WOOD

• It is the hard, fibrous substance found beneath the bark of trees and shrubs.

• It is valued in construction because of its varied properties and availability.

• The products of different trees differ in color, density, grain pattern, hardness, texture, and strength.

• Wood is classified as hardwood or softwood, but these terms bear no relation to actual hardness.

WHAT IS WOOD?

• Wood have been one of our most important building materials from early Paleolithic times, both for building and manufactu8re of tools, weapons, and furniture.

• From the earlier times, the use of wood involved consideration of quality, cost and availability, as well as the intended use of product.

• From the tenth to the eighteenth centuries in Europe, wood was the material primarily used for buildings, tools, machines, mills, carts, buckets, shoes, furniture and barrels, to name just a few of the thousands of kinds of wood products of the time.

• Most of the machines and inventions to make possible the machine age were formed of wood during the period.

HISTORY OF WOOD

• Wood has historically played a key role in the transportation of people and their possessions, both as a fuel and as a raw material.

• Sledges made of wood were used in northern Europe as early as 7000 BC.

• Wood for water transport evolved from the early barges and hollowed out logs of 4500 BC to the sleek sail-powered clipper ships of the mid nineteenth century. Steam for power and steel for ship construction made that uneconomical by the end of the century, however.

• The architecture from the early colonists from Europe used wood intensively, adapting the concepts used in their homelands to the cultural conditions of the times and the availability of materials.

CONT. HISTORY

• Wood has been the dominant material for furniture construction since early times. Decoration and style of furniture have evolved as part of the artistic, cultural and technical development of society. Design and complexity were greatly enhanced by the development of copper tools. Efficiency and economy of wood use were spurred by the gradual depletion of fine furniture woods and increasing international trade in both furniture and the woods from which it was made.

CONT. HISTORY

• Hardwoods are produced by broad-leaved trees, such as:

ASH LINDEN BEECH TEAK OAK

• Most hardwoods usually go into furniture.

HARDWOODS

• Softwoods are obtained from conifers, or needle-leaved trees such as:

SPRUCE DOUGLAS FIR PINE RED CEDAR• Most softwoods are used for building construction.

SOFTWOODS

• Wood is essentially composed of:

- cellulose

- hemicelluloses

- lignin

- extractives

COMPOSITION OF WOOD

TABLE OF CHEMICAL COMPOSITION

Chemical Composition of Some Wood Species

• Cellulose constitutes 70% of the dry cell wall and is more important economically.

• It is a polymerized carbohydrate; many glucose molecules are linked together in long chains to form macromolecules.

• The cellulose becomes arranged in long, threadlike fibrils. The cellulose in this fashion is as strong as an equivalent thickness of steel.

• Lignin fills the spaces within the cellulose network. • Lignins also add rigidity to the cell wall.

CELLULOSE AND LIGNIN

• Wood is a poor conductor of heat and therefore useful as an insulator.

• It does not conduct electricity.• Moreover, wood can be recycled many times.

It is easy to fasten, shape, smooth, and reshape, and it is enduring.

• Wooden structures many hundreds of years old have remained in good condition with minimal care.

PROPERTIES OF WOOD

• Different woods have different uses because the properties of wood differ from species to species.

• Density, the weight per unit volume, is compared to an equal volume of water to yield the specific gravity.

• Most woods have specific gravity less than 1.0—they are lighter than water and therefore float—because of the numerous air spaces.

DENSITY

• The hardness of wood, which varies greatly, refers to the resistance of a wood to saw or an ax across the grain.

• Hardness is dependent primarily on weight, degree of seasoning, and the structure of the wood elements.

HARDNESS

• Durability is the ability of woods to resist decay, insect infestation, chemicals, fungi, and marine organisms.

• The most decay resistant species are often used where decay could be a problem.

• Catalpa, cedar, chestnut, black locust, and Osage orange trees are resistant to decay; aspen, cottonwood, fir, and willow are prone to decay.

DURABILITY

• Wood grain, or the arrangement of the cells, is specific to each species and is a desirable property in decorative wood.

