Lumber

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Wood cut from Victorian Eucalyptus regnans Wood from victoria mountain ash.jpg
Wood cut from Victorian Eucalyptus regnans
The harbor of Bellingham, Washington, filled with logs, 1972 Bellingham, Washington, harbor, filled with logs, 1972.jpg
The harbor of Bellingham, Washington, filled with logs, 1972

Lumber is wood that has been processed into dimensional lumber, including beams and planks or boards, a stage in the process of wood production. Lumber is mainly used for construction framing, as well as finishing (floors, wall panels, window frames). Lumber has many uses beyond home building. Lumber is sometimes referred to as timber as an archaic term and still in England, while in most parts of the world (especially the United States and Canada) the term timber refers specifically to unprocessed wood fiber, such as cut logs or standing trees that have yet to be cut.

Contents

Lumber may be supplied either rough-sawn, or surfaced on one or more of its faces. Beside pulpwood, rough lumber is the raw material for furniture-making, and manufacture of other items requiring cutting and shaping. It is available in many species, including hardwoods and softwoods, such as white pine and red pine, because of their low cost. [1]

Finished lumber is supplied in standard sizes, mostly for the construction industry – primarily softwood, from coniferous species, including pine, fir and spruce (collectively spruce-pine-fir), cedar, and hemlock, but also some hardwood, for high-grade flooring. It is more commonly made from softwood than hardwoods, and 80% of lumber comes from softwood. [2]

Terminology

In the United States and Canada, milled boards are called lumber, while timber describes standing or felled trees. [3]

In contrast, in Britain, and some other Commonwealth nations and Ireland, the term timber is used in both senses. (In the UK, the word lumber is rarely used in relation to wood and has several other meanings.)

Re-manufactured lumber

Re-manufactured lumber is the result of secondary or tertiary processing of previously milled lumber. Specifically, it refers to lumber cut for industrial or wood-packaging use. Lumber is cut by ripsaw or resaw to create dimensions that are not usually processed by a primary sawmill.

Re-sawing is the splitting of 25 by 300 millimetres (1 by 12 in) hardwood or softwood lumber into two or more thinner pieces of full-length boards. For example, splitting a 3-metre (10 ft) long 50 by 100 mm (2 by 4 in) into two 25 by 100 mm (1 by 4 in) of the same length is considered re-sawing.

Plastic lumber

Structural lumber may also be produced from recycled plastic and new plastic stock. Its introduction has been strongly opposed by the forestry industry. [4] Blending fiberglass in plastic lumber enhances its strength, durability, and fire resistance. [5] Plastic fiberglass structural lumber can have a "class 1 flame spread rating of 25 or less, when tested in accordance with ASTM standard E 84," which means it burns more slowly than almost all treated wood lumber. [6]

History

The basic understanding of lumber, or “sawn planks,” came about in North America in the 17th century. [7] Lumber is the most common and widely used method of sawing logs. Plain sawn lumber is produced by making the first cut on a tangent to the circumference of the log. Each additional cut is then made parallel to one before. This method produces the widest possible boards with the least amount of log waste. [8]

Lumber manufacturing globally is determined by the preferred style of building; areas with a "wood building culture" (homes were built from wood rather than other materials like brick) are the countries with significant sawmilling industries. Historical wood-frame home building regions are: Europe, North America, Japan.
Different areas of the world are recognized as significant timber suppliers, however these areas (Indonesia, Sarawak, New Guinea, etc) are exporters of raw logs and do not have a significant domestic lumber producing industry.

Currently the largest lumber manufacturing regions in the world are: China (18%); United States of America (17%); Canada (10%); Russian Federation (9%); Germany (5%); Sweden (4%). [9]

In early periods of society to make wood for building, the trunks of trees were split with wedges into as many and as thin pieces as possible. If it was necessary to have them still thinner, they were hewn, by some sharp instrument, on both sides, to the proper size. [10]
This simple but wasteful manner of making boards has been still continued in some places, to the present time.

Otherwise, logs were sawn using a two-person whipsaw, or pit-saw, using saddleblocks to hold the log, and a pit for the pitman who worked below.

In 1420 the island of Madeira -- an archipelago comprising four islands off the northwest coast of Africa and an autonomous region of Portugal -- was discovered. King Henry VI sent settlers to Madeira and ordered sawmills to be erected for the purpose of cutting the various species of excellent timber with which the island abounded.
About the year 1427, the first sawmill in Germany was built. [10]

Cornelis Corneliszoon (or Krelis Lootjes) was a Dutch windmill owner from Uitgeest who invented the first mechanical sawmill, which was wind-powered, on December 15, 1593. This made the conversion of log timber into planks 30 times faster than previously. [11]

The circular saw, as used in modern sawmills, was invented by an Englishman named Miller in 1777. It was not until the Nineteenth Century, however, that it was generally applied, and its great work belongs to that period. The first insertable teeth for this saw were invented by W. Kendal, an American, in 1826. [12]

