Lumber
[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.
[2] In the United States and Canada, milled boards are called lumber, while timber describes standing or felled trees.
[6] A timber mark is a code beaten on to cut wood by a specially made hammer to show the logging licence.
Dimensional lumber made from softwood is typically used for construction, while hardwood boards are more commonly used for making cabinets or furniture.
[13] 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.
Individual pieces of lumber exhibit a wide range in quality and appearance with respect to knots, slope of grain, shakes and other natural characteristics.
[17] Canada has grading rules that maintain a standard among mills manufacturing similar woods to assure customers of uniform quality.
[21][22] 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.
[23] In Europe, strength grading of rectangular sawn lumber/timber (both softwood and hardwood) is done according to EN-14081[24] and commonly sorted into classes defined by EN-338.
[28] In North America, market practices for dimensional lumber made from hardwoods[a] varies significantly from the regularized standardized 'dimension lumber' sizes used for sales and specification of softwoods – hardwood boards are often sold totally rough cut,[b] or machine planed only on the two (broader) face sides.
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;[c] 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).
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.
Under the prescription of the Method of Construction (營造法式) issued by the Song dynasty government in the early twelfth century, timbers were standardized to eight cross-sectional dimensions.
However, it also faces several potential threats to service life, including fungal activity and insect damage – which can be avoided in numerous ways.
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: Wood is a hygroscopic material, which means it naturally absorbs and releases water to balance its internal moisture content with the surrounding environment.
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.
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.
Preserved wood is used most often for railroad ties, utility poles, marine piles, decks, fences and other outdoor applications.
Chromated copper arsenate, once the most commonly used wood preservative in North America began being phased out of most residential applications in 2004.
[37] Studies show manufacturing wood uses less energy and results in less air and water pollution than steel and concrete.
[41] 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.
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.
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.
[50] A 2020 study conducted by Edinburgh Napier University demonstrated the proportional waste stream of recovered lumber in the UK.
Lumber has a high potential to be used as a secondary raw material at various stages, as listed below: Circular economy practices offer effective solutions concerning waste.
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.
