholes shall be tested according to Section 7.18 and 20 according to Section 7.19. 

Samples with knots and/or knotholes tested according to Section 7.18 shall meet dry 

concentrated static and impact requirements, conformance criteria and additional test set options 

of Table 2 and Sections 6.2.2.1.(a) and 6.2.2.1.(b). For each lot of 20, 95% of the samples with 

knots and/or knotholes tested according to Section 7.19 shall not exhibit delamination extending 

radially more than 19.1 mm (3/4 in.) beyond the boundary of the knot or knothole and across the 

width of a full sector or the continuous equivalent of the width of a full sector as measured by 

Section 7.19.4. 

Additional tests – If no more than two samples with knots or knotholes in a lot of 20 fail to meet 

the test requirements, another lot of 20 tests for that requirement shall be permitted. If all 

specimens pass the additional tests, the requirements shall be considered satisfied. 

6.2.5 Adhesive performance 

6.2.5.1 Adhesive mold resistance 

Four panels shall be tested according to the procedures of Section 7.14. 

a. Plywood shall be considered to have satisfactory adhesive mold resistance if each test group 

(see Section 7.14.2 for group definition) over the 20-week period shows an average glueline 

shear load of at least 90% of the control. In addition, no more than two groups shall rate less 

than 80%, and no single group shall rate less than 75%. 

b. Other panels shall be considered to have satisfactory mold resistance if no test group average 

is less than the control sample average minus 1.8 times the control sample standard deviation. 

6.2.5.2 Adhesive resistance to elevated temperature 

Adhesives satisfying the moisture-cycling requirements of Section 6.2.4.1 shall be considered to 

have satisfactory resistance to elevated temperature. 

6.2.5.3 Adhesive resistance to bacteria 

At least four panels shall be tested according to procedures of Section 7.15. 

a. Plywood shall be considered to have adhesive resistance to bacteria if each test group (see 

Section 7.15.2 for group definition) over the 12-week test shows an average load of at least 

80% of the control. No single group shall rate below 70% of the control. 

4 Because of the extreme severity of the six-cycle test, the strength retention requirement relates to bond performance and does not 

relate to structural design values. 

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b. Other panels shall be considered to have satisfactory bacteria resistance if no test group 

average is less than the control sample average minus 1.8 times the control sample standard 

deviation. 

6.3 Mill specification 

When a product passes the appropriate performance qualification tests of Section 6.2, a 

proprietary mill specification unique to the product and mill shall be written based on product 

evaluation under this section. 

The product evaluation shall be based on values developed in this standard and unique 

characteristics of the same materials supplied by the manufacturer for performance qualification 

testing. Reference values (see Section 2.10) shall be established during product evaluation or 

from applicable performance requirements in this standard (Section 5) and shall be the basis for 

quality evaluation of future production. Reference values for mechanical properties may be 

based on Sections 6.3.2.1 or 6.3.2.2. Minimum industry reference values for small bending tests 

are found in Tables 7 and 8. Mill specific small bending values based on Section 7.6 or mill 

specific 1" x 5" bending reference values based on Section 7.7 may be determined based on 

certification agency approved methods. For plywood and composite panels, the grade and 

construction requirements are permitted for use in lieu of reference values for quality evaluation 

purposes. These values or characteristics will be used by both the individual mill quality 

procedures and by an inspection program of a qualified inspection and testing agency (see 

Section 8.2) in conjunction with its policies. 

In addition to the panel characteristics specifically evaluated in this section, any unique 

manufacturing techniques that influence product qualification shall be included in the individual 

mill specification. This includes special coatings; heat, water or chemical treatments; overlays; 

additives; or other manufacturing-related activities. In addition, the maximum size knot or 

knothole tested according to Section 6.2.4.2 shall be included in the mill specification. 

6.3.1 Panel construction 

6.3.1.1 Plywood panels 

Panels shall be defined as to species and veneer construction for the mill specification and 

evaluated under Sections 6.3.2 and 6.3.3, but excluding Section 6.3.3.2. 

6.3.1.2 Composite panels 

Wood-based material shall be evaluated as required in Sections 6.3.2, 6.3.3.1 and 6.3.4. In 

addition, the finished (veneered) panel shall be evaluated by the provisions of Sections 6.3.2, 

6.3.3.1, 6.3.3.3 and 6.3.4. 

6.3.1.3 Mat-formed panels 

Mat-formed panels shall be evaluated under the provisions of Sections 6.3.2, 6.3.3 and 6.3.4. 

6.3.2 Mechanical properties 

6.3.2.1 Large-panel bending stiffness and strength 

Twenty tests (specimens taken from at least 10 panels) shall be evaluated for bending stiffness 

both along and across the panel strength axis according to the procedures of Section 7.5. 

Stiffness reference values for each panel direction shall be the lower value of a 90% confidence 

interval established on the average. 

Strength reference values for each panel direction shall be the minimum observed value, or the 

sample average minus 1.8 times the sample standard deviation, whichever is the higher value. 

6.3.2.2 Small specimen bending stiffness and strength 

For OSB and other mat-formed panels, 20 samples (of at least two specimens) taken from at 

least 10 panels shall be evaluated for dry bending strength and stiffness both along and across 

the panel strength axis according to the procedures of Section 7.6. 

Reference values for Quality Assurance for OSB are found in Table 8. 

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ADVISORY NOTE: Reference values in Table 8 are based on properties and statistical limits 

from representative industry samples that were tested for and met structural performance 

requirements in Section 6.2.2.1 and Table 2. Reference values for other mat-formed panels 

should be based on the statistical principles in Section 6.3.4.2. 

Table 8. Quality assurance minimum reference values for dry small specimen bending stiffness and 

strength, using Section 7.6, small static bending test(a)(c) 

End Use -

Span Rating or 

Performance Category 

BENDING STIFFNESS, EI x 103 BENDING STRENGTH, MM 

Stress Applied 

Parallel to 

Strength Axis(b) 

Stress Applied 

Perpendicular to 

Strength Axis(b) 

Stress Applied 

Parallel to Strength 

Axis (b) 

Stress Applied 

Perpendicular to 

Strength Axis(b) 

Nmm2/ 

mm 

lbfin. 

2/ft 

width 

Nmm2/mm 

lbfin. 

2/ft 

width 

Nmm/mm lbf-in./ft 

width 

Nmm/mm 

lbfin./ft 

width 

Sheathing 

Roof – 24 292 31 85 9 330 880 130 350 

Roof - 24/Subfloor -16 395 42 94 10 390 1,040 140 370 

Roof - 32/Subfloor - 16 490 52 113 12 460 1,250 190 520 

Roof - 40/Subfloor - 20 1,240 132 358 38 810 2,170 360 970 

Roof - 48/Subfloor - 24 1,790 190 763 81 920 2,480 510 1,380 

Structural I Sheathing 

3/8 292 31 85 9 330 880 130 350 

7/16 395 42 141 15 390 1,040 220 580 

15/32 490 52 245 26 460 1,250 320 860 

1/2 490 52 273 29 460 1,250 330 900 

19/32 & 5/8 1,240 132 471 50 810 2,170 500 1,360 

23/32 & 3/4 1,790 190 763 81 920 2,480 650 1,760 

Single Floor 

Single Floor - 16 876 93 198 21 650 1,740 230 630 

Single Floor - 20 1,110 118 264 28 710 1,910 240 650 

Single Floor - 24 1,600 170 546 58 910 2,450 320 850 

Single Floor - 32 4,170 443 1,270 135 1,570 4,240 600 1,610 

Single Floor - 48 8,660 920 2,110 224 2,080 5,600 820 2,200 

(a) Test criteria shall not be used for design properties. 

(b) The strength axis is parallel to the face and back orientation of the flakes or strands unless otherwise indicated. 

(c) Other reference values may be established through acceptable performance based on procedures in Section 

6.2.2.1. 

6.3.3 Physical properties 

6.3.3.1 Panel thickness 

Finished panel thickness shall be evaluated on each of 20 panels by the procedures of Section 

7.12. The reference value shall be the average less 1.932 standard deviations for 20 panels (the 

95% lower tolerance limit at 75% confidence based on ASTM D-2915). 

6.3.3.2 Moisture content 

Panel moisture content shall be measured on one specimen from each of 20 panels according 

to Section 7.11. The reference value shall be the maximum panel moisture content. A reference 

value shall be established only if necessary under dimensional stability performance testing per 

Section 6.2.3. 

6.3.3.3 Linear expansion 

Reference values for linear expansion are to be based on specimens taken from at least 20 

panels per the instructions in either Procedure A or Procedure B of Section 7.8. If the average 

linear expansion based on Procedure A exceeds 0.5%, reference values shall be based on 

specimens taken from 20 panels evaluated using Section 7.8.2.1. The reference value shall be 

the highest observed value, or the sample average plus 1.8 times the sample standard deviation, 

whichever is the lower value. If Procedure B is used, the reference value shall be 0.5%. 

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For composite panels and for mat-formed panels containing non-oriented furnish, one specimen 

75 mm x 300 mm (3 in. x 12 in.) shall be prepared perpendicular to the machine direction only 

from each panel to be tested. 

For OSB and other mat-formed panels containing oriented furnish, one 75 mm x 300 mm (3 in. x 

12 in.) specimen parallel and one perpendicular to the panel strength axis shall be prepared from 

each panel to be tested. Separate parallel and perpendicular reference values shall be 

determined when using Section 7.8.2.1 Procedure A. 