Logging in the USA began in 1607 when the Jamestown settlers cut timber to build the first settlement in the new world. [13] America’s first sawmill was built at the Falls of Piscatauqua, on the line between Maine and New Hampshire, in 1634. Unauthenticated records, however, claim that as early as 1633 several mills were operating in New York State. [10]

The American Colonies were essential to England in the role of supplier of lumber for the mighty British fleet. By the 1790s New England was exporting 36 million feet of pine boards and at least 300 ship masts per year to the British Empire. [14] The timber supply began to dwindle at the start of the 20th century due to significant harvest volumes, so the logging industry was forced to seek timber elsewhere; hence, the expansion into the American West. [15]

Conversion of wood logs

A sawmill with the floating logs in Kotka, Finland L' usine de transformation de bois Kotkamills Oy a Kotka.jpg
A sawmill with the floating logs in Kotka, Finland

Logs are converted into lumber by being sawn, hewn, or split. Sawing with a rip saw is the most common method, because sawing allows logs of lower quality, with irregular grain and large knots, to be used and is more economical. There are various types of sawing:

Dimensional lumber

A common 50 by 100 mm (2 by 4 in) board 2 By 4 Clue Stick.jpg
A common 50 by 100 mm (2 by 4 in) board

Dimensional lumber is lumber that is cut to standardized width and depth, often specified in millimetres or inches. Carpenters extensively use dimensional lumber in framing wooden buildings. Common sizes include 2×4 (pictured) (also two-by-four and other variants, such as four-by-two in Australia, New Zealand, and the UK), 2×6, and 4×4. The length of a board is usually specified separately from the width and depth. It is thus possible to find 2×4s that are four, eight, and twelve feet in length. In Canada and the United States, the standard lengths of lumber are 6, 8, 10, 12, 14, 16, 18, 20, 22 and 24 feet (1.8, 2.4, 3.0, 3.7, 4.3, 4.9, 5.5, 6.1, 6.7 and 7.3 m). For wall framing, precut "stud" lengths are available, and are commonly used. For ceilings heights of 8, 9 or 10 feet (2.4, 2.7 or 3.0 m), studs are available in 92+58 inches (2.35 m), 104+58 inches (2.66 m), and 116+58 inches (2.96 m).[ citation needed ]

North American softwoods

The length of a unit of dimensional lumber is limited by the height and girth of the tree it is milled from. In general the maximum length is 24 ft (7.32 m). Engineered wood products, manufactured by binding the strands, particles, fibers, or veneers of wood, together with adhesives, to form composite materials, offer more flexibility and greater structural strength than typical wood building materials. [16]

Pre-cut studs save a framer much time, because they are pre-cut by the manufacturer for use in 8-, 9-, and 10-foot ceiling applications, which means the manufacturer has removed a few inches or centimetres of the piece to allow for the sill plate and the double top plate with no additional sizing necessary.

In the Americas, two-bys (2×4s, 2×6s, 2×8s, 2×10s, and 2×12s), named for traditional board thickness in inches, along with the 4×4 (89 mm × 89 mm), are common lumber sizes used in modern construction. They are the basic building blocks for such common structures as balloon-frame or platform-frame housing. Dimensional lumber made from softwood is typically used for construction, while hardwood boards are more commonly used for making cabinets or furniture.

Lumber's nominal dimensions are larger than the actual standard dimensions of finished lumber. Historically, the nominal dimensions were the size of the green (not dried), rough (unfinished) boards that eventually became smaller finished lumber through drying and planing (to smooth the wood). Today, the standards specify the final finished dimensions and the mill cuts the logs to whatever size it needs to achieve those final dimensions. Typically, that rough cut is smaller than the nominal dimensions because modern technology makes it possible to use the logs more efficiently. For example, a "2×4" board historically started out as a green, rough board actually 2 by 4 inches (51 mm × 102 mm). After drying and planing, it would be smaller by a nonstandard amount. Today, a "2×4" board starts out as something smaller than 2 inches by 4 inches and not specified by standards, and after drying and planing is minimally 1+12 by 3+12 inches (38 mm × 89 mm). [17]

North American softwood dimensional lumber sizes
NominalActualNominalActualNominalActualNominalActualNominalActual
inchesinchesmminchesinchesmminchesinchesmminchesinchesmminchesinchesmm
1 × 234 × 1+1219 × 382 × 21+12 × 1+1238 × 38   
1 × 334 × 2+1219 × 642 × 31+12 × 2+1238 × 64   
1 × 434 × 3+1219 × 892 × 41+12 × 3+1238 × 894 × 43+12 × 3+1289 × 89  
1 × 534 × 4+1219 × 114    
1 × 634 × 5+1219 × 1402 × 61+12 × 5+1238 × 1404 × 63+12 × 5+1289 × 1406 × 65+12 × 5+12140 × 140 
1 × 834 × 7+1419 × 1842 × 81+12 × 7+1438 × 1844 × 83+12 × 7+1489 × 184 8 × 87+12 × 7+12191 × 191
1 × 1034 × 9+1419 × 2352 × 101+12 × 9+1438 × 235   
1 × 1234 × 11+1419 × 2862 × 121+12 × 11+1438 × 286   

