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Wood lecture thursday andrea wheeler

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Wood lecture thursday andrea wheeler

  1. 1. WOOD Andrea Wheeler ARCH 542 Sci-Tech 2 Week 11 Part 2
  2. 2. CONTENT (Lectures and Lab Thurs/ Friday) 1. Review: The timber yard and supply chain – the sustainable sourcing of wood. 2. Wood composites, laminated timber and new materials. 3. Wood rot, and insects. 4. Construction uses for wood and timber framing. 5. Fastenings, and connections – more Lab (Friday) 6. Case studies of timber in structure and construction (throughout) – more Lab (Friday)
  3. 3. Attendance question ? Describe the stages involved in the “processing” of timber for constructional use? How can we ensure the process is “green”? ARCH 542
  4. 4. PREPARATION OF TIMBER FOR COMMERCIAL USE: Manufacturing process of timber The production of wood for construction – from log to board: • Sourcing – mature trees felled / identified by the forest Stewart involved sustainable forestry management. • Stacked for transport to mill (some free water dissipating) - floated downstream to mill • sawing/cutting (before logs are sawn debarked and inspected) • seasoning, • planing/ surfacing, • preservative treatment, • grading, • distribution.
  5. 5. Sourcing – Sustainable Forestry • Certified Forest/ Forest Stewardship Council two types of certification Forest Management and Chain of Custody. (10 principles, 57 criteria.) FSC-certified wood was found to be the most specified green-building product in LEED certified buildings. • Sustainable Forestry Initiative (SFI), which provides a comprehensive system of principles, guidelines and performance standards that balance the perpetual growing and harvesting of trees with environmental protection and conservation. The Sustainable Forestry Initiative (SFI) is a 'forest certification standard‘.
  6. 6. Sustainable forestry principles PRINCIPLE #3: INDIGENOUS PEOPLES’ RIGHTS - The legal and customary rights of indigenous peoples to own, use and manage their lands, territories, and resources shall be recognized and respected. PRINCIPLE #4: COMMUNITY RELATIONS AND WORKER’S RIGHTS - Forest management operations shall maintain or enhance the long-term social and economic well being of forest workers and local communities. PRINCIPLE # 5: BENEFITS FROM THE FOREST - Forest management operations shall encourage the efficient use of the forest’s multiple products and services to ensure economic viability and a wide range of environmental and social benefits. PRINCIPLE #6: ENVIRONMENTAL IMPACT - Forest management shall conserve biological diversity and its associated values, water resources, soils, and unique and fragile ecosystems and landscapes, and, by so doing, maintain the ecological functions and the integrity of the forest. PRINCIPLE #7: MANAGEMENT PLAN - A management plan — appropriate to the scale and intensity of the operations — shall be written, implemented, and kept up to date. The long-term objectives of management, and the means of achieving them, shall be clearly stated.
  7. 7. The importance of the supply chain FSC Chain-of-Custody certification traces the path of products from forests through the supply chain, verifying that FSC-certified material is identified or kept separated from non-certified material throughout the chain. Any company in this supply chain, including harvesters, processors, manufacturers, distributors, printers, retailers or anyone that is taking ownership of the forest product before the end user, needs to be FSC certified to be able to label or promote their products as FSC certified. The Chain-of-Custody process ensures the consumer that the FSC-certified products they purchase are coming from responsibly managed sources. For a consumer to purchase an FSC-certified product, every company that previously had ownership of the forest product material components of the end product would have had to be FSC certified.
  8. 8. LEED Standard The requirements for the credit are: “Use a minimum of 50% of wood-based materials and products, which are certified in accordance with the Forest Stewardship Council’s (FSC) Principles and Criteria, for wood building components. These components include, but are not limited to, structural framing and general dimensional framing, flooring, sub-flooring, wood doors and finishes. Only include materials permanently installed in the project. Furniture may be included, providing it is included consistently in MR Credits 3–7.” - LEED NC V2.2
  9. 9. Does LEED or FSC certified standards mean sustainable architecture? ARCH 558
  10. 10. Transport by truck or downstream to the mill
  11. 11. Sawing The debarked log is evaluated by scanners with "electronic eyes". The scanners use lasers to determine the size of the log and the best possible cuts. A computer then sets up the longitudinal cuts using an edge saw. The sawyer's cut decisions are based on: Species of wood ;Log diameter ;Intended use of the lumber ; Yield ;Market costs for different grades and sizes of lumber. The sawyer is a very important person at the mill because he determines whether or not the mill will make money based on his evaluation of the log.