6.3.4 Adhesive bond properties 

6.3.4.1 Exposure 1 bond performance for OSB 

The reference values for an OSB mill specification shall be established based on 20 samples 

evaluated parallel to the strength axis according to Section 7.6 after cycling according to Section 

7.16, or based on procedures as described in Section 6.3.4.2 or based on the tabulated values 

in Table 7. 

6.3.4.2 Exposure 1 bond performance for composites and mat-formed panels. 

For composite and mat-formed panels classified Exposure 1, a minimum of 20 samples, one 

taken from each of 20 panels, shall be moisture cycled according to the procedures of Section 

7.16 (single cycle soak-dry test) using specimens described in Section 7.7. For composite and 

mat-formed panels classified Exposure 1, a minimum of 20 samples, one taken from each of 20 

panels, shall be moisture cycled according to the procedures of Section 7.17 (6-cycle test) using 

specimens described in Section 7.7. Immediately after cycling, composite samples will be 

evaluated for delamination based on procedures described in Section 7.13. Moisture-cycled 

samples shall then be tested according to the procedures of Section 7.13. The individual panel 

reference value for each qualification shall be the lowest observed breaking load (five-specimen 

average) or the sample average minus 1.8 times the sample standard deviation, whichever is the 

higher value. In addition, for Exposure 1 panels tested according to Sections 7.16 and 7.7, the 

lower 90% confidence interval shall be established on the qualification average. 

6.3.4.3 Exposure 1 bond performance of plywood panels 

Reference values for bond performance of Exposure 1 plywood panels shall be as specified in 

Section 6.2.4.1.(b). 

6.3.4.4 Bond performance associated with knots and knotholes 

Reference values for bond performance associated with knots and knotholes shall be as 

specified in Section 6.2.4.2 for knots and knotholes tested according to Section 7.19. 

ADVISORY NOTE: Assessment of bond performance associated with knots and knotholes on 

a quality auditing basis should be conducted when a maximum-sized knot or knothole appears 

in the routine bond performance samples. When available, they should be tested according to 

Section 7.19 and meet the criteria of Section 6.2.4.2. 

7 TEST METHODS 

7.1 Concentrated static and impact load test 

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

The test span shall be 19.2 inch 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 one-sided wetting, then tested wet. The 

wet/redry condition shall be exposure to three days of continuous one-sided wetting, followed by 

drying. The panel moisture content at the time of testing for the wet/redry condition shall be within 

+/- 3% of the as-shipped moisture content. 

7.1.1 Specimen preparation 

ASTM E-661 shall be followed with regard to specimen preparation, and Section 6.2.2.1 of PS 2 

shall be followed with regard to the number of specimens required. Specimens shall also be 

moisture cycled as required. 

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7.1.2 Test procedure 

Concentrated static – Procedures of ASTM E-661 shall be followed, except that a test frame of 

steel rather than lumber, using fasteners that simulate nails, shall be permitted. During 

measurement of deflection, the loading rate shall be 445 N (100 lbf) per 30 seconds. Following 

measurement of deflection, the rate of loading shall yield failure within five minutes if a handpumped hydraulic loading system is used. 

Concentrated impact – Procedures of ASTM E-661 Method A shall be followed, except: 

1. A test frame of steel rather than lumber, using fasteners that simulate nails, shall be 

permitted. 

2. For span ratings greater than 24, the shot bag shall weigh 27 kg (60 lbs). 

The width of individual test pieces shall be at least 610 mm (24 in.) for span ratings up to 24, and 

1,220 mm (48 in.) for greater span ratings. 

7.2 Uniform load test 

7.2.1 General 

This method covers a procedure for determining the performance of wood structural panels under 

uniform loads such as snow, wind and occupancy loads. The uniform load shall be applied by 

drawing a vacuum under the test specimen. This causes atmospheric pressure to apply a 

uniform load to the test specimen. The specimen shall be mounted on fully supported framing 

members in a vacuum chamber. 

7.2.2 Equipment 

Vacuum chamber – The vacuum chamber (Figures 1 and 2) shall consist of a sealed box with 

the panel to be tested forming the top. A 0.15-mm (6-mil) polyethylene sheet or equivalent, the 

perimeter of which shall be 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 supported so as to resist deflection or rotation 

under applied load. 

Deflection gages – The deflection gages shall be mounted to rigid tripods whose legs shall rest 

above the joists. Deflection shall be measured to the nearest 0.025 mm (0.001 in.). 

7.2.3 Specimen preparation 

Samples selected shall be representative of the product being tested. 

Length – The specimen length perpendicular to the framing members shall be equal to twice the 

center-to-center spacing. 

Width – The specimen width shall be at least 595 mm (23.5 in.). 

Thickness – The specimen thickness shall be measured and recorded after conditioning. 

Conditioning – Prior to testing, specimens shall be conditioned as specified in Table 3. 

7.2.4 Test procedure 

Following preparation of specimens in Section 7.2.3, the specimen to be tested shall be mounted 

on framing members in the vacuum chamber at the spacing for which the panel is being rated, 

following the specified 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 shall be set in its 

proper position with the gages positioned to read deflection at the point of maximum deflection5 

within the two outer spans (Figures 3 and 4). 

5 The point of maximum deflection for a uniformly loaded two-span system occurs at 0.4215 times (S) measured from the centerline 

of the outer joist, where S equals the center-to-center joist spacing. 

20 
 

 

Figure 1. Vacuum Test Chamber Equipment 

Diagram shows strength axis across supports. 

Figure 2. Vacuum Test Chamber Equipment 

Diagram shows strength axis parallel to supports. 

21 
 

 

Figure 3. Uniform Load Test Specimen 

Diagram shows Strength axis across supports. 

Figure 4. Uniform Load Test Specimen 

Diagram shows strength axis parallel to supports. 

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The panel shall be loaded at a uniform rate of 2.4 kPa (50 lbf/ft2) per minute, recording deflections 

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. 

7.3 Wall racking load test 

7.3.1 General 

The principles of Section 14 of ASTM E-72 for wall racking shall be followed. 

7.3.2 Specimen preparation 

Test specimens 2.4 m x 2.4 m (8 ft x 8 ft) shall be prepared as in ASTM E-72, except that the 89 

mm x 89 mm (nominal 4 in.x 4 in.) timber attached to the upper plate shall be reinforced with a 

100 mm x 150 mm (4 in. x 6 in.) steel tube to prevent excessive deformation. An additional 

vertical deflection gage shall be positioned in the lower right corner of the wall (Figure 7 of ASTM 

E-72) to record crushing of the lower plate. 

Stud framing shall be Douglas-fir or southern pine stud grade, with a moisture content of 15% or 

less. Nail size and spacing shall be as specified in Table 5. When 3.8 mm x 76 mm (0.148 in. 

x 3.0 in.) nails are used, 64 mm (nominal 3 in.) wide framing shall be used for the center stud (at 

panel joint) to prevent splitting of framing member. 

Specimens shall be tested in the dry condition (see Table 5, footnote b). 

7.3.3 Test procedure 

Load shall be applied continuously at a uniform rate of load. The rate of loading shall be chosen 

such that the 1-times test load shall be reached in not less than two minutes. The loading rate 

for the subsequent loading cycles shall be the same as the 1-times test load cycle. 

Deflection measurements shall be recorded as the wall is being loaded. At least 10 sets of 

uniformly-spaced deflection readings shall be taken prior to failure to establish the loaddeformation curve. At 1-times and 2-times the test load specified in Table 5, the load shall be 

removed and the wall shall be allowed to recover for five minutes. At 2.5 times the test load, the 

deflection gages may be removed and the wall shall be loaded to failure. 

Deflection shall be reported after removing panel uplift, base slip, and crushing components from 

the total deflection measurement. Ultimate load shall be recorded. 

7.4 Fastener-holding resistance test 

7.4.1 General 

Tests shall measure the single-shear resistance of a nail to lateral movement of the panel. The 

procedure shall generate data that are to be compared to data from other panel products, but the 

procedure shall not be used to produce joint design information. 

Direct withdrawal loads shall also be measured. 

Conditioning – Prior to testing, specimens shall be conditioned as specified in Table 6. 

7.4.2 Specimen preparation 

Lateral loads – Each specimen shall measure 150 mm x 150 mm (6 in. x 6 in.). To serve as test 

points, four points shall be marked on the centerline of each specimen axis, 25 mm (1 in.) in from 

each edge. Nail size shall be as required in Table 6. 

Nails shall be driven perpendicular to the face of the panel following conditioning. Nail 

penetration shall be such that the nail head lies flush with the panel face. A backing shall be 

used to prevent the nail from tearing away the back during driving. All nails shall be driven 

immediately prior to testing. 

Direct withdrawal loads – Test specimens shall be of convenient size (at least 75 mm x 150 

mm [3 in. x 6 in.]) trimmed from the lateral resistance specimens. Nail size shall be as required. 

Following conditioning, nails shall be driven through the panel perpendicular to the face and at 

least 12 mm (1/2 in.) of the shank portion shall project above the surface of the material. 

