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"Timber" redirects here. For other uses, see Timber (disambiguation) and Lumber (disambiguation).
Timber in storage for later processing at a sawmill
Wood cut from Victorian Eucalyptus regnans
The harbor of Bellingham, Washington, filled with logs, 1972

Lumber (American English;[1] timber in Australian English, British English, Hiberno-English, and New Zealand English[2]) is wood that has been processed into beams and planks, a stage in the process of wood production.


Lumber is mainly used for structural purposes but has many other uses as well. It is classified more commonly as a softwood than as a hardwood, because 80% of lumber comes from softwood.[4]


In Australia, Ireland, New Zealand and Britain, the term timber describes sawn wood products, such as floor boards. In the United States and Canada, generally timber describes standing or felled trees, before they are milled into boards, which are called lumber.

Timber there also describes sawn lumber not less than 5 inches (127 mm) in its smallest dimension.[5] The latter includes the often partly finished lumber used in timber-frame construction.

In the United Kingdom, the word lumber is rarely used in relation to wood, and timber is almost universally used in its place; but lumber has several other meanings in Britain, including unused or unwanted items.

Remanufactured lumber[edit]

Remanufactured lumber is the result of secondary or tertiary processing/cutting of previously milled lumber. Specifically, it is 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.

Resawing is the splitting of 1-inch through 12-inch hardwood or softwood lumber into two or more thinner pieces of full-length boards. For example, splitting a ten-foot 2x4 into two ten-foot 1x4s is considered resawing.

Plastic lumber[edit]

Structural lumber may also be produced from recycled plastic and new plastic stock. Its introduction has been strongly opposed by the forestry industry.[6] Blending fiberglass in plastic lumber enhances its strength, durability, and fire resistance.[7] 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 slower than almost all treated wood lumber.[8]

Conversion of wood logs[edit]


  • Plain sawn (flat sawn, through and through, bastard sawn)—A log sawn through without adjusting the position of the log and the grain runs across the width of the boards.
  • Quarter sawn and rift sawn—These terms have been confused in history but generally mean lumber sawn so the annual rings are reasonably perpendicular to the sides (not edges) of the lumber.
  • Boxed heart—The pith remains within the piece with some allowance for exposure.
  • Heart center—the center core of a log.
  • Free of heart center (FOHC)—A side-cut timber without any pith.
  • Free of knots (FOK)—No knots are present.

Dimensional lumber[edit]

A 2×4.

Dimensional lumber is lumber that is cut to standardized width and depth, specified in 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 the 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 (1.83, 2.44, 3.05, 3.66, 4.27, 4.88, 5.49, 6.10, 6.71 and 7.32 meters). For wall framing, "stud" or "precut" sizes are available, and are commonly used. For an eight-, nine-, or ten-foot ceiling height, studs are available in 92 58 inches (235 cm), 104 58 inches (266 cm), and 116 58 inches (296 cm). The term "stud" is used inconsistently to specify length; where the exact length matters, one must specify the length explicitly.

North American softwoods[edit]





North American softwood dimensional lumber sizes
Nominal Actual Nominal Actual Nominal Actual
1 × 2 34 × 1 12 19 × 38 2 × 2 1 12 × 1 12 38 × 38 4 × 4 3 12 × 3 12 89 × 89
1 × 3 34 × 2 12 19 × 64 2 × 3 1 12 × 2 12 38 × 64 4 × 6 3 12 × 5 12 89 × 140
1 × 4 34 × 3 12 19 × 89 2 × 4 1 12 × 3 12 38 × 89 4 × 8 3 12 × 7 14 89 × 184
1 × 6 34 × 5 12 19 × 140 2 × 6 1 12 × 5 12 38 × 140 6 × 6 5 12 × 5 12 140 × 140
1 × 8 34 × 7 14 19 × 184 2 × 8 1 12 × 7 14 38 × 184 8 × 8 7 14 × 7 14 184 × 184
1 × 10 34 × 9 14 19 × 235 2 × 10 1 12 × 9 14 38 × 235
1 × 12 34 × 11 14 19 × 286 2 × 12 1 12 × 11 14 38 × 286

Early standards called for green rough lumber to be of full nominal dimension when dry. However, the dimensions have diminished 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 US 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.[10]


Grades and standards[edit]



The move to set national standards for lumber in the United States began with 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.[11]


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)[13] is responsible for writing, interpreting and maintaining Canadian lumber grading rules and standards. The Canadian Lumber Standards Accreditation Board (CLSAB)[14] monitors the quality of Canada's lumber grading and identification system.



