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T E D T I M B E R
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8/21/2019 CLT USA Complete Document
© 2013 FPInnovations and Binational Softwood Lumber Council. All rights reserved.
The U.S. Edition of the CLT Handbook: cross-laminated timber can be electronically downloaded without charge from the website www.masstimber.com. Additional information can be obtained by visiting the websites of FPInnovations, USFPL, American Wood Council
(AWC), APA and U.S. WoodWorks. Hard copies can be obtained through AWC (www.awc.org).
No part of this published Work may be reproduced, published, or transmitted for commercial purposes, in any form or by any means,
electronic, mechanical, photocopying, recording or otherwise, w hether or not in translated form, without the prior written permission of FPInnovations and Binational Softwood Lumber Council.
The information contained in this Work represents current research results and technical information made available from many sources,
including researchers, manufacturers, and design professionals. The information has been reviewed by professionals in wood design including professors, design engineers and architects, and wood product manufacturers. While every reasonable effort has been made to insure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-
the-art, none of the above-mentioned parties make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this published work, nor assume any responsibility for the accuracy or completeness of the information or its fitness for any particular purpose.
This published Work is designed to provide accurate, authoritative information but is not intended to provide professional advice. It is the responsibility of users to exercise professional knowledge and judgment in the use of the information.
Edited by
FPInnovations
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R O S S - L A M I N A T E D T I M B E R
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FPInnovations
222 Catoctin Circle SE Suite 201 Leesburg, VA 20175 www.awc.org
Library and Archives Canada Cataloguing in Publication
CL handbook : cross-laminated timber / edited by Erol Karacabeyli, Brad Douglas. -- U.S. ed.
(Special publication, ISSN 1925-0495 ; SP-529E) Co-published by U.S. Department o Agriculture, Forest Service, Forest
Products Laboratory, Binational Sofwood Lumber Council (BSLC). Includes bibliographical reerences. Issued also in electronic ormat.
ISBN 978-0-86488-553-1 1. Laminated wood. 2. Laminated wood construction. 3. Engineered
wood construction. 4. Laminated wood--Standards. 5. Laminated wood-- Handbooks, manuals, etc. I. Karacabeyli, Erol, 1954- II. Douglas, Brad, 1960- III. Forest Products Laboratory (U.S.) IV. FPInnovations (Institute)
V. Binational Sofwood Lumber Council VI. itle: Cross-laminated timber. VII. Series: Special publication (FPInnovations (Institute)) ; SP-529E
A666.C57 2013 624.1’84 C2012-908154-X
Library and Archives Canada Cataloguing in Publication
CL handbook [electronic resource] : cross-laminated timber / edited by Erol Karacabeyli, Brad Douglas. -- U.S. ed.
(Special publication, ISSN 1925-0509 ; SP-529E) Co-published by U.S. Department o Agriculture, Forest Service, Forest
Products Laboratory, Binational Sofwood Lumber Council (BSLC). Includes bibliographical reerences. Electronic monograph in PDF ormat. Issued also in print ormat. ISBN 978-0-86488-554-8
1. Laminated wood. 2. Laminated wood construction. 3. Engineered wood construction. 4. Laminated wood--Standards. 5. Laminated wood--
Handbooks, manuals, etc. I. Karacabeyli, Erol, 1954- II. Douglas, Brad, 1960- III. Forest Products Laboratory (U.S.) IV. FPInnovations (Institute)
V. Binational Sofwood Lumber Council VI. itle: Cross-laminated timber. VII. Series: Special publication (FPInnovations (Institute) : Online) ; SP-529E
A666.C57 2013 624.1’84 C2012-908155-8
AMERICAN
WOOD
COUNCIL

Designing to new building heights with Light Frame Wood Construction Revival o Heavy Timber Frame Construction
Adoption o Cross-laminated Timber (CL)
Facilitating Hybrid Construction
Tere are concerted efforts both in Canada and in the United States towards realizing that goal. In act, the Canadian provinces o British Columbia and uebec went even urther and created specific initiatives to support the use o wood in those applications.
Tis Handbook is ocused on one o these options – adoption o cross-laminated timber (CL). CL is an innovative wood product that was introduced in the early 1990s in Austria and Germany and has been gaining
popularity in residential and non-residential applications in Europe. Te Research and Standards Subcommittee o the industry’s CL Steering Committee identified CL as a great addition to the “ wood product toolbox ” and
expects CL to enhance the re-introduction o wood-based systems in applications such as 5- to 10-story buildings where heavy timber systems were used a century ago. Several manuacturers have started to produce CL in North America, and their products have already been used in the construction o a number o buildings.
CL, like other structural wood-based products, lends itsel well to preabrication, resulting in very rapid construction, and dismantling at the end o its service lie. Te added benefit o being made rom a renewable resource makes all wood-based systems desirable rom a sustainability point o view.
In Canada, in order to acilitate the adoption o CL, FPInnovations published the Canadian edition o the CL Handbook in 2011 under the ransormative echnologies Program o Natural Resources Canada. Te broad acceptance o the Canadian CL Handbook in Canada encouraged this project, to develop a U.S. Edition o the CL Handbook. Funding or this project was received rom the Binational Sofwood Lumber Council, Forestry Innovation Investment in British Columbia, and three CL manuacturers, and was spearheaded by a Working Group rom FPInnovations, the American Wood Council (AWC), the U.S. Forest Products Laboratory, APA-Te Engineered Wood Association and U.S. WoodWorks. Te U.S. CL Handbook was developed by a team o over
40 experts rom all over the world. Both CL handbooks serve two objectives:
Provide immediate support or the design and construction o CL systems under the alternative or innovative solutions path in design standards and building codes;
Provide technical inormation that can be used or implementation o CL systems as acceptable solutions in building codes and design standards to achieve broader acceptance.
Te implementation o CL in North America marks a new opportunity or cross-border cooperation, as five organizations worked together with the design and construction community, industry, universities, and regulatory officials in the development o this Handbook. Tis multi-disciplinary, peer-reviewed CL Handbook is designed to acilitate the adoption o an innovative wood product to enhance the selection o wood-based solutions in non- residential and multi-storey construction.
Credible design teams in different parts o the world are advocating or larger and taller wood structures, as high as30 stories. When asked, they identified the technical inormation compiled in this Handbook as what was needed or those applications.
A Renaissance in wood construction is underway; stay connected.
ACKNOWLEDGEMENTS Te great challenge with this U.S. Edition o the CL Handbook was to gather experts rom the United States, Canada and Europe to bring together their expertise and knowledge into a state-o-the-art reerence document. Te realization o this Handbook was made possible with the contribution o many
people and numerous national and international organizations.
Such a piece o work would not be possible without the support rom financing partners and, as such, we would like to express our special thanks to Binational Sofwood Lumber Council, Forestry Innovation Investment (FII), Nordic Engineered Wood, Structurlam, and CL Canada or their financial contribution to this project.
First and most o all, we would like to express our gratitude to AWC, APA, USFPL, FPInnovations, U.S. WoodWorks and their staff or providing the effort and expertise needed to prepare this work. We
would also like to express our special thanks to all chapter authors, co-authors, and reviewers who shared their precious time and expertise in improving this manual.
Our very special thanks go to Loren Ross at AWC and Sylvain Gagnon at FPInnovations or their work as project leaders and or their special efforts in gathering the expertise o everyone into a unique document. Special thanks also go to the Working Group, Dr. Borjen Yeh rom APA, Dave Kretschmann
rom the U.S. Forest Products Laboratory, and Lisa Podesto rom U.S. WoodWorks. Tanks also toMadeline Leroux or her work on the drawings, Odile Fleury or her help with bibliographic reerences, and Marie-Claude Tibault or her support in editing and coordination work.
