Lumber

Lumber, also called timber or fine wood in the United Kingdom, Australia, and New Zealand, is wood that has been processed into uniform and useful sizes, such as beams and planks or boards. It is mainly used for construction framing and finishing, like floors, wall panels, and window frames.

Lumber has many uses beyond building homes. In some places, like the United States and Canada, the word timber refers to unprocessed wood fiber, such as cut logs or standing trees that have not yet been cut.

Lumber can be supplied rough-sawn or surfaced on one or more of its faces. Rough lumber is the raw material for making furniture and other items that need cutting and shaping. It comes in many types, including hardwoods and softwoods, like white pine and red pine, because of their low cost.

Finished lumber is supplied in standard sizes, mostly for the construction industry. It is made mostly from softwood, from coniferous species like pine, fir, and spruce (called spruce-pine-fir), cedar, and hemlock, but also some hardwood for high-grade flooring. Softwood is used more often than hardwood, and about 80% of lumber comes from softwood.

Terminology

In the United States and Canada, processed wood boards are called lumber, while the word timber refers to trees that are still standing or have been cut down.

In places like Britain, Ireland, and some other countries, the word timber is used for both processed boards and whole trees. In the UK, the word lumber is not commonly used for wood and means something else.

Re-manufactured lumber

See also: Timber recycling

Re-manufactured lumber comes from processing wood that has already been cut and shaped. It is often made for industrial use or for packaging. This wood can be cut again using special tools to make thinner pieces that are not usually made in regular sawmills.

Re-sawing is when a piece of wood, like a long board, is split into two or more thinner boards of the same length.

Plastic lumber

Further information: Plastic lumber, Fiber-reinforced composite, and Wood-plastic composite

Some types of structural wood can also be made from recycled plastic and new plastic. Adding fiberglass to this plastic wood makes it stronger, longer-lasting, and more resistant to fire. This plastic-based wood can burn very slowly compared to most treated wood products.

History

The word lumber for cut pieces of wood started being used in the 1600s in North America.

Long ago in 1420, people from the Portuguese Empire settled on the islands of Madeira. They cut down many trees to make space for farming. These trees were cut into planks at special mills and sent to the mainland.

A man named Cornelis Corneliszoon from Uitgeest created the first wind-powered sawmill in 1593. This new machine made cutting wood into planks much quicker—about thirty times faster than older ways that used only people to saw by hand.

Conversion of wood logs

Logs are turned into lumber by being cut, shaped, or split. Cutting with a rip saw is the most common way because it lets us use logs that are not perfect and saves money. There are different ways to cut the logs:

• Plain sawn (flat sawn, through and through, bastard sawn) – This means cutting the log without moving it, so the grain runs across the width of the boards.
• Quarter sawn and rift sawn – These terms mean cutting the log so the growth rings are mostly perpendicular to the sides of the wood.
• Boxed heart – The center part of the log, called the pith, stays inside the wood.
• Heart center – This is the central core of a log.
• Free of heart center (FOHC) – This is wood cut on the side without any pith.
• Free of knots (FOK) – This wood has no knots in it.

Dimensional lumber

Dimensional lumber is wood cut to standard sizes, often in millimeters or inches. Carpenters use it a lot for building wooden structures. Common sizes include 2×4, 2×6, and 4×4. The length of a board can vary, with standard lengths in feet ranging from 6 to 24 feet.

In North America, two-by sizes like 2×4s and 2×6s are very common in construction. Softwood, like pine or fir, is usually used for building, while hardwood, like oak or maple, is often used for furniture or cabinets. The nominal size of lumber is bigger than the actual size after drying and planing. For example, a "2×4" board starts larger but ends up smaller after processing.

North American softwoods

The length of lumber depends on the tree it comes from. Engineered wood products, made by binding wood strands or fibers with adhesives, offer more flexibility and strength than regular wood. Pre-cut studs save time for builders, especially for ceilings of certain heights.

Grades and standards

Lumber varies in quality due to natural features like knots or grain slope. Standards for lumber in the United States began in 1924 and have changed over time. Current standards are set by the American Lumber Standard Committee. Design values for wood are determined by ASTM standards, considering factors like strength and safety. Canada has its own grading rules managed by the National Lumber Grades Authority.

In Europe, lumber strength grading follows EN-14081 standards, with classes like C16, C18, C24, and C30 for softwoods. Hardwoods have classes like D24, D30, up to D70.

North American hardwoods

Hardwood lumber in North America is often sold rough-cut or planed on two sides. It is sold by the board-foot, a measure of 144 cubic inches. Hardwoods are sometimes sold in a "quarter" system for thickness, like 4/4 for 1-inch thick board.

Hardwoods for furniture are cut in fall or winter to keep their natural color.