As previously noted, less wood is needed to produce a given finished size than when standards called for the green lumber to be the full nominal dimension. However, even the dimensions for finished lumber of a given nominal size have changed over time. In 1910, a typical finished 1-inch (25 mm) board was 1316 in (21 mm). In 1928, that was reduced by 4%, and yet again by 4% in 1956. In 1961, at a meeting in Scottsdale, Arizona, the Committee on Grade Simplification and Standardization agreed to what is now the current U.S. standard: in part, the dressed size of a 1-inch (nominal) board was fixed at 34 inch; while the dressed size of 2 inch (nominal) lumber was reduced from 1+58 inch to the current 1+12 inch. [18]

Dimensional lumber is available in green, unfinished state, and for that kind of lumber, the nominal dimensions are the actual dimensions.

Grades and standards

The longest plank in the world (2002) is in Poland and measures 36.83 metres (about 120 ft 10 in) long. The longest board in the world (2002).jpg
The longest plank in the world (2002) is in Poland and measures 36.83 metres (about 120 ft 10 in) long.

Individual pieces of lumber exhibit a wide range in quality and appearance with respect to knots, slope of grain, shakes and other natural characteristics. Therefore, they vary considerably in strength, utility, and value.

The move to set national standards for lumber in the United States began with the publication of the American Lumber Standard in 1924, which set specifications for lumber dimensions, grade, and moisture content; it also developed inspection and accreditation programs. These standards have changed over the years to meet the changing needs of manufacturers and distributors, with the goal of keeping lumber competitive with other construction products. Current standards are set by the American Lumber Standard Committee, appointed by the U.S. Secretary of Commerce. [19]

Design values for most species and grades of visually graded structural products are determined in accordance with ASTM standards, which consider the effect of strength reducing characteristics, load duration, safety, and other influencing factors. The applicable standards are based on results of tests conducted in cooperation with the USDA Forest Products Laboratory. Design Values for Wood Construction, which is a supplement to the ANSI/AF&PA National Design Specification® for Wood Construction, provides these lumber design values, which are recognized by the model building codes. [20]

Canada has grading rules that maintain a standard among mills manufacturing similar woods to assure customers of uniform quality. Grades standardize the quality of lumber at different levels and are based on moisture content, size, and manufacture at the time of grading, shipping, and unloading by the buyer. The National Lumber Grades Authority (NLGA) [21] is responsible for writing, interpreting and maintaining Canadian lumber grading rules and standards. The Canadian Lumber Standards Accreditation Board (CLSAB) [22] monitors the quality of Canada's lumber grading and identification system.

Attempts to maintain lumber quality over time have been challenged by historical changes in the timber resources of the United States – from the slow-growing virgin forests common over a century ago to the fast-growing plantations now common in today's commercial forests. Resulting declines in lumber quality have been of concern to both the lumber industry and consumers and have caused increased use of alternative construction products. [23] [24]

Machine stress-rated and machine-evaluated lumber are readily available for end-uses where high strength is critical, such as trusses, rafters, laminating stock, I-beams and web joints. Machine grading measures a characteristic such as stiffness or density that correlates with the structural properties of interest, such as bending strength. The result is a more precise understanding of the strength of each piece of lumber than is possible with visually graded lumber, which allows designers to use full-design strength and avoid overbuilding. [25]

In Europe, strength grading of rectangular sawn lumber/timber (both softwood and hardwood) is done according to EN-14081 [26] and commonly sorted into classes defined by EN-338. For softwoods, the common classes are (in increasing strength) C16, C18, C24, and C30. There are also classes specifically for hardwoods and those in most common use (in increasing strength) are D24, D30, D40, D50, D60, and D70. For these classes, the number refers to the required 5th percentile bending strength in newtons per square millimetre. There are other strength classes, including T-classes based on tension intended for use in glulam.