Erol Karacabeyli, P.Eng. and Brad Douglas, P.E. Co-editors CLT Handbook, U.S. Edition
CONTENTS Introduction
Lateral design o
cross-laminated timber buildings
Duration o load and creep actors or cross-laminated timber panels
Vibration perormance o cross-laminated timber floors
Fire perormance o cross-laminated timber assemblies
Sound insulation o cross-laminated timber assemblies
Building enclosure design orcross-laminated timber construction
Environmental perormance o cross-laminated timber
Lifing and handling o cross-laminated timber elements
C H A P T E R
12
I
n t r o d u c t i o n t o c r o s s - l a m i n a t e d t i m
b e r
Authors
Sylvain Gagnon, Eng., FPInnovations E.M. (Ted) Bilek, Ph.D., USDA Forest Products Laboratory
Lisa Podesto, M.S., P.E., WoodWorks Pablo Crespell, Ph.D., FPInnovations
Te U.S. Edition o the CL Handbook: cross-laminated timber combines the work and knowledge o American, Canadian and European specialists. Te handbook is based on the original Canadian Edition o the CL Handbook: cross-laminated timber , that was developed using a series o reports initially prepared by FPInnovations
and collaborators to support the introduction o CL in the North American market. A multi-disciplinary team revised, updated and implemented their know-how and technologies to adapt this document to U.S. standards.
Te publication o this handbook was made possible with the special collaboration o the ollowing partners:
Te editing partners would also like to express their special thanks to Binational Sofwood Lumber Council, Forestry Innovation Investment (FII), Nordic Engineered Wood, Structurlam, and CL Canada or their financial contribution to studies in support o the introduction o cross-laminated timber products in the United States o America.
ACKNOWLEDGEMENTS
AMERICAN
WOOD
COUNCIL
The U.S. Edition of the CLT Handbook: cross-laminated timber can be electronically downloaded without charge from the website www.masstimber.com. Additional information can be obtained by visiting the websites of FPInnovations, USFPL, American Wood Council (AWC), APA and U.S. WoodWorks. Hard copies can be obtained through AWC (www.awc.org).
No part of this published Work may be reproduced, published, or transmitted for commercial purposes, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, whether or not in translated form, without the prior written permission of FPInnovations and Binational Softwood Lumber Council.
The information contained in this Work represents current research results and technical information made available from many sources, including researchers, manufacturers, and design professionals. The information has been reviewed by professionals in wood design including professors, design engineers and architects, and wood product manufacturers. While every reasonable effort has been made to insure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-the-art, none of the above-mentioned parties make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this published work, nor assume any responsibility for the accuracy or completeness of the information or its fitness for any particular purpose.
iii
ABSTRACT
Cross-laminated timber (CL), a new generation o engineered wood product developed initially in Europe, has been gaining increased popularity in residential and non-residential applications in several countries. Many impressive low- and mid-rise buildings built around the world using CL showcase the many advantages this
product has to offer to the construction sector.
In this Chapter, we put orward an introduction to CL as a product and CL construction in general, along with different examples o buildings and other types o structures made with CL panels. CL is now available in North America and several projects already built in Canada and the United States, using CL, are presented in this Chapter. An assessment o market opportunity or CL based on the latest construction statistics or the United States is also presented.
GENERAL NOE: Te information contained in this Handbook represents current research results and technical information made available from many sources, including researchers, manufacturers, and design
professionals. Te information has been reviewed by wood design professionals including professors, design engineers and architects, and wood product manufacturers. While every reasonable effort has been made to ensure the accuracy of the information presented, and special effort has been made to assure that the information reflects state of the art, neither of the participating parties assume any responsibility for the accuracy or completeness of the information or its fitness for any particular purpose. It is the responsibility of users to exercise professional knowledge and judgment in the use of the information.
1 Brie History 1
3 Definition o Cross-laminated imber (CL) 3
4 Key Advantages o Cross-laminating 6
5 Manuacturing Process 9
6 Structural Design and Serviceability Considerations o CL 12
6.1 Proposed Analytical Design Methods 13
6.2
Lateral Design o CL Buildings 13 6.3 Connections and Construction o CL Structures 15
6.4 Duration o Load and Creep Behavior 16
6.5 Vibration Perormance o Floors 16
6.6 Fire Perormance o Cross-laminated imber Assemblies 16
6.7 Sound Insulation o Cross-laminated imber Buildings 17
6.8 Building Enclosure Design o Cross-laminated imber Construction 18
7 Environmental Perormance o CL 19
8 CL in Construction 20
8.1 Considerations or ransportation and Construction Site Limitations 20
8.2 Materials on the Construction Site 20
8.3 Lifing and Handling o CL Elements 22
8.4 Construction Accessories and Materials 22
9.1 Methodology 23
9.1.2 Construction Statistics 23
9.1.3 Sample Selection 23
9.1.5 CL Assembly Costs 24
9.2 Results 25
10 Building Examples 28
10.1 Residential Buildings 28
Figure 2 Examples o CL panel cross-sections 4
Figure 3 Example o CL panel cross-sections and direction o fibers o the top layers 5
Figure 4 CL vs. glulam panel 6
Figure 5 (a) Floor assembly made o our 3-ply CL panels acting in one direction and (b) Floor assembly made o one 3-ply CL panel acting in both directions. Distance “a” may reach 10 f. (3 m) 7-8
Figure 6 CL wall 10
Figure 7 CL floor or roo 11
Figure 8 Seven-story CL building tested at E-Deense Laboratory in Miki as a part o the SOFIE Project and CL test assembly at FPInnovations 14
Figure 9 CL test assembly at FPInnovations 15
Figure 10 Storage on construction site – individually wrapped bundles stacked on lumber skids 21
Figure 11 ruck platorms lef on construction site – will be recovered on the next trip 21
Figure 12 Lifing and handling o CL elements by cableway 22
Figure 13 Unit shell cost by story class and rame material apartments 25
Figure 14 Estimated demand 2015 (5% scenario, 000 f.3) 27
Figure 15 Single-amily house in Rykkinn, Norway 28
Figure 16 Single-amily house in Klagenurt, Austria 29
Figure 17 Country house in uébec, Canada 30
Figure 18 Garlick Residence, Oroville, WA, United States 31
Figure 19 Multi-amily building in Judenburg, Austria 32
Figure 20 Multi-amily building in Chibougamau, uebec, Canada 33
Figure 21 Multi-amily building in Berlin, Germany 34
Figure 22 Multi-amily building in Växjö, Sweden 35
Figure 23 10-story apartment building in Australia 36-37
Figure 24 Impulsezentrum, Graz, Austria 38
Figure 25 Montana Long Hall 39
Figure 26 Viken Skog BA, Høneoss, Norway 40
Figure 27 Juwi head office, Wörrstadt, Germany 41
Figure 28 Werkstatte, Fügen, Austria 42
Figure 29 Kommissionshalle, Katsch, Austria 43
Figure 30 Parking garage in Innsbruck, Austria 44
Figure 31 Residential building in South Carolina, United States 45
1 BRIEF HISTORY
Cross-laminated timber (CL) is a relatively new building system o interest in the North American construction and is helping to define a new class o timber products known as massive or “mass” timber. It is a potentially cost-competitive, wood-based solution that complements the existing light rame and heavy timber options, and
is a suitable candidate or some applications that currently use concrete, masonry and steel. CL is an innovative wood product that was introduced in the early 1990s in Austria and Germany and has been gaining popularity in residential and non-residential applications in Europe.
In the mid-1990s, Austria undertook an industry-academia joint research effort that resulted in the development o modern CL. Afer several slow years, construction in CL increased significantly in the early 2000s, partially driven by the green building movement but also due to better efficiencies, product approvals, and improved marketing and distribution channels. Another important actor has been the perception that CL, like masonry and concrete, is a heavy construction system. Such systems are typical in single-amily buildings and multi-story residential construction in many European countries.
