Standard for Performance-Rated Engineered Cross-Laminated Timber

American National Standard
ANSI/APA PRG 320-201x
Standard for Performance-Rated
Engineered Cross-Laminated Timber
APA – The Engineered Wood Association
Pre-Draft: September 2010
Approved xxxx xx, 201x
American National Standards Institute
Pre-Draft Standard PRG-320 (September 2010) Page 1 of 13

Foreword (This Foreword is not a part of American National Standard
ANSI/APA PRG 320-201x)
This Standard provides requirements and test methods for qualification and quality
assurance for performance-rated engineered cross-laminated timber (CLT), which is
manufactured from solid-sawn lumber intended for use in construction applications.
Product performance classes are also specified.
The development of this consensus American National Standard was achieved by
following the Operating Procedures for Development of Consensus Standards of APA –
The Engineered Wood Association, approved by the American National Standards
Institute (ANSI).
Inquires or suggestions for improvement of this Standard should be directed to APA –
The Engineered Wood Association at 7011 South 19th Street, Tacoma, WA 98466,
www.apawood.org.
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1. Scope
1.1 An engineered cross-laminated timber (CLT) is a rectangular-shaped, straight,
and plane product manufactured from solid-sawn lumber manufactured specifically to
meet the performance requirements of CLT in wood frame construction.
1.2 Unless otherwise specified, the term “engineered cross-laminated timber”
referenced in this standard represents the CLT products defined in Section 3.2.3 and
qualified under this standard.
1.3 This standard provides dimensions and tolerances, performance requirements,
test methods, quality assurance, and trademarking for CLT.
1.4 CLT shall be used in dry service conditions where the mean equilibrium moisture
content of solid-sawn lumber is less than 16%.
1.5 Products carrying a CLT trademark are to be used in accordance with the
installation requirements prescribed in the code, if available, or product evaluation
report, and the recommendations published by the CLT manufacturer, or its approved
agency or trade association.
1.6 The annex and discussion contained in this standard are mandatory, and notes
and appendix are non-mandatory. This standard incorporates the U.S. customary units
as well as the International System of Units (SI). The values given in the U.S. customary
units are the standard and the SI values given in parentheses are for information only.
2. Referenced Documents
This standard incorporates dated references. These normative references are cited at
the appropriate places in the text. Subsequent amendments or revisions to these
references apply to this standard only when incorporated into this standard by
amendments or revisions.
2.1 ASTM Standards:
D 9-09 Standard Terminology Relating to Wood and Wood-Based Products
D 198-09 Standard Test Methods of Static Tests of Lumber in Structural Sizes
D 1037-06a Standard Test Methods for Evaluating Properties of Wood-Base Fiber and
Particle Panel Materials
D 2395-07 Standard Test Methods for Specific Gravity of Wood and Wood-Base
Materials
D 2915-03 Standard Practice for Evaluating Allowable Properties for Grades of
Structural Lumber
D3501-05a Standard Test Methods for Wood-Based Structural Panels in Compression
D 3737-08 Standard Practice for Establishing Stresses for Structural Glued Laminated
Timber (Glulam)
D 4761-05 Standard Test Methods for Mechanical Properties of Lumber and Wood-
Based Structural Material
D 5456-09 Standard Specification for Evaluation of Structural Composite Lumber
Products
F 1667-05 Standard Specification for Driven Fasteners: Nails, Spikes, and Staples
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2.2 Other Standards:
ANSI/AF&PA NDS-2005 National Design Specification for Wood Construction
ANSI/AF&PA SDPWS-2008 Special Design Provisions for Wind and Seismic
ANSI/AITC 405-2008 Standard for Adhesives for Use in Structural Glued Laminated
Timber
ANSI/AITC A190.1-2007 Structural Glued Laminated Timber
ANSI/ASME Standard B18.2.1-1996 Square and Hex Bolts and Screws (Inch Series)
CSA B111-1974 (R2003) Wire Nails, Spikes and Staples
CSA O86-09 Engineering Design in Wood
CSA O112.10-08 Evaluation of Adhesives for Structural Wood Products (Limited
Moisture Exposure)
CSA O122-06 Structural Glued-Laminated Timber
US Product Standard PS 1-07 Structural Plywood
3. Terminology
3.1 Definitions: See the referenced documents for definitions of terms used in this
standard.
