Lumber

Background

Lumber is a generic term that applies to various lengths of wood used as construction materials. Pieces of lumber are cut lengthwise from the trunks of trees and are characterized by having generally rectangular or square cross sections, as opposed to poles or pilings, which have round cross sections.

The use of wood as a construction material predates written history. The earliest evidence of wood construction comes from a site near Nice, France, where a series of post holes seems to indicate that a hut 20 ft (6m) wide by 50 ft (15 m) long was built there 400,000 years ago using wood posts for support. The oldest wood construction found intact is located in northwest Germany, and was built about 7,300 years ago. By 500 b.c. iron axes, saws, and chisels were commonly used to cut and shape wood. The first reference to cutting wood in a sawmill, rather than using hand tools, comes from northern Europe and dates from about 375. The sawmill was powered by the flow of water.

In North America, European colonists found vast forests of trees, and wood became the principal building material. The circular saw, which had been developed in England, was introduced in the United States in 1814 and was widely used in sawmills. A large-scale bandsaw was developed and patented by Jacob R. Hoffman in 1869 and replaced the circular saw for many sawmill operations.

Lumber produced in early sawmills had varying dimensions depending on the customer's specific order or the mill's standard practice. Today, lumber pieces used in construction have standard dimensions and are divided into three categories, depending on the thickness of the piece. Lumber with nominal thicknesses of less than 2 in (5 cm) are classified as boards. Those with nominal thicknesses of 2 in (5 cm) but less than 5 in (13 cm) are classified as dimension. Those with nominal thicknesses of 5 in (12.5 cm) and greater are classified as timbers. The nominal widths of these pieces vary from 2-16 in (5-40 cm) in 1 in (2.5 cm) increments. Most rough-cut lumber pieces are dried and then finished, or surfaced, by running them through a planer to smooth all four sides. As a result, the actual dimensions are smaller than the nominal dimensions. For example, a standard two-by-four piece of dried, surfaced dimension lumber actually measures 1.5 in (3.8 cm) by 3.5 in (8.9 cm).

Pieces of lumber that are not only surfaced, but also machined to produce a specific cross sectional shape are classified as worked lumber or pattern lumber. Decorative molding, tongue-and-groove flooring, and shiplap siding are examples of pattern lumber.

Today, processing wood products is a billion-dollar, worldwide industry. It not only produces construction lumber, but also plywood, fiberboard, paper, cardboard, turpentine, rosin, textiles, and a wide variety of industrial chemicals.

Raw Materials

The trees from which lumber is produced are classified as hardwoods or softwoods. Although the woods of many hardwoods are hard, and the woods of many softwoods are soft, that is not the defining characteristic. Most hardwood trees have leaves, which they shed in the winter. Hardwood trees include oaks, maples, walnuts, cherries, and birches, but they also include balsa, which has one of the softest and lightest of all the woods. Softwood trees, on the other hand, have needles instead of leaves. They do not shed their needles in the winter, but remain green throughout the year and are sometimes called evergreens. Softwood trees include pines, firs, hemlocks, spruces, and redwoods.

Hardwoods are generally more expensive than softwoods and are used for flooring, cabinetry, paneling, doors, and trimwork. They are also extensively used to manufacture furniture. Hardwoods are available in lengths from 4-16 ft (1.2-4.8 m). Softwoods are used for wall studs, joists, planks, rafters, beams, stringers, posts, decking, sheathing, subflooring, and concrete forms. They are available in lengths from 4-24 ft (1.2-7.3 m).

Both hardwood and softwood lumber pieces are graded according to the number and size of defects in the wood. Defects include knots, holes, pitch pockets, splits, and missing pieces on the edges or corners, called wanes. These defects primarily affect the appearance, but may also affect the strength of the piece. The higher grades are called select grades. Hardwoods may also be graded as firsts or seconds, which are even higher than select. These grades have very few defects and are used for trim, molding, and finish woodwork where appearance is important. The higher the grade, the fewer the number of defects. The lower grades are called common grades and are used for general construction where the wood will be covered or where defects will not be objectionable. Common grades are designated in descending order of quality by a number such as #1 common, #2 common, and so on. Pieces of softwood common grade lumber may also be designated by an equivalent name, such as select merchantable, construction, and so on. Lumber intended for uses other than construction, such as boxes or ladders, are given other grading designations.

