Selecting Lumber

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Selecting Lumber

• Intro to Ag
• Project Design and Construction

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Characteristics of Wood and Lumber

• Annual rings form grain
• Rings old bundles of xylem and phloem that
  harden
• New bundles each year
• Characteristics vary for different species
• Soft vs. hard
• Resist rotting better than others
• Very attractive vs. plain
• Stronger vs. weaker

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Classifying Trees

• 2 types
• Softwood
• Hardwood
• Can be misleading!
• Example southern pine (softwood) harder than
  poplar (hardwood)
• Classification based on whether tree sheds leaves
  during winter
• Deciduous trees hardwoods
• Evergreens softwoods

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Classification of Wood

• Hardwoods usually best suited for furniture
  manufacturing
• Examples oak, maple, cherry, mahogany, walnut
• Softwoods used extensively for construction
  purposes, such as framing
• Examples pine, spruce

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Lumber Grades

• Hardwood lumber graded according to amount of
  usable, clear lumber
• Clear no knots or other obvious defects
• Knots result from limbs that grow from a tree
• Weaker lumber
• More difficult to cut and mill

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Hardwood Grades

• FAS highest hardwood grade
• First and seconds
• FAS 1
• Only one side of board meets specifications of
  FAS
• Sometimes FAS and FAS 1 sold together as Face
  or Better

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Hardwood Grades

• Number 1 Common (1C)
• Average for most of the lumber sold
• Lower grade than FAS
• Number 2 Common (2C)
• Number 3AC

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Hardwood Grades
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Softwood Grades

• Most classified as yard lumber
• Three broad grades
• Select
• Common
• Dimension

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Softwood Grades

• Select appearance is important minor defects
  that can be covered
• Grade A Select
• Grade B Select
• Grade C Select
• Grade D Select

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Softwood Grades

• Common construction purposes appearance not a
  factor
• Number 1 Common highest quality
• Number 2 Common
• Number 3 Common
• Number 4 Common
• Number 5 Common lowest quality

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Softwood Grades

• Dimension strength is needed
• Based on straightness, strength, and rigidity
• Common uses
• Rafters
• Studs
• Joists
• General framing
• Divided into
• Number 1 Dimension
• Number 2 Dimension
• Number 3 Dimension

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Sawing Method

• Broadly classify according sawing method
• Plain sawn (slash sawn)
• Parallel passes straight through log
• Grain appears wide apart
• Structural grade lumber

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Sawing Method

• Quartersawn
• Divide log into quarters and saw at angle to
  center axis
• Some hardwoods
• Grain more attractive
• Less tendency to warp or twist

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Lumber Curing

• Must be properly cured for most uses
• When first sawed, called green
• Very high moisture content
• Example freshly sawn oak board
• 1 x 8 wide x 3 long
• Gallon of water bound inside
• Moisture chemically bound within cells
• NOT from rainfall

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Lumber Curing

• Green lumber 120 to 130 moisture content
• Construction purposes about 15 moisture
• Furniture 6 to 8 moisture
• How do you figure moisture??
• Weight of dry lumber / weight of green lumber
• Use moisture meter

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Lumber Curing

• Improperly dried lumber
• Crack
• Shrink
• Or otherwise distort in a few weeks

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Lumber Curing Process

• Stack lumber so air can move through
• Use stacking sticks (1 x 1)
• Laid in rows - sides close but not touching
• Air cure for 1 year for every inch of thickness

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Lumber Curing Process

• Kiln huge oven
• Heats boards at a steady rate
• Removes moisture slowly
• Time a few days or a few weeks
• Depends on moisture content and type of wood
• If dried to quickly, dries unevenly
• Causes splitting, warping, and/or cracking

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Lumber Finish

• Planer machine that cuts lumber down to exact
  size and leaves it smooth
• Lumber generally purchased with all sides and
  edges smooth
• Can be purchased in following 4 categories
• Rough
• S2S
• S4S
• Sanded

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Lumber Finish

• Rough
• Not planed
• Delivered as it comes from sawmill
• Width and thickness varies from piece to piece
• S2S
• Surfaced two sides
• Edges are not planed
• All pieces same thickness
• Widths vary

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Lumber Finish

• S4S
• Surfaced four sides
• Sides and edges planed to exact dimensions
• Sanded
• Width and thickness dimensions exact on all
  pieces
• All surfaces are sanded

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Standard Lumber Sizes

• Name given to cuts of lumber reflects nominal or
  approximate size
• Real or actual sizes are ½ less than nominal
  sizes
• 2 x 4
• Actual size 1 ½ x 3 ½

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Standard Lumber Sizes
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Standard Lumber Sizes
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Standard Lumber Sizes