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Questions and Answers
What characterizes latewood in trees?
What characterizes latewood in trees?
Which term describes the fineness of the wood structure?
Which term describes the fineness of the wood structure?
What does the term 'fiber saturation point' typically refer to?
What does the term 'fiber saturation point' typically refer to?
Which of the following is NOT a type of timber defect?
Which of the following is NOT a type of timber defect?
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What is the process of drying out water from timber commonly known as?
What is the process of drying out water from timber commonly known as?
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Which environmental factors can affect the rate at which wood reaches equilibrium moisture content?
Which environmental factors can affect the rate at which wood reaches equilibrium moisture content?
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Which type of lumber is made from layers of wood veneer glued together?
Which type of lumber is made from layers of wood veneer glued together?
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What aspect of wood does 'coarse grained' refer to?
What aspect of wood does 'coarse grained' refer to?
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What defines timber in relation to wood?
What defines timber in relation to wood?
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Which characteristic of timber indicates its performance under stress?
Which characteristic of timber indicates its performance under stress?
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What distinguishes hardwood from softwood?
What distinguishes hardwood from softwood?
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What is the primary use of sapwood in a tree?
What is the primary use of sapwood in a tree?
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What is the relation between specific gravity in sapwood and heartwood?
What is the relation between specific gravity in sapwood and heartwood?
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Which type of wood typically has a specific gravity range of 0.25 to 0.65?
Which type of wood typically has a specific gravity range of 0.25 to 0.65?
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What process do trees undergo to add growth each year?
What process do trees undergo to add growth each year?
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Which of the following is a feature of straight-grain timber?
Which of the following is a feature of straight-grain timber?
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What is a significant environmental benefit of using Glulam?
What is a significant environmental benefit of using Glulam?
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Which of the following is NOT a mechanical property of lumber?
Which of the following is NOT a mechanical property of lumber?
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In which direction does lumber typically exhibit the highest strength?
In which direction does lumber typically exhibit the highest strength?
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Which of the following applications is NOT commonly associated with Glulam?
Which of the following applications is NOT commonly associated with Glulam?
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What describes the stability of Glulam compared to traditional lumber?
What describes the stability of Glulam compared to traditional lumber?
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What type of structures can Glulam beams and columns effectively replace?
What type of structures can Glulam beams and columns effectively replace?
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Which statement is true about the cost effectiveness of Glulam?
Which statement is true about the cost effectiveness of Glulam?
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Which type of water-soluble preservative is more likely to be leachable?
Which type of water-soluble preservative is more likely to be leachable?
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What is the primary characteristic of the charring method used in lumber preservation?
What is the primary characteristic of the charring method used in lumber preservation?
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What is the primary characteristic that makes wood an orthotropic material?
What is the primary characteristic that makes wood an orthotropic material?
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Which method of applying preservatives allows the most thorough penetration?
Which method of applying preservatives allows the most thorough penetration?
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What is a key advantage of spraying as a method of applying preservatives?
What is a key advantage of spraying as a method of applying preservatives?
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Which type of preservative is characterized by the inclusion of a fixative salt?
Which type of preservative is characterized by the inclusion of a fixative salt?
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Which method is most often used for applying oil preservatives to seasoned lumber?
Which method is most often used for applying oil preservatives to seasoned lumber?
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What is the primary disadvantage of using injecting under pressure as a method of application?
What is the primary disadvantage of using injecting under pressure as a method of application?
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Which of the following applications is suitable for water-soluble preservatives?
Which of the following applications is suitable for water-soluble preservatives?
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What is one of the main advantages of plywood regarding moisture?
What is one of the main advantages of plywood regarding moisture?
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How is chipboard primarily produced?
How is chipboard primarily produced?
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What characteristic of plywood helps minimize thermal movement?
What characteristic of plywood helps minimize thermal movement?
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What is a disadvantage of chipboard compared to plywood?
What is a disadvantage of chipboard compared to plywood?
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Which of the following statements about glulam is true?
Which of the following statements about glulam is true?
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What impact does exposure to high temperatures have on plywood?
What impact does exposure to high temperatures have on plywood?
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What can affect the structural integrity of glulam?
What can affect the structural integrity of glulam?
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In terms of cost, how does chipboard compare to plywood?
In terms of cost, how does chipboard compare to plywood?
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What is compression strength parallel to the grain?
What is compression strength parallel to the grain?
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What does tensile strength measure in lumber?
What does tensile strength measure in lumber?
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Which of the following describes shear strength in lumber?
Which of the following describes shear strength in lumber?
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Which type of preservative is characterized by high toxicity and protection against termites?
Which type of preservative is characterized by high toxicity and protection against termites?
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Which testing method is commonly used to measure the hardness of wood?
Which testing method is commonly used to measure the hardness of wood?
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What is a characteristic of organic solvent type preservatives?
What is a characteristic of organic solvent type preservatives?
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Which type of load leads to static bending in lumber?
Which type of load leads to static bending in lumber?
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What is the purpose of preserving lumber?
What is the purpose of preserving lumber?
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Study Notes
Timber and Lumber
- Timber is wood suitable for engineering construction.
- Lumber is wood that has been processed by a mill.
- Timber is derived from the English word "timbrian".
- Wood is an organic material obtained from trees.
- Wood is primarily made of cellulose.
Learning Outcomes
- Learners will understand the meaning of timber and lumber.
- Learners will be able to define and describe the characteristics of timber.
- Learners will know about the moisture content of timber.
- Learners will be able to explain the manufacturing process of timber.
- Learners will know the different types of timber.
Timber Characteristics
- Properties: Fibrous and elastic, it performs better under tension than compression. It undergoes varying moisture movement. Straight-grain is stronger than irregular grain and is easier to work with.
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Types:
- Hardwoods: Broad leaves that shed annually, high strength and durability and higher specific gravity (0.15+). More expensive than softwoods.
- Softwoods: Needle-like or scale-like leaves, shed when damaged or unused. Lower specific gravity (0.25-0.65). Often used for structural timber due to softness and straightness.
Timber Characteristics - continued
- Growth: Trees grow by adding new layers of cells to the outside.
- Sapwood: Stores nutrients and supports the tree.
- Heartwood: Inner layers that stop storing nutrients but provide support. In some species heartwood is more resistant to decay.
- Earlywood/Springwood: Fast-growing cells that are lighter and less dense.
- Latewood/Summerwood: Slower-growing cells that are denser and stronger.
Timber Characteristics - continued
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Grain and Texture:
- Texture refers to the fineness of the wood's structure.
- Grain refers to the growth rings.
- Close-grained or coarse-grained refers to the width of the growth rings.
- Straight-grained or cross-grained refers to the direction of the fibers (parallel or at an angle).
- Examples of grain include straight grain, irregular grain, diagonal grain, spiral grain, and interlocked grain.
Timber Defects
- Defects can include:
- Splits
- Knotholes
- Wane (lack of wood on an edge)
- Cup
- Crook
- Checks (cracks)
- Shake (splits through the wood)
- Bow
- Twist
- Knots
- Shakes
Moisture Content
- Water is found in the cell cavities and walls of wood.
- Expressed as a percentage using the weight of the wood prior to drying and after drying.
- Freshly sawn wood from trees typically has a moisture content exceeding 100%.
- The fiber saturation point is when the cell walls are saturated (typically about 30%).
- Equilibrium moisture content is reached based on the surrounding humidity and temperature.
- Seasoning is the process of drying water from timber, often referred to as "seasoned timber."
Moisture Content - continued
- Rate of reaching equilibrium depends on:
- Degree to which the wood is enclosed/sealed
- Environmental conditions
- Wood species.
Types of Lumber
- Plywood: Made by bonding veneers at right angles. Resistant to moisture, stronger than traditional timber and flexible. Extreme heat can cause charring and hollowing.
- Chipboard: Made from wood particles with an additive. Used for furniture and low cost applications. Susceptible to warping and splitting, less impact-resistant than plywood.
- Glulam (Glued Laminated Timber): Produced by adhesively bonding dry lumber pieces. Parallel grains allows for curved shapes for architectural purposes. Suitable for strength in tension and compression but defects can reduce structural strength.
Manufacturing Process of Glulam
- Converting and cutting
- Applying Adhesives
- Planing
- Drying
- Strength Grading
- Finger Jointing
- Pressing and curing
- Final plaining
Benefits of Using Glulam
- Environmentally friendly
- Aesthetically pleasing
- Strong, durable, stable, and fire-resistant
- Cost effective
- Versatile
Applications of Glulam
- Used as an alternative to steel or concrete in commercial and residential buildings.
- Commonly used for beams, columns, roofs, domes, and bridges.
Mechanical Properties of Lumber
- Orthotropic material: Properties vary depending on the direction of the grain (longitudinal, tangential, radial).
- Strength is 20-30 times higher when parallel to the grain.
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Strength: The ability to bear loads.
- Types: Compressive (withstanding loads), tensile (being stretched), transverse (being bent).
- Direction of the load affects the compressive strength of the timber.
- Hardness: A measure of the resistance of wood to wear. Janka hardness test is used to measure this.
Preservation of Lumber
- Aims to increase lumber life and durability.
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Types:
- Oil type (e.g., coal tar creosote, high toxicity, suitable for outdoors)
- Organic solvent type (e.g., copper or zinc naphthenates, flammable, varied solubility)
- Water-soluble type (e.g., leachable type, fixed type, odorless, less flammable)
Preservation of Lumber - continued
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Methods:
- Charring (traditional method, burning lumber surface)
- Brushing
- Spraying
- Injecting under pressure
- Dipping and wetting
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Description
This quiz covers the essential concepts related to timber and lumber, including definitions, properties, and types. Learners will explore the characteristics of timber, its manufacturing process, and moisture content. Ideal for students seeking a solid understanding of wood used in construction.
