Engineered Wood Products

From www.forestworld.com

Wood products are an integral part of our lives. We use more wood by weight than all plastics, metals, and cements combined. North America’s demand for lumber, panels, paper, and other wood products continues to increase. Explosive population growth and per capita consumption are contributing to even greater demand as we enter the next millennium.

Living sustainably means meeting our material needs by choosing renewable resources whenever possible. Converting non-renewable raw materials into useful products takes more energy, while creating more waste and pollution. Engineered Wood Products are allowing us to make even better use of our available forest resources. Excellent wood products are now being produced from smaller, lower quality, and once undesireable trees.

Although we’ve been harvesting wood in the forests of America for four centuries, growth now exceeds harvest by 35%! Despite the increasing volume of standing timber, much of today’s timber is second and third growth. This means wood that is less stable and more prone to warping than that from increasingly unavailable old growth. However, through technology we are finding ways to effectively and efficiently utilize smaller, faster growing, and lower quality trees to make excellent products.

Glued Engineered Wood Products are manufactured by bonding together wood strands, veneers, lumber or other forms of wood fiber to produce a larger composite material. Engineered Wood represents the culmination of centuries of forestry (and wood-working) knowledge, modern technology, and efficient use of our natural resources.

Many factors are contributing to the remarkable growth of Engineered Wood Products. These products are cost-effective, easy to use, environmentally sensitive, strong, and their predictable qualities lead to less rework. The performance advantages of these building materials are becoming increasingly accepted by builders.

APA - The Engineered Wood Association develops and maintains industry standards for glued Engineered Wood Products. These are classified into four general groups:

The most widely used Engineered Wood Products are structural wood panels. They may be the most versatile also, being used in scores of construction and industrial applications. The three major types are plywood, oriented strand board (OSB), and composite panels.

Structural Panels are used for many applications, from siding, to floor, wall, and roof sheathing, single-layer flooring, soffits, stair treads and risers, webs for wood I-joists, concrete forming, pallets, crates, bins, transportation equipment, furniture, and boats. In 1980, North American Structural Wood Panel production was 19.3 billion square feet. By 1994, this had grown to 32.6 billion square feet.

The original structural wood panel, plywood, consists of veneers arranged in perpendicular layers. The layers may consist of a single veneer ply or two or more plies laminated with the grain running in the same direction. There are usually an odd number of layers, with the grain of the face layers typically oriented parallel to the long dimension of the panel. It is the cross-laminated layup of layers of veneer that gives plywood its excellent strength, stiffness and dimensional stability. In addition to a variety of sheathing, siding, sanded and concrete form grades, many manufacturers can produce custom layups for specialized applications. However, the demand for plywood is forecast to decline in the coming years, as the demand for OSB continues to grow rapidly.

OSB consists of wood strands bonded with adhesives to form a mat. Like the veneer in plywood, these mats are layered and oriented perpendicular to each other for maximum strength, stiffness and stability. The individual strands are typically three to four inches long. OSB is widely used as construction sheathing, as the web material for wood I-joists, as the structural membranes of structural insulated panels, and in a growing number of other applications. Its popularity is reflected in the great number of new OSB mills being built, and in the plant expansions of several current major OSB producers. In 1995, the wholesale value of OSB production surpassed $3 billion, an increase of 50% over the last 10 years. Performance-rated OSB is approved by all major North American model building code associations.

Structural composite panels consist of veneer faces bonded to a wood-base core material, such as OSB. The structural composite panels are manufactured in three- or five-layer arrangements. A three-layer panel has a wood fiber core and a veneer face and back, while a five-layer panel also has a veneer crossband in the center. When manufactured in a one-step pressing operation, voids in the veneers are filled automatically by the particles or strands as the panel is pressed in the bonding process. Typical composite panel applications include sheathing, siding and industrial applications, but they aren’t as common as plywood and OSB.

Glulam is an engineered stress-rated product created by bonding together individual layers of lumber having a thickness of two inches (50 mm) or less. Individual pieces of lumber in these layers are finger-jointed together to create long lengths referred to as laminations. These laminations are then face-bonded together to create the finished product. Glulam is also among the most versatile of the engineered wood products. It can be shaped into forms ranging from straight beams to complex curved members, and is used in a wide variety of residential and nonresidential building construction applications, including headers, floor girders, ridge beams and purlins, cantilever beam systems, arches, domes and exposed applications such as bridges, marinas and utility structures.

Since we’re using a wider range of lumber resources to produce glulams, we’re minimizing the demand on fiber from older growth forests. Large, wooden beams can be made from the lumber that is produced from smaller trees. Some of the largest wood structures in the world have been framed using glulam components. And it’s popularity and strength are only getting better. Research into using synthetics and laminated veneer lumber (LVL) to improve performance and lower the cost is under way at a number of university, government, and industry laboratories. U.S. production of glulam beams grew from 259 million board feet in 1994 to 276 million board feet in 1995.