Grading rules for African and South American sawn lumber have been developed by ATIBT [29] according to the rules of the Sciages Avivés Tropicaux Africains (SATA) and is based on clear cuttings – established by the percentage of the clear surface. [30]

North American hardwoods

In North America, market practices for dimensional lumber made from hardwoods [lower-alpha 1] varies significantly from the regularized standardized 'dimension lumber' sizes used for sales and specification of softwoods – hardwood boards are often sold totally rough cut, [lower-alpha 2] or machine planed only on the two (broader) face sides. When hardwood boards are also supplied with planed faces, it is usually both by random widths of a specified thickness (normally matching milling of softwood dimensional lumbers) and somewhat random lengths. But besides those older (traditional and normal) situations, in recent years some product lines have been widened to also market boards in standard stock sizes; these usually retail in big-box stores and using only a relatively small set of specified lengths; [lower-alpha 3] in all cases hardwoods are sold to the consumer by the board-foot (144 cubic inches or 2,360 cubic centimetres), whereas that measure is not used for softwoods at the retailer (to the cognizance of the buyer). [lower-alpha 4]

North American hardwood dimensional lumber sizes
Nominal (rough-sawn size)S1S (surfaced on one side)S2S (surfaced on two sides)
12 in38 in (9.5 mm)516 in (7.9 mm)
58 in12 in (13 mm)716 in (11 mm)
34 in58 in (16 mm)916 in (14 mm)
1 in or 44 in78 in (22 mm)1316 in (21 mm)
1+14 in or 54 in1+18 in (29 mm)1+116 in (27 mm)
1+12 in or 64 in1+38 in (35 mm)1+516 in (33 mm)
2 in or 84 in1+1316 in (46 mm)1+34 inches (44 mm)
3 in or 124 in2+1316 in (71 mm)2+34 in (70 mm)
4 in or 164 in3+1316 in (97 mm)3+34 in (95 mm)

Also in North America, hardwood lumber is commonly sold in a "quarter" system, when referring to thickness; 4/4 (four quarter) refers to a 1-inch-thick (25 mm) board, 8/4 (eight quarter) is a 2-inch-thick (51 mm) board, etc. This "quarter" system is rarely used for softwood lumber; although softwood decking is sometimes sold as 5/4, even though it is actually one-inch thick (from milling 18 in or 3.2 mm off each side in a motorized planing step of production). The "quarter" system of reference is a traditional North American lumber industry nomenclature used specifically to indicate the thickness of rough sawn hardwood lumber.

In rough-sawn lumber it immediately clarifies that the lumber is not yet milled, avoiding confusion with milled dimension lumber which is measured as actual thickness after machining. Examples – 34-inch, 19 mm, or 1x. In recent years[ when? ] architects, designers, and builders have begun to use the "quarter" system in specifications as a vogue of insider knowledge, though the materials being specified are finished lumber, thus conflating the separate systems and causing confusion.

Hardwoods cut for furniture are cut in the fall and winter, after the sap has stopped running in the trees. If hardwoods are cut in the spring or summer the sap ruins the natural color of the lumber and decreases the value of the wood for furniture.

Engineered lumber

Engineered lumber is lumber created by a manufacturer and designed for a certain structural purpose. The main categories of engineered lumber are: [31]

Various pieces and cuts

Timber piles

In the United States, pilings are mainly cut from southern yellow pines and Douglas firs. Treated pilings are available in Chromated copper arsenate retentions of 0.60, 0.80 and 2.50 pounds per cubic foot (9.6, 12.8 and 40.0 kg/m3) if treatment is required.

Historical Chinese construction

Under the prescription of the Method of Construction (營造法式) issued by the Song dynasty government in the early 12th century, timbers were standardized to eight cross-sectional dimensions. [32] Regardless of the actual dimensions of the timber, the ratio between width and height was maintained at 1:1.5. Units are in Song Dynasty inches (31.2 mm).

Classheightwidthuses
1st96great halls 11 or 9 bays wide
2nd8.255.5great halls 7 or 5 bays wide
3rd7.55great halls 5 or 3 bays wide or halls 7 or 5 bays wide
4th7.24.8great halls 3 bays wide or halls 5 bays wide
5th6.64.4great halls 3 small bays wide or halls 3 large bays wide
6th64pagodas and small halls
7th5.253.2pagodas and small great halls
8th4.53small pagodas and ceilings

Timber smaller than the 8th class were called "unclassed" (等外). The width of a timber is referred to as one "timber" (材), and the dimensions of other structural components were quoted in multiples of "timber"; thus, as the width of the actual timber varied, the dimensions of other components were easily calculated, without resorting to specific figures for each scale. The dimensions of timbers in similar applications show a gradual diminution from the Sui Dynasty (580–618) to the modern era; a 1st class timber during the Sui was reconstructed as 15×10 (Sui Dynasty inches, or 29.4 mm). [33]

Defects in lumber

Defects occurring in lumber are grouped into the following four divisions:

Conversion

During the process of converting timber to commercial forms of lumber the following defects may occur:

Defects due to fungi and animals

Fungi attack wood (both timber and lumber) when these conditions are all present:

Wood with less than 25% moisture (dry weight basis) can remain free of decay for centuries. Similarly, wood submerged in water may not be attacked by fungi if the amount of oxygen is inadequate.