Te use o CL panels in buildings has increased over the last ew years in Europe. Hundreds o impressive buildings and other structures built around the world using CL show the many advantages this product can offer to the construction sector. Te European experience shows that CL construction can be competitive, particularly in mid-rise and high-rise buildings. Easy handling during construction and a high level o preabrication acilitate rapid project completion. Tis is a key advantage, especially in mid-rise construction (e.g., 5 to 10 stories). Lighter
panels mean that oundations do not need to be as large. Tey also mean that smaller cranes can be used to lif panels higher. Good thermal insulation, good sound insulation and good perormance under fire are added benefits that come as a result o a massive wood structure.
In this Chapter, we put orward an introduction to CL as a product and CL construction in general, along with different examples o buildings and other types o structures made with CL panels. CL is now available in North America and several projects already built in Canada and the United States, using CL, are presented in this Chapter.
2
Te driving orce behind the development o CL in North America is the need to provide alternative wood-based products and systems to architects, engineers and contractors. While this product is well established in Europe, work on the implementation o CL products and systems has just begun in the United States and Canada.
Interest in the use o CL in North America and other industrialized countries outside o Europe is increasing.
Significant progress has been achieved in Canada with the publication o the Canadian edition o the CL Handbook (FPInnovations, 2011) currently used or acilitating design and construction o CL under the “Alternative Solutions” path in the Canadian building codes. Tis peer-reviewed Handbook was welcomed by the Canadian design and construction community, and it is being used in the design o early CL projects. Te technical inormation in the Handbook will also be instrumental in realizing CL’s inclusion in the Canadian Standard or Engineering Design in Wood (CSA O86) and in the National Building Code o Canada.
Tis U.S. edition o the CL Handbook is intended to assist the U.S. design and construction industry and provide a similar path to CL’s code and standard inclusion as is being pursued in Canada. Tis comprehensive document provides key technical inormation related to the manuacturing, design and perormance o CL in construction in the ollowing areas:
• Cross-laminated timber manuacturing
• Structural design o cross-laminated timber elements
• Lateral design (including wind and seismic perormance) o cross-laminated timber buildings
• Connections in cross-laminated timber buildings
• Duration o load and creep actors or cross-laminated timber panels
• Vibration perormance o cross-laminated timber floors
• Fire perormance o cross-laminated timber assemblies
• Sound insulation o cross-laminated timber assemblies
• Building enclosure design o cross-laminated timber construction
• Environmental perormance o cross-laminated timber • Lifing and handling (including transportation) o cross-laminated timber elements
A harmonized North American CL product standard, Standard or Perormance-Rated Cross-Laminated Timber (ANSI/APA PRG 320), has been developed by the ANSI/APA CL Standard Committee and published in December 2011 (ANSI, 2011). Tis standard was developed based on the consensus standard development
process o APA–Te Engineered Wood Association as a standards developer accredited by the American National Standards Institute (ANSI). Te ANSI/APA PRG 320 standard has been approved by the Structural Committee o the International Code Council (ICC) or the 2015 International Building Code (IBC).
2 DEVELOPMENT OF CLT
3
CL panels consist o several layers o lumber boards stacked crosswise (typically at 90 degrees) and glued together on their wide aces and, sometimes, on the narrow aces as well. Besides gluing, nails or wooden dowels can be used to attach the layers. Innovative CL products such as Interlocking Cross-laminated imber (ICL) are in
the process o development in the United States as well. However, non-glued CL products and systems are out o the scope o this Handbook.
A cross-section o a CL element has at least three glued layers o boards placed in orthogonally alternating orientation to the neighboring layers. In special configurations, consecutive layers may be placed in the same direction, giving a double layer (e.g., double longitudinal layers at the outer aces and/or additional double layers at the core o the panel) to obtain specific structural capacities. CL products are usually abricated with an odd number o layers; three to seven layers is common and even more in some cases.
Tickness o individual lumber pieces may vary rom 5/8 inch to 2.0 inches (16 mm to 51 mm) and the width may vary rom about 2.4 inches to 9.5 inches (60 mm to 240 mm). Boards are finger jointed using structural adhesive. Lumber is visually graded or machine stress rated and is kiln dried. Panel sizes vary by manuacturer; typical
widths are 2 f. (0.6 m), 4 f. (1.2 m), 8 f. (2.4 m) and 10 f. (3 m) while length can be up to 60 f. (18 m) and the thickness can be up to 20 inches (508 mm). ransportation regulations may impose limitations to CL panel size.
Lumber in the outer layers o CL panels used as walls are normally oriented up and down, parallel to gravity loads, to maximize the wall’s vertical load capacity. Likewise, or floor and roo systems, the outer layers run
parallel to the major span direction.
Figure 1 illustrates a CL panel configuration, while Figure 2 shows examples o possible CL panel cross- sections. Figure 3 illustrates a 5-layer CL panel with its two cross-sections.
3 DEFINITION OF
Figure 2 Examples o CL panel cross-sections
o n o f
f i b e
t o p l a y e
r
b
D
Variable

Figure 3 Example o CL panel cross-sections and direction o fibers o the top layers
6
Cross-laminated timber used or preabricated wall and floor panels offers many advantages. Te cross-laminating process provides improved dimensional stability to the product which allows or preabrication o long, wide floor slabs, long single-story walls and tall plate heights conditions as in clerestory walls or multi-story balloon ramed
configurations. Additionally, cross-laminating provides relatively high in-plane and out-o-plane strength and stiffness properties, giving it two-way action capabilities similar to a reinorced concrete slab. Te ‘reinorcement’ effect provided by the cross-lamination in CL also considerably increases the splitting resistance o CL or certain types o connection systems.
Figure 4 illustrates the primary difference between CL and glulam products. Figure 5a shows a floor built with our individual CL panels acting mostly in one direction, while Figure 5b illustrates the same floor, this time built with one CL panel only, acting most likely in two directions (i.e., two-way action).
Cross-Laminated Timber
4 KEY ADVANTAGES OF
8
a
l
(b)
Figure 5 (a) Floor assembly made o our 3-ply CL panels acting in one direction and (b) Floor assembly made o one 3-ply CL panel acting in both directions. Distance “a” may reach 10 f. (3 m)
PROCESS
A typical manuacturing process o CL includes the ollowing steps: lumber selection, lumber grouping and planing, adhesive application, panel lay-up and pressing, product cutting, surace machining, marking and packaging. Te key to a successul CL manuacturing process is consistency in the lumber quality and control o
the parameters that impact the quality o the adhesive bond. Stringent in-plant quality control tests are required to ensure that the final CL products will fit or the intended applications.
ypically, lumber must be kiln dried to a moisture content o 12% ± 3%. Proper moisture content prevents dimensional variations and surace cracking. Lumber can be procured dried or urther drying may be needed at the actory. rimming and finger jointing are used to obtain the desired lengths and quality o lumber. Finger jointed CL panels are also available in Europe, but are out o the scope o the North American ANSI APA/PRG 320 CL product standard at this time.
Panel dimensions vary by manuacturer. Te assembly process can take rom 15 to 60 minutes depending on equipment and adhesive. Adhesive is the second material input in CL. ypes o adhesives used in North America must meet the same requirements as those used in glued laminated timber manuacturing and include qualified
polyurethane, melamine and phenolic-based adhesives. Both ace and edge gluing can be used. Once adhesive is applied, the assembly is pressed using hydraulic (more common) or vacuum presses and compressed air depending on panel thickness and adhesive used. Te assembled panels are usually planed and/or sanded or a smooth surace at the end o the process. Panels are cut to size and openings are made or windows, doors and service channels, connections and ducts using CNC (Computer Numerical Controlled) routers which allow or high precision. For quality control purposes, compliance with product requirements prescribed in the product standard are typically checked at the actory (e.g., bending strength, shear strength, delamination).
