A Handbook for the Sustainable Use of Timber in Construction i A Handbook for the Sustainable Use of Timber in Construction Jim Coulson This edition first published 2021 © 2021 John Wiley & Sons Ltd All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions. The right of Jim Coulson to be identified as the author of this work has been asserted in accordance with law. 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Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential or other damages. Library of Congress Cataloging‐in‐Publication Data Names: Coulson, Jim (James C.), author. | Wiley-Blackwell (Firm), publisher. Title: A handbook for the sustainable use of timber in construction / Jim Coulson. Description: [Hoboken, NJ] : Wiley-Blackwell, 2021. | Includes index. Identifiers: LCCN 2020025971 (print) | LCCN 2020025972 (ebook) | ISBN 9781119701095 (cloth) | ISBN 9781119701149 (adobe pdf) | ISBN 9781119701132 (epub) Subjects: LCSH: Sustainable construction. | Timber--Standards. | Wood products--Standards. | Sustainable buildings--Design and construction. Classification: LCC TH880 .C688 2021 (print) | LCC TH880 (ebook) | DDC 691/.1--dc23 LC record available at https://lccn.loc.gov/2020025971 LC ebook record available at https://lccn.loc.gov/2020025972 Cover Design: Wiley Cover Image: © Chris Rogers/Getty Images Set in 10/12pt PalatinoLTStd by SPi Global, Chennai, India 10 9 8 7 6 5 4 3 2 1 Contents Preface xiii PART ONE How Timber Works: Wood as a Material – Its Main Processes and Uses 1 1 Wood as a Material 3 1.1 Tree growth and wood formation 5 1.2 Cellulose, carbon dioxide, and oxygen 7 1.3 The essential cell structure of wood 9 1.4 Wood grain 11 1.5 Dimensional changes in wood 15 1.6 Cambium, pith, heartwood, and sapwood 17 1.7 Natural durability 20 1.8 Permeability in timber 21 1.9 Pits 24 1.10 Chapter summary 26 2 More on Wood – With Some Comments about Timber Trading 29 2.1 Should we call it ‘wood’ or ‘timber’ (or even ‘lumber’)? 29 2.2 Wood species and timber trading 30 2.3 Softwoods and hardwoods 30 2.4 Some more information on wood’s cell structure 33 2.5 The significance of ‘trade names’ versus ‘scientific names’ 38 2.6 Growth rings 42 2.7 Earlywood and latewood 43 2.8 Rate of growth in softwoods 43 2.9 Rate of growth in hardwoods 45 2.10 Chapter summary 48 v vi Contents 3 Two Fundamental Factors in Using Wood: Fire and Water 49 3.1 Wood and fire 49 3.2 Wood and moisture 54 3.3 Kiln drying 66 3.4 Air drying 69 3.5 Problems with timber as it dries 72 3.6 Timescales for drying timber 79 3.7 Chapter summary 81 4 Specifying Timber: For Indoor or Outdoor Uses – With Some Information on the Biological Attack of Wood 83 4.1 British and European standards 83 4.2 Durability and treatability of different wood species 84 4.3 Use classes 85 4.4 Examples of the use of timbers in different use class situations 86 4.5 Hazard and risk – and their relative importance 87 4.6 Use class 1: examples 87 4.7 Insects that can attack wood 91 4.8 Treatment against insect attack 94 4.9 Use class 2: examples 95 4.10 Use class 3: examples 97 4.11 Use class 4: examples 102 4.12 Wet rot and ‘dry rot’ 107 4.13 Modified wood 109 4.14 Use class 5: examples – plus two marine organisms which can eat wood 110 4.15 Chapter summary 112 5 Wood Preservatives and Wood Finishes 115 5.1 Rule number one: treat the timber last! 115 5.2 Wood preservative types 117 5.3 ‘Old’ and ‘new’ treatments 117 5.4 Basic methods of timber treatment 117 5.5 Preservative chemicals 120 5.6 ‘Treated’ timber 123 5.7 Chapter summary 131 6 Timber Quality: Defects in Wood and Grading for Appearance 133 6.1 The need for grading 134 6.2 ‘Quality’ or ‘grade’? 