The Manufacturing
Process

In the United States, most trees destined to be cut into lumber are grown in managed forests either owned by the lumber company or leased from the government. After the trees have reached an appropriate size, they are cut down and transported to a lumber mill where they are cut into various sizes of lumber.

Here is a typical sequence of operations for processing trees into lumber.

Felling

• 1 Selected trees in an area are visually inspected and marked as being ready to be cut down, or felled. If a road does not already exist in the area, one is cut and graded using bulldozers. If operations are expected to extend into the rainy season, the road may be graveled, and culverts may be installed across streams to prevent washouts.
• 2 Most tree felling is done with gasoline-powered chain saws. Two cuts are made near the base, one on each side, to control the direction the tree will fall. Once the tree is down, the limbs are trimmed off with chain saws, and the tree is cut into convenient lengths for transportation.
• 3 If the terrain is relatively level, diesel-powered tractors, called skidders, are used to drag the fallen tree sections to a cleared area for loading. If the terrain is steep, a self-propelled yarder is used. The yarder has a telescoping hydraulic tower that can be raised to a height of 110 ft (33.5 m). Guy wires support the tower, and cables are run from the top of the tower down the steep slopes to retrieve the felled trees. The tree sections, or logs, are then loaded on trucks using wheeled log loaders.
• 4 The trucks make their way down the graded road and onto public highways on their way to the lumber mill. Once at the mill, giant mobile unloaders grab the entire truck load in one bite and stack it in long piles, known as log decks. The decks are periodically sprayed with water to prevent the wood from drying out and shrinking.

Debarking and bucking

• 5 Logs are picked up from the log deck with rubber-tired loaders and are placed on a chain conveyor that brings them into the mill. In some cases, the outer bark of the log is removed, either with sharp-toothed grinding wheels or with a jet of high-pressure water, while the log is slowly rotated about its long axis. The removed bark is pulverized and may be used as a fuel for the mill's furnaces or may be sold as a decorative garden mulch.
• 6 The logs are carried into the mill on the chain conveyor, where they stop momentarily as a huge circular saw cuts them into predetermined lengths. This process is called bucking, and the saw is called a bucking saw.

Headrig sawing large logs

• 7 If the log has a diameter larger than 2-3 ft (0.6-0.9 m), it is tipped off the conveyor and clamped onto a moveable carriage that slides lengthwise on a set of rails. The carriage can position the log transversely relative to the rails and can also rotate the log 90 or 180 degrees about its length. Optical sensors scan the log and determine its diameter at each end, its length, and any visible defects. Based on this information, a computer then calculates a suggested cutting pattern to maximize the number of pieces of lumber obtainable from the log.
• 8 The headrig sawyer sits in an enclosed booth next to a large vertical bandsaw called the headrig saw. He reviews the suggested cutting pattern displayed on a television monitor, but relies more on his experience to make the series of cuts. The log is fed lengthwise through the vertical bandsaw. The first cut is made along the side closest to the operator and removes a piece of wood called a slab. The outer surface of the slab has the curvature of the original tree trunk, and this piece is usually discarded and ground to chips for use in paper pulp.
• 9 The carriage is returned to its original position, and the log is shifted sideways or rotated to make subsequent cuts. The headrig sawyer must constantly review the log for internal defects and modify the cutting pattern accordingly as each successive cut opens the log further. In general, thinner pieces destined to be made into boards are cut from the outer portion of the log where there are fewer knots. Thicker pieces for dimension lumber are cut next, while the center of the log yields stock for heavy timber pieces.

Bandsawing small logs

• 10 Smaller diameter logs are fed through a series of bandsaws that cut them into nominal 1 in (2.5 cm), 2 in (5 cm), or 4 in (10 cm) thick pieces in one pass.