Chapter 2, entitled Cross-laminated timber manuacturing , provides general inormation about CL manuacturing targeted mainly to engineers, designers, and specifiers. Te inormation contained in this Chapter may also be useul to potential U.S. CL manuacturers.
Figures 6 and 7 illustrate a typical CL wall and floor assembly, respectively.
U p t o 1 0 f t .
5 5 ~
12
CL panels are typically used as load-carrying plate elements in structural systems such as walls, floors and roos. For floor and roo CL elements, key critical characteristics that must be taken into account are the ollowing :
• In-plane and out-o-plane bending strength, shear strength, and stiffness
• Short-term and long-term behavior:
• Vibration perormance o floors
• Compression perpendicular to grain issues (bearing)
• Fire perormance
• Durability.
For wall elements, the ollowings are key characteristics that must be taken into account at the design stage:
• Load-bearing capacity (critical criterion)
• Fire perormance
• Durability.
Te ollowing sections provide a brie summary o the key design and perormance attributes o CL panels and assemblies.
6 STRUCTURAL DESIGN
13
6.1 Proposed Analytical Design Methods Various different design methods have been adopted in Europe or the determination o basic mechanical properties o CL. Some o these methods are based on testing while others are more analytical. For floor elements, a testing method o evaluation involves determination o flexural properties by testing ull-size panels or sections o panels with a specific span-to-depth ratio. Te problem with the testing based approach is that every time the lay-up, type o material, or any other manuacturing parameters change, more testing is needed to evaluate the bending and shear properties o such new product configurations.
Analytical approach, once verified with the test data, offers a more general and less costly alternative. An analytical approach generally predicts strength and stiffness properties o CL panels based on the input material properties o the laminate boards that make up the CL panel. Some o the proposed European methods are described in detail in the Canadian edition o the CL Handbook (FPInnovations, 2011). One o them, the shear analog y method, is the method used by ANSI APA/PRG 320 or determining the bending and shear stiffness o various lay-ups (ANSI, 2012).
Te proposed analytical procedures or determining basic mechanical properties o CL panels or designers aregiven in Chapter 3 entitled Structural design o cross-laminated timber elements.
6.2 Lateral Design o CL Buildings Based on both a literature review o research work conducted around the world and the results o a series o quasi- static tests conducted at FPInnovations on regular and tall walls, CL wall panels can be used as an effective lateral load resisting system (Ceccotti, 2008). Results rom small- and large-scale shake table seismic tests on two CL buildings in Japan by the rees and imber Research Institute o Italy (CNR-IVALSA) in 2009 demonstrated that CL structures perorm quite well when subjected to seismic orce (Figure 8).
FPInnovations’ shearwall and assembly tests to date have also shown that the CL wall panels demonstrated
adequate seismic perormance when nails or slender screws are used with steel L-brackets to connect the walls tothe floors below (this ensures a ductile ailure in the connection instead o a brittle ailure in the panel). Te use o hold-downs installed with nails on each end o the walls tends to urther improve their seismic perormance. Use o diagonally placed long screws to connect CL walls to the floor below is not recommended in high seismic zones due to lower ductility and brittle ailure mechanisms. Use o hal-lapped joints in longer walls can be an effective solution not only to reduce the wall stiffness and thus reduce the seismic input load, but also to improve
wall ductility. imber rivets in smaller groups with custom made brackets were ound to be effective connectors or CL wall panels due to their potentially high ductility. Further research in this field is needed to clariy the use o timber rivets in CL and to veriy perormance o CL walls under seismic loading with alternative types o connection systems (e.g., bearing types). A 2-story CL assembly has also been tested at FPInnovations and the results confirmed the shake table tests conducted by CNR-IVALSA (Figure 9).
While most CL buildings are platorm ramed, they are ar less susceptible to develop sof story ailure
mechanisms than other platorm ramed structural systems. Since the nonlinear behavior (and the potentialdamage) is localized in the hold-down and L-bracket connection areas, the panels—that are also the vertical load carrying elements—are virtually lef intact in place and uncompromised, even afer ailure o the connections. In addition, all CL walls on a single level contribute to the lateral and gravity resistance, providing a degree o redundancy and a system sharing effect. Vertical and lateral load sharing can also take place between levels, creating a honeycomb effect.
Chapter 4 entitled Lateral design o cross-laminated timber buildings provides general inormation about lateral design o CL structures. Recommendations related to seismic modification actors are also made.

Figure 8 Seven-story CL building tested at E-Deense Laboratory in Miki as a part o the SOFIE Project and CL test assembly at FPInnovations
6.3 Connections and Construction o CL Structures Connections in timber construction, including those built with CL, play an important role in maintaining the integrity o the timber structure and in providing strength, stiffness, stability and ductility. Consequently, they require thorough attention o the designers.
raditional and innovative connection systems have been used in CL assemblies in Europe and North America.
Common types o connections in CL assemblies include: panel-to-panel (floors, walls and roos), wall-to- oundation, wall-to-wall intersections and wall-to-floor/roo assemblies. Basic panel-to-panel connection can be established through single or double exterior splines made with engineered wood products, single or double interior splines, or hal-lapped joints. Metal brackets, hold-downs and plates are used to transer orces at the wall to floor/roo interaces and in wall-to-wall intersections. Innovative types o connection systems can also be used
which lead to enhanced perormance or quicker assembly.
Researchers in Europe have developed design procedures or traditional connections in CL. Tese include dowels, wood screws, and nails, which are commonly used in Europe or designing CL assemblies. Empirically based equations were developed or the calculation o characteristic embedment properties o each type o astener (i.e., dowels, screws, nails), depending on the location with respect to the plane o the panel (perpendicular to or on edge). Tose equations were verified with testing and results seem to correspond well with calculated
predictions (Uibel and Blass, 2006 and 2007). Yield mode equations were adopted or the design using CL astener embedment strength equations. Empirical equations have also been developed or the calculation o the withdrawal resistance o the various types o asteners in CL based on hundreds o tests. Based on limited exploratory validation tests conducted at FPInnovations using sel-tapping screws on European CL, the proposed embedment equations seem to provide reasonable predictions o both the lateral and withdrawal capacity based on the Canadian timber design provisions (Muñoz et al., 2010). More work is needed, however, to validate the
proposed equations using North American made CL and different types o asteners.
Due to the reinorcing effect o cross-lamination in CL, it is speculated that current minimum geometric requirements given in the National design specification (NDS) or wood Construction or dowels, screws and nails in solid timber or glulam could be applicable to CL. However, designers need to be cautious about this as urther
16
verification is needed, considering the specific eatures o individual panel types. Brittle ailure modes, which have not yet been investigated, also need to be taken into account.
Chapter 5, entitled Connections in cross-laminated timber assemblies, is mainly ocused on CL assemblies.
However, since all buildings are considered to be mixed construction to a certain extent, the scope covers hybrid construction, where traditional wood-based systems (e.g., light rame, glulam, etc.) or materials such as concrete or steel are mixed with CL to resist vertical and lateral loads.
6.4 Duration o Load and Creep Behavior Cross-laminated timber products are used as load-carrying slabs and wall elements in structural systems, thus load duration and creep behavior are critical characteristics that must be addressed in structural design. Given its lay-up configuration with orthogonal arrangement o layers bonded with structural adhesive, CL is more prone to time- dependent deormations under load (creep) than other engineered wood products such as glued-laminated timber.
ime dependent behavior o structural wood products is addressed in design standards by load duration actors
that adjust design properties. Since CL has been recently introduced into the North American market, thecurrent design standards and building codes do not speciy load duration and creep adjustment actors or CL. Until this can be rectified, options are proposed or those speciying CL systems in Chapter 6, entitled
Duration o load and creep actors or cross-laminated timber panels. Tese include not only load duration and service actors, but also an approach or accounting or creep in CL structural elements.