3.2 Description of terms specific to this standard:
3.2.1 Approved Agency – An established and recognized agency regularly
engaged in conducting tests or furnishing inspection services, when such agency has
been approved by regulatory bodies (see Qualified Inspection Agency and Qualified
Testing Agency).
3.2.2 Characteristic Values – The structural property estimate, typically a
population mean for stiffness properties or a tolerance limit (5 th percentile with 75%
confidence) for strength properties, as estimated from the test data that is representative
of the population being sampled.
3.2.3 Cross-Laminated Timber (CLT) – A prefabricated solid engineered wood
product made of at least three orthogonally bonded layers of solid-sawn lumber that are
laminated by gluing of longitudinal and transverse layers to form a solid rectangularshaped,
straight, and plane timber intended for roof, floor, or wall applications.
3.2.4 Edge Joints – Joints made by gluing of the edges of adjacent laminations
within a CLT layer.
3.2.5 End Joints – Joints made by gluing of the finger joints of the same
laminations within a CLT layer.
3.2.6 Layups – Arrangement of layers of timber of different species, grades, and
thickness into a CLT product.
3.2.7 Mill Specification -- A manufacturing specification based on product
evaluation to be used for quality assurance purposes by the manufacturer and the
approved agency.
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3.2.8 Qualified Inspection Agency – An agency meeting the following
requirements:
(a) Has trained personnel to verify that the grading, measuring, species, construction,
bonding, workmanship, and other characteristics of the products as determined by
inspection comply with all applicable requirements specified in this standard,
(b) Has procedures to be followed by its personnel in performance of the inspection,
(c) Has no financial interest in, or is not financially dependent upon, any single company
manufacturing the product being inspected,
(d) Is not owned, operated, or controlled by any such company, and
(e) Is accredited under ISO/IEC 17020.
3.2.9 Qualified Inspection Agency – An agency meeting the following
requirements:
(a) Has access to the facilities and trained technical personnel to conduct testing on the
characteristics of the products by sampling and testing in compliance with all
applicable requirements specified in this standard,
(b) Has procedures to be followed by its personnel in performance of the testing,
(c) Has no financial interest in, or is not financially dependent upon, any single company
manufacturing the product being tested,
(d) Is not owned, operated, or controlled by any such company, and
(e) Is accredited under ISO/IEC 17025.
3.2.10 Structural Composite Lumber (SCL) – An engineered wood product that is
intended for structural use and bonded with adhesives, and meets the definition and
requirements of ASTM D 5456.
3.2.11 Structural Glued-Laminated Timber (glulam) – An engineered, stress rated
product of a timber laminating plant comprising assemblies of specially selected and
prepared wood laminations securely bonded together with adhesives, and meets the
definition and requirements of ANSI/AITC A190.1 or CSA O122.
4. Dimensions and Dimensional Tolerances
4.1 The thickness of CLT shall not exceed 20 inches (508 mm).
4.2 The thickness of the CLT shall not deviate from the target thickness by more than
� 5/64 inch (2 mm) or 2% of the thickness, whichever is the greater.
4.3 Dimensional tolerances - Dimension tolerances permitted at the time of
manufacture for CLT shall be as follows:
Thickness – Tolerances shall be xx.
Width – Plus or minus 1/x inch (x mm), measured to 1/32 inch or 0.79 mm).