135 6.3 Quality 136 Contents vii 6.4 Grade 137 6.5 Different types of grading 137 6.6 ‘Appearance’ grading 137 6.7 Appearance grading based on selection by inherent defects 138 6.8 Scandinavian appearance grades 141 6.9 Unsorted, fifths, and sixths 143 6.10 Russian appearance grades 144 6.11 Saw falling 145 6.12 European appearance grades 145 6.13 North American appearance grades 146 6.14 Clears, merchantable, and commons 148 6.15 A comparison of Scandinavian and North American grades 149 6.16 Appearance grading based on ‘cuttings’ 149 6.17 NHLA grades 150 6.18 Malaysian grades 154 6.19 Rules are made to be bent (within reason!) 157 6.20 Shipper’s usual 157 6.21 J classes 158 6.22 Exposed face 159 6.23 Chapter summary 160 7 Strength Grading and Strength Classes 163 7.1 Appearance versus strength 166 7.2 Visual strength grades 166 7.3 GS and SS strength grades 167 7.4 Strength classes for softwoods 168 7.5 BS EN 1912 168 7.6 SC3, SC4: C16 and C24 169 7.7 Machine grading 171 7.8 Other strength grades: Europe and North America 172 7.9 Select structural, no. 1 and no. 2 structural, and stud grades 172 7.10 TR26 173 7.11 CLS 175 7.12 Specifying a strength class or wood species: things to think about 176 7.13 Hardwood strength grading 177 7.14 Tropical hardwoods 178 7.15 Temperate hardwoods 178 7.16 The ‘size effect’ 179 7.17 Hardwood strength classes 180 7.18 Marking of strength-graded timber 181 7.19 Chapter summary 183 viii Contents 8 Wood-Based Sheet Materials 185 8.1 Plywood construction 186 8.2 Two fundamental properties of plywood 186 8.3 The basic types of plywood 188 8.4 Problems with veneer ‘layup’ 192 8.5 ‘WBP’ 192 8.6 Exterior 194 8.7 EN 636 plywood types 194 8.8 Adhesives used in plywood 195 8.9 BS 1088 marine plywood 196 8.10 Plywood glue bond testing 197 8.11 Plywood face quality 199 8.12 Appearance grading of face veneers 199 8.13 Plywood certification 202 8.14 Particleboards 205 8.15 Fibreboards 208 8.16 Chapter summary 212 9 Principles of Timber Engineering (by Iain Thew) 215 9.1 Timber as an ‘engineering material’ 216 9.2 Loads: their actions on structures 217 9.3 Load transfer 218 9.4 Bending, compression, and tension stresses 218 9.5 The use of strength classes 220 9.6 Load duration and its significance 222 9.7 Effects of timber moisture content on engineering properties 223 9.8 Load sharing 224 9.9 Deflection and ‘creep’ 224 9.10 Trussed rafters 225 9.11 ‘Engineered timber’ joists 226 9.12 Glulam and LVL 227 9.13 Cross-laminated timber 229 9.14 Chapter summary 230 PART TWO Using Timber and Wood-Based Products in Legal and Sustainable Way 231 10 Some Things You Should Know About Wood, Trees, and Forests 233 10.1 Some very basic comments on how trees grow 233 10.2 How long can trees live for – and how ‘old’ is an old tree? 235 10.3 The properties of different timbers 236 10.4 Distribution of tree types 236 10.5 Natural forests 238 Contents ix 10.6 Managed forests: conifers 242 10.7 Managed forests: broadleaved trees 245 10.8 Plantations: both softwoods and hardwoods 247 10.9 Planting trees to help with climate change 253 11 The Concept of ‘Sustainability’ 255 11.1 Being sustainable: a definition – and a target 255 11.2 What can we do to help? 258 11.3 Should we be cutting down trees? 259 11.4 Using the forest resource: the economic argument 262 11.5 Legal harvesting 263 11.6 The UK Timber Trade Federation and its ‘responsible purchasing policy’ 265 12 Voluntary Timber Certification Schemes 269 12.1 Some more details about the RPP 269 12.2 Checking legality I: the Corruption Perceptions Index 271 12.3 Checking legality II: FLEGT 275 12.4 Checking legality III: MYTLAS 277 12.5 Checking legality IV: other ‘legality’ certification schemes 278 12.6 Checking sustainability: chain-of-custody certification 280 12.7 UKWAS 286 12.8 Third-party assurance 287 12.9 How chain-of-custody schemes operate 287 13 UK Government, EU, and Other Countries’ Regulations: Legally Trading in World Timbers 289 13.1 Checking up on the checkers: CPET and beyond 289 13.2 Help with legality and sustainability requirements in a UK context 290 13.3 The UK government’s requirements for TPP 290 13.4 Category A and category B: ‘proof of compliance’ 291 13.5 Current and future supplies of certified timber 293 13.6 The EUTR: Europe’s compulsory ‘timber legality scheme’ 294 13.7 Due Diligence 294 13.8 How to Satisfy the EUTR (or now, in the UK, the UKTR) 295 13.9 Putting together a due diligence system 297 13.10 Maintaining a due diligence system 298 13.11 ‘First placer on the market’ 299 13.12 CE marking and the CPR 300 13.13 CITES: what exactly is It? 301 x Contents 14 Softwoods Used in Construction – With Their Main Properties and Sustainability Credentials 307 14.1 European redwood, or scots pine (Pinus sylvestris) 308 14.2 European whitewood (principally Picea abies) 310 14.3 Sitka spruce (Picea sitchensis) 311 14.4 Western hemlock (Tsuga heterophylla) 312 14.5 ‘Douglas fir’ (Pseudotsuga menziesii) 313 14.6 Larch (mainly Larix decidua and Larix kaempferi/Larix leptolepis) 314 14.7 ‘Western red cedar’ (Thuja plicata) 315 14.8 Southern pine (Pinus spp., principally Pinus elliottii, Pinus echinata, Pinus palustris, and Pinus taeda) 316 14.9 Yellow pine (Pinus strobus) 317 14.10 Species groups 318 15 Some Hardwoods Used in Construction – With  Their Main Properties and Sustainability Credentials 321 15.1 ‘Vulnerable’ timbers 322 15.2 Timber names: a bit more information 323 15.3 Ash, American (Fraxinus spp.) 324 15.4 Ash, European (Fraxinus excelsior) 326 15.5 Ayan (Distemonanthus benthamianus) 326 15.6 Basralocus (Dicorynia guianensis or Dicorynia paraensis) 328 15.7 Beech, European (Fagus sylvatica) 328 15.8 Bilinga 329 15.9 Birch, European (mainly Betula pubescens, sometimes Betula pendula) 329 15.10 Cherry, American (Prunus serotina) 330 15.11 Chestnut, sweet (Castanea sativa) 330 15.12 Cupiuba 331 15.13 Ekki (Lophira alata) 331 15.14 Eucalyptus 332 15.15 Eveuss (Klainedoxa gabonensis) 332 15.16 Gedu nohor (Entandrophragma angolense) 332 15.17 Greenheart (Chlorocardium rodiei; formerly Ocotea rodaiei) 332 15.18 Guariuba (Clarisia racemosa) 333 15.19 Idigbo (Terminalia ivorensis) 333 15.20 Iroko (Milicia excelsa) 334 15.21 Kabukalli (Goupia glabra) 334 15.22 Kapur (Dryobalanops spp.) 335 15.23 Keruing (Dipterocarpus spp.) 335 Contents xi 15.24 Kosipo (Entandrophragma candollei) 336 15.25 Mahogany, African (principally Khaya ivorensis and Khaya anthotheca) 337 15.26 Mahogany, Central American (Swietenia macrophylla) 337 15.27 Maple (Acer saccharum) 338 15.28 Majau (Shorea spp.) 338 15.29 Massaranduba (Manilkara spp.) 338 15.30 Meranti (Shorea spp.) 339 15.31 Merbau (Intsia bijuga) 340 15.32 Missanda (Erythrophleum guineense and Erythrophleum ivorense) 340 15.33 Movingui 341 15.34 Oak, American red (principally Quercus rubra and Quercus falcata) 341 15.35 Oak, American white (principally Quercus alba and Quercus prinus, but also Quercus lyrata and Quercus michauxii) 341 15.36 Oak, European (mainly Quercus robur, but also Quercus petraea) 342 15.37 Obeche (Triplochiton scleroxylon) 343 15.38 Omu 343 15.39 Opepe (Nauclea diderrichii) 343 15.40 Padauk (Pterocarpus soyauxii) 344 15.41 ‘Red grandis’ (really Eucalyptus grandis) 344 15.42 Sapele (Entandrophragma cylindricum) 345 15.43 Tatajuba (Bagassa guianensis) 346 15.44 Teak (Tectona grandis) 346 15.45 Tali 347 15.46 Tiama 347 15.47 Tulipwod 347 15.48 Utile (Entandrophragma utile) 347 15.49 Walnut, American (Juglans nigra) 348 15.50 Walnut, European (Juglans regia) 348 15.51 Whitewood, American or tulipwood (Liriodendron tulipifera) 349 16 The Use and Reuse of Timber and Wood-Based Products: The Carbon Cycle, End-of-Life Disposal, and Using Wood as Biomass 351 16.1 Should we ‘save’ all the trees? 351 16.2 The true ‘carbon cycle’ 352 16.3 End-of-life disposal of timber and wood-based products 353 16.4 Recycled timber 354