Engineered lumber

Engineered lumber is made for specific structural uses. Types include:

• Laminated veneer lumber (LVL) – thick beams for support over large spans.
• Wooden I-joists – used for floor joists with long spans.
• Finger-jointed lumber – lengths made longer by joining small pieces.
• Glulam beams – beams made by gluing together smaller pieces of wood.
• Manufactured trusses – pre-fabricated roof supports.

Various pieces and cuts

Lumber comes in many shapes and uses, such as planks, slats, battens, boards, and lath. It can also be found in rod forms like poles or dowels.

Timber piles

In the United States, pilings are often made from southern yellow pines or Douglas-fir. Treated pilings are available in different retention levels for protection.

Historical Chinese construction

In the Song dynasty, timbers were standardized to eight cross-sectional sizes with a width-to-height ratio of 1:1.5. Smaller timbers were called "unclassed." Dimensions of other components were based on the timber width, making calculations easier.

Defects in lumber

Lumber can have different problems or defects that happen during its making or while it is stored. These defects come from four main areas.

First, problems can happen when turning trees into lumber. Some of these issues include marks left by chips, improper cutting of the wood, small dents from tools, or parts of the tree's natural rounded shape showing through.

Second, wood can be attacked by fungi and insects. Fungi like blue stain, brown rot, and dry rot can damage wood when it is wet and warm. Insects such as woodboring beetles, termites, and carpenter ants can also harm lumber.

Third, natural forces can cause defects. For example, wood can develop cracks or splits called shakes, especially in types like eastern hemlock. These cracks can weaken the wood and make it look worse. Changes in moisture can also make wood warp, twist, or bend.

Lastly, when wood is dried—a process called seasoning—it can develop defects like splits or bowing. Proper drying helps reduce these problems.

Durability and service life

When wood is taken care of properly, it lasts a long time. But it can face problems like fungi and insects. There are ways to protect wood, such as controlling moisture, using strong materials, and following good building practices.

Wood naturally takes in and lets out water. To keep it safe, we try to stop water from getting into buildings and keep the wood's moisture level just right. Sometimes, wood is treated with special chemicals to make it last longer, especially when it might get very wet. These treatments can help wood last much longer than untreated wood. There are different ways to treat wood, including using pressure to push the chemicals deep into the wood. These treatments are checked for safety by government agencies.

Main article: Wood preservation

Timber framing

Main article: Timber framing

Timber framing is a way to build things using big pieces of wood, like posts and beams. These big pieces are cut from tree trunks and shaped with tools before being put together without using nails. Since the 1970s, more people in the United States have started using this style of building again.

Environmental effects of lumber

Green building aims to reduce the impact of construction on the environment. Wood is a key building material because it can grow again, making it a renewable resource. Using wood for building often uses less energy and creates less pollution compared to materials like steel and concrete. However, cutting down too many trees for wood can lead to the loss of forests.

Some countries are turning to biomass, which means using organic materials like leftover wood from logging, saw mills, and paper production for energy. This helps reduce the use of oil and gas, supports local economies, and can lower greenhouse gas emissions. Companies in the wood and paper industries often use leftover materials to create electricity and heat, which helps power their operations and dry wood products.

Environmental impacts

Lumber is a friendly choice for building because it helps protect our planet. Using wood instead of materials like concrete and steel cuts down on harmful gases that warm the Earth. Making concrete and steel creates a lot of these gases, but wood can actually trap some of them, helping to keep the air cleaner.

Wood has some great benefits. In a fire, the outside of wood can char, which helps protect the inside and keep the structure standing for a while. It also keeps buildings cooler naturally, which is good for windows and doors. Building with wood can be quicker and uses less material, making construction cleaner and faster.

End-of-life

Studies show what happens to wood waste after it’s no longer used. In the United States, most wood waste—about 67%—ends up in landfills. Some, around 16%, is burned to create energy, and about 17% is recycled.

In the United Kingdom, a study found that waste from homes and packaging made up smaller parts of the waste. Most waste, about 52%, came from building and demolition work. The rest came from industries.

Edinburgh Napier University packaging waste

In the circular economy

The lumber industry makes a lot of waste, especially during manufacturing. This waste includes wood pieces, harmful gases, and water leftovers.

A study in Hong Kong looked at how to handle wood waste better. There are ways to improve how we reuse lumber. We can make rules to help use recycled lumber, improve how we remove old buildings, and give incentives for using recycled wood in new constructions.

Secondary raw material

The term secondary raw material means using old or waste materials that have been recycled and turned back into useful products. Lumber can be reused in many ways. For example, branches and leaves from trees can be collected and used to help plants grow by acting like fertiliser.

When making lumber, some wood pieces are left over. These pieces, like woodchips, can be used to create heat energy. Old lumber products can also be broken into chips and used as material to make heat. This helps save energy and is good for the environment. Using materials in this way is part of a circular economy, where waste is reduced, reused, and recycled whenever possible. There are many chances to use these ideas in the wood industry that have not been fully explored yet.