Fungi lumber/timber defects:

Following are the insects and molluscs which are usually responsible for the decay of timber/lumber:

Natural forces

There are two main natural forces responsible for causing defects in timber and lumber: abnormal growth and rupture of tissues. Rupture of tissue includes cracks or splits in the wood called "shakes". "Ring shake", "wind shake", or "ring failure" is when the wood grain separates around the growth rings either while standing or during felling. Shakes may reduce the strength of a timber and the appearance thus reduce lumber grade and may capture moisture, promoting decay. Eastern hemlock is known for having ring shake. [34] A "check" is a crack on the surface of the wood caused by the outside of a timber shrinking as it seasons. Checks may extend to the pith and follow the grain. Like shakes, checks can hold water promoting rot. A "split" goes all the way through a timber. Checks and splits occur more frequently at the ends of lumber because of the more rapid drying in these locations. [34]

Seasoning

The seasoning of lumber is typically either kiln- or air-dried. Defects due to seasoning are the main cause of splits, bowing and honeycombing. Seasoning is the process of drying timber to remove the bound moisture contained in the walls of the wood cells to produce seasoned timber. [35]

Durability and service life

Under proper conditions, wood provides excellent, lasting performance. However, it also faces several potential threats to service life, including fungal activity and insect damage – which can be avoided in numerous ways. Section 2304.11 of the International Building Code addresses protection against decay and termites. This section provides requirements for non-residential construction applications, such as wood used above ground (e.g., for framing, decks, stairs, etc.), as well as other applications.

There are four recommended methods to protect wood-frame structures against durability hazards and thus provide maximum service life for the building. All require proper design and construction:

Moisture control

Wood is a hygroscopic material, which means it naturally absorbs and releases water to balance its internal moisture content with the surrounding environment. The moisture content of wood is measured by the weight of water as a percentage of the oven-dry weight of the wood fiber. The key to controlling decay is controlling moisture. Once decay fungi are established, the minimum moisture content for decay to propagate is 22 to 24 percent, so building experts recommend 19 percent as the maximum safe moisture content for untreated wood in service. Water by itself does not harm the wood, but rather, wood with consistently high moisture content enables fungal organisms to grow.

The primary objective when addressing moisture loads is to keep water from entering the building envelope in the first place and to balance the moisture content within the building itself. Moisture control by means of accepted design and construction details is a simple and practical method of protecting a wood-frame building against decay. For applications with a high risk of staying wet, designers specify durable materials such as naturally decay-resistant species or wood that has been treated with preservatives. Cladding, shingles, sill plates and exposed timbers or glulam beams are examples of potential applications for treated wood.

Controlling termites and other insects

For buildings in termite zones, basic protection practices addressed in current building codes include (but are not limited to) the following:

Preservatives

Special fasteners are used with treated lumber because of the corrosive chemicals used in its preservation process. Treated timber.jpg
Special fasteners are used with treated lumber because of the corrosive chemicals used in its preservation process.

To avoid decay and termite infestation, untreated wood is separated from the ground and other sources of moisture. These separations are required by many building codes and are considered necessary to maintain wood elements in permanent structures at a safe moisture content for decay protection. When it is not possible to separate wood from the sources of moisture, designers often rely on preservative-treated wood. [36]

Wood can be treated with a preservative that improves service life under severe conditions without altering its basic characteristics. It can also be pressure-impregnated with fire-retardant chemicals that improve its performance in a fire. [37] One of the early treatments to "fireproof lumber", which retard fires, was developed in 1936 by the Protexol Corporation, in which lumber is heavily treated with salt. [38] Wood does not deteriorate simply because it gets wet. When wood breaks down, it is because an organism is eating it. Preservatives work by making the food source inedible to these organisms. Properly preservative-treated wood can have 5 to 10 times the service life of untreated wood. Preserved wood is used most often for railroad ties, utility poles, marine piles, decks, fences and other outdoor applications. Various treatment methods and types of chemicals are available, depending on the attributes required in the particular application and the level of protection needed. [39]

There are two basic methods of treating: with and without pressure. Non-pressure methods are the application of preservatives by brushing, spraying, or dipping the piece to be treated. Deeper, more thorough penetration is achieved by driving the preservative into the wood cells with pressure. Various combinations of pressure and vacuum are used to force adequate levels of chemical into the wood. Pressure-treating preservatives consist of chemicals carried in a solvent. Chromated copper arsenate, once the most commonly used wood preservative in North America began being phased out of most residential applications in 2004. Replacing it are amine copper quat and copper azole.