  12. 12. Air drying programs will take more than a year. Kiln drying programs
  13. 13. The sustainable timber yard: wastage in the timber yard. Almost all the parts of a tree are commercially useful. Bark: used for fuel or mulch Lower-grade logs are processed into paper Low grade boards and scraps from sawing processed into paper.
  14. 14. Grading Finally, machines and workers inspect the lumber and rate it based on the amount of defects present. BSW produce strength graded timber to specifications laid down in British Standards - BS4978 for visual grading and BS EN 14081 for machine grading. Timber is graded to strength classes. The most commonly specified grade for softwood carcassing is C16.
  15. 15. Grading USA – Types of Timber Boards: 1 to 1.5 inches thick, 2 inches and wider Dimension Lumber: 2 to 4 inches thick, 2 inches and wider (Dimension lumber is further subdivided into five categories based on size classifications. These classes are structural joists and planks, studs, decking, light framing, and structural light framing. After the dimension lumber has been separated, the grader assigns a grade). Timbers: 5 inches and thicker, 5 inches and wider
  16. 16. Board lumber is graded by evaluating the better face of the board. Natural and manufacturing defects are considered, but strength is not a critical factor (unlike the grading of dimension lumber). •The highest classification of board lumber is called select grade. Select grade is further divided into three categories: B & Better, C Select, and D Select. B is the best but all of the select grades are used in demanding finishing applications. •The next classification is called common grade. Common grade boards generally contain more knots than the select grade. Common grade is divided numerically from 1 to 5 with 1 being the best in appearance. No. 3 and No. 4 common grades are most frequently used for such applications as sheathing or sub- flooring.
  17. 17. Visual Grading is the most common type of grading performed on lumber in the U.S. A grade stamp on each piece of lumber as it leaves the mill. Visual grading is done based on both appearance and strength factors. The grader marks each piece of lumber according to such factors as: •Number, size, and position of knots and holes •Bark on edges •Decay •Checks and splits •Machining defects •Twisting, bowing, and warp •Species Rules for grading are established by the U.S. Department of Commerce and maintained by the American Lumber Standards Committee. These standards are enforced by regional organizations. Three years of training are required to become a grader. Visual Grading
  18. 18. After kiln drying to an average moisture content of below 20%, the timber is passed through a highly automated grading line where a combination of measurements are taken which closely relate to strength. From this, the machine determines the Strength Class of the piece of timber. The machines are calibrated daily. DIMENSIONAL LUMBER - Machine graded (strength is the factor)
  19. 19.
  20. 20. The species of lumber is stamped, and is also abbreviated. Some common examples include: •"S-P-F" represents spruce-pine-fir, a common grouping for some of the Eastern softwoods. "DF-L" refers to Douglas fir and Western larch. "Hem- fir" stands for Western hemlock and true firs. In the U.S., there are six associations that develop and publish grade rules and issue grade stamps. • Redwood Inspection Service (R1S); • Northeastern Lumber Manufacturers Association (NELMA); • Northern Hardwood and Pine Manufacturers Association (NHPMA); • Southern Pine Inspection Bureau (SPIB); • West Coast Lumber Inspection Bureau (WCLB); • and Western Wood Products Association (WWPA). The mill identification name or number is also included. The grade itself is indicated. A lumber grade is the quality-control standard for lumber that has been in place since such standards were instituted in 1960. Lumber is graded using the American Lumber Standards, which are based on the structural integrity of a board. These grades take into account the size and location of defects, as well as the slope of grain, in order to predict the load-bearing capacity of the board. You'll also find the moisture content of the wood, which is determined at the mill when the stamp is applied. Under the National Grading Rule, there are three moisture-content conditions: "S-GRN" (surfaced green) means that the moisture content is above 19%. Most lumber is dried to the "S-DRY" (surfaced dry) condition, meaning that that the moisture content is less than 19%. "MC15" means that the moisture content is less than 15%. Select" = at least 80% clear wood "#1 Structural" = at least 75% clear wood; "#2 Structural" = at least 66% clear wood; "#3 Structural" ("stud" grade) = at least 50% clear wood; "Construction Grade" = at least 57% clear wood; "Standard Grade" = at least 43% clear wood; and "Utility Grade" = at least 29% clear wood
  21. 21. Preservative treatments (CCA – Copper Chromium Arsenic) Timber products such as construction, fencing, landscaping and decking are subject to preservative treatments to enhance durability and lifespan. When exposed to certain conditions, in particular when the moisture content is allowed to rise it is susceptible to attack from fungi and insects. CCA (Copper Chromium Arsenic) Pressure Treated treatment is effective - for example, extending the life of softwood posts from a few years to 40 years. Partial or complete restriction of CCA occurs in a number of countries including Japan, Indonesia, Sweden and Germany. The main concern with CCA is that it contains arsenic. While not a mutagen, arsenic acts as a carcinogen when ingested at rates above certain tolerable limits. It may initiate skin and liver cancers. A link between handling CCA-treated timber (using recommended procedures) and cancer has not been demonstrated,
  22. 22. During CCA treatment, timber is impregnated with the preservative solution using controlled vacuum/pressure processes.