In Europe, strength grading of sawn softwood is done according to EN-14081-1/2/3/4 and sorted into nine classes; in increasing strength these are: C14, C16, C18, С22, С24, С27, С30, С35 and С40[18]

  • C14 used for scaffolding and formwork
  • C24 general construction
  • C30 prefab roof trusses and where design requires somewhat stronger joists than C24 can offer
  • C40 usually seen in glulam


North American hardwoods[edit]

In North America, sizes for dimensional lumber made from hardwoods varies from the sizes for softwoods. Boards are usually supplied in random widths and lengths of a specified thickness, and sold by the board-foot (144 cubic inches or 2,360 cubic centimetres). This does not apply in all countries; for example, in Australia many boards are sold to timber yards in packs with a common profile (dimensions) but not necessarily consisting of boards of identical lengths.

North American hardwood dimensional lumber sizes

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. The "quarter" system of reference is a traditional lumber industry nomenclature used specifically to indicate the thickness of rough sawn hardwood lumber. It immediately clarifies that the lumber is not yet milled, avoiding confusion with milled lumber which is measured as actual thickness after machining. Examples- 3/4", 19mm, or 1x. In recent years 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.


Engineered lumber[edit]

Main article: Engineered lumber


    Freshly cut logs showing sap running from beneath bark

Various pieces and cuts[edit]

For more details on this topic, see Woodworking.
  • Square and rectangular forms: Plank, slat, batten, board, lath, strapping (typically 34 in × 1 12 in), cant (A partially sawn log such as sawn on two sides or squared to a large size and later resawn into lumber. A flitch is a type of cant with wane on one or both sides). Various pieces are also known by their uses such as post, beam, (girt), stud, rafter, joist, sill plate, wall plate.

Timber piles[edit]

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.

Defects in lumber[edit]

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



  • Diagonal grain: improper sawing of timber
  • Wane: presence of original rounded surface in the finished product

Defects due to fungi[edit]

Fungi attack timber when these conditions are all present:

  • The environment is sufficiently warm
  • Oxygen (O2) is present


Fungi timber defects:


Natural forces[edit]

Main article: wood warping

There are two main natural forces responsible for causing defects in timber: 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.[21] 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.[21]


The seasoning of lumber is typically either kiln- or air-dried. Defects due to seasoning are the main cause of splinters and slivers.[citation needed]

Durability and service life[edit]



  • Controlling moisture using design techniques to avoid decay
  • Providing effective control of termites and other insects
  • Providing quality assurance during design and construction and throughout the building’s service life using appropriate maintenance practices

Moisture control[edit]



Controlling termites and other insects[edit]



• Covering exposed ground in any crawl spaces with 6-mil polyethylene film and maintaining at least 12 to 18 inches (300 to 460 mm) of clearance between the ground and the bottom of framing members above (12 inches to beams or girders, 18 inches to joists or plank flooring members)

• Supporting post columns by concrete piers so that there is at least 6 inches (150 mm) of clear space between the wood and exposed earth


• Where appropriate, ventilating crawl spaces according to local building codes

• Removing building material scraps from the job site before backfilling.



Main article: Wood preservation
Special fasteners are used with treated lumber because of the corrosive chemicals used in its preservation process




All wood preservatives used in the United States and Canada are registered and regularly re-examined for safety by the US Environmental Protection Agency and Health Canada's Pest Management and Regulatory Agency, respectively.[26]

Timber framing[edit]

Main article: Timber framing


Environmental effects of lumber[edit]

Green building minimizes the impact or "environmental footprint" of a building. Wood is a major building material that is renewable and uses the sun’s energy to renew itself in a continuous sustainable cycle.[28] Studies show manufacturing wood uses less energy and results in less air and water pollution than steel and concrete.[29] However, demand for lumber is blamed for deforestation.[30]

Residual wood[edit]

The conversion from coal to biomass power is a growing trend in the United States.[31]



See also[edit]


  1. ^
  3. ^ "Southern Pine Cost Estimates". 
  4. ^
  8. ^ "SAFPLANK Interlocking Decking System"
  9. ^ Naturally:wood
  11. ^ American Lumber Standard Committee: History.
  12. ^ WoodWorks
  13. ^ National Lumber Grades Authority (Canada)
  14. ^ Canadian Lumber Standards Accreditation Board
  16. ^ University of Washington, School of Forest Resources. Material substitution in the US residential construction industry.
  17. ^ Naturally:wood
  18. ^
  19. ^
  21. ^ a b U. S. Department of Agriculture. "Shake", The Encyclopedia of Wood. New York: Skyhorse Pub., 2007. Print.
  22. ^ WoodWorks Durability and Service Life
  25. ^ Canadian Wood Council About treated wood
  26. ^ Canadian Wood Council About Treated Wood
  28. ^ Canadian Wood Council
  30. ^ Peter Dauvergne and Jane Lister, Timber (Polity Press, 2011).
  31. ^ EERE News: EERE Network News
  32. ^ US Department of Agriculture, US Department of Energy Biomass as a Feedstock for a Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply, 2005 Executive Summary

Further reading[edit]

External links[edit]