Since cross-laminated timber is not yet covered by the NDS, the intent is to recommend a suitable approach that accounts or the duration o load and creep actors in the design o CL.
6.5 Vibration Perormance o Floors Studies at FPInnovations ound that bare CL floor systems differ rom traditional lightweight wood joisted
floors with typical mass around 4 lb./f. 2
(20 kg/m 2
) and undamental natural requency above 15 Hz, and heavyconcrete slab floors with a mass above 40 lb./f.2 (200 kg/m2) and undamental natural requency below 9 Hz. Based on FPInnovations’ test results, bare CL floors were ound to have mass varying rom approximately 6 lb./f.2 (30 kg/m2) to 30 lb./f.2 (150 kg/m2), and a undamental natural requency above 9 Hz. Due to these special properties, the standard vibration controlled design methods or lightweight and heavy floors may not be applicable or CL floors.
Some CL manuacturers have recommended that deflection under a uniormly distribution load (UDL) be used to control floor vibration problems. Using this approach, the success in avoiding excessive vibrations in CL floors relies mostly on the designer’s judgment. Besides, static deflection criteria can only be used as an indirect control method because they ignore the influence o mass characteristics o the floors. Tereore, a new design methodology is needed to determine the vibration controlled spans or CL floors.
A proposed design methodology or controlling vibrations o CL floors under normal walking is g iven in Chapter 7 entitled Vibration perormance o cross-laminated timber floors.
6.6 Fire Perormance o Cross-laminated imber Assemblies Cross-laminated timber panels have great potential or providing cost-effective building solutions or residential, commercial and institutional buildings as well as large industrial acilities in accordance with the International Building Code (IBC).
17
Te intent o the IBC is to establish the minimum requirements or public saety. Te code is addressing such things as structural strength and stability, means o egress, lie saety and protection o property rom fire as well as providing saety or firefighters and emergency responders during emergency operations. As such, fire saety issues such as providing adequate structural integrity, limiting impact to people and property as well as limiting
fire spread through a building and/or to adjacent properties during a fire are critical or every building design and structural system.
Structural integrity and fire spread capability o building assemblies can be assessed by conducting ull-scale fire- resistance tests in accordance with ASM E119 standard test methods. Fire resistance is defined as the ability o a material or their assemblies to prevent or retard the passage o excessive heat, hot gases or flames under conditions o fire. A fire-resistance rating is defined as the period o time a building element, component or assembly maintains the ability to confine a fire (separating unction), and/or continues to perorm a given structural unction. More specifically, a standard fire-resistance test entails three ailure/acceptance criteria:
1. Mechanical resistance: the assembly must support the applied load or the duration o the test;
2. Integrity: the assembly must prevent the passage o flame or gases hot enough to ignite a cotton pad;
3. Insulation: the assembly must prevent the temperature rise on the unexposed surace rom being greaterthan 325°F (180°C) at any location, or an average o 250°F (140°C) measured at a number o locations, above the initial temperature.
Te time at which the assembly can no longer satisy any one o these three criteria defines its fire-resistance rating.
In order to acilitate uture Code acceptance or the design o CL panels or fire resistance, a research project has recently been completed at FPInnovations. Te main objective o the project was to develop and validate a generic calculation procedure to calculate the fire-resistance ratings o CL wall and floor assemblies. A series o ull-scale fire-resistance experiments in accordance with ASM E119 standard time-temperature curve were conducted to allow a comparison between the fire resistance measured during a standard fire-resistance test and that calculated using the proposed procedure.
Results o the ull-scale fire tests show that CL panels have the potential to provide excellent fire resistance ofen comparable to typical heavy construction assemblies o non-combustible construction. Due to the inherent nature o thick timber members to slowly char at a predictable rate, CL panels can maintain significant structural capacity or an extended duration o time when exposed to fire.
In addition to the fire-resistance calculation method o CL assemblies, Chapter 8, entitled Fire perormance o cross-laminated timber assemblies, provides requirements related to fire saety in buildings, namely in regards to the types o construction prescribed in the IBC, fire-resistance requirements, connection detailing, interior finishes, through-penetrations and exterior walls.
6.7 Sound Insulation o Cross-laminated imber Buildings
Adequate levels o noise/sound control in multi-amily buildings are mandatory requirements o most buildingcodes in the world. In many jurisdictions, these requirements are as strictly enorced as those or structural sufficiency and fire saety.
Chapter 9, entitled Sound insulation o cross-laminated timber buildings, first attempts to answer simple questions related to the definition o sound, its sources, quantification and methods o measurement, acceptable levels o sound, differences between sound and noise, etc. O course, when verbalizing such questions, some obvious answers naturally emerge in the reader’s mind.
18
Tis Chapter also introduces the International Building Code’s (IBC) requirements or sound insulation. State o the art construction details or CL walls and floor/ceiling assemblies generally meeting IBC requirements are
provided based on the results o tests perormed in various laboratories and fields. A step by step guide finally leads the reader to assemblies that will meet the occupants’ satisaction.
6.8 Building Enclosure Design o Cross-laminated imber Construction Building envelope design has important implications or the energy perormance and durability o the structure as well as indoor air quality. Te key perormance requirements o the envelope, discussed in Chapter 10 entitled
Building enclosure design o cross-laminated timber construction, are prevention o water intrusion and control o heat, air, and moisture flow.
Te use o preabricated CL panels does not modiy the basic heat, air, and moisture control design principles or an exterior wall or roo assembly. However, the design o CL assemblies requires attention due to the unique characteristics o this product. CL panels are made rom massive, solid wood elements and thereore
provide some level o thermal insulation and thermal mass. Although CL panels may have an inherent level o air tightness as a panel product produced with high precision, an additional air barrier is recommended, and it is critical that panel joints and interaces as well as penetrations such as windows and doors be properly air sealed. CL panels have a relatively high capacity to store moisture, but relatively low vapor permeability. I exposed to excessive wetting during construction, the panels may absorb a large amount o moisture, which may result in slow drying.
Tis Chapter provides guidance on heat, a ir, and moisture control in wall and roo assemblies that utilize CL panels in various North American climate zones. Te overarching strategies are to place insulation in such a way that the panels are kept warm and dry, to prevent moisture rom being trapped or accumulating within the panels, and to control airflow through the panels and at the joints and interaces between them. In certain climates,
preservative treatment o CL is recommended to provide additional protection against potential hazards such
as termites.
It is intended that these guidelines should assist practitioners in adapting CL construction to North American conditions and ensuring a long lie or their buildings. However, these guidelines are not intended to substitute or the input o a proessional building scientist.
Te environmental ootprint o CL is requently discussed as potentially beneficial when compared to unctionally equivalent non-wood alternatives, particularly concrete systems.
In Chapter 11, entitled Enironmental perormance o cross-laminated timber , the role o CL in sustainable design is addressed. Te embodied environmental impacts o CL in a mid-rise building are discussed, with preliminary results rom a comprehensive lie cycle assessment (LCA) study.
Chapter 11 discusses other aspects o CL’s environmental profile, including impact on the orest resource and impact on indoor air quality rom CL emissions. Te ability o the North American orest to sustainably support a CL industry is an important consideration and is assessed rom several angles, including a companion discussion regarding efficient use o material. Market projections and orest growth-removal ratios are applied to reach a clear conclusion that CL will not create a challenge to the sustainable orest practices currently in place in North America and saeguarded through legislation and/or third party certification programs.