Length – xxx
5. Component Requirements
5.1 Lumber
5.1.1 Lumber species
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Any softwood lumber species recognized by American Lumber Standards Committee
(ALSC) or Canadian Lumber Standards Accreditation Board (CLSAB) with a minimum
published specific gravity of 0.42 may be used for CLT manufacturing provided that
other requirements specified in this section are satisfied. Lumber specifies may be
mixed within the same CLT product except at the same layer.
5.1.2 Lumber grades
For floor or roof applications, the minimum grade of lumber shall be 1650f-1.5E or
visual grade No. 2 or better. For wall applications, the vertical layer shall be visual grade
No. 2 or better and the horizontal layup shall be No. 3 or better. The top and bottom
layers shall be the same lumber grade and thickness (balanced layup), while the inner
layers are permitted to be of lower grade and thickness from top and bottom layers.
5.1.3 Lumber sizes
The net width of the lumber shall be 1-1/2 inches (38 mm) or wider. The thickness of
the lumber shall not be less than 3/4 inch (19 mm) or more than 3-1/2 inches (89 mm).
5.1.4 Moisture content
The moisture content of the lumber at the time of the CLT manufacturing shall be 12
± 2% with the variance within the same CLT of 4% maximum.
5.1.5 Dimension tolerances
The dimension tolerances for lumber shall be in accordance with the governing
lumber grading rules with the exception that the thickness of the lumber shall not deviate
by more than 1/xx inch (0.xx mm) within the same layer of lumber in a CLT product.
5.2 Adhesives
5.2.1 Adhesives used for CLT manufacturing shall meet all requirements of
ANSI/AITC 405 in the U.S. and CSA O112.10 in Canada with the exceptions noted in
this section.
5.2.2 Section 2.1.6, durability based on either ASTM D 3434 or CSA O112.9, of
ANSI/AITC 405 shall not be required.
5.2.3 The Bunsen burner test specified in DOC PS1 shall be required.
5.3 Lamination joints
5.3.1 General
The lamination joints of CLT shall meet the requirements specified in this section.
5.3.2 Strength of End Joints in Laminations
The strength of the end joints shall be tested in accordance with Section xx of
ANSI/AITC A190.1 and meet the requirements specified therein.
5.3.3 Strength of Edge Joints in Laminations
The strength of the edge joints, when required, shall be tested in accordance with
Section xx of ANSI/AITC A190.1 and meet the requirements specified therein.
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5.3.4 Strength of Face Joints between Laminations
5.3.4.1 The strength of the face joints between laminations shall be tested in
accordance with Section xx of this standard and meet the requirements specified in this
section.
5.3.4.2 To Be Complete
6. CLT Performance Criteria
CLT shall meet the performance requirements established in this section.
6.1 Layup requirements
6.1.1 Layers made of laminations shall be orthogonally arranged and specified in
the manufacturing standard of each CLT plant when qualified in accordance with the
requirements specified in this section and recognized by an approved agency.
6.2 Sampling
6.2.1 Test samples shall be representative of typical production and shall be
sampled at the manufacturing facility by an approved agency using the layup intended
for qualification.
6.2.2 The sample size required for stiffness capacities shall be sufficient for
estimating the population mean within 5% precision with 75% confidence, or 10
specimens, whichever is greater. In general, a sample size larger than 10 is needed
when the coefficient of variation is greater than 13%.
6.2.3 The sample size required for strength capacities shall be sufficient for
estimating the characteristic value with 75% confidence in accordance with ASTM D
2915.
6.3 Structural Performance Requirements
6.3.1 Structural performance shall be evaluated for each CLT layup unless
otherwise noted in this section.
6.3.2 CLT shall meet the minimum structural performance shown in Table 1 based
on the test methods described in Section 7.
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Table 1. Required Test Values (a) for CLT
CLT Grades
CLT-A1 (Floor or Roof)
CLT-A2 (Floor or Roof)
CLT-B1 (Wall)
CLT-B2 (Wall)
For SI: 1 in. = 25.4 mm, 1 lbf/ft = 0.0146 N/mm, 1 lbf = 4.448 N
6.4 Durability Requirements
To be complete
6.4.1 Samples used for evaluating the durability of CLT shall be prepared from
those products required in Section xx.
