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ACH 121 Lecture 07 (Wood) Part 1
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ACH 121 Lecture 07 (Wood) Part 1

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  • Bark PROTECTIVE LAYER OUTSIDE IS DEAD - INSIDE ALIVE Cambium VERY THIN CREATES NEW CELLS Sapwood STORE NUTRIENTS & TRANSMITS SAP THICK - LIVING Heartwood DEAD WOOD PROVIDES STRUCTURAL STABILITY Pith EARLY YEARS GROWTH SMALL - WEAK
  • Primarily Hollow, Cylindrical Cells - “TRACHEIDS” Axis running parallel to the tree Tough Cellulose bond by Lignin IMAGINE A GROUP OF STRAWS Impact on the properties of wood PARALLEL WITH GRAIN (TUBE) STRONG PERPENDICULAR - WEAK
  • Springwood (earlywood) Faster growth Cells larger and less dense Summerwood (latewood) Slower growth Cells smaller and denser APPEARS DARKER HENCE - THE RINGS
  • Transcript

    • 1. WOOD CONSTRUCTION Uses and Characteristics Types of Wood Manufacturing Process (milling & seasoning) Part 1 Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
    • 2. Sustainability in Wood Construction
      • Only major renewable structural material
      • Forestry Practices
        • Sustainable forestry
        • Clearcutting & replanting
      • Mill Practices – Lumber Recovery Factor (LRF)
      • Transportation
      • Embodies Energy Content
      • Construction Process
    • 3. CHARACTERISTICS OF WOOD
      • Qualities of Wood
        • High strength relative to it’s weight
          • In compression & tension
          • Bending & resistance to impact
        • Easy to work with
          • Simple tools to create desired shapes
        • Highly durable
        • Excellent insulating qualities
        • Fastened quickly & economically
        • Recyclable
        • Biodegradable
        • Renewable Resource
    • 4. CHARACTERISTICS OF WOOD
      • Undesirable Qualities of Wood
        • Not perfectly straight nor precise
        • Size & shape affected by moisture
        • Contains growth defects
        • Can spilt & warp
        • Burns easily
        • Decays
        • Susceptible to Insect Damage
    • 5. USES OF WOOD
      • Structural
        • Light-wood framing
        • Heavy-timber framing
      • Non-Structural
        • Interior partitions (studs), blocking
        • Finished Carpentry
          • Flooring, panels, moldings, shelving
        • Architectural Woodwork
          • Cabinetry/Furniture, drawers, cornices, mantels
    • 6. TYPES OF WOOD
      • Hardwoods
        • “ Leafy” (oak, cherry, etc.)
          • Deciduous (loses leaves)
        • Overall generally stronger
        • Grow slower
        • $$$$ cost more
        • Used for trim lumber
          • Flooring, cabinetry/furniture, interior paneling
    • 7. TYPES OF WOOD
      • Softwoods
        • “ Needles” (evergreens)
          • Non-deciduous (does not lose leaves)
          • Called “conifer”, bears cones
        • Overall generally weaker
        • Grow quicker & Cost less
        • Used for framing lumber
          • Sheathing (roofing & exterior panels)
        • Types of trees
          • SPF (spruce-pine-fir)
          • Hem-fir (hemlock & fir)
          • Yellow pine
    • 8.