Resawing

• 11 The large cut pieces from the headrig saw, called cants, are laid flat and moved by chain conveyor to multiple-blade bandsaws, where they are cut into the required widths and the outside edges are trimmed square. The pieces that were cut from smaller logs may also pass through multiple-blade bandsaws to cut them to width. If the pieces are small enough that they do not need further cutting, they may pass through a chipper, which grinds the uneven edges square.

Drying or seasoning

• 12 The cut and trimmed pieces of lumber are then moved to an area to be dried, or "seasoned." This is necessary to prevent decay and to permit the wood to shrink as it dries out. Timbers, because of their large dimensions, are difficult to thoroughly dry and are generally sold wet, or "green." Other lumber may be air dried or kiln dried, depending on the required moisture content of the finished piece. Air-dried lumber is stacked in a covered area with spacers between each piece to allow air to circulate. Air-dried woods generally contain about 20% moisture. Kiln-dried lumber is stacked in an enclosed area, while 110-180°F (44-82°C) heated air is circulated through the stack. Kiln-dried woods generally contain less than 15% moisture and are often specified for interior floors, molding, and doors where minimal shrinkage is required.

Planing

• 13 The dried pieces of lumber are passed through planers, where rotating cutting heads trim the pieces to their final dimensions, smooth all four surfaces, and round the edges.

Grade stamping and banding

• 14 Each piece of lumber is visually or mechanically inspected and graded according to the amount of defects present. The grade is stamped on each piece, along with information about the moisture content, and a mill identification number. The lumber is then bundled according to the type of wood, grade, and moisture content, and the bundle is secured with steel bands. The bundle is loaded on a truck or train and shipped to a lumber yard for resale to customers.

Quality Control

There are very few pieces of perfect lumber. Even though great care is taken to avoid or minimize defects when sawing the wood to the required sizes, there are almost always some defects present. The number and location of these defects determines the grade of the lumber, and the purchaser must choose the grade that is appropriate for each specific application.

The Future

As the number of older trees available for logging diminishes, so does the lumber industry's ability to selectively cut pieces of lumber to the sizes needed for construction. Many of the trees being logged today are second-generation or third-generation trees that are younger and smaller in diameter than the original old-growth trees. These younger trees also contain a higher percentage of juvenile wood, which is less dimensionally stable than older wood.

To counter this trend, the lumber industry is literally taking trees apart and putting them back together again to manufacture the sizes, strengths, and stability required for construction. Actually, they have been doing this for decades in the form of plywood and glue-laminated beams, and some of the new products use similar technology.

One of the new manufactured lumber products is called parallel strand lumber. It begins much like plywood with a thin veneer of wood being peeled off a log. The veneer passes under a fiber-optic scanner that spots defects and cuts them out, sort of like an automated cookie cutter. The veneer is then dried and cut into 0.5 in (1.3 cm) wide strips. The strips are fed into one end of a machine, which coats them with a phenolic resin glue and stacks them side-to-side and end-to-end to form a solid 12 in by 17 in (30 cm by 43 cm) beam of wood. The beam is zapped with 400,000 watts of microwave energy, which hardens the glue almost instantly. As the beam emerges from the other end of the machine, it is cut into 60 ft (18.3 m) lengths. It is then further cut into various sizes of lumber, and sanded smooth. The resulting pieces are significantly stronger and more dimensionally stable than natural wood, while being attractive enough to be used for exposed beams and other visible applications.

Where to Learn More

Books

Bramwell, Martyn, ed. The International Book of Wood. Simon and Schuster, 1976.

Forest Products Laboratory. Wood Handbook: Wood as an Engineering Material. United States Department of Agriculture, 1987.

Hoadley, R. Bruce. Understanding Wood: A Craftsman's Guide to Wood Technology. The Taunton Press, 1980.

Hornbostel, Caleb. Construction Materials, 2nd Edition. John Wiley and Sons, Inc., 1991.

Vila, Bob. This Old House Guide to Building and Remodeling Materials. Warner Books, Inc., 1986.

Periodicals

Crosby, Bill. "The New Lumber." Sunset (Central West edition), November 1995, pp. 72-76.