23 
 

 

 

 

 

 

 

 

 

 

Figure 5. Exploded View of Test Apparatus for Measuring the 

Lateral Nail-Holding Capacity of Structural Panel Products 

7.4.3 Test procedure 

Lateral loads – The fastener shall be loaded in single shear. Apparatus similar to that shown in 

Figure 5 shall be employed. The nail shank shall be rigidly clamped. Rollers shall be present to 

ensure vertical movement by providing lateral restraint to the panel. Load shall be applied 

through a yoke-type loading head. One such loading head is illustrated in Figure 5. 

The test specimen shall be loaded continuously throughout the test by uniform motion of the 

movable crosshead of the test machine at a rate of 5 mm (0.2 in.) per minute. 

Direct withdrawal loads – Nail holding tests shall be made on nails driven through the thickness 

of the panel to measure the resistance to withdrawal in a plane perpendicular to the face. 

Method of loading shall be in accordance with ASTM D-1761, Section 10.2. 

The specimen shall be loaded continuously throughout the test by uniform motion of the movable 

head of the testing machine at a rate of 5 mm (0.2 in.) per minute. 

7.5 Large panel bending test 

7.5.1 General 

This test procedure determines large panel bending strength and stiffness. The general 

provisions of ASTM D-3043 Method C shall be followed. 

7.5.2 Specimen preparation 

Specimens shall be prepared according to ASTM D-3043 Method C, except specimen sizes not 

less than 310 mm x 1,220 mm (12 in. x 48 in.) shall be permitted. 

7.5.3 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 panel strength axis, and maximum bending moment shall 

be determined as required. 

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7.6 Small static bending test for OSB 

7.6.1 General 

This test is intended to develop bending strength and stiffness information to be used for quality 

assurance purposes. The test method follows the principles of ASTM D-3043, Method D. The 

information developed shall not be considered as appropriate for the purposes of developing 

design data. 

7.6.2 Specimen preparation 

Specimens are cut from each sample according to ASTM D-3043 Section 8.2, except that 

specimen width shall be 115 mm (4.5 in.). 

7.6.3 Test procedure 

The principles of ASTM D-3043 Sections 8.1 – 8.6 are followed, except that specimens shall be 

cut to the following length: 

355 mm (14 in.) for panels with Performance Category of 1/2 and less, 

510 mm (20 in.) for panels with Performance Category greater than 1/2 up to 3/4, 

610 mm (24 in.) times Performance Category plus 50 mm (2 in.) for panels with Performance 

Category greater than 3/4. 

7.7 Small static (25 mm x 125 mm [1 in. x 5 in.]) bending test for composites and mat-formed 

panels 

7.7.1 General 

This test is intended to develop strength information that acts as a measure of bond integrity. 

The test shall be run on control and moisture-cycled specimens. 

7.7.2 Specimen preparation 

Fifteen 25 mm x 125 mm (1 in. x 5 in.) test specimens shall be cut from each sample to be tested 

(15 from each direction in the case of panels that exhibit directional properties). Side-by-side 

matching shall be observed for comparison of control, single-cycle and six-cycle exposures. 

Specimens prepared from panels containing veneer shall be cut with the grain of the veneer 

parallel to the 125 mm (5 in.) dimension. Specimens prepared from mat-formed panels shall be 

cut so that the 125 mm (5 in.) dimension of the specimens shall be parallel to the panel strength 

axis except for panels exhibiting directional properties, in which case five specimens shall be cut 

along both axes. Specimens shall then be tested following appropriate conditioning. 

7.7.3 Test procedure 

Each specimen shall be tested as a beam across a 100 mm (4 in.) clear span with the loading 

head and supports measuring 19.1 mm (3/4 in.) in diameter. The load shall be applied at midspan at a rate not to exceed 25 mm (1 in.) per minute until failure occurs. Specimens from 

veneered composite panels shall be oriented so that the thickness of the specimen acts as the 

depth of the beam. Specimens from mat-formed panels shall be oriented so that the 25 mm 

(1 in.) cut dimension acts as the depth of the beam and the panel thickness acts as the beam 

width. The breaking load for each specimen shall be measured to ±4.4 N (±1 lbf). The average 

breaking load for each panel shall be calculated. In the case of panels that exhibit directional 

properties, separate averages shall be determined for each specimen direction. Average values 

shall be reported. 

7.8 Linear expansion test measured from oven-dry or 50% relative humidity to vacuumpressure soak 

7.8.1 General 

This test method provides evaluation of a panel’s dimensional stability.

7.8.2 Specimen preparation 

Test specimens shall be cut at least 75 mm (3 in.) wide by at least 300 mm (12 in.) long and 

prepared for both panel directions. 

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Specimens shall be selected to avoid large characteristics such as knotholes, knots, or splits in 

the outer veneers (when veneers are present), especially near the eyelet locations. Otherwise, 

normal grade features shall be included as they occur. 

Fixed reference points that serve as measuring points on the centerline of each specimen shall 

be located 25 mm (1 in.) in from each end. Brass eyelets placed in pre-bored holes have been 

found to be suitable reference points. Use of the reference measuring points shall permit 

determination of linear expansion independent of any additional swelling that might take place at 

the exposed panel edge. 

7.8.2.1 Test procedure 

Specimen pre-conditioning: 

Procedure A 

Specimens shall be oven-dried at 103 +/- 2 °C (217 +/- 4 °F) for 24 hours or until constant weight 

is attained. Constant weight shall be assumed when consecutive readings taken at least two 

hours apart agree within 0.2%. 

Procedure B 

Specimens shall be conditioned at 50% +/- 5% relative humidity and 21 +/- 6 °C (70 +/- 10°F) 

until constant weight is attained. Constant weight shall be assumed when consecutive readings 

taken at least 24 hours apart agree within 0.2%. 

Measurement and vacuum-pressure soak cycle: 

After pre-conditioning using either Procedure A or B, the specimen shall then be placed in a 

flattening jig to remove any out-of-plane distortions, and the distance between gage points shall 

be measured to the nearest 0.025 mm (0.001 in.) with a bar-type trammel equipped with a dial 

gage. 

Following the pre-conditioned measurements, specimens shall be placed in a pressure cylinder, 

flooded with 18±6°C (65±10°F) tap water and subjected to a vacuum of 91 +/- 7 kPa (27 +/- 2 in. 

of mercury) for one hour (time shall not begin until full vacuum is achieved). Specimens shall 

then be subjected to two hours of atmospheric or applied pressure not to exceed 690 kPa (100 

psi). After wet exposure, specimens shall be removed from the cylinder and remeasured for 

length. 

Expansion values shall be calculated as a percentage of the pre-conditioned (oven-dry or relative 

humidity) dimension, as given in the following equations: 

Calculation: 

Procedure A (oven-dry) 

100 

L

L - L

 Change Percent

d

dw =

where: Lw = dimension saturated 

Ld = dimension oven-dry 

Procedure B (relative humidity) 

 100

L

L - L

 Change Percent

50%

50%w

= 

where: Lw = dimension saturated 

L50% = dimension equilibrated at 50% RH. 

7.9 Linear expansion and thickness swell test measured after wetting one side 

7.9.1 General 

This performance test is designed to measure linear expansion and edge thickness swell. 

7.9.2 Specimen preparation 

Each 1,220 mm x 1,220 mm (48 in. x 48 in.) specimen shall have only one cut edge; the remaining 

three being as prepared by the manufacturer. To serve as measuring points for linear expansion, 

brass eyelets shall be placed in four pre-bored holes on the centerline of each specimen axis, 25 

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mm (1 in.) in from each edge. This shall result in a nominal 1,170 mm (46 in.) gage distance 

both along and across the panel strength axis. 

Additionally, points shall be marked on each uncut side of the specimen for thickness swell 

evaluation. Thickness shall be measured according to Section 7.12. 

Moisture content (oven-dry basis) shall be measured according to Section 7.11 prior to testing in 

a panel from the same lot. When the moisture content of the specimens exceeds 12%, the 

specimens shall be conditioned to constant weight at 20 +/- 3°C (68 +/- 6°F) and 65 +/- 5% 

relative humidity to achieve equilibrium moisture content. Constant weight shall be assumed 

when consecutive readings taken at least 24 hours apart agree within 0.2%. 

7.9.3 Test procedure 

Linear expansion specimens shall be placed in a flattening jig to remove any out-of-plane 

distortions, and the distance between gage points shall be measured to the nearest 0.025 mm 

(0.001 in.) with a bar-type trammel equipped with a dial gage. Thickness shall be measured 

along the edge to the nearest 0.025 mm (0.001 in.) with a micrometer, applying ratchet pressure 

during measuring. 

Following these as-received measurements, unrestrained specimens shall be mounted within 30 

degrees of vertical and shall be wetted on one side with water at 18 +/- 6°C (65 +/- 10°F). The 

period of continuous wetting shall be 14 days. No liquid water shall impinge on the back. The 

back shall be exposed to any water vapor present. All factory edges shall be exposed to water 

except the freshly-cut edge. The cut edge shall be the top edge, and protection with an edge 

sealer shall be permitted. After wet exposure, the specimens shall be remeasured. 

Expansion values shall be calculated to express results as a percentage of the original 

dimension, as given in the equation: 

 100

L

L - L

 Change Percent

ar

w ar =

where: Lw = dimension saturated 

Lar = dimension as received (less than 12% MC). 

7.10 Linear and thickness expansion test measured by exposure to relative humidity 

7.10.1 General 

This method measures linear expansion in accordance with ASTM D-1037, Section 24, Linear 

Variation with Change in Moisture Content. 