Finally, to assess potential impact on indoor air quality, CL products with different thicknesses and glue lines were tested or their volatile organic compounds (VOCs) including ormaldehyde and acetaldehyde emissions. CL was ound to be in compliance with European labeling programs as well as the most stringent CARB limits or ormaldehyde emissions. esting was done on Canadian species, as there was no U.S. supplier o CL at the time o this writing; because VOC emissions are affected by species, this work should be repeated or products made rom different species.
7 ENVIRONMENTAL
20
Te preabricated nature o CL permits high precision and a construction process characterized by aster completion, increased saety, less demand or skilled workers on site, less disruption to the surrounding community and less waste. Openings or windows, doors, staircases and utilities are pre-cut using CNC
(Computer Numerical Controlled) machines at the actory. Buildings are generally assembled on site but panels are preabricated and transported to the site, where they are connected by means o mechanical astening systems such as bolts, lag bolts, sel-tapping screws, ringed annual shank nails, and so on.
CL as a building system is quite adaptable, perorming well in long spans in floors, walls and roos, with the potential or a high degree o exterior and interior finishes preinstalled off-site. Its ability to be used as either a panelized or a modular system makes it ideally suited or additions to existing buildings. It can be used jointly with any other building material, such as light wood rame, heavy timber, steel or concrete, and accepts a range o finishes. CL panels can also be built compositely with reinorced concrete to enable longer spans (i.e., longer than 30 eet or 10 m). Good thermal insulation, good sound insulation and an impressive perormance under fire conditions are added benefits which result rom the massiveness o the wood structure.
8.1 Considerations or ransportation and Construction Site Limitations Beore undertaking the design o a CL building, a plan should be drawn up or transporting the preabricated CL elements and storing them on site. ransporting CL panels can be costly and, depending on the size o the element, may require specialized transportation services. Te construction site itsel may have restrictions due to size or to local regulations. It is best to start by making sure that the route rom the plant to the construction site
will allow movement o the truck, including its load, without any obstacles. Tis is especially critical or oversize loads. Considerations or transportation o CL elements are presented in Chapter 12 entitled Lifing and handling o cross-laminated timber elements.
8.2
Materials on the Construction Site Wood-based building materials must be stored properly on the site i not used immediately. Good planning is essential to ensure that CL assemblies have the necessary handling space and proper material flow during construction. Stacking o the panels on the construction site must match the planned installation sequence to avoid additional costs and to reduce the risk o accidents or breaking.
When CL panels are stored on site, great care must be taken to protect them against the elements and vandalism. I panels must be placed temporarily on the ground prior to installation, they should be put down on skids o sufficient number to protect the panels rom standing water. Te panels must also be completely protected rom the weather by appropriate wrapping or by other measures.
8 CLT IN
21
Figure 10 shows CL panel packs in the process o being unloaded rom a truck or storage on site. In this example, the packs are completely wrapped (six aces) and are placed on wood skids to protect them rom standing
water. Although this packaging practice may be adequate, it is crucial to also use high-quality tarpaulin and to ensure that the packs remain sealed. I there are openings, water could infiltrate and remain trapped.
Figure 10 Storage on construction site – individually wrapped bundles stacked on lumber skids
Figure 11 shows truck platorms lef on construction site. Tey will be recovered on the next trip. Tis can reduce costs by allowing independent scheduling o transportation and unloading.
Figure 11 ruck platorms lef on construction site – will be recovered on the next trip
22
8.3 Lifing and Handling o CL Elements Te emerging CL construction industry has developed a range o techniques or lifing and handling CL
panels. Te complexity o the structure or its location ofen dictates the techniques and systems to be used. Naturally, erecting an 8-story building in a downtown area typically requires more preparation and skill than a single-amily residence built in the country. But i that country house is to be perched high in the mountains, more efforts may be required (Figures 12).
Figure 12 Lifing and handling o CL elements by cableway (courtesy o KLH)
Tere are several types o lifing equipment that can be used on construction sites. Each has its own characteristics or lifing and handling heavy loads such as CL panels. Tereore, it is essential to choose the right lifing and handling system or each type o component. Several lifing and handling systems and techniques are presented in Chapter 12.
8.4 Construction Accessories and Materials Numerous construction accessories and materials are required on a construction site. In addition to the items and tools normally required in conventional wood construction, suggestions are made in Chapter 12 or products, tools, and accessories that may be useul or essential on a construction project using CL panels.
23
Tis assessment o market opportunity relies on the latest construction statistics or the United States only. Tese statistics (floor area by building type) were multiplied by use actors and hence volumes or CL were estimated.
9.1 Methodology A 3-tier approach was ollowed:
1. Estimation o manuacturing costs;
2. Assessment o cost competitiveness o the building shell; and
3. Use o different market penetration scenarios to estimate the market opportunity.
Tese points are explained below. All costs are presented in U.S. dollars.
9.1.1 CLT Assembly Costs
In-house simulation work established the average production cost o CL at $19.20 per cubic oot1. wo panel thicknesses were used: 3-ply 4 ¼ in. (108 mm) or walls and 5-ply 7 in. (178 mm) or floors. Te cost o the assembly per square oot was calculated as a unction o thickness plus a 25% profit markup. Connectors and erection costs were also included ($0.70 and $1.24 per sq. f., respectively). Similarly, the cost o engineering and CAD work by the manuacturer was added at $1.00/sq. f. Tis resulted in assembly costs o approximately $12 and $19 per square oot or walls and floors, respectively. Tese prices may increase i visual grade is desired or i lumber prices go up with respect to the baseline o this study
9.1.2 Construction Statistics
Market size was calculated using the McGraw-Hill 2011, with 1 to 10 stories as base. Te year 2011 was selected as a proxy or mid-term demand (2015) based on available orecasts rom the same source2. Te 10+ story segment
was not included though it is easible to expect some uture penetration in this height class (currently 10+ story
apartments represent 10% o the 1 to 10 stories apartment floor area).
9.1.3 Sample Selection

9 ASSESSMENT
OF MARKETOPPORTUNITY
1 Delivered within a 300-mile radius. otal lumber costs, including remanuacturing and post dry, amount to $400/MBF. 2 2011 values were multiplied by 1.79 to reflect expected demand levels or 2015.
9.1.4 Shell Unit Costs and Competitiveness
Shell unit costs ($/sq. f. o floor area) were obtained rom simulations on conceptual buildings (average) perormed using the square cost estimator eature o Costworks™, an appraisal tool rom RSmeans. Normally, each situation included costing 4-6 material choices, sometimes including light wood rame. A side-by-side comparison o shell unit costs or CL vs. the incumbent materials allowed the estimation o cost competitiveness (see Section 9.2.1 or more details).
9.1.5 CLT Assembly Costs
Te square ootage o each assembly (e.g., total sq. f. o exterior walls) was calculated rom Costworks™ using average parameters and dimensions by building type. Tese square ootages were multiplied by CL’s unit assembly costs (e.g., $/sq. f. o wall area) to calculate the total cost by assembly and shell. Te CL assembly configuration varied according to building type. Te deault exterior wall assembly consisted o:
• 3-ply CL
• Vinyl siding
• 3 in. expanded polystyrene (EPS)
• Vapor retarder.
Industrial buildings considered metal siding (corrugated steel) and interior fire-rated (or ype X) gypsum. Floors consisted o 5-ply CL plus plywood underlayment. It is acknowledged that some situations may call or thicker
panels, or instance a 7-ply CL panel.
Roo consisted o a gang-nailed wood truss assembly or all buildings except industrial. Industrial buildings considered metal deck with open web steel joists, beams, and hollow steel columns. All roo assemblies considered roo coverings (built-up) and insulation (2 in. EPS + 1 in. perlite).