All wood preservatives used in the United States and Canada are registered and regularly re-examined for safety by the U.S. Environmental Protection Agency and Health Canada's Pest Management and Regulatory Agency, respectively. [39]

Timber framing

Timber framing is a style of construction that uses heavier framing elements (larger posts and beams) than modern stick framing, which uses smaller standard dimensional lumber. The timbers are cut from log boles and squared with a saw, broadaxe or adze, and then joined together with joinery without nails. Modern timber framing has been growing in popularity in the United States since the 1970s. [40]

Environmental effects of lumber

Green building minimizes the impact or "environmental footprint" of a building. Wood is a major building material that is renewable and replenishable in a continuous cycle. [39] Studies show manufacturing wood uses less energy and results in less air and water pollution than steel and concrete. [41] However, demand for lumber is blamed for deforestation. [42]

Residual wood

The conversion from coal to biomass power is a growing trend in the United States. [43]

The United Kingdom, Uzbekistan, Kazakhstan, Australia, Fiji, Madagascar, Mongolia, Russia, Denmark, Switzerland, and Eswatini governments all support an increased role for energy derived from biomass, which are organic materials available on a renewable basis and include residues and/or byproducts of the logging, saw milling and paper-making processes. In particular, they view it as a way to lower greenhouse gas emissions by reducing the consumption of oil and gas while supporting the growth of forestry, agriculture and rural economies. Studies by the U.S. government have found the country's combined forest and agriculture land resources have the power to sustainably supply more than one-third of its current petroleum consumption. [44]

Biomass is already an important source of energy for the North American forest products industry. It is common for companies to have cogeneration facilities, also known as combined heat and power, which convert some of the biomass that results from wood and paper manufacturing to electrical and thermal energy in the form of steam. The electricity is used to, among other things, dry lumber and supply heat to the dryers used in paper-making.

Environmental impacts

Lumber is a sustainable and environmentally friendly construction material that could replace traditional building materials (e.g. concrete and steel). Its structural performance, capacity to fixate CO2 and low energy demand during the manufacturing process make lumber an interesting material.

Substituting lumber for concrete or steel avoids the carbon emissions of those materials. Cement and concrete manufacture is responsible for around 8% of global GHG emissions while the iron and steel industry is responsible for another 5% (half a ton of CO2 is emitted to manufacture a ton of concrete; two tons of CO2  are emitted in the manufacture of a ton of steel). [45]

Advantages of lumber:

End-of-life

An EPA study showed the typical end-of-life scenario for wood waste from municipal solid waste (MSW), wood packaging, and other miscellaneous wood products in the US. Based on the 2018 data, about 67% of wood waste was landfilled, 16% incinerated with energy recovery, and 17% recycled. [48]

A 2020 study conducted by Edinburgh Napier University demonstrated the proportional waste stream of recovered lumber in the UK. The study showed that timber from municipal solid waste and packaging waste made up 13 and 26% of waste collected. Construction and demolition waste made up the biggest bulk of waste collectively at 52%, with the remaining 10% coming from industry. [49]

In the circular economy

The Ellen MacArthur Foundation defines the circular economy as “based on the principles of designing out waste and pollution, keeping products and materials in use, and regenerating natural systems.”

The circular economy can be considered as a model that aims to eliminate waste by targeting materials, and products at their maximum value of utility and time. In short, it is a whole new model of production and consumption that ensures sustainable development over time. It is related to the reuse of materials, components, and products over a longer life cycle.

Wood is among the most demanding materials, which makes it important to come up with a model of the circular economy. The lumber industry creates a lot of waste, especially in its manufacturing process. From log debarking to finished products, there are several stages of processing that generate a considerable volume of waste, which includes solid wood waste, harmful gases, and residual water. [50] Therefore it is important to identify and apply measures to reduce environmental contamination, giving a financial return to the industries (e.g., selling the waste to wood chippings manufacturers) and maintaining a healthy relationship between the environment and industries.

Wood waste can be recycled at its end of life to make new products. Recycled chips can be used to make wood panels, which is beneficial for both the environment and industry. Such practice reduces the use of virgin raw materials, eliminating emissions that would have otherwise been emitted in its manufacturing.

One of the studies conducted in Hong Kong [50] was done using life-cycle assessment (LCA). The study aimed to assess and compare the environmental impacts of wood waste management from building construction activities using different alternative management scenarios in Hong Kong. Despite various advantages of lumber and its waste, the contribution to the study of the circular economy of lumber is still very small. Some areas where improvements can be made to improve the circularity of lumber is as follows:

  1. First, regulations to support recycled lumber use. For example, establishing grading standards and enforcing penalties for improper disposal, especially in sectors that produce big quantities of wood waste, such as the construction and demolition sector.
  2. Second, creating a stronger supply force. This can be achieved by improving demolition protocol and technology and enhancing the secondary raw materials market through circular business models.
  3. Third, increase demand by introducing incentives to the construction sector and new homeowners to use recycled lumber. This can be in the form of reduced taxes for the construction of the new build.