Thickness expansion, where applicable, shall be measured as described in Sections 7.10.2 and 

7.10.3. 

7.10.2 Specimen preparation 

From each sample, two specimens shall be cut according to the procedures of ASTM D-1037, 

Sections 108 to 111. Test specimens shall be cut 75 mm wide by 1,040 mm long (3 x 41 in.). 

Shorter lengths shall be permitted, but specimens shall not be less than 300 mm (12 in.) long. 

To serve as measuring points for linear expansion, brass eyelets shall be placed in pre-bored 

holes on the centerline of each specimen, 25 mm (1 in.) in from each end. This shall result in a 

nominal 990 mm (39 in.) gage distance. 

Additionally, points shall be selected and marked on the centerline of the specimen 75 mm (3 in.) 

in from each end to serve as measuring points for thickness expansion. 

7.10.3 Test procedure 

The procedures of ASTM D-1037, Section 24, shall be followed for linear expansion testing, 

except that specimens shall be placed in a flattening jig to remove any out-of-plane distortions, 

and the distance between gage points shall be measured to the nearest 0.025 mm (0.001 in.) 

with a bar-type trammel equipped with a dial gage. Thickness shall be measured to the nearest 

0.025 mm (0.001 in.) with a micrometer, applying ratchet pressure during measuring. 

Expansion values shall be calculated to express results as a percentage of the 50% conditioned 

dimension, as given in the equation: 

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100 

L

L - L

 Change Percent

50

5090

= 

where: L90 = dimension equilibrated at 90% RH 

L50 = dimension equilibrated at 50% RH. 

7.11 Panel moisture content determination 

7.11.1 General 

This procedure defines the method of determining panel moisture content by the oven-dry 

method according to the principles of ASTM D-4442, method B. 

7.11.2 Specimen preparation 

From each panel, a specimen shall be cut at least 50 mm (2 in.) from any edge. If the specimen 

size is less than 150 mm x 150 mm (6 in. x 6 in.), the entire specimen shall be used. 

7.11.3 Test procedure 

The specimen weight shall be obtained (+/- 0.2%) and the specimen placed in a drying oven at 

103 +/- 2°C (217 +/- 4°F) until constant weight is achieved. Constant weight shall be assumed 

when consecutive readings taken at least two hours apart agree within 0.2%. 

The moisture content shall be calculated as: 

100

W

W - W M

d

dw













=

where: 

M = Moisture content (percent) 

Ww = Initial weight (grams or similar units) 

Wd = Oven-dry weight (grams or similar units). 

7.12 Panel thickness determination 

7.12.1 General 

This method defines the procedure for determining panel thickness. 

7.12.2 Specimen preparation 

Panel condition at the time of measurement shall be noted. 

7.12.3 Measurement method 

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) with the anvil center at 19 mm to 25 

mm (3/4 in. to 1 in.) from the panel edge. The location of the measurements shall be 

representative of panel thickness mid-length,+/- 50 mm (2 in.) along each edge of the panel 

and the average of the four measurements shall be taken as the thickness of that panel. If a 

measurement point contains a permissible grade characteristic that affects panel thickness, 

then the measurement point shall be shifted from that point. 

7.13 Probe test for delamination 

7.13.1 General 

This test procedure defines a method for the determination of delamination in composite panels. 

7.13.2 Equipment 

The probe used shall measure 6.4 mm (1/4 in.) wide at the tip by 0.3 mm (0.012 in.) thick and 

shall increase in thickness to about 0.64 mm (0.025 in.), 12 mm (1/2 in.) from the tip. The 6.4 

mm (1/4 in.) width shall increase to a width of 16 mm (5/8 in.) at 25 mm (1 in.) from the end. The 

probe shall be of any convenient length. The tip of the probe shall be squared off and not sharp 

so that when probing delaminations, fibers across the delaminated area will not be cut. 

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7.13.3 Specimen preparation 

Five specimens shall be cut from each sample to 25 x 125 mm (1 x 5 in.) dimensions, avoiding 

knots, knotholes and other voids permitted in the grade, with grain of the outer plies in the long 

direction. Measurement of delamination shall take place prior to any mechanical test. 

7.13.4 Test procedure 

Delamination shall be evaluated according to the following procedure. The specimen shall be 

examined visually for delamination. Any separations in the specimen periphery in veneer-toveneer or veneer-to-wood-based material glueline shall be probed to determine depth of 

delamination. A separation that is 6.4 mm (1/4 in.) deep for a continuous length of 25 mm (1 in.) 

shall be considered as having failed the test for delamination. Use of slight pressure is necessary 

when inserting the probe into the delaminated areas. The pressure shall be limited to that which 

is applied by gripping the probe between the thumb and first finger. In no case shall any prying 

action be used. 

The number of specimens failing this test shall be reported. 

7.14 Adhesive mold test 

7.14.1 Equipment 

Cabinets shall be used to house test specimens under mold-producing conditions. Each cabinet 

shall be divided into three interconnecting compartments with adjustable specimen trays, each 

with a sealed door in the front. On each side of the trays, toweling shall be suspended vertically 

with the lower ends in a water pan acting as wicking in order to provide maximum wet surface 

area. These pans shall rest on the floor of the mold cabinet under each compartment. The water 

level in these pans shall be kept 65 mm to 75 mm (2-1/2 in. to 3 in.) in depth. 

In order to maintain a uniform temperature within the mold cabinets, a walk-in housing shall 

surround the cabinets. The temperature within this housing shall be maintained at 27 °C (80 °F) 

with a 500-watt heater controlled by a thermostat. Fan-forced air circulation sufficient to avoid 

stratification shall be used to ensure even temperature in all areas of the housing. No air 

circulation shall occur within the mold cabinets, since mold growth is dependent upon still air. 

A uniform temperature shall be maintained in the housing around the cabinets. 

7.14.2 Specimen preparation 

Test specimens to be used for determination of mold resistance of the adhesive agent in the 

panel shall depend on the construction of the panels being tested. Plywood shall be tested by 

preparing plywood shear specimens as described in PS 1, kerfed to pull lathe checks closed for 

maximum breaking load. 

Test specimens for testing composite panels and mat-formed panels shall be 25 mm x 125 mm 

(1 in. x 5 in.) in dimension. Composite panel specimens shall be cut with the veneer grain in the 

125 mm (5 in.) dimension. Mat-formed panels shall be cut with the 125 mm (5 in.) dimension 

parallel to the panel strength axis, except in the case of panels containing oriented furnish, in 

which case two complete sets of specimens as described below shall be prepared, one set 

parallel and one set perpendicular to the panel strength axis. 

The four panels to be mold tested shall be cut into 100 pairs of specimens (two sets of 100 pairs 

each in the case of oriented furnish). These paired specimens (mold test specimen and adjacent 

control specimen) shall be completely randomized and assembled into 10 groups of 20 

specimens each for each direction tested (10 test specimens and 10 controls). The controls and 

test specimens for each group shall then be separated. 

7.14.3 Test procedure 

Prior to placing plywood specimens in the mold cabinet, they and their controls shall be stickered, 

given a five-second dip in tap water at room temperature, and then conditioned for one week at 

95% (+/- 2%) relative humidity and a temperature of 27 °C (80 °F) in a separate conditioning 

chamber. After one week, test and control specimens shall be removed. Test specimens shall 

be dusted with soybean flour and placed flat on green pine sapwood veneer strips that have been 

stored in the mold cabinet. A stack of these veneer strips and test specimens shall then be 

placed in the mold cabinet. The control specimens shall be allowed to dry at room conditions. 

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At two-week intervals, the designated mold groupings shall be removed from the cabinet and 

allowed to dry at room conditions for one week. Test specimens and corresponding control 

specimens shall then be tested as required. Ten of these groups shall be sufficient to test moldresistant properties of plywood products. 

Mold test specimens for composites and mat-formed products shall be subjected to the fivesecond dip in tap water and the one-week exposure at 95% (+/- 2%) relative humidity and a 

temperature of 27 °C (80 °F) in a separate humidity chamber. 

Control test specimens from composites and mat-formed products shall be subjected to testing 

according to Section 7.16. At two-week intervals, composites and mat-formed products from the 

mold test and moisture-cycled control specimens shall be dried at room conditions for one week 

and then tested according to Section 7.7. 

7.15 Adhesive bacteria test 

7.15.1 General 

This method determines if an adhesive system possesses sufficient resistance to bacterial attack 

to retain bond integrity under conditions that promote bacterial growth. 

7.15.2 Specimen preparation 

Test specimen size shall depend on panel construction. Plywood panels shall use shear 

specimens described in PS 1, kerfed to pull lathe checks closed for maximum breaking load. 

Other panels shall use a specimen 25 mm x 125 mm (1 in. x 5 in.). Panels containing veneer 

shall be cut with the 125 mm (5 in.) dimension parallel to the grain. The veneer shall be 

completely free of knots, knotholes, and other voids permitted in the grade. 

Specimens from mat-formed panels shall be cut parallel to the panel strength axis, except for 

panels containing oriented furnish, in which case two complete sets of specimens shall be cut, 

one parallel and one perpendicular to the panel strength axis. 

Sufficient material is needed to provide 80 specimens per set as required. Specimens within 

each set shall be numbered consecutively 1 through 80 as cut, with odd-numbered specimens 

destined for bacteria exposure and the adjacent even-numbered specimens destined for control. 