Partitions considered 3-ply CL plus 5/8 in. ype X gypsum board on both sides. wenty percent o partitions were considered to be load-bearing and using CL, the balance assuming metal studs. Non-CL buildings considered drywall on metal studs.
Shafs assumed a 5-ply panel.
Parking garages considered 5-ply CL or all assemblies. Tey also included glulam beams and columns (22 in. x 22 in.), including connectors and installation costs. Epoxy coating was included too.
Not included:
• ime savings (time savings estimated at 20% vs. concrete).
9.2 Results 9.2.1 Shell Cost Competitiveness
Light wood rame is the most economical system in low-rise projects, with CL becoming normally morecompetitive only at higher building heights or sizes (Figure 13). Most industrial buildings and—to some extent—parking garages showed similar or slightly higher shell costs or CL and thereore may represent an attractive choice or CL given their relatively regular ootprint and repetitive layout. Besides mid-rise and industrial, retail (1-2 stories) and educational (2-3 stories) buildings are also good bets or CL. It must be noted that shell costs normally account or about 20-30% o the total cost o a finished concrete/steel building and, thereore, is expected that some o these differences in shell costs will be less noticeable when considering total unit costs.
CLT Non-
0
10
20
30
S h e l l C o s t ( $ / s q .
f t .
3 5 8
Figure 13 Unit shell cost by story class and rame material apartments
9.2.2 Assessment of Demand
wo market penetration scenarios were considered: 5% and 15%. Based on shell costs, a competitiveness actor was assigned to each situation. Tis ‘c-actor’ acted as a multiplier on the floor area per situation. Building code
limitations were considered too. For instance, only low-rise health buildings are included in the assessment. For other building types, it is assumed that code will allow CL in the uture. For a more conservative demand estimate, the reader may choose considering only the 1-4 story segment (94%).
In summary, the U.S. market opportunity or CL is estimated at 0.9 to 2.7 BBF (able 1) approximately 3. o provide a ramework or these numbers, total consumption o sofwood lumber in the United States in 2011
was estimated at 85.4 million m3. No reliable orecast or 2015 is available in order to estimate the equivalency or share o those 1.5-4.5 million m3 o potential opportunity. o put these numbers in perspective, the assessment
3 CL buildings consume 0.1 to 1+ f3 o CL per sq. f. o floor area, with an average around 0.6 f.3/sq. f.
26
represents a potential increase o 2 to 7 percent in total U.S. sofwood lumber demand over 2011 consumption. Tis demand is equivalent to somewhere between two and six billion dollars o CL shell value4. Demand is concentrated on the East Coast, the Great Lakes States, exas, and Caliornia (Figure 14).
Table 1 Market opportunity (2015)
1,104,889368,296 1,069,591 35,298356,530
180,98360,328 180,835 14860,278
883,458294,486 864,449 19,010288,150
123,30841,103 123,270 3741,090
2,292,638764,213 2,238,145 54,493746,048
432,4061 44, 13 5 3 11 ,3 03 1 21 ,1 03103,768
432,4061 44, 13 5 3 11 ,3 03 1 21 ,1 03103,768
2,725,044908,348 2,549,448 175,595849,816Grand total
Total
N o n - r e s i d e n t i a l
R e s i d e n t i a l
Project Header
Com- mercial
Indus- trial
Institu- tional
Miscel- laneous
1BF=Board eet
Clearly, the 1-4 story segment represents the largest market opportunity given its share o the market. Tis is especially true or the non-residential market, notably commercial and institutional buildings making up 87% o the non-residential opportunity. Conversely, in the case o apartments, nearly 40% o the opportunity comes rom the 5 to 10-story height class. However, recent trends towards cheaper or rent wood-ramed apartment buildings might hinder the inroad o CL into this segment.
Tis estimate does not include possible inroads into the high-end single-amily market.
4 25% GC overhead and profit included.
B y S t a t e
B y M e t r o A r e a
A p a r t m e n t s
B y S t a t e a n d
U s e
P r o j e c t l i s t

28
Te purpose o this section is to introduce interesting examples o buildings built around the world using CL elements.
10.1 Residential Buildings
10 BUILDING EXAMPLES

Figure 16 Single-amily house in Klagenurt, Austria (courtesy o KLH)

Figure 18 Garlick Residence, Oroville, WA, United States (courtesy o Structurlam Products Ltd.)

Figure 19 Multi-amily building in Judenburg, Austria (courtesy o KLH)

Figure 20 Multi-amily building in Chibougamau, uébec, Canada (courtesy o Nordic Engineered Wood)
37



Figure 25 Montana Long Hall (photo courtesy o Darryl Byle in connection with IS Smartwoods)

Figure 26 Viken Skog BA, Høneoss, Norway (courtesy o Moelven)
Figure 27 Juwi head office, Wörrstadt, Germany (courtesy o Binderholz)
Figure 30 Parking garage in Innsbruck, Austria (courtesy o KLH)

Figure 31 Residential building in South Carolina, United States (courtesy o Binderholz)
®FPInnovations, its marks and logos are registered trademarks of FPInnovations. Special Publication SP-529E
www.fpinnovations.ca
570, boul. St-Jean Pointe-Claire, QC Canada H9R 3J9 514 630-4100
www.fpinnovations.ca
1 Gifford Pinchot Drive Madison, WI USA 53726 608 231-9200
www.fpl.fs.fed.us
P.O. Box 45029 Ocean Park RPO Surrey, BC Canada V4A 9L1 604 536-7730
www.softwoodlumber.org
222 Catoctin Circle SE Suite 201 Leesburg, VA USA 20175 202 463-2766
www.awc.org
7011 S 19th Street Tacoma, WA USA 98466-5333 253 565-6600
www.apawood.org
1111 19th Street NW Suite 800 Washington, DC USA 20036 866 966-3448
www.woodworks.org
1130 West Pender Street Suite 1200 Vancouver, BC Canada V6E 4A4 604 685-7507
www.bcfii.ca
AMERICAN
WOOD
COUNCIL
C
r o s s - l a m i n a t e d t
i m b e r m a n u f a c t u
r i n g
Authors
Borjen Yeh, Ph.D., P.E., APA Dave Kretschmann, P.E., USDA Forest Products Laboratory
Brad (Jianhe) Wang, Ph.D., FPInnovations
Peer Reviewers
Conroy Lum, P.Eng., FPInnovations Julie Frappier, Eng., Nordic Engineered Wood
Andre Morf, Structurlam
Te U.S. Edition o the CL Handbook: cross-laminated timber combines the work and knowledge o American, Canadian and European specialists. Te handbook is based on the original Canadian Edition o the CL Handbook: cross-laminated timber , that was developed using a series o reports initially prepared by FPInnovations
and collaborators to support the introduction o CL in the North American market. A multi-disciplinary team revised, updated and implemented their know-how and technologies to adapt this document to U.S. standards.
Te publication o this handbook was made possible with the special collaboration o the ollowing partners:
Te editing partners would also like to express their special thanks to Binational Sofwood Lumber Council, Forestry Innovation Investment (FII), Nordic Engineered Wood, Structurlam, and CL Canada or their financial contribution to studies in support o the introduction o cross-laminated timber products in the United States o America.
ACKNOWLEDGEMENTS
AMERICAN
WOOD
COUNCIL
The U.S. Edition of the CLT Handbook: cross-laminated timber can be electronically downloaded without charge from the website www.masstimber.com. Additional information can be obtained by visiting the websites of FPInnovations, USFPL, American Wood Council (AWC), APA and U.S. WoodWorks. Hard copies can be obtained through AWC (www.awc.org).
No part of this published Work may be reproduced, published, or transmitted for commercial purposes, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, whether or not in translated form, without the prior written permission of FPInnovations and Binational Softwood Lumber Council.