• When a log is cut, different grain patterns are visible, depending on whether the wood is cut perpendicular to the grain (crosscut) or parallel to the grain.

• Parallel cut can be either along the radius of the log or tangential to the log.

WOOD GRAIN

• Contract with heat and moisture• Have lower density than hardwoods (good for acoustic &

thermal insulation)• Good for interior finishes & for furniture• Solid but soft• Flexible and strong• Not water resistant• Cost: low

PROPERTIES OF SOFTWOOD

• Contract with heat and moisture • Stronger, denser, & homogenous than hardwoods (good

fro framing system)• Good for interior finishes & for furniture • Resist fire better than softwood • Nearly impervious to water (some varieties)• Cost: high

PROPERTIES OF HARDWOOD

COMPARATIVE ANALYSIS

• LUMBER. Waste materials from logs , including edgings, trimmings, shavings, and sawdust, are used extensively.

• For example, slabs and trimmings are used for pulp and particleboard, and bark as mulch.

• Pulpwood is used mostly for paper. One source of pulpwood is from timber species unsuitable for lumber.

• Chips and sawdust from the milling process are also used, as are selected eastern hardwoods.

FUNCTION OF WOOD

• FUELWOOD. In North America only 10% of the timber harvest is used for fuel.

• Usage is increasing, however, because of rising costs of petroleum products.

• VENEERS, PARTICLEBOARD, AND PLYWOOD. These wood products are used in construction for facing large areas and in the manufacture of furniture.

• Veneers and plywood are both thin, laminar pieces of wood glued together to form a strong product.

• Particle board is composed of wood chips and shavings combined with a bonding agent to form panels.

• Veneer is a thin slice of log cut in sheet form. • Other veneers are glued together in layers with the grain of

one layer lying perpendicular to that of the next. This strong, durable product is called plywood.

FUNCTION OF WOOD

• POST, POLES, AND PILINGS. Close to 500 million posts, poles and pilings are required each year in the United States.

• Fence posts are usually made from cedar, cypress, Osage orange, or black locust because of their durability.

• Douglas fir, southern pine, and lodgepole pine are favored for telephone poles.

• RAYON. Rayon, the first commercially produced synthetic fiber, is still used for textiles and tire cord. In rayon production, pulp is broken down chemically to free the cellulose, processed, hardened into fine filaments, and spun together to form rayon thread or yarn.

FUNCTIONS OF WOOD

FLOORING

APPLICATIONS OF WOOD

Wood flooring is any product manufactured from timber that is designed for use as flooring, either structural or aesthetic.

DOORS AND WINDOWS

APPLICATIONS

OUTDOOR DECK

CEILING PANEL AND JOISTS

RAILING AND BALUSTRADE

EXPOSED STRUCTURAL MEMBER

PANELING

FURNITURE AND CABINETS

STRUCTURAL MEMBERS AND FRAMING

WOOD ARTICULATION

WOOD ARTICULATION

WOOD ARTICULATION

WOOD INSTALLATION

INSTALLATION SYSTEM:• Tongue-and-groove: One side and one end of the plank have a

groove, the other side and end have a tongue (protruding wood along an edge’s center). The tongue and groove fit snugly together, thus joining or aligning the planks, and are not visible once joined. 

• “Click Systems”: there are a number of patented "click" systems that now exist. These click systems are either "unilin" or "fiboloc" A "click" floor is similar to tongue-and-groove, but instead of fitting directly into the groove, the board must be angled or "tapped" in to make the curved or barbed tongue fit into the modified groove. No adhesive is used when installing a "click" floor, making board replacement easier.

• Floor connection system: There are a wide range of connection systems, as most of them are mill-specific manufacturing techniques. The general principle is to have grooves on all four sides of the plank with a separate, unconnected, piece that is inserted into the grooves of two planks to join them. The piece used for the connection can be made from wood, rubber, or plastic. 

TONGUE-AND-GROOVE INSTALLATION

CLICK SYSTEM INSTALLATION

FLOOR CONNECTION SYSTEM INSTALLATION

WOOD FABRICATION