Ten odd-numbered specimens and their matching 10 even-numbered specimens shall then 

comprise an exposure group and control for that group. Four such groups shall be made up from 

the 80 specimens for each direction tested. 

7.15.3 Test procedure 

Plywood specimens, including the controls, shall be subjected to one-half hour vacuum and onehalf hour pressure under tap water following the cycle used in the PS 1 vacuum-pressure test for 

Exterior plywood. Control specimens shall then be tested as required in the wet condition. The 

breaking load shall be recorded and control averages shall be determined for each of the 

exposure groups. 

For composites and mat-formed products, all specimens shall be subjected to the vacuum-soak 

portion of the moisture cycle test of Section 7.16. Control specimens shall be dried according to 

the drying provisions of Section 7.16 and broken dry according to the procedures of Section 7.7, 

with the breaking load recorded and control averages determined for each of the exposure 

groups. 

All specimens designated for the bacteria exposure shall be floated flat in a slurry of soybean 

flour, water and alder sawdust consisting of 7% soybean flour, 83% water and 10% alder sawdust 

(sawdust at 18% moisture content). To this slurry shall be added 0.3% by weight of a 50% 

solution of sodium hydroxide. The slurry shall be poured into trays, filling them to a depth of 25 

mm (1 in.). (Note: Do not use copper trays.) These trays containing slurry and specimens shall 

then be placed into a cabinet described and maintained according to Section 7.14. 

One exposure group shall be removed from the cabinet every three weeks over the 12-week 

period of the test. Plywood specimens shall be tested wet according to the standard plywood 

shear test method. Specimens of composite and mat-formed products shall be dried according 

to the drying cycle of Section 7.16 and broken according to Section 7.7. 

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7.16 Moisture cycle test for bond performance (single cycle test) 

7.16.1 General 

This moisture cycle test is a quality control method to accelerate bond degradation. Following 

moisture cycling, a mechanical test is generally performed. 

7.16.2 Specimen preparation 

Specimen size and configuration shall depend upon the test to follow moisture cycling. 

7.16.3 Test procedure 

The specimens shall be placed in racks to ensure free movement of water and air around the 

specimens. The specimens shall then be placed in a vacuum-pressure vessel, which is then 

filled with 66 °C (150 °F) water. A vacuum of 50.6 kPa (15 in. of mercury) shall be drawn on the 

vessel for 30 minutes. The vacuum shall then be released and the specimens shall be allowed 

to soak in the water at atmospheric pressure for 30 minutes. The vessel shall then be drained 

and the specimens dried at 82 °C (180 °F) in an oven with fan-forced air circulation of 45 to 50 

air changes per hour until the dry test condition (see section 2.23) is achieved. The specimens 

shall then be tested dry according to the appropriate test method. 

7.17 Moisture cycle test for delamination and strength retention (six-cycle test) 

7.17.1 General 

This moisture cycle is used in evaluation of delamination and strength retention of products rated 

as Exposure 1. 

7.17.2 Specimen preparation 

Specimen size and configuration shall depend on the test to follow moisture cycling. 

7.17.3 Test procedure 

Specimens shall be placed in racks to ensure free movement of water and air around the 

specimens. The specimens shall then be placed in a vacuum-pressure vessel, which is then 

filled with 66 °C (150 °F) water. A vacuum of 50.6 kPa (15 in.) of mercury shall be drawn on the 

vessel for 30 minutes. The vacuum shall then be released, and the specimens shall be allowed 

to soak in the water at atmospheric pressure for 30 minutes. They shall afterwards be removed 

and dried for six hours at 82 °C (180 °F) in an oven with fan-forced air circulation of 45 to 50 air 

changes per hour. Specimens shall then be returned to the pressure vessel and the vacuumsoak cycle repeated. Following the second vacuum-soak cycle, specimens shall again be placed 

in the oven and dried for 15 hours. This shall complete two cycles. Testing shall be continued 

for two additional days until six cycles have been completed with the final step of redrying to 

achieve the dry test condition (see section 2.23). The specimens are then tested according to 

the appropriate test method. 

7.18 Bond performance test for plywood with knots and knotholes 

7.18.1 General 

This is a moisture cycle and loading procedure for verifying resistance to deflection and damage 

under concentrated static and impact loads applied at the location of the maximum knot or 

knothole. The method is used to evaluate knots and knotholes greater than 51 mm (2 in.) but 

not exceeding 76 mm (3 in.) in width measured across the grain of Exposure 1 plywood panels. 

7.18.2 Specimen preparation 

From 10 1,220 mm x 2,440 mm (48 in. x 96 in.) panels, a specimen at least 595 mm (23.5 in.) 

wide by twice the span in length shall be cut. The test specimen shall be configured such that 

the subject knot or knothole is along a mid-test-span line and at least 295 mm (11-5/8 in.) from 

either edge. The subject knot shall be the maximum size (+0, –13 mm [+0, –1/2 in.]) permitted 

within the grade. 

Each specimen shall be placed vertically in a tank and sprayed with water on both faces 

continuously for 72 hours. As an alternative to spraying, soaking panels continuously for 72 

hours shall be permitted provided the height of the water level above the panels does not exceed 

600 mm (24 in.). Panels shall then be redried until constant weight is reached at 20 +/- 3 °C (68 

+/- 6 °F) and 65 +/- 3% relative humidity. 

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7.18.3 Test procedure 

Concentrated static load – Procedures of ASTM E-661 and Section 7.1 of PS 2 shall be 

followed except that: 

1. The specimen shall be placed in the test frame with the subject knot or knothole in the tension 

zone when a bending load is applied. 

2. The load shall be applied over the subject knot or knothole on the face opposite the knot or 

knothole. 

Concentrated impact load – Procedures of ASTM E-661 and Section 7.1 of PS 2 shall be 

followed, except that: 

1. The specimen shall be placed in the test frame with the subject knot or knothole in tension. 

2. The impact shot bag shall be dropped once from a height of 760 mm (30 in.). 

3. The shot bag shall be dropped over the subject knot or knothole on the face opposite the 

knot or knothole. 

7.19 Radial probe test 

7.19.1 General 

This method defines a procedure for determining delamination associated with knots and 

knotholes in plywood panels. 

7.19.2 Equipment 

The probe used shall measure 6.4 mm (1/4 in.) wide at the tip by 0.3 mm (0.012 in.) thick and 

shall increase in thickness to about 0.6 mm (0.025 in.), 12 mm (1/2 in.) from the tip. The 6.4 mm 

(1/4 in.) width shall increase to a width of 16 mm (5/8 in.) at 25 mm (1 in.) from the tip. The probe 

is to be of any convenient length. The tip of the probe shall be squared off and not sharp so that 

when probing delaminations, fibers across the delaminated area will not be cut. In addition, the 

probe shall be fitted with a mechanism that is capable of limiting the force to the maximum level 

specified. 

7.19.3 Specimen preparation 

One knot or knothole per sample panel shall be selected. The knot or knothole selected shall be 

the maximum size (+0, –13 mm [+0, –1/2 in.]) permitted within the grade. Each specimen shall 

be cut 300 mm x 300 mm (12 in. x 12 in.) with the knot or knothole approximately centered. 

Specimens shall be moisture cycled and redried according to one of the following three cycles: 

The 72-hour water spray cycle specified in Section 7.18. After exposure, specimens shall be 

redried until constant weight is reached at 20 +/- 3 °C (68 +/- 6 °F) and 65 +/- 3% relative humidity. 

1. The 72-hour water soak cycle specified in Section 7.18 (as an alternative to the 72-hour water 

spray cycle). After exposure, specimens shall be redried until constant weight (weight 

change  0.2% within two hours) is reached at 20 +/- 3 °C (68 +/- 6 °F) and 65 +/- 3% relative 

humidity. 

2. Specimens shall be placed in a pressure cylinder, flooded with water at 49 +/- 6 °C (120 +/-

10 °F) and subjected to a vacuum of 91 +/- 7 kPa (27 +/- 2 in. of mercury) for three hours. 

Specimens shall then be subjected to three hours of pressure not to exceed 414 kPa (60 

psi). This shall be followed by a second vacuum exposure of 91 +/- 7 kPa (27 +/- 2 in. of 

mercury) for two hours. After exposure, the specimens shall be redried until constant weight 

(weight change  0.2% within two hours) is reached at 20 +/- 3 °C (68 +/- 6 °F) and 65 +/-

3% relative humidity. 

7.19.4 Test procedure 

Each specimen shall be cut into eight sectors with radii intersecting at center of knot or knothole. 

The area surrounding the knot or knothole shall be visually inspected for delamination. Where 

separations are visible, the probe shall be inserted with a force of 35.5 +/- 4.5 N (8 +/- 1 lbf). No 

prying action or lateral movement shall be applied. 

For each sector, the radial distance from the tip of the sector to the boundary of separation 

beyond the knot or knothole shall be measured along both edges of the sector and recorded. 

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Where a separation is not found, the distance from the tip of the sector to the boundary of the 

knot or knothole shall be measured and recorded. 

The total area of separation for each specimen shall be calculated as: 

2 A = R 

where: A = total area of separation (mm2 or in.

2) 

R = average radius of separation, calculated as the average of 16 distances 

(measured at edges of sectors) from the tips of the sectors to either the 

boundary of separation or the boundary of the knot or knothole (mm or 

in.). 