The information contained in this Work represents current research results and technical information made available from many sources, including researchers, manufacturers, and design professionals. The information has been reviewed by professionals in wood design including professors, design engineers and architects, and wood product manufacturers. While every reasonable effort has been made to insure the accuracy of the information presented, and special effort has been made to assure that the information reflects the state-of-the-art, none of the above-mentioned parties make any warranty, expressed or implied, or assume any legal liability or responsibility for the use, application of, and/or reference to opinions, findings, conclusions, or recommendations included in this published work, nor assume any responsibility for the accuracy or completeness of the information or its fitness for any particular purpose.
iii
ABSTRACT
Tis Chapter provides general inormation about the manuacturing o CL that may be o interest to the design community. Te inormation contained in this Chapter may also provide guidance to CL manuacturers in the development o their plant operating specification document.
ypical steps o the CL manuacturing process are described, and key process variables affecting adhesive bond quality o CL products are discussed. Te manuacturing, qualification, and quality assurance requirements in accordance with the American National Standard or Perormance-Rated Cross-Laminated imber, ANSI/APA PRG 320, are discussed.
3.2
4.1 Primary Lumber Selection 11
4.1.1 Lumber Moisture Content and emperature 11
4.1.2 Lumber Characteristics Affecting Adhesive Bond uality 12
4.2 Lumber Grouping 12
4.3 Lumber Planing 12
4.5 Adhesive Application 13
4.7 Assembly Pressing 13
4.9 Product Marking, Packaging and Shipping 15
5.1 Plant Pre-qualification 16
5.3 Process Change ualification 18
5.4 uality Assurance 18
5.5.1 Delamination ests 19
7 Conclusions 21
vi
List o ables Table 1 Required characteristic strengths and moduli o elasticity or PRG 320 CL laminations 6
Table 2 Allowable design capacities or CL (or use in the United States) 7
Table 3 Response to process changes according to ANSI/APA PRG 320 18
List o Figures Figure 1 Cross-section o a 5-layer CL panel 1
Figure 2 Te manuacturing process o CL products 10
Figure 3 Lumber shrinkage relie 14
Figure 4 Block shear (“B”) and delamination (“D”) specimen locations 17
1 INTRODUCTION
Cross-laminated timber (CL) is defined as a preabricated solid engineered wood product made o at least three orthogonally bonded layers o solid-sawn lumber or structural composite lumber (SCL) that are laminated by gluing o longitudinal and transverse layers with structural adhesives to orm a solid rectangular-shaped, straight,
and plane timber intended or roo, floor, or wall applications (see Figure 1). While this engineered wood product has been used in Europe or over 15 years, the production o CL and design o CL structural systems have
just begun in North America with some manuacturers currently being in production or in the process o product qualification.
Perpendicular LayerParallel Layer
Figure 1 Cross-section o a 5-layer CL panel
For the acceptance o new construction materials or systems such as CL in North America, a consensus-based product standard is essential to the designers and regulatory bodies. In recognition o this need, APA – Te Engineered Wood Association in the United States and FPInnovations in Canada initiated a joint standard development process in 2010. Te intent was to develop a bi-national CL standard or North America using the consensus standard development process o APA as a standards developer accredited by the American National Standards Institute (ANSI). Afer 22 months o intensive committee meetings and balloting, the first North
American CL standard was completed as the ANSI/APA PRG 320-2011 Standard or Perormance-Rated Cross- Laminated Timber [1] in December 2011. Tis Chapter describes and documents the background inormation and some key issues that were considered during the development o the ANSI/APA PRG 320 CL standard.
REQUIREMENTS
CL is manuactured with laminations o dimension lumber or SCL, such as laminated veneer lumber (LVL), laminated strand lumber (LSL), or oriented strand lumber (OSL), which are bonded with structural adhesives through ace joints, end joints and/or edge joints. Nail-laminated CL or other CL products manuactured
without ace bonds are outside the scope o the ANSI/APA PRG 320 standard.
Components (lumber/SCL laminations and adhesives) selected or CL and the manuacturing processes (adhesive application, panel pressing, etc.) need to be careully considered to ensure a reliable and consistent
product. CL products evaluated or code compliance by a recognized product certification agency or evaluation service as meeting ANSI/APA PRG 320 provide designers with an assurance or product quality and perormance.
2.1 Laminations ANSI/APA PRG 320 utilizes the European experience in engineering theories and manuacturing processes o CL, and takes into consideration the characteristics o the North American lumber resource, manuacturing
preerence, and end-use expectations. For example, the standard permits the use o any sofwood lumber species or species combinations recognized by the American Lumber Standards Committee (ALSC) under PS 20 [2] or the Canadian Lumber Standards Accreditation Board (CLSAB) under CSA O141 [3] with a minimum specific gravity (SG) o 0.35, as published in the National Design Specification or Wood Construction (NDS) [4] in the United States or the Engineering Design in Wood (CSA O86) [5] in Canada. One advantage o using standard- grade lumber is that such lumber will typically be marked as “H” (heat treated), meaning that the resulting CL
product will also meet national and international phytosanitary requirements when the traceability (chain-o- custody) requirements o the lumber laminations can be properly demonstrated and certified.
Te minimum SG o 0.35 is intended as the lower bound or the CL connection design since it is the near minimum value o commercially available wood species in North America, Western Woods in the United States and Northern Species in Canada. o avoid differential mechanical and physical properties o lumber, the standard requires the same lumber species or species combinations be used within the same layer o the CL,
while permitting adjacent layers o CL to be made o different species or species combinations. Te standard also permits the use o SCL when qualified in accordance with ASM D5456 [6]. In reality, however, it is still years away beore SCL would be used in CL production because o apparent challenges in the ace bonding o SCL to SCL or SCL to lumber. Due to the thickness variation and surace oxidation or inactivation o SCL, surace
planing or sanding may be required or SCL beore gluing. Another consideration is its cost competitiveness with lumber. Nonetheless, the advantage o SCL that can be produced in a long and wide billet orm is one important actor that the ANSI/APA PRG 320 Committee elected to include SCL in the standard. Other attractive actors also include ree o natural deects such as wane, shake, and knots, more uniorm stiffness and strength, and greater dimensional stability.
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Lumber grades in the parallel layers o CL are required to be at least 1200-1.2E MSR or visually graded No. 2, and visually graded No. 3 or perpendicular layers. Remanuactured lumber is permitted as equivalent to solid-
sawn lumber when qualified in accordance with ANSI/AIC A190.1 [7] in the United States or SPS 1, 2, 4, or 6 [8,9,10,11] in Canada. Proprietary lumber grades meeting or exceeding the mechanical properties o the lumber grades specified above are permitted provided that they are qualified in accordance with the requirements o an approved agency, which is defined in the standard as an independent inspection agency accredited under ISO/IEC 17020 [12] or an independent testing agency accredited under ISO/IEC 17025 [13] in the United States, or a certification agency accredited under ISO Guide 65 [14] in Canada. Tis allows or a great flexibility in the utilization o orest resources in North America.
Te net lamination thickness or all CL layers at the time o gluing is required to be at least 5/8 inch (16 mm), but not thicker than 2 inches (51 mm) to acilitate ace bonding. In addition, the lamination thickness is not
permitted to vary within the same CL layer except when it is within the lamination thickness tolerances—at the time o ace bonding, variations in thickness across the width o a lamination is limited to ±0.008 inch (0.2 mm) or less, and the variation in thickness along the length o a lamination is limited to ±0.012 inch
(0.3 mm). Tese maximum tolerances may need to be adjusted during qualification as so to produce acceptable ace bond perormance.
Te net lamination width is required to be at least 1.75 times the lamination thickness or the parallel layers in the major strength direction o the CL.

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