      • SOFTWOODS
        • 75% lumber in country
        • Fir, white pine, hemlock, cedar, aspen, spruce, cypress
      • HARDWOODS
        • Grows mostly in central region
        • Maple, birch, beech, ash, cherry, poplar, walnut, oak, hickory
    • 9. PARTS OF A TREE (wood growth)
      • Pith: absolute center of tree
      • Heartwood: inactive cells that provide structural support for tree
      • Cambium layer: 3-5 cell thick zone of active cell growth just beneath the inner bark
      • Sapwood: carries sap (food) from roots to leaves
      Fig. 6.1-3
    • 10. PARTS OF A TREE (wood growth)
      • Rays: run perpendicular to fibers and carry food across the grain; these produce the decorative grain effects
      • Inner bark: carries food (oxygen) from leaves to tree & roots)
      • Outer bark: dry, dead tissue; protects tree
      • Growth ring: made up by summer wood & spring wood; shows age of tree in years
    • 11. Tree Composition
      • Bark
      • Cambium
      • Sapwood
      • Heartwood
      • Pith
    • 12. Tree Cells
      • Primarily Hollow, Cylindrical Cells
        • Axis running parallel to the tree (grain direction)
        • Tough Cellulose bound by Lignin
      • Impacts the properties of wood
    • 13. Professor Brandi R. Shepard© ACH 121-Materials and Methods 1
    • 14. Tree Growth
      • Springwood (earlywood)
        • Faster growth
        • Cells larger and less dense
      • Summerwood (latewood)
        • Slower growth
        • Cells smaller and denser
    • 15. GROWTH CHARACTERISTICS
      • Knots
        • Formed by branches
      • Shakes
        • Grain separation between growth layers
      • Pitch Pockets
        • Grain separation that contains solid or liquid resin
    • 16. MANUFACTURING PROCESS
      • Sawing, edging and trimming logs into square or rectangular pieces of wood
      • Yard lumber
        • Boards
          • Sheathing, siding, flooring, paneling, trim, patterned millwork
        • Dimension Stock
          • Light framing, joists, planks, roof & floor decking
        • Timbers
          • Posts, beams, stringers
    • 17. MANUFACTURING PROCESS
      • Trees are cut and transported to mill
      • Logs are cut into shorter lengths
        • Cut to fit machinery or to certain length
      • Logs are sent through debarker
        • Bark is removed by peeling, scraping or blasting using high-pressure water jets
      • Log is sent through a headsaw
        • Circular saw or band saw
    • 18. MANUFACTURING PROCESS
      • Rough cants, timbers, planks & boards are sent through an edger
        • Removes rounded edges
        • Rips lumber into desired width
      • Lumber is then moved onto trimmer
        • Saws trim off rough ends & defects
      • Next step is green chain, where edged, trimmed lumber are sorted visually
        • According grade, species and size
    • 19. MANUFACTURING PROCESS
      • Plainsawing:
        • Better yield from the log
        • Cheaper (better yield)
        • Uneven grain patterns
        • Uneven shrinkage (warps)
        • Used for framing lumber
      • Quartersawing:
        • Less yield from the log
        • Expensive (less yield)
        • Even grain patters
        • Even shrinkage (no warps)
        • Used for trim lumber
      Milling
    • 20. Typical Sawing Method Typical Sawing of a Large Log
    • 21. Typical Sawing Method
    • 22. MANUFACTURING PROCESS
      • After sawmilling, lumber is seasoned.
        • Kiln-dried or air-dried
      • Drying Effects
        • Shrinkage
        • Reduced weight
        • Increase of strength and stiffness
        • More dimensional stable
    • 23. MANUFACTURING PROCESS
      • Moisture Content:
      • Amount (percentage) of moisture (water) in the lumber
      • More moisture, more shrinkage!!
      Shrinkage creates problems!! A N D Seasoning
    • 24. SEASONING- Shrinkage
      • Heartwood: oldest and strongest part of the tree
      • More shrinkage PERPENDICULAR to the grain
      • Lumber defects
        • Warps
        • Cracks in finish work
        • Checks
    • 25. SEASONING- Shrinkage
      • Lumber Defects
        • Crook
        • Cup
        • Twist
        • Bow
        • Splits
        • Checks
      These are called seasoning defects
    • 26.
    • 27. SEASONING- Moisture Content
      • Moisture content varies
        • 26-32% when cut
        • 19% MAXIMUM for framing-”kiln-dried”
        • 15% when shrinkage is a concern
      • Over 19% moisture content is considered “GREEN” (not good…)
    • 28. MANUFACTURING PROCESS
      • Lumber is then sent to planing mill
        • Sizing and surfacing
        • Then graded, tallied and prepared for shipment
      Rough sawn (not surfaced)
      • Purpose for surfacing
        • Smooth
        • Dimensional precision
      • Surfacing typically performed after drying
    • 29. Additional Resources The Encyclopedia of Wood by: Aidan Walker
      • Check out class WebCT site:
        • Articles from Fine Homebuilding Magazine
        • Website links