7.20 Dead weight stiffness capacity (EI) test (non-mandatory) 

7.20.1 General 

This procedure provides an estimate of full panel stiffness capacity. Dead weight stiffness is not 

a requirement. 

7.20.2 Equipment 

Sawhorses may be used for support, but the metal frame shown in Figure 6 is recommended. 

The supports shall be at least 1,220 mm (48 in.) wide, fixed to the floor or weighted, level and 

parallel to each other. The deflection gage shall have a range of 0 to 50 mm (0 to 2 in.) and be 

graduated in 0.025 mm (0.001 in.) increments. Loading bars shall be 1,220 mm (48 in.) long and 

25 mm to 38 mm (1 in. to 1.5 in.) wide. The weight of the bars shall be determined to the nearest 

0.5 N (0.1 lb). Load bars are typically in the range of 44.5, 89.0, and 178.0 N (10, 20 and 40 lb). 

Figure 6. Steel Test Frame for Dead Weight Stiffness Test 

7.20.3 Specimen preparation 

The number of samples will be prescribed by the certification agency. When measuring stiffness 

parallel to the strength axis, 1,220 mm x 2,440 mm (48 in. x 96 in.) panels shall be tested. Other 

lengths are allowable when measuring stiffness perpendicular to the strength axis. It may be 

useful to mark lines across the panel back at 1,220 mm (4 ft) width at 150 mm (6 in.) from either 

end and across the panel top at mid-length (Figure 7). On the bottom side, also mark an "X" at 

the panel's center. 

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Figure 7. Panel Alignment Marks 

On the reverse side of the panel, mark an "X" at the panel's center: 

7.20.4 Test procedure 

The typical span for testing the 2,400 mm (96 in.) axis shall be 2,135 mm (84 in.) and 915 mm 

(36 in.) for the 1,220 mm (48 in.) axis. Place the panel on top of the supports and align it so the 

ends are parallel to the supports, with equal length of panel overhanging each support. The lines 

drawn on the panel should be useful for alignment. Place the surface up, in accordance with the 

manufacturer's use recommendations. The deflection gage should be placed under the panel in 

an adjustable fixture, perpendicular to the panel and with the tip of the gage directly under the 

"X" (see Section 7.20.3). 

Place load bars at mid-span, parallel to the supports. Preloads are applied first to settle the 

panel, removing the possible effects of warp, and should result in complete contact of the panel 

across the support. Discard excessively warped panels. Preloads of 44.5 N (10 lb) are 

recommended for panels with Performance Category between 3/8 and 7/16 and 89.0 N (20 lb) 

for panels with Performance Category greater than 15/32. 

Record the deflections to the nearest 0.025 mm (0.001 in.). In order to obtain accurate stiffness 

capacity, the difference between the preload and the final load deflections should be in the range 

of 6.4 mm to 8.9 mm (0.25 in. to 0.35 in.) for panels with Performance Category of 3/4 or less. 

Panels with a Performance Category of greater than 3/4 should have sufficient weight to result 

in 5 mm (0.2 in.) deflection and may be cut to 610 mm (24 in.) width to accommodate deflection 

requirements. 

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Table 9. Typical pre-loads and test loads 

Performance 

Category 

Pre-load Test Load 

Panel Test Direction 

Along 

Strength Axis 

Across 

Strength Axis 

N lb N lb mm in. mm in. 

3/8, 7/16 44.5 10 44.5 10 2,135 84 915 36 

15/32 – 5/8 89.0 20 89.0 20 2,135 84 915 36 

23/32 – 7/8 89.0 20 178.0 40 2,135 84 915 36 

Greater than 7/8 89.0 20 * * 2,135 84 915 36 

*If larger weights are not available and deflection is less than recommended, it may be 

appropriate to reduce the panel width (e.g., from 1,220 mm [48 in.] to 610 mm [24 in.]) 

Two people should always be involved because of the need for immediate deflection readings 

after applying the preload and final load. The gage shall be read immediately after application of 

the preload bar. Apply additional load(s) after reading the preload deflection. Record the second 

deflection reading immediately after applying the final load bar. 

The general equation for calculating dead weight stiffness is: 

K b (D )D-

(P )P - 

EI 

12

3

12





=



where: EI = Panel stiffness, N-mm2/mm (lbf-in.

2/ft) 

P1 = Pre-load, N (lbf) 

P2 = Total load, N (lbf) 

 = Span, mm (in.) 

b = Width, mm (in.) 

D1 = Deflection after preload, mm (in.) 

D2 = Deflection after final load, mm (in.) 

K = Constant (48 when b is measured in mm, 

4 when b is measured in inches). 

8 TRADEMARKING AND CERTIFICATION 

8.1 Certification 

Panels represented as conforming to this standard shall bear the stamp of a qualified inspection 

and testing agency that (1) inspects the manufacture (with adequate sampling, testing, and 

examination for quality) or (2) has tested a randomized sampling of the finished panels in the 

shipment being certified for conformance with this standard. 

8.2 Qualified inspection and testing agency definitions 

8.2.1 A qualified inspection agency is defined as one that is accredited to ISO/IEC 17020, Conformity 

Assessment – Requirements for the Operation of Various Types of Bodies Performing 

Inspections. An agency accredited to ISO/17065, Conformity Assessment – Requirements for 

Bodies Certifying Processes and Services and meets the applicable requirements of ISO/IEC 

17020 and has inspections included in its certification scheme meets the definition of qualified 

inspection agency. 

8.2.2 A qualified testing agency is defined as one that is accredited to ISO/IEC 17025, General 

Requirements for the Competence of Testing and Calibration Laboratories. An agency 

accredited to ISO/17065, Conformity Assessment – Requirements for Bodies Certifying 

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Processes and Services and meets the applicable requirements of ISO/IEC 17025 and has 

testing included in its certification scheme meets the definition of qualified testing agency. 

8.3 Panel marking 

All Sheathing, Structural I Sheathing, Single Floor and Structural I Single Floor panels 

represented as conforming to this standard shall be identified with a mark bearing the grade 

name appropriate under these specifications, and 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. The panel grade, span rating, 

bond classification and the symbol PS 2-18 signifying conformance to this standard shall be 

included in the mark. Any supplemental application specifications of the manufacturer shall be 

clearly marked on each panel. The mark shall maintain legibility after weather exposure during 

construction. Mat-formed panels with oriented furnish shall be marked to show the direction of 

the strength axis. The optional notation “Size for Spacing” (see Section 2.19) is permitted. 

ADVISORY NOTE: The following abbreviations in the panel mark are permitted: 

• Sheathing – SHTG 

• Structural I – Struc I 

• Exposure 1 – EXP 1 

• Exterior – EXT 

The panel fractional Performance Category (see Section 5.2.1.2) and term “Performance

Category” or abbreviation (i.e., PERF CAT, CAT or Category) shall be labeled on the panel. In 

addition, the thickness in 1,000ths of an inch within the permitted tolerance (see Section 5.2.1.2) 

for the Performance Category shall be labeled on the panel. 

ADVISORY NOTE: See Appendix D for a table of recommended thickness labels. 

8.3.1 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 identified by means of a 100 x 125 mm (4 x 5 in.) minimum size 

mark carrying the legend, “Shop-cutting panel – all other [agency] marks void” (See definition of

shop-cutting panel), or 

Other panels rejected as not conforming shall be plainly identified by a mark placed next to, and 

be no less prominent than the original mark, carrying the legend, “REJECT – All other agency 

marks void.” 

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

conforming to all of the applicable provisions of this standard. 

9 EFFECTIVE DATE AND IDENTIFICATION 

This standard became effective on March 30, 2019. As of that date, reference to this standard is 

permitted in contracts, codes, advertising, invoices, product labels, and the like; however, a 

product shall not be advertised nor represented in any manner that in any way might imply 

approval or endorsement of that product by the National Institute of Standards and Technology 

and/or the U.S. Department of Commerce. 

The following suggested statements are permitted in representing products as conforming to the 

requirements of this standard: 

• “This [e.g, panel, shipment] conforms to all requirements established in Voluntary Product 

Standard PS 2-18, ‘Performance Standard for Wood Structural Panels,’ in accordance with 

the U.S. Department of Commerce Procedures for the Development of Voluntary Product 

Standards. Full responsibility for the conformance of this product to the standard is assumed 

by (name and address of producer and/or distributor).”

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10 

• “Conforms to Voluntary Product Standard PS 2-18, (name and address of producer and/or 

distributor).”

STANDARD REVIEW COMMITTEE 

A Standard Review Committee has been established to assist in keeping this standard current. 

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 Standard Review 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. 

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APPENDIX A. (Nonmandatory) 

A1 SHIPMENT REINSPECTION PRACTICES 

A1.1 General 

This information is based on industry practice and is offered to wood structural panel purchasers. 

A1.2 Request for reinspection 

Any request by the buyer for the reinspection of any item or lot of panels 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 panels certified as conforming 

to this standard shall be construed as involving agreement to submit such panels to reinspection 

by the qualified inspection and testing agency whose trademark was used. 

