A General Introduction to Wood Construction

1. A General Introduction to Wood Construction

2. Journal of Architectural Education An Exploration of the Relationships between Houses and Forests in American History William Gould Sturges University of Oregon

3. There is a Supply & Demand Imbalance for Wood Products In 1986 we consumed 57.2 Billion Board Feet (bbf) of Wood Products, yet only 70% was Produced Domestically This is 40% greater Consumption than in the 50's and 60's The Trend is Getting More Acute In 2040, the estimates are >70bbf

4. Forests Provide: species habitat watershed protection biological gene banks medicine i.e.. taxol

5. Primeval Forests: 1620

6. Primeval Forests: 1850

7. Primeval Forests: 1989

8. Population Density Maps: 1776, 1876, 1976

9. Annual Housing Unit Production

10. Iroquois Longhouse

11. Iroquois Longhouse Minimal Impact on the Forest High Density Configuration Same Quantity of Wood as Today�s SF Detached BUT... they housed 50 - 60 people compared to today's average family of 2.5 persons

12. Log Cabin

13. Log Cabin First Response to Housing Need Forests were Viewed as an Impediment to Agriculture 9216 in3/lf

14. Timber Framing

15. Timber Framing Coincided with the Development of Sawmills Maine ca. 1620 Water Powered Mortise and Tenon Labor Intensive 6210 in3/lf

16. Balloon Framing

17. Balloon Framing Coincided with the Development of: Steam Powered Sawmills Machine Made Nail 4234 in3/lf

18. Western Platform Framing

19. Western Platform Framing Coincided with the Development of Veneer Panel Products early 1900's 1368 in3/lf

20. Wood Use per Lineal Ft of 8' High Wall

21. Energy Consumption* of Common Building Materials

22. Strategies for the Future Sustainable Forests Create Housing with Less Demand

23. Sustainable Forest Farming Forest Stewardship Council (FSC) Limit Timber Removal to Prevent Decline in Quality/Quantity Provide Variety of Ages Allow Trees to Mature Fully Maintain Plant and Animal Habitat Protect the Soil

24. Create Housing w/ Less Demand Recycle Don't Over-design Engineered Wood Products Higher Density Configurations

25. Wood Construction Topics Wood Botany Lumber Panels Products Engineered Wood Products

26. Tree Structure Bark Cambium Layer Sapwood - conduction, storage and support Heartwood - support only Growth (Annual) Rings Late Wood - summer/fall, small, densely packed cells Early Wood - spring, large cells

27. Cross Section through a Tree

28. Wood Botany Two Major Groups Coniferous Deciduous

29. Coniferous Softwoods (not a measure of hardness) Gymnosperms - naked seeds Evergreen e.g. Douglas fir, larch, pine Narrow leaf Coniferous trees lack vessels

30. Deciduous Hardwoods (not a measure of hardness) Angiosperms - covered seeds Shed leaves annually Broadleaf e.g. oak, maple, cherry Deciduous trees have vessels for support and conduction of nutrients

31. Wood is Anisotropic An anisotropic material has physical properties that are different with respect to their three major orthogonal planes

32. Three Major Planes Longitudinal - along the length of the log Radial - with respect to the center of the log Tangential - with respect to the growth rings

33. Wood is Hygroscopic An hygroscopic material has an affinity for water molecules which causes swelling and shrinking as the material reaches equilibrium with its environment

34. Wood is Viscoelastic enough is enough!

35. Moisture Content the weight of water as a percentage of the weight of an oven dry sample of wood freshly cut lumber can range from 30% to200%

36. Fiber Saturation Point the point at which the cell cavities are empty but the cell walls are full of water approx. 28% MC

37. Moisture Content

38. Wood Product Moisture Content

39. Shrinkage Relative to the Major Planes

40. Manufacture of Sawn Lumber

41. Surfacing S4S, surfaced four sides S-Green, surfaced at >19% MC S-Dry, surfaced at 19% or less

42. Categories of Dimension / Stress Rated Framing Lumber

43. How Do We Determine the Strength of Lumber

44. Visual Grading by Certified Graders based upon tested strength of clear sample reductions in strength (grade) made based upon defects, grain direction etc

45. Grade Stamps

46. Machine Testing every board is tested and stamped according to results

47. Machine Stress Rated Lumber

48. In-Grade Testing North American In-Grade Testing Program, 1977 testing of 70,000 full size pieces (1 million board feet) created a database of empirical design values Bending values went up for narrows and high grades, down for wides and lower grades

49. Engineered Wood Products

50. Engineered Wood Products attempt to improve the basic properties of lumber strength appearance dimensional stability cost use fast-growing, low-density wood species in combination with plastic resins

51. Engineered Wood Products potential disadvantages out-gassing from formaldehydes deterioration under certain conditions FRT plywood appearance

52. Engineered Wood Products Sheathing and Decking Main Structural Members Stress Skin Foam Panels

53. Sheathing and Decking Plywood Oriented Strand Board (OSB) and Waferboard

54. Main Structural Members Light Frame Trusses Glue Laminated Lumber (Glulam) Laminated Veneer Lumber (LVL) Parallel Strand Lumber (PSL) Prefabricated Wood I-Joists

55. Light Frame Trusses Flat Plate Connectors Stamped metal plates hydraulically pressed into wood to make connections Suitable for floors and roofs Proprietary Connectors Wood Top and Bottom Chord Fab. Steel Element for Web w/ Integral Fastener Split Ring Connector For Custom-Designed, Field-Fabricated Trusses Increase Effective Area of Joint

56. Glue Laminated Lumber (Glulam) Old Technology Headers, Beams, Girders and Columns Strength Depends on Wood Species and Quality Limitless Variety of Straight and Curved Configurations

57. Glulam Manufacture

58. Laminated Veneer Lumber (LVL) Based on Plywood Technology Headers, Beams and Girders Sized to Flush Frame with Platform Framing i.e. 1 3/4" x 9 1/4" Fb = 2800 psi, E= 2,000,000 psi

59. LVL Manufacture

60. Parallel Strand Lumber (PSL) Based on Cross between Plywood & OSB Technology Strands are up to 8' long and 1/2" thick Headers, Beams, Girders and Columns Sized to Flush Frame with Platform Framing i.e. 1 3/4" x 9 1/4" Potential Applications in Finish and Cabinet Work

61. PSL Manufacture

62. Prefabricated Wood I-Joists Profile Similar to Steel Beams Top and Bottom Flanges Resist Compressive and Tensile Stresses Respectively Solid Wood LVL Glulam Web Resists Shear Forces Plywood OSB

63. Stress Skin Foam Panels Walls, Floors and Roofs Foam Core Bonded to Structural Skin Modular Design Principles Joints between Panel Are Key to Usability

64. Joint Types Dual Spline e.g. R-Control Special Piece e.g. Ray-Core Stud Cam Lock