Secondary raw material

The term secondary raw material denotes waste material that has been recycled and injected back into use as productive material. Lumber has a high potential to be used as a secondary raw material at various stages, as listed below:

Recovery of branches and leaves for use as fertilisers
Timber undergo multiple processing stages before lumber of desired shapes, size, and standards are achieved for commercial use. The process generates a lot of waste which in most cases is disregarded. But being an organic waste, the positive aspect of such waste is that it can be used as a fertiliser or to protect the soil in severe weather conditions.
Recovery of woodchips for thermal energy generation
Waste generated during the manufacturing of lumber products can be used to produce thermal energy. Lumber products after their end-of-life can be downcycled into chips and be used as biomass to produce thermal energy. [51] It is beneficial for industries that need thermal energy.

Circular economy practices offer effective solutions concerning waste. It targets its unnecessary generation through waste reduction, reuse, and recycling. There is no clear explicit evidence of circular economy in the wood panel industry. However, based on the circular economy concept and its characteristics, there are opportunities present in the wood panel industry from the raw material extraction phase to its end-of-life. Therefore, there lies a gap yet to be explored. [50]

See also

Explanatory notes

  1. Because working expensive hardwoods is far more difficult and costly, and because an odd width might well be conserved and be of use in making such surfaces as a cabinet side or tabletop joined from many smaller widths, the industry generally only does minimal processing, preserving as much board width as is practicable. This leaves culling and width decisions totally in the hands of the craftsman building cabinets or furniture with the boards.
  2. In quarter sawn thicknesses, meaning the thickness and width dimensions as they come out of the sawmill's table. Because lengths vary most with temperature, hardwood boards in the US often have a bit of extra length.
  3. Small set of specified lengths: Fixed-length hardwood boards in the United States are most common in 4–6 ft (1.2–1.8 m) lengths, with a good representation of 8 ft (2.4 m) lengths in a variety of widths, and a few widths with occasional dimensional sizes to 12 ft (3.7 m) lengths. Often the longer sizes need be special ordered.
  4. Fixed board lengths do not apply in all countries; for example, in Australia and the United States, many hardwood boards are sold to timber yards in packs with a common width profile (dimensions) but not necessarily consisting of boards of identical lengths.

Related Research Articles

<span class="mw-page-title-main">Wood</span> Fibrous material from trees or other plants

Wood is a porous and fibrous structural tissue found in the stems and roots of trees and other woody plants. It is an organic material – a natural composite of cellulose fibers that are strong in tension and embedded in a matrix of lignin that resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or woodchips or fiber.

<span class="mw-page-title-main">Plywood</span> Manufactured wood panel made from thin sheets of wood veneer

Plywood is a material manufactured from thin layers or "plies" of wood veneer that are glued together with adjacent layers having their wood grain rotated up to 90 degrees to one another. It is an engineered wood from the family of manufactured boards which include medium-density fibreboard (MDF), oriented strand board (OSB) and particle board (chipboard).

The board foot or board-foot is a unit of measurement for the volume of lumber in the United States and Canada. It equals the volume of a one-foot (305 mm) length of a board, one foot wide and one inch (25.4 mm) thick.

<span class="mw-page-title-main">Engineered wood</span> Range of derivative wood products engineered for uniform and predictable structural performance

Engineered wood, also called mass timber, composite wood, man-made wood, or manufactured board, includes a range of derivative wood products which are manufactured by binding or fixing the strands, particles, fibres, or veneers or boards of wood, together with adhesives, or other methods of fixation to form composite material. The panels vary in size but can range upwards of 64 by 8 feet and in the case of cross-laminated timber (CLT) can be of any thickness from a few inches to 16 inches (410 mm) or more. These products are engineered to precise design specifications, which are tested to meet national or international standards and provide uniformity and predictability in their structural performance. Engineered wood products are used in a variety of applications, from home construction to commercial buildings to industrial products. The products can be used for joists and beams that replace steel in many building projects. The term mass timber describes a group of building materials that can replace concrete assemblies. Broad-base adoption of mass timber and their substitution for steel and concrete in new mid-rise construction projects over the coming decades could help mitigate climate change.

<span class="mw-page-title-main">Deck (building)</span> Surface similar to a floor, but typically constructed outdoors and connected to a building

In architecture, a deck is a flat surface capable of supporting weight, similar to a floor, but typically constructed outdoors, often elevated from the ground, and usually connected to a building. The term is a generalization from the deck of a ship. A level architectural deck may be intended for use by people, e.g., what in the UK is usually called a decked patio. "Roof deck" refers to the flat layer of construction materials to which the weather impervious layers are attached to a form a roof. It is known as the "roof deck", and they may be either level or sloped.

<span class="mw-page-title-main">Joist</span> Horizontal framing structure

A joist is a horizontal structural member used in framing to span an open space, often between beams that subsequently transfer loads to vertical members. When incorporated into a floor framing system, joists serve to provide stiffness to the subfloor sheathing, allowing it to function as a horizontal diaphragm. Joists are often doubled or tripled, placed side by side, where conditions warrant, such as where wall partitions require support.