6.4.2 Tests shall be conducted in accordance with the procedures provided in
Section x.
6.4.3 The mean durability shall be at least 75% of the mean capacity determined
from Section 7.2.
6.5 Physical Properties Requirements
6.5.1 Samples used for establishing the physical properties of CLT shall be
prepared from those products required in Section xx.
7. Test Methods
7.1 General
7.1.1 Test methods provided in this section shall be used to establish the structural
capacities of CLT.
7.2 Test Method 1
7.2.1 Specimen preparation
7.2.2 Test procedures
7.3 Test Method 2
7.3.1 Specimen preparation
7.3.2 Test procedures
8. Product Evaluation
8.1 Qualification Tests
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Required qualification tests and criteria are detailed in Section 6 of this standard.
Retesting shall be conducted using a new independent sample set.
8.2 Mill Specification
Upon conformance with the requirements specified in this standard, a manufacturing
specification unique to the product and mill shall be written based on product evaluation.
This specification shall be used for quality assurance purposes by the manufacturer and
the approved agency. Product evaluation will be accomplished on the same lot supplied
by the manufacturer for qualification testing. Reference values shall be established
during product evaluation or from applicable performance requirements in this standard,
as specified in Section 9.
8.3 Trademarking and Certification
8.3.1 Certification
All CLT products represented as being in conformance with this standard shall bear the
stamp of an approved agency which (1) either inspects the manufacture or (2) has
tested a random sampling of the finished products in the shipment being certified for
conformance with this standard.
8.3.2 Product Marking
All CLT products represented as conforming to this standard shall be identified with
marks giving the following information:
a) CLT Grade qualified in accordance with this standard.
b) The CLT thickness
c) The mill name or identification number
d) The approved agency name or logo
e) The symbol of “ANSI/APA PRG 320” signifying conformance with this standard.
f) Any manufacturer’s designations which shall be separated from the grade-marks or
trademarks of the qualified agency by not less than 6 inches (152 mm).
8.3.3 Voiding Marks
CLT 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.
Note: This can be performed by blocking out the stamp with permanent black ink or light
sanding.
9. Quality Assurance
9.1 Objective
This section is intended for use with CLT that has qualified for trademarking under this
standard. The purpose of this section is to assure product quality by detecting changes
in properties which may adversely affect the CLT performance. In all cases, the criteria
to which the CLT is tested will be provided in the Mill Specification.
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9.2 Referenced Standards
9.2.1 CLT quality assurance requirements may be considered satisfied when the
requirements for the referenced standards in Section 2 and any additional requirements
listed in Section x are met.
9.2.2 Referenced standards shall be specified by product type to define appropriate
procedures and/or guidelines for quality assurance. If a product trademarked under this
standard is trademarked under another standard, samples shall be taken for both
standards.
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Annex A. Design Properties for ANSI/APA PRG-320 CLT
Table A1. Allowable Design Values for CLT
Table A2. Limit States Design Values for CLT
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Appendix A. History of Standard (Non-Mandatory)
In March 2010, the APA Standards Committee on Standard for Performance-Rated
Engineered Cross-Laminated Timber was formed to develop a national standard under
the consensus processes accredited by the American National Standards Institute
(ANSI). This national consensus standard, designated as ANSI/APA PRG 320, is
developed based on broad input from around the world.
The names of the ANSI/APA PRG 320 Committee members when the standard is
published are as follows. The current list of the committee membership is available from
the committee secretariat upon request.
Name Affiliation
Inquiries or suggestions for improvement of this standard should be directed to:
Secretariat, ANSI/APA PRG 320
APA – The Engineered Wood Association
7011 South 19 th Street
Tacoma, WA 98466
www.apawood.org
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Appendix B. ASD-to-LSD Conversion Factors (Non-Mandatory)
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