  23. 23. Common Chemicals Threaten Our Brains, Say Studies WASHINGTON—There exists a “silent pandemic” of toxins that has been damaging the brains of unborn children, according to a recent study by researchers from Harvard University and Mount Sinai School of Medicine. The researchers listed 12 chemicals—substances found in both the environment and items such as furniture and clothing—that they believed to be causing lower IQs, as well as ADHD and autism. Paints, adhesives, preservatives
  24. 24. Timber as a sustainable material and the supply chain? • Does a certificate mean timber is “sustainable” are the criteria for our assessment adequate? • Does LEED = sustainable architecture? • What is the role of health and wellbeing in designing sustainable buildings? • What is the limits of the architects’ decision making to allow him/her to question the ethics of the building process or the supply chain? How green can you be? GREEN ARCHITECTURE
  25. 25. The Woodmans’ Cottage. BBC documentaries with Kevin McCloud
  26. 26. The Woodmans’ Cottage No LEED certification No FSC certificate Supply chain – transport minimal Processing of the wood – minimal? Labor costs – minimal? One material
  27. 27. Engineered wood products: Wood composites, laminated timber and new materials Characterized by fibres, strands, laminar, veneers – bonded with adhesives to maximize strength of these products. 1. Orientated strand board (OSB) and plywood panels 2. Structural composite lumber (SCL) includes: Laminated Veneer Lumber (LVL), Parallel Strand Lumber (PSL) Laminated Stand Lumber (LSL) Orientated Strand Lumber (OSL) 3. Structural glued laminated timber / glulam 4. I-joists 5. Non-structural products: Particle Board, Hardboard, Medium density siding, Fiberboard, Medium density fiber board, Decorative plywood
  28. 28. 1. Orientated strand board (OSB) and plywood panels used in timber framed buildings add stability to the framed structure – commonly used throughout the US in domestic construction.
  29. 29. Orientated Strand Board
  30. 30. Plywood Made by gluing wood veneers under heat and pressure. The veneers are glued such that the grain direction in each veneer is oriented at right angle to the grain of the next veneer. Urea formaldehyde – toxic glue used in manufacture.
  31. 31. 2. Structural composite lumber (SCL) is manufactured timber designed to be free from warping, splitting and shrinking. Performance can be predicted with confidence. The grade and quality of each layer is closely controlled in manufacture. Purpose to overcome the natural variability in timber.
  32. 32. Laminated Veneer Lumber (LVL) Laminated veneer lumber (LVL) is made by gluing together dried wood veneers. The grain runs in the same direction (note the difference with plywood where the veneers are cross grained.
  33. 33. Parallel Strand Lumber (PSL)/ or Parallam
  34. 34. Laminated Stand Lumber (LSL)
  35. 35. Orientated Strand Lumber Made with wood strands • Alternate layers of strands are oriented at right angles to each other • The several layers are glued under heat and pressure. • Used only for structural applications (panels cannot be stained or painted). Also OSB panels cannot be treated with preservatives.
