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Questions and Answers
What is the actual size of a seasoned, surfaced 2x4?
What is the actual size of a seasoned, surfaced 2x4?
- 1.5” thick and 4” wide
- 1.5” thick and 3.5” wide (correct)
- 1” thick and 4” wide
- 2” thick and 4” wide
What major weaknesses of wood do chemical treatments aim to counteract?
What major weaknesses of wood do chemical treatments aim to counteract?
- Grain patterns and wane
- Color variations and knots
- Combustibility and susceptibility to decay (correct)
- Shrinkage and swelling
Which of the following is considered a manufacturing defect in lumber?
Which of the following is considered a manufacturing defect in lumber?
- Decay
- Knots
- Bowing (correct)
- Cupping
What is the term for the irregular rounding of the edges or faces of lumber due to improper sawing?
What is the term for the irregular rounding of the edges or faces of lumber due to improper sawing?
Which of the following is a property of wood that affects its suitability as a construction material?
Which of the following is a property of wood that affects its suitability as a construction material?
Which defect in lumber is characterized by decay caused by fungi?
Which defect in lumber is characterized by decay caused by fungi?
What is the process called that involves drying wood to reduce its moisture content?
What is the process called that involves drying wood to reduce its moisture content?
What is a common classification of lumber that includes both coniferous and deciduous types?
What is a common classification of lumber that includes both coniferous and deciduous types?
What is the primary purpose of seasoning lumber?
What is the primary purpose of seasoning lumber?
Which method of drying lumber tends to take longer but is generally less costly?
Which method of drying lumber tends to take longer but is generally less costly?
Which statement accurately describes the primary difference between softwoods and hardwoods?
Which statement accurately describes the primary difference between softwoods and hardwoods?
What is green lumber?
What is green lumber?
What is the main factor that affects the structural strength of wood?
What is the main factor that affects the structural strength of wood?
What is the moisture content (MC) of wood referenced as?
What is the moisture content (MC) of wood referenced as?
How do nominal dimensions differ from actual dimensions in lumber?
How do nominal dimensions differ from actual dimensions in lumber?
Which cutting method produces more lumber per log and offers better structural properties?
Which cutting method produces more lumber per log and offers better structural properties?
What is one of the main purposes of fire-retardant treatments in wood?
What is one of the main purposes of fire-retardant treatments in wood?
Which of the following defects is most likely to occur in improperly seasoned wood?
Which of the following defects is most likely to occur in improperly seasoned wood?
Which of the following best describes growth defects in lumber?
Which of the following best describes growth defects in lumber?
What is the primary advantage of kiln drying over air drying?
What is the primary advantage of kiln drying over air drying?
In terms of performance, which characteristic is generally considered higher in hardwoods compared to softwoods?
In terms of performance, which characteristic is generally considered higher in hardwoods compared to softwoods?
Which process involves stripping the bark and cutting the log into slabs?
Which process involves stripping the bark and cutting the log into slabs?
Why is wood generally stronger parallel to the grain than perpendicular to it?
Why is wood generally stronger parallel to the grain than perpendicular to it?
Which type of wood is primarily used for flooring and furniture as per common classifications?
Which type of wood is primarily used for flooring and furniture as per common classifications?
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Study Notes
Lumber
- Lumber production starts with the felling of trees followed by logging and hauling to the sawmill
- Logs are soaked or steamed before sawing into rough dimensional lumber
- Rough lumber is dried to specific moisture content in a process called seasoning
- After seasoning, lumber is planed to precision dimensions through surfacing
- Finally, lumber is assessed for quality through grading
Sawing
- Logs are cut into different sizes depending upon the application
- The bark is stripped from the log
- The log is passed through a saw to produce slabs of lumber
- Slabs are further cut into desired widths for efficient use of lumber
- Lumber is rough-textured (or rough-sawn) at this stage with slight variations in dimension
- Plainsawing produces the most lumber per log and better structural properties per piece of lumber
Seasoning
- Moisture content (MC) is the weight of water in the wood as a percentage of the weight of the dry wood
- Growing wood has an MC of 30% to 200%
- Reducing MC causes shrinkage and increases strength and stiffness
- Moisture content is reduced by air drying or kiln drying
- Most shrinkage occurs perpendicular to the grain and a piece of lumber shrinks more in width than in length
- Green lumber is lumber that has not been seasoned
Kiln Drying
- KD is quicker than air drying, taking a few days and producing fewer distortions and a more uniform quality
- It is more expensive than air drying, which can take several weeks
Wood Defects
- Knots are caused by growth characteristics
- Knotholes are caused by growth characteristics
- Decay is caused by wood-decay fungus digesting moist wood
- Splits are a result of manufacturing characteristics
- Bowing is a result of manufacturing characteristics
- Cupping is a result of manufacturing characteristics
- Wane is caused by sawing pieces too close to the perimeter of the log
- Twisting is a result of manufacturing characteristics
- Checking is a type of defect where cracks appear in the wood
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