<span class="mw-page-title-main">Lath and plaster</span> Finish mainly for interior dividing walls and ceilings

Lath and plaster is a building process used to finish mainly interior dividing walls and ceilings. It consists of narrow strips of wood (laths) which are nailed horizontally across the wall studs or ceiling joists and then coated in plaster. The technique derives from an earlier, more primitive process called wattle and daub.

<span class="mw-page-title-main">Log house</span> House built from wooden logs

A log house, or log building, is a structure built with horizontal logs interlocked at the corners by notching. Logs may be round, squared or hewn to other shapes, either handcrafted or milled. The term "log cabin" generally refers to a smaller, more rustic log house, such as a hunting cabin in the woods, that may or may not have electricity or plumbing.

<span class="mw-page-title-main">Laminated veneer lumber</span>

Laminated veneer lumber (LVL) is an engineered wood product that uses multiple layers of thin wood assembled with adhesives. It is typically used for headers, beams, rimboard, and edge-forming material. LVL offers several advantages over typical milled lumber: Made in a factory under controlled specifications, it is stronger, straighter, and more uniform. Due to its composite nature, it is much less likely than conventional lumber to warp, twist, bow, or shrink. LVL is a type of structural composite lumber, comparable to glued laminated timber (glulam) but with a higher allowable stress.

<span class="mw-page-title-main">Framing (construction)</span> Construction techique

Framing, in construction, is the fitting together of pieces to give a structure support and shape. Framing materials are usually wood, engineered wood, or structural steel. The alternative to framed construction is generally called mass wall construction, where horizontal layers of stacked materials such as log building, masonry, rammed earth, adobe, etc. are used without framing.

Wood shingles are thin, tapered pieces of wood primarily used to cover roofs and walls of buildings to protect them from the weather. Historically shingles, also known as shakes, were split from straight grained, knot free bolts of wood. Today shingles are mostly made by being cut which distinguishes them from shakes, which are made by being split out of a bolt.

<span class="mw-page-title-main">Wood drying</span> Also known as seasoning, which is the reduction of the moisture content of wood prior to its use

Wood drying reduces the moisture content of wood before its use. When the drying is done in a kiln, the product is known as kiln-dried timber or lumber, whereas air drying is the more traditional method.

<span class="mw-page-title-main">Wall stud</span>

A wall stud is a vertical repetitive framing member in a building's wall of smaller cross section than a post. It is a fundamental element in frame building.

<span class="mw-page-title-main">Quarter sawing</span> Woodworking process

Quarter sawing or quartersawing is a woodworking process that produces quarter sawn or quarter-cut boards in the rip cutting of logs into lumber. The resulting lumber can also be called radially-sawn or simply quartered. There is widespread confusion between the terms rift sawn and quarter sawn with the terms defined both with opposite meanings and as synonyms.

This glossary of woodworking lists a number of specialized terms and concepts used in woodworking, carpentry, and related disciplines.

<span class="mw-page-title-main">Wood flooring</span>

Wood flooring is any product manufactured from timber that is designed for use as flooring, either structural or aesthetic. Wood is a common choice as a flooring material and can come in various styles, colors, cuts, and species. Bamboo flooring is often considered a form of wood flooring, although it is made from bamboo rather than timber.

<span class="mw-page-title-main">Parallel-strand lumber</span>

Parallel-strand lumber (PSL) is a form of engineered wood made from parallel wood strands bonded together with adhesive. It is used for beams, headers, columns, and posts, among other uses. The strands in PSL are clipped veneer elements having a least dimension of not more than 0.25 inches (6.4 mm) and an average length of at least 300 times this least dimension. It is a member of the structural composite lumber (SCL) family of engineered wood products.

<span class="mw-page-title-main">Reclaimed lumber</span> Processed wood reused for other applications

Reclaimed lumber is processed wood retrieved from its original application for purposes of subsequent use. Most reclaimed lumber comes from timbers and decking rescued from old barns, factories and warehouses, although some companies use wood from less traditional structures such as boxcars, coal mines and wine barrels. Reclaimed or antique lumber is used primarily for decoration and home building, for example for siding, architectural details, cabinetry, furniture and flooring.

<span class="mw-page-title-main">I-joist</span>

An engineered wood joist, more commonly known as an I-joist, is a product designed to eliminate problems that occur with conventional wood joists. Invented in 1969, the I-joist is an engineered wood product that has great strength in relation to its size and weight. The biggest notable difference from dimensional lumber is that the I-joist carries heavy loads with less lumber than a dimensional solid wood joist. As of 2005, approximately 50% of all wood light framed floors used I-joists. I-joists were designed to help eliminate typical problems that come with using solid lumber as joists.

The wood industry or timber industry is the industry concerned with forestry, logging, timber trade, and the production of primary forest products and wood products and secondary products like wood pulp for the pulp and paper industry. Some of the largest producers are also among the biggest owners of timberland. The wood industry has historically been and continues to be an important sector in many economies.

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Further reading