A1.3 Responsibility of the buyer 

A request to the seller for reinspection is permitted: 

a. for panel grade – within 30 days6 after arrival at the first point of receipt from the mill, if the 

grade of any item, as invoiced, is in doubt; 

b. for glue bond quality of Exterior panels – when delamination is visibly evident; 

c. for bond quality and bond performance associated with knots and knotholes of Exposure 1 

panels – within six months after arrival at first point of receipt from the mill, if delamination is 

visibly evident; 

d. for structural performance, such as resistance to concentrated loads on panels – within six 

months after arrival at first point of receipt from the mill; 

e. for physical properties, such as linear expansion of panels – within six months after arrival at 

first point of receipt from the mill. 

All panels of disputed grade shall be kept intact and properly protected from damage, 

deterioration, and from direct exposure to moisture that could interfere with a fair reinspection. 

All panels of disputed quality 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. 

A1.4 Responsibility of the seller 

A request for reinspection shall be promptly acknowledged by the seller following its receipt. 

A1.5 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 A1.6. If the panels pass the reinspection, said 

expenses shall be borne by the buyer. The buyer shall lend all reasonable assistance to facilitate 

the reinspection. 

A1.6 Reinspection procedures and settlement 

A1.6.1 Condition of panels 

All panels designated as complying with this standard shall be subject to reinspection in the asmanufactured condition only. This requirement does not apply to reinspections for bond quality. 

A1.6.2 Sampling for panel grade, size and thickness reinspections 

At buyer’s or seller’s option, grade, size, and thickness reinspections may include all panels of 

an item whose conformance to this standard is in dispute. However, buyer and seller may agree 

upon a reduced basis for sampling provided at least 20% or 300 panels, whichever is smaller 

and which represents only those items as invoiced that 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 

6 For unitized shipments, the 30-day limit shall be extended to include the period dating from receipt of shipment to breaking of the 

first bundle, but not exceeding six months, provided the requirement for keeping the disputed panels intact is observed and the 

panels in question are held for at least 30 days following the request for reinspection. 

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found to be below grade or out of tolerance for size and thickness shall have improper trademarks 

obliterated and shall be re-marked with appropriate designation with a special inspection mark 

registered by the qualified agency conducting the reinspection and applied by that agency’s

authorized representative. 

A1.6.3 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 item fails to pass the reinspection and the 

nonconforming panels need not be accepted. If reinspection establishes that a disputed item is 

5% or less below grade or out of dimensional tolerance, it passes the reinspection and the 

disposition of the nonconforming panels shall be as agreed upon between the 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 plugged 

crossbands and jointed crossbands, as set forth in PS 1. 

A1.6.4 Sampling for bond quality, bond performance associated with knots and knotholes, 

structural performance, or physical properties reinspections 

For test purposes, 20 panels, or 5% of the panels, whichever is less, shall be selected at random 

from the item, lot, or shipment that is in dispute. The number of panels required shall be 

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 bond 

requirements, testing and evaluation shall apply separately to each category. 

A1.6.5 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 Sections 7 and A1.6.4 above. If the reinspection tests 

establish that the glue bond quality does not meet the requirements of Section 6.2.4 as applicable, the item, lot, or shipment fails to pass the reinspection and may be rejected by the buyer. If 

the glue bond quality requirements are met, the item, lot or shipment passes the reinspection, 

and the buyer shall accept the item, lot or shipment as invoiced, except that the buyer need not 

accept any delaminated Exterior panels. 

A1.6.6 Reinspection for bond performance associated with knots and knotholes 

Unless otherwise agreed upon between buyer and seller, reinspections for bond performance 

associated with knots and knotholes shall be limited to knots and knotholes greater than 50 mm 

(2 in.) but not exceeding 76 mm (3 in.) in width measured across the grain. Knots and knotholes 

within this range shall be reinspected according to Sections 7.18 and 7.19. If the panels were 

not exposed to weather prior to reinspection sampling, they shall be moisture conditioned 

according to the cycle specified in Sections 7.18 and 7.19 prior to reinspection. 

If reinspection tests establish that the bond performance associated with knots and knotholes 

requirements are not met, the item, lot or shipment fails to pass the reinspection and may be 

rejected by the buyer. If the reinspection requirements are met, the item, lot or shipment passes 

the reinspection and the disposition of the nonconforming panels shall be as agreed upon 

between the buyer and seller. 

A1.6.7 Structural performance reinspections 

Unless otherwise agreed upon between buyer and seller, structural performance reinspections 

are limited to concentrated loads (Section 5.3.1.1). If the buyer and seller agree to additional 

tests, a larger number of panels than those given in Section A1.6.4 may be needed. If the 

reinspection tests establish that the concentrated load requirements are not met, the item, lot, or 

shipment fails to pass the reinspection and may be rejected by the buyer. If the concentrated 

load requirements are met, the item, lot, or shipment passes the reinspection and the disposition 

of the nonconforming panels shall be as agreed upon between the buyer and seller. 

39 
 

 

 

 

 

A1.6.8 Physical property reinspections 

Unless otherwise agreed upon between buyer and seller, physical property reinspections shall 

be limited to linear expansion (Section 5.3.2.1). If the reinspection tests establish that the linear 

expansion requirements are not met, the item, lot, or shipment fails to pass the reinspection and 

may be rejected by the buyer. If the linear expansion requirements are met, the item, lot or 

shipment passes the reinspection and the disposition of the nonconforming panels shall be as 

agreed upon between the buyer and seller. 

Reinspection Flow Chart 

PRIOR AGREEMENT

BETWEEN BUYER &

SELLER?

REVISED TEST

PLAN

YES

NO

CONCENTRATED

LOAD TESTS PER

SECTION 5.3.1.1

DETERMINE NEED

FOR

ADDITIONAL PANELS

(SEE A1.6.4)

TESTS MEET

CONCENTRATED LOAD

REQUIREMENTS?

CONCENTRATED LOAD

AND OTHER

REQUIREMENTS MET?

CONCENTRATED LOAD

TESTS PER

SECTION 5.3.1.1, PLUS

ADDITIONAL TESTING

BUYER MAY REJECT LOT

REINSPECTION PASSES,

BUYER MUST ACCEPT

LOT

YES

YES

NO

NO

40 
APPENDIX B. (Nonmandatory) 

PS 2 Qualification Flow Chart 

RANDOMLY SELECTED

QUALIFICATION SAMPLE

QUALIFICATION TESTING

MILL SPECIFICATION

DEVELOPMENT FOR

ONGOING QUALITY

ASSURANCE

STRUCTURAL TESTS

• Uniform Load

• Concentrated Load

- Static

- Impact

• Nail Holding

• Racking Shear

PERFORMANCE

CRITERIA

SATISFIED?

CERTIFICATION

 OF

 SPAN RATING

MILL SPECIFICATION

QUALITY ASSURANCE

VALUES ASSIGNED

MECHANICAL PROPERTIES

• Panel Flexure

- Stiffness

- Strength

PRODUCT PROPERTIES

• Linear Expansion

• Small Bending

• Bond Performance

• Wood Failure (plywood)

YES

MILL STAFF

ACCEPTANCE?

NO

MILL QUALITY PROCEDURES

&

AGENCY ROUTINE

QUALITY ASSURANCE

PERFORMANCE-RATED PANEL QUALIFICATION

FOR

ROOF, SUBFLOOR, SINGLE FLOOR AND WALL APPLICATIONS

RANDOMLY

SELECT

REQUALIFICATION

SAMPLE

 

 PRODUCT PROPERTIES

• Dimensional Stability

• Small Bending

• Bond Performance

PANEL PROPERTIES

• Grade

• Thickness

NO

YES

Q:\QSD\PS2Rev\PS2flowchart.vsd

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APPENDIX C. (Nonmandatory) 

History of the Standard and Comments on the Current Edition 

C1 History of PS 2 

In September 1988, a special Bi-national Committee (BNC) was formed and charged with the 

task of fostering the mutual objective of the United States and Canada with respect to the 

development and implementation of harmonized standards with regard to performance 

requirements for plywood. This action was a consequence of the implementation of the Free 

Trade Agreement (FTA) of 1987. In accordance with the Agreement, U.S. tariffs on plywood and 

other structural panels could not be removed until the trade issues involving plywood standards 

were resolved. Of concern to the United States was the fact that certain grades of plywood 

permitted in PS 1 were not covered in Canadian plywood standards, and consequently not 

acceptable under Canadian building codes. 

The BNC began its task by reviewing the existing industry standard APA – The Engineered Wood 

Association (APA), APA PRP-108, Performance Standards and Policies for Structural-Use 

Panels, and the Canadian Standards Association (CSA) standard CAN/CSA-O325, Construction 

Sheathing, to identify the technical differences and to consider the roles the standards might play 

in resolving the plywood trade issues. It concluded that the development of common criteria 

embodied in performance-based national standards offered means to resolve the trade issue. 

Next, the BNC sponsored a joint U.S./Canadian study designed to produce additional 

comparative information on U.S. and Canadian plywood. Based on BNC’s assessment of the 

technical differences in the APA and CSA standards and the data derived from the joint study, 

the BNC in November 1990 submitted new U.S. and Canadian draft standards, respectively, to 

the National Institute of Standards and Technology (NIST) in the United States and the CSA in 

Canada for processing as national consensus standards. 

In March 1991, APA signed an agreement with NIST to support development of the proposed 

U.S. performance standard as a Voluntary Product Standard (VPS) under procedures of the U.S. 

Department of Commerce. In April 1991, NIST established a Standard Review Committee under 

the VPS Program to assume responsibility for development of the U.S. standard. On October 

15, 1991, after two 30-day review periods and some editorial changes, the Committee 

recommended unanimously that the proposed standard be prepared for public review and 

acceptance as a Voluntary Product Standard. 