  36. 36. Orientated Strand Lumber used in domestic property
  37. 37. 3. Structural glued laminated timber / glulam made up of individual wood laminar or layers. Depths of beams 6 inches to 6 feet and lengths up to 100 feet. Increasing the predictability of performance and can be used for large long span structures.
  38. 38. Can be used in domestic properties but also in structurally innovative building forms – e.g. domed stadium roofs and to extend the structural potential of timber.
  39. 39. Glulam Glue-laminated wood (glulam) is made from individual lengths of dimension lumber that are glued together to form a large cross section.
  40. 40. Glulam arches of Sheffield Winter Gardens
  41. 41. Niall McLaughlin Architects Bishop Edward King Chapel. Oxford
  42. 42. 4. I Joists Engineered wood components shaped like the letter I. Floor joists and roof rafters.
  43. 43. CLASS QUESTION: Name some uses for timber in architecture?
  44. 44. Peter Zumthor, Brother Claus Field Chapel, Mechernich, Germany.
  45. 45. Construction uses for wood 1. Structural framing. Approximately 90% of buildings constructed in the US each year are framed with wood, whilst that percentage is only 15 – 20 percent in the UK. 2. Subfloors and roof sheathing. 3. Siding (weatherboards) 4. Finishes/ cabinetry and trim
  46. 46. 1. Timber framing
  47. 47. Historic timber framing Each joint must be sufficient to carry the load, and the post must not break. Traditional joints mortise and tenon. This tie beam often carries floor loads.
  48. 48. The three-bay, side- entrance barn, common throughout western New England and New York after about 1800, made use of the tiebelow- plate tying joint. The rafters were additionally supported by continuous purlin plates at their midspan.
  49. 49. barn at great coxwell mid 1200’s berkshire, uk “the greatest piece of architecture in england” william morris joint detail from barn at coggeshall approx. 1140 essex, uk
  50. 50. springton manor barn 1800’s pennsylvania 1700’s dutch barn
  51. 51. Peter Zumthor, Swiss Pavilion, Expo 2000
  52. 52. 2.Wooden flooring
  53. 53. Timber as material finish
  55. 55. Name Workability Uses Notes Western Red Cedar - good joinery & cladding weathers to grey, smells good Douglas Fir - excellent const. to furniture grows fast and straight – in USA Southern Pine - excellent const. to furniture grows fast and straight – in USA Spruce - good const. & scrap lower quality and not durable Yew - difficult furniture & joinery limited availability Yellow Poplar - medium const. & moldings little grain – paints well Ash - good joinery & veneer decorative, sim. to oak Bubinga - medium veneer African exotic, dark red Cherry - good joinery, veneer, furn. medium color to light red Elm - medium joinery & furniture wiped out in US by disease Mahogany - good joinery & furniture dark color, medium grain Maple - medium veneer & flooring light grain, takes stain poorly Red Oak - medium veneer, joinery, furn. red to brown, course, strong grain White Oak - good veneer, joinery, floors lighter brown, hard, stains well Padauk - good joinery & furniture strong red, limited availability Teak - medium joinery & furniture warm brown, questionable sources FOREST STEWARSHIP COUNCIL (FSC) : CERTIFIED FOREST PRODUCTS COUNCIL :
  56. 56. Beetles, fungus and other rots Types of insects that cause deterioration of wood carpenter ants, beetles, and termites Carpenter ants prefer higher moisture content and softer wood that has begun to decay while powder post beetles prefer low moisture content in both softwoods and hardwoods.
  57. 57. Meg, the Dry Rot Dog, Sniffs out fungus in buildings out-dry-rot-fungus.html
  58. 58. Timber is a material with a unique charisma – it was, after all, once living, and its organic origins are clear in its appearance and texture. It also has an historic resonance, since a thousand-year tradition is still evident in the great frames and roofs of the medieval period and earlier. Overall, its appeal to designers is based principally on its: • Visual tactile qualities • Material properties • Environmental credentials.
  59. 59. CASE STUDIES In Timber (Lab Friday)
  60. 60. Labs: 4 groups GROUP RESEARCH THEMES 1. Is wood a sustainable construction material? The case for new innovative wood based construction materials. 2. Why have we seen a development in structural connections and fastenings in timber: From the Old English Barn, log structures to Shiguru Ban? 3. The structural limits of timber structures: How high can we go? 4. Designing with wood – new materials and new methods of engineering, design and construction.