This group includes laminated veneer lumber (LVL), parallel strand lumber (PSL), and oriented strand lumber (OSL).

LVL is the most widely used of the structural composite lumber products, particularly in header and beam applications. It is produced by bonding thin wood veneers together in a large billet so that the grain of all veneers is parallel to the long direction. The LVL billet is then sawn to desired dimensions depending on the construction application. Some of the product’s many uses are headers and beams, hip and valley rafters, scaffold planking, and the flange - or edge material - for prefabricated wood I-joists.

North American production of LVL is expected to increase from 35.5 million cubic feet in 1995 to nearly 60 million cubic feet by the year 2000. It will undoubtedly continue to be the main flange component for prefabricated wood I-joist and the product of choice for such applications as scaffold planking where a high degree of structural reliability is essential. The strength of LVL is very predictable.

PSL consists of long veneer strands laid in parallel formation and bonded together with an adhesive to form the finished structural section. Like LVL and glulams, this product is used for beam and header applications where high bending strength is needed. PSL is also frequently used as load bearing columns.

Similar to PSL, oriented strand lumber is made from flaked wood strands that have a high length-to-thickness ratio (much longer than they are thick). Combined with an adhesive, the strands are oriented and formed into a large mat or billet and pressed. OSL is used in a variety of applications from studs to millwork components.

Prefabricated Wood I-joists, used extensively in residential construction, continue to be the fastest growing of the Glued Engineered Wood Products. Although these products have been available for more than 25 years, their use has seen significant growth in all markets during the past decade as design professionals and builders have become more familiar with the inherent advantages associated with I-joists.

Also referred to as I-beams, wood I-joists are structural, load-carrying products. I-joists are typically available in long lengths up to 60 feet, and because they are very light, they can be easily handled at the job site without the need for costly handling equipment. Their I configuration provides high bending strength and stiffness characteristics. The flange material for I-joists is typically dimension lumber or LVL: the web material is OSB or plywood.

The supply of high quality wide dimension lumber for floor joists is expected to continue its decline, creating a ready market for I-joist growth. APA has developed a performance standard for residential floor wood I-joists that is expected to result in a market share increase from approximately 20% in 1996 (for U.S. residential floor construction) to as much as 50% by the year 2000.

An engineered wood product which doesn’t fit into the above groups is called Finger Jointed lumber. This is usually 2 x 4 or 2 x 6 lumber stock from which all the defects, such as knots, are removed - resulting in shorter clear pieces. Defect free lumber is then joined together with glue and special tight-fitting interlocking joints. There are various styles of cuts used, but contrary to popular thought, the strongest part of these beams is always at the joints. Since they are made of short straight sections, they resist twisting.

The use of finger-jointed studs have expanded as its use becomes more popular among homebuilders. Western Wood Products Association, or WWPA, provides grading services to more finger-jointed lumber producers than any other agency in North America.

The most significant non-structural engineered wood products are particleboard and medium density fiberboard (MDF). Particleboard is a wood panel product that is used widely in the manufacture of furniture, cabinets, floor underlayment in home construction, and in many other applications. MDF is made in much the same way as particleboard, however the surface is flat, smooth, uniform, and denser. MDF allows intricate and precise machining and finishing techniques for superior products, such as stereo cabinets and relieved door fronts and mouldings.

Particleboard was developed in the United States and Europe during the 1930’s. Germany, with a lack of wood panel material, quickly moved into commercial production in 1941. The parallel development of urea formaldehyde and phenol formaldehyde resins for the bonding agents was an important advancement.

Particleboard is a wood panel product consisting of wood particles of various sizes that are bonded together with a synthetic resin or binder under heat and pressure. The recovery and use of residual wood in the manufacture of particleboard and MDF helps to make optimal use of our forest resources. Wood chips, edging, and planer shavings are all utilized.

Medium Density Fiberboard has been one of the most rapidly growing composite board products to enter the world market in recent years. MDF is made by rubbing apart fiber bundles instead of mechanically breaking them apart, as in preparation for particleboard. MDF is an excellent substitute for solid wood in many interior applications except where the higher stiffness of solid wood is required.

MDF has grown in favor to become a premier substrate for wood veneer, vinyl films, low and intermediate basis weight papers, resin-saturated papers and heat transfer foils. This is due primarily to its smooth surface, and edge finishing qualities. MDF is uniform throughout. (A substrate is a material that provides the surface on which an adhesive or coating is spread).

When wood is combined with other materials such as gypsum, cement and plastic we end up with composite building materials. There are quite a few new products coming out in this market. Many of them have characteristics that fill a unique niche in the building products industry.

One of our greatest needs is an ability to fully understand and appreciate exponential growth. If we divide the number 70 by the compound