In March 1992, the proposed VPS standard was distributed to a list of manufacturers, distributors, 

consumers, and others who might have interest in the subject standard, and on April 8, 1992, 

NIST announced in the Federal Register the public circulation of the proposed standard and 

invited public comments. A 75-day comment period was allowed. Following public review of the 

standard, which ended June 22, 1992, NIST determined that the responses indicated consensus 

among producers, distributors, and consumers in accordance with the published procedures. 

The standard was originally approved for publication by NIST as Voluntary Product Standard PS 

2-92, Performance Standard for Wood-Based Structural-Use Panels, on August 27, 1992. 

The new U.S. standard was not intended to replace existing standards such as Voluntary Product 

Standard PS 1-83, Construction and Industrial Plywood, but to serve as an alternative 

performance-based standard that would relate to a variety of forms of structural panels: plywood, 

oriented strand board, waferboard, structural particleboard, and composite panels. 

C2 Edition PS 2-04 

After considerable technical review, PS 2-04 was revised and accepted in December 2004. The 

PS 2-04 edition contained many revisions. The major technical revisions included the following. 

42 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

C2.1 Revision to Exposure 1 bond performance methods 

This edition of the standard introduced a new method for determining Exposure 1 bond 

performance for mat-formed panels. As an alternate to using the 1 inch by 5 inch edgewise 

bending method, stiffness and strength criteria based on larger flatwise bending specimens were 

introduced. 

C2.2 Linear expansion method 

Revisions to the linear expansion method were made based on a need to reflect industry 

performance and serviceability requirements. Industry samples were benchmarked for linear 

expansion, and a suitable cycle and criteria were evaluated. The criterion was established at an 

average level, which is common for serviceability applications. The cycle was based on 

equilibrium at 50% relative humidity, which is viewed to be more representative of installed 

conditions than the oven-dry condition. Industry surveys were conducted and reviewed to 

determine acceptable performance using the revised criteria, and test methods and verification 

of the methods was conducted on a representative subset of products. 

C2.3 Pass/fail provisions for structural performance 

General comments on the structural performance sections indicated the instructions were not as 

clear as they could be and even sometimes in conflict. In addition, concerns were expressed 

about applying structural performance criteria to daily mill quality assurance evaluations. Finally, 

there were questions about the linearity of deflection requirements for a given increase in spans. 

The following changes were made: 

a. Revisions to the sections describe the test provisions more clearly. Each possible scenario 

is described independently. The actual percentage resulting in passing results is specified 

for each test and criterion explicitly. 

b. Where appropriate, a clause was added to each performance test stating that the average of 

the tests should meet the designated requirement. 

C2.4 Exposure 2 

This exposure classification was deleted due to the lack of use by the industry. 

C2.5 Stability Index 

The stability index was deleted due to the use of linear expansion as the primary method to 

determine dimensional stability. 

C3 Edition PS 2-10 

After considerable technical review by members of the PS 2 Standing Committee, the standard 

was revised to address the following technical and informational aspects. 

C3.1 Labeling of panel thickness 

In response to consumer complaints regarding panel thickness tolerances that created the 

potential for 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. 

C3.2 Formaldehyde appendix 

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

products, an informational appendix was added to review those regulations with respect to PS 2 

panels. 

C3.3 Environmental attributes and green building rating systems. 

An informational appendix was added to review environmental attributes of PS 2 panels with 

respect to various green building rating systems. 

43 
 

 

 

 

 

 

 

 

 

 

 

C3.4 Technical revisions. 

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

practice. These included revisions to clarify the dry test condition and the “20” span rating.

Fastener load values were modified to better reflect panel performance characteristics and to 

respond to increased code provisions for fastening requirements. 

C4.0 Current Edition PS 2-18 

After considerable technical review by members of the PS 2 Standing Committee, the standard 

was revised to address the following technical and informational aspects. 

C4.1 Measurement of dimensions 

Additional details were added regarding measurement of dimensions. The term “sized for 

spacing” was added to denote panels that are sized for compatibility to recommended application

for construction uses. 

C4.2 Structural I Single Floor 

Technical requirements were added for this new grade of panels. 

C4.3 Deflection limits for wall sheathing 

Deflection criteria for wall sheathing under uniform loads was added to the standard to provide 

suitable performance for construction applications. 

C4.4 Other technical and editorial revisions 

Other technical and editorial revisions were made to reflect industry practices, including: 

• Simplification of the Appendix on labeling 

• Deletion of the Appendix on Green Building Provisions 

• Clarification that linear expansion requirements are met by testing to one method and 

criteria 

• The title was revised to reflect the term used by U.S. model codes 

• Revised definition of qualified testing and inspection agency 

• Corrected air exchange rate for moisture exposure test 

• Added abbreviations commonly used for labeling. 

44 
 

 

 

 

 

 

 

 

APPENDIX D. (Nonmandatory) 

Recommended Thickness Labels 

D1 Recommended thickness labels 

Section 5.2.1.2 specifies thickness tolerances and Performance Categories for panels. Section 

8.3 specifies that the panels shall be labeled with a thickness label in 1,000ths of an inch and 

that labeled quantity shall be within the minimum and maximum thickness specification for that 

Performance Category. Table D1 presents recommended thickness labels. 

D2 Regulations on labeling 

See Appendix E for discussion of regulations dealing with labeling. 

TABLE D1. RECOMMENDED THICKNESS LABELING FOR PANELS 

Thickness Requirements for Panels1 

Performance 

Category2 

Minimum Thickness 

in. (mm) 

Maximum Thickness 

in. (mm) 

Recommended 

Thickness Label(3) 

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

5/16 PERF CAT 0.281 (7.14) 0.344 (8.73) Thickness 0.289 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. 

9/16 PERF CAT 0.531 (13.49) 0.594 (15.08) Thickness 0.547 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. 

1Thickness requirements are based on a tolerance of +/- 0.8 mm (1/32 in.) for panels with Performance 

Categories of 13/16 and less and +/- 5% for panels with Performance Categories greater than 13/16 unless a 

closer tolerance is determined through qualification testing. Inch units are presented as primary units due to 

customary practice in the United States. 

2 Acceptable abbreviations are PERF CAT, CAT or Category. 3 The panel manufacturer may label with any thickness value provided the product complies with 

Section 5.2.1.2. The recommended thickness label for categories less than 9/16 is 3% above the 

minimum. The recommended thickness label for categories greater than or equal to 9/16 are the 

minimum values for PS 1 sanded panels. 

45 
 

 

 

 

 

APPENDIX E. (Nonmandatory) 

Labeling Guidelines Based on the Uniform Packaging and Labeling Regulations of 

NIST Handbook 130 and Handbook 133 

E1 Summary 

E1.1 When intended for sale or distribution, the labeling of the panels should meet the requirements 

of the Uniform Packaging and Labeling Regulation. This section provides references to 

standards applicable to labeling and packaging. 

E2 Background 

E2.1 The 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 Procedures used by Weights and Measures inspectors are included in NIST Handbook 133, 

“Checking the Net Contents of Packaged Goods”E2.3 For information, a complete copy of the 

most recent version of NIST Handbook 130 and 133 are available at: 

https://www.nist.gov/publications/ 

46 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

APPENDIX F. (Nonmandatory) 

Formaldehyde 

F1 General 

Formaldehyde is a simple naturally occurring chemical made of carbon, oxygen, and hydrogen. 

It is produced by the human body and animals and plants. It is also formed by combustion and 

is an industrial chemical widely used in the manufacture of many consumer products. 

Background information on formaldehyde and health concerns related to elevated levels in indoor 

air can be found at www.epa.gov/iaq/formalde.html. 

F2 Formaldehyde regulations 

F2.1 There are no national or state regulations of formaldehyde emissions expressly stated for PS 2 

structural panels. This is mainly due to the very low emission rates demonstrated by PS 2 

Wood Structural Panels. 

F2.2 U.S. Department of Housing and Urban Development Rules and Regulations 24 CFR 3280 for 

manufactured housing includes § 3280.308 “Formaldehyde emission controls for certain wood 

products,” that deals with formaldehyde emissions from particleboard and plywood. The

regulations establish limits for formaldehyde emission levels and ongoing evaluation 

requirements as follows: 

(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 2 Plywood is made predominantly with phenol-formaldehyde adhesives. When made as 

such, it is exempt from the HUD requirements. Other PS 2 Structural Panels are not explicitly 

referenced in the HUD requirements. 

F2.3 California Air Resources Board (CARB) Air Toxic Control Measure (ATCM) 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 2 Structural Panels and other 

structural wood products from the scope of the standard as follows: 

(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. 

F2.4 National “Formaldehyde Standards for Composite Wood Act”

The Formaldehyde Standards for Wood Composites Act was signed into law on July 7, 2010. 

With respect to PS 2 panels, this law is identical to the CARB ATCM for Composite Wood (see 

Section F2.3). PS 2 panels are exempt from the scope of the Formaldehyde Standards for 

Composite Wood Act. For further information, see: https://www.epa.gov/ 

47 
F3 Formaldehyde emission from PS 2 Structural Panels 

F3.1 Information on formaldehyde emission from PS 2 panels is available from APA in Technical 

Note J330, “Formaldehyde and Engineered Wood Products” (see: www.apawood.org). 

48