A Handbook for the Sustainable Use of Timber in Construction

JIM COULSON is a Past President of the Institute of Wood Science, a Fellow of the Institute of Materials Minerals and Mining (IOM3), a Fellow of the Faculty of Building and a Chartered Environmentalist. He is a member of the Board of the Wood Technology Society (part of IOM3), a member of the UK Timber Grading Committee and a member of two BSI Committees concerned with Structural Uses for Wood-Based Materials and the Sustainability of Construction Works. He is also a member of the International Research Group on Wood Protection and a member of the ICOMOS (International Council on Monuments and Sites) International Wood Committee. He has an encyclopedic knowledge of the uses of timber and wood-based products in both historic and present-day construction. He has been a Visiting Lecturer to Schools of Architecture and Engineering at Newcastle and Durham Universities, as well as Leeds College of Building. He is founder of TFT Woodexperts Limited - a consultancy practice dealing with all technical aspects of timber and wood-based materials, their processing and uses. He also sets cryptic crossword puzzles for The Times, The Daily Telegraph, the Sunday Telegraph and Materials World (the House Magazine of IOM3). IAIN THEW is a structural engineer, with a particular interest in the use of wood in construction. He studied Structural Engineering with Architecture at The University of Edinburgh, gaining a Masters degree in Engineering. He is secretary of the Wood Technology Society, a Materials Division of the IOM3 and sits on the B/518 BSI Committee on Structural Timber. He is also a Chartered Member of the Institution of Structural Engineers and a qualified timber grader. He works for Structural & Civil Consulting Ltd, a consultancy which specialises in wood in construction and historic buildings, and has worked on projects as varied as the Rievaulx Abbey Visitor Centre and the Castle Howard Palladian Dome.

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 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 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 s