Timber and Lumber Overview

Timber is wood that's suitable for construction or engineering purposes. It's a processed form of wood, suitable for building.

Lumber is a term used in North America for wood that has been processed by a mill for construction. It's essentially the same as timber, but the word 'lumber' is more common in North America.

Timber is fibrous and elastic, meaning it bends and can withstand some force. It's stronger under tension (pulling) than compression (pushing). It also changes shape with moisture levels.

Straight-grain timber is timber with a consistent grain alignment. It makes the timber stronger and easier to work with.

Hardwood comes from trees with broad leaves and sheds them annually. It's strong, durable, and expensive. Softwood comes from trees with needles or scales and is less expensive, easier to work with, and commonly used for structural timber.

Sapwood is the outer layer of a tree that stores nutrients and supports the tree. It's the active part of the tree.

Heartwood is the inner layer of a tree that has stopped storing nutrients and only supports the tree. It is often more resistant to decay.

Earlywood/springwood is the fast-growing wood produced in the spring when the tree is growing rapidly. It is less dense.

Earlywood is the wood that grows in the spring, has large cells and is less dense. Latewood is the wood that grows in the summer, has smaller cells and is denser.

Wood grain refers to the pattern formed by the growth rings. Wood texture describes the fineness or coarseness of the wood structure.

Timber defects are flaws or imperfections that affect the strength and quality of wood, including splits, knots, wane, cup, crook, checks, shake, bow, and twist.

The percentage of water in wood. It is calculated by comparing the weight of the wood after oven drying to its weight before drying.

The point at which the cell walls of wood are fully saturated with water, usually around 30% moisture content.

The moisture content of wood that balances with the surrounding humidity and temperature, leading to a stable state.

The process of drying out water from timber to reduce moisture content. This improves its durability and reduces the risk of warping.

There are different types of lumber, including plywood (thin sheets of wood veneer glued together), chipboard (made from wood chips), and Glulam (strong beams made of glued layers of wood).

In plywood, veneers are arranged with their grain directions perpendicular to each other. This arrangement provides strength in both directions and minimizes warping due to changes in temperature and humidity.

Plywood is a good insulator, meaning it resists the transfer of heat. The layers of wood and the trapped air between them help slow down the flow of heat.

Plywood can withstand moderate heat, but at temperatures between 90 and 150 degrees Celsius, it will char and hollow out.

Depending on the adhesive used, plywood is resistant to moisture and humidity. It won't warp or crack easily when exposed to water.

Chipboard is made from wood particles (like sawdust) mixed with an adhesive and pressed into sheets.

Chipboard is less strong and more likely to warp, split, and deform compared to plywood.

The wood layers in Glulam timber have their grains running parallel to each other, creating a strong, continuous structure.

Glulam timbers are made by bonding together layers of dry lumber, which are precisely glued and pressed under controlled conditions.

Measures how much force a piece of wood can withstand when pushed directly along the grain direction. Think of it like pushing on the end of a wooden column.

Measures how much force a piece of wood can withstand when pushed at a right angle to the grain direction. Think of it like pushing on a beam or a column from the side.

Measures the wood's resistance to being pulled apart. It's the maximum force the wood can withstand before it breaks when stretched or pulled.

Measures the wood's resistance to slipping or sliding apart along the grain direction. Think of it like pushing a wood block parallel to its grain.

Measures the strength of a piece of wood when bent or flexed. Think of it like bending a wooden beam.

Measures the wood's resistance to being dented, scratched or worn down. It's a measure of how hard the wood is.

Preservatives that use oils, like coal tar creosote, to protect wood from decay and pests. These are often used for outdoor applications.

Preservatives that use organic solvents to dissolve salts that protect wood. These are often flammable.

Substances that protect wood from decay, insects, and weathering. They are usually chemicals applied to the wood.

Examples of oil-soluble wood preservatives, often used for outdoor applications.

A type of wood preservative that is oil-soluble. It's used to protect against fungal decay and insects.

These preservatives dissolve in water and are commonly applied to outdoor structures like decks and fences.

A type of water-soluble preservative that washes away over time but is good for initial protection.

A type of water-soluble preservative that includes a fixative to prevent it from leaching out as quickly.

Burning the surface of wood to create a protective layer against decay and insects. A traditional method.

Various techniques for applying preservatives to the wood, including brushing, spraying, injecting, dipping, and wetting.

Glulam stands for Glued Laminated Timber. It's a type of engineered wood made by joining together multiple layers of wood, glued under high pressure. These layers are usually arranged with their grain running in the same direction to enhance strength and stability.

Glulam offers many advantages over traditional materials like steel or concrete. It's environmentally friendly as it's made from renewable resources. It's aesthetically pleasing, strong, stiff, durable, stable, fire-resistant, cost-effective, and versatile.

Glulam is a popular choice in construction due to its versatility. It's used as a sustainable alternative to steel or concrete in commercial and residential buildings. It's often used for beams and columns, but can also be found in roofs, domes, and bridges.

Lumber, being a natural material, exhibits different mechanical properties based on its grain structure. It possesses strength, meaning its ability to bear loads. But this strength varies depending on the direction of the grain.

Compressive strength refers to the ability of lumber to withstand compressing or pushing forces. It's a crucial property when designing structures that need to bear downward loads.

Wood is considered an orthotropic material. This means its properties, like strength, depend on the direction of the grain. So, its strength differs along the length (longitudinal), around the circumference (tangential), and across the width (radial) of the wood.

The strength of lumber is different in various directions due to the grain structure. Strength properties parallel to the grain (lengthwise) are significantly higher than the properties perpendicular to the grain (across the width).

Lumber is typically 20-30 times stronger parallel to the grain compared to the strength perpendicular to the grain. This difference in strength is vital for structural design considerations.