McCafferty, Phil. "Reinventing Wood." Popular Science, May 1990, pp. 96-99, 117.

McCafferty, Phil. "New Strengths For Lumber." Popular Science, January 1992, pp. 68-69, 95.

Wardell, C. "Engineered Lumber From the Top Down." Popular Science, October 1995, p. 53.

—ChrisCavette

LUMBER INDUSTRY

LUMBER INDUSTRY. The production of lumber, wood split or sawed for use as boards, beams, planks, and the like, has been a critical economic activity throughout American history. Whereas Indian peoples altered North America's woodlands through the extensive use of fire, European colonists introduced the first mass cuttings of trees for both trade and subsistence purposes. Although most felled trees were cut to provide firewood and to open fields for agriculture, timber products were important commodities for trade with Europe from the inception of British North America. Indeed, the Pilgrims' first shipment home in 1621 was dominated by milled wood for their comparatively timber-starved mother country. Lumber from North America was consumed and shipped to other British colonies and to Europe for a wide variety of uses, including barrel staves, building construction, furniture, and shingle manufacture. Colonial society was comparatively lumber rich. European travelers were often staggered by the colonists' unwillingness to use any but the finest of wood for even the most pedestrian purposes. As one observer wrote of eighteenth-century New Englanders:

The richest and straightest trees were reserved for the frames of the new houses; shingles were rived from the clearest pine; baskets, chair bottoms, cattle bows, etc., were made from brown ash butts; all the rest of the timber cleared was piled and burned on the spot.…All the pine went first. Nothing else was fit for building purposes in those days. Tables were 2½ feet wide from a single board, without knot or blemish.

The white pine, the largest of New England's trees, was the most important tree for export. Indispensable for ship masts and increasingly scarce in Europe, the pines were actively sought by the Royal Navy, which by the end of the seventeenth century mandated fines for unauthorized cutting of large specimens.

Because of their abundant stands of large white pine, Maine and New Hampshire were the most important commercial lumbering centers in colonial times. More than two dozen sawmills were in operation in southern Maine by the 1680s. Lumbermen used draft animals to pull downed trees over frozen winter ground to the nearest waterway, where they floated to sawmills in the spring. Although many logs were sawed by hand throughout the colonial period, New England's mills resorted to water-power more extensively than did their English counter parts.

The nineteenth century brought an intensification of lumbering as the new nation grew in size. For a time, Maine held its dominant position in the industry. By one estimate, Bangor was the world's largest lumber-producing site in the early nineteenth century. But soon the industry began to move westward on the "timber frontier" in search of relatively unharvested forests, particularly the still valuable white pine. By 1840, upstate New York and Pennsylvania had supplanted northern New England as the largest producers of lumber. In the 1850s, lumbermen began cutting the large pine forests of the Great Lakes states, and by 1880, Michigan produced more lumber than any other state. White pine remained the single most important commercial tree in the nineteenth century, accounting for about half of all lumber sawed each year through the 1870s. By the early twentieth century, however, the enormous redwood, pine, and fir forests of the Far West and the South's piney woods provided most of the nation's lumber. While different regions produced their own owners, firms, and laborers, many New Englanders moved westward with the industry and continued to wield disproportionate influence over it well into the twentieth century. At the height of the Great Lakes white pine harvest, for example, four-fifths of the 131 most influential lumber entrepreneurs hailed from the northeastern United States or eastern Canada, as did many of their most experienced laborers.

The nineteenth century lumber industry was part and parcel of the industrialization of the United States. Before the widespread use of coal after the Civil War, wood likely supplied more than 90 percent of the nation's energy needs for heat, light, and rail and steamship transportation. Rapid population growth on the timber-poor Great Plains helped make timber production a true industry, with operators harvesting and milling wood near the Great Lakes and shipping wood to build homes in Kansas and Nebraska. The burgeoning railroad network made such transportation possible even as it increased demand for timber. Railroads needed lumber to construct rail cars, stations, fences, and cross ties in addition to the massive amounts of wood they burned for fuel. Each year railroads needed some 73 million ties for the construction of new rail lines and the maintenance of old ones, estimated by the magazine Scientific American in 1890. From the 1870s to 1900, railroads used as much as a fourth of national timber production. The mining industry similarly used large amounts of lumber to support underground diggings and to maintain its own rail beds. Indeed, many mining companies ran their own local logging and sawing operations.

The internal structure of the lumber industry changed to meet these economic circumstances. Individuals and families had operated single sawmills to make lumber of

raw logs, either for the direct use of the log provider or for sale to wholesalers. In the 1850s, many operators began buying multiple mills, acquiring their own timberlands, and operating their own lumberyards in market centers such as Chicago. The rise of the Weyerhaeuser timber company epitomized this consolidation. Starting in 1860 with a single sawmill on the Mississippi River in Rock Island, Illinois, the German immigrant Frederick Weyerhaeuser directed the energies of some 20,000 employees a decade later. By the early twentieth century, he and his business partners owned more than 2 million acres of forest and perhaps 15 billion feet of valuable pine. The "lumber king," a private man in comparison with other industrial giants of the era, may have been the world's richest man by his death in 1914.

Consolidating ownership led to other changes in the production and marketing of timber. Operations like Weyerhaeuser's had significant advantages over their smaller and less-capitalized competitors. The exhaustion of timber stands near waterways large enough to drive lumber created the need for railroad spurs to connect inland sawmills to the national rail network. The companies that constructed their own rail lines, an expensive proposition, were for the first time also able to ship mass quantities of hardwoods, especially oak, hickory, ash, and maple, all of which were too heavy to easily float, to market, allowing for a more intensive and profitable cutting of woodlands.

Away from the timber harvest sites, corporate lumberyards began sorting lumber into standardized categories to ensure higher prices for finer products. By the 1890s, regional grading schemes were in place. Firms in urban timber markets began shipping manufactured building components, such as doors and sashes and in some cases entire structures, as early as the 1860s. Standardization and reliable transportation by rail allowed for the extensive use of the distinctly American "balloon-frame" construction technique, in which light, mass-produced boards were nailed together to create a strong building skeleton. The balloon frame allowed fewer and less-skilled workers to follow easily repeatable plans in the erection of even large buildings.

After the Civil War, the production of lumber thus became a modern and highly specialized industry. In Chicago, the nation's largest lumber market, for example, twelve miles of docks were devoted exclusively to unloading lumber. Enormous piles of stacked wood dominated entire blocks of the city. "The timber yards are a considerable part of the city's surface," wrote a British traveler, "there appearing to be enough boards and planks piled up to supply a half-dozen states." The city's lumber wholesaling was such an important business that by 1880 its operators owned several times more capital than did all of Chicago's banks combined.

The very size of the industry raised the prospect that it would cut over the nation's woodlands, leaving nothing of value to replace the once majestic pine forests. As early as 1876 the Canadian lumber entrepreneur James Little argued that those cutting the Great Lakes forests were "not only burning the candle at both ends…but cutting it in two, and setting the match to the four ends to enable them to double the process of exhaustion." In the next three decades, the spread of such fears, reflected in increasing prices and decreasing sawlog size, prompted the development of professional forestry and the creation of what became the national forest system. Although federal lands never accounted for more than one-fifth of the national timber harvest, their existence reflected the concern that private enterprise was unable to use timber resources on a sustainable basis.

The industry's rapid growth also created a large demand for labor. Logging itself remained a winter activity until the twentieth century. Work crews, consisting largely of farmers idled by the season, moved into place in late fall and early winter, working until spring thawed the waterways and called them home to plant their fields. Before the Civil War, crews consisted of around a dozen men, but the postwar florescence gave rise to camps of as many as several hundred. Loggers lived amidst the trees to be harvested, generally in temporary wooden structures. Their isolation and the perennial cash flow problems for the still seasonal cutting meant that many were paid in company store scrip or abruptly were fired in economic downturns and periods of low stumpage price. Work in the mills and yards was year-round by contrast. By the dawn of the twentieth century, immigrants made up most of the lumber industry's workforce. Large waves of strikes swept through timber country in the 1910s, resulting in sporadic wage increases and amelioration of working conditions. Organized labor secured an institutional presence in the industry in the 1930s and 1940s.

The development of new technologies created some changes in the nature of timber labor. Sawmills became increasingly mechanized. In the early nineteenth century, the machine-driven circular saw replaced the water-driven "muley saw," but the circular saw was replaced later by the more efficient and more expensive band saw, essentially a giant chainsaw fixed in place. The process of logging continued to rely on axes and handsaws to fell trees well into the twentieth century, until the post–World War II mass adoption of portable chainsaws. Trucks and forest roads allowed the cutting of less accessible areas, especially in the mountainous West. In the last decades of the century, the most heavily capitalized logging outfits began using large machines able to cut trees, delimb them, and stack them for transport to the mill. With such equipment, loggers were able to cut ten times more stumpage than their predecessors.

In the twentieth century, the lumber industry lost most of its frontier characteristics. Although Alaskan forests began to produce large volumes of timber, the exhaustion of most of the continent's uncut woods forced companies to make already-cut lands productive again. Remaining stands of old-growth forest were still lucrative targets for cutting, but by the 1960s, federal lands policies and environmentalist opposition removed many of these tracts from timber harvesting. Forest nurseries, tree farms, and reforestation efforts became essential to the industry's survival. Indeed, in the South intensively managed tree plantations largely replaced the management of natural forests for timber production. Moreover new wood products, such as pulp for paper manufacture, plywood, and wood fibers for wallboard and insulation, allowed companies to shift their focus from cutting large softwoods such as the white pine to using a much greater variety of trees, particularly the species that replaced pines in the most heavily cut regions. At the end of the twentieth century, the Southeast and Northwest were the most important lumber-producing regions, and imports accounted for nearly one-third of national softwood consumption.

BIBLIOGRAPHY

Chase, Alston. In a Dark Wood: The Fight over Forests and the Rising Tyranny of Ecology. Boston: Houghton Mifflin, 1995.

Cronon, William. Changes in the Land: Indians, Colonists, and the Ecology of New England. New York: Hill and Wang, 1983.

———. Nature's Metropolis: Chicago and the Great West. New York: Norton, 1991.

Hidy, Ralph W., Frank Ernest Hill, and Allan Nevins. Timber and Men: The Weyerhauser Story. New York: Macmillan, 1963.

Holbrook, Stewart. The American Lumberjack. New York: Collier, 1962.

Larson, Agnes M. History of the White Pine Industry in Minnesota. Minneapolis: University of Minnesota Press, 1949.

Williams, Michael. Americans and Their Forests: A Historical Geography. New York: Cambridge University Press, 1989.

Benjamin H.Johnson

See alsoConservation ; Forestry .

lum·ber¹ / ˈləmbər/ • v. [intr.] move in a slow, heavy, awkward way: a truck filled his mirror and lumbered past | [as adj.] (lumbering) Bob was the big, lumbering, gentle sort | fig. a lumbering bureaucracy. lum·ber² • n. timber sawn into rough planks or otherwise partly prepared. • v. [intr.] [usu. as n.] (lumbering) cut and prepare forest timber for transport and sale: the traditional resource industries of the nation, chiefly fishing and lumbering.

lumber2 useless odds and ends XVI; roughly prepared timber XVII. poss. f. LUMBER1, but later assoc. with lumber(house), Lumber Street var. of lombard (XVII) pawnshop (considered as a storehouse of odds and ends); see LOMBARD.

lumber1 move clumsily or heavily. XIV (lomere). perh. of symbolic orig.

lumber. Timber sawn and split for use.

lumber •blubber, clubber, grubber, lubber, rubber, scrubber, snubber •Columba, cumber, encumber, Humber, lumbar, lumber, number, outnumber, rumba, slumber, umber •cucumber • landlubber •Addis Ababa • Córdoba •Aqaba • djellaba • mastaba •Berber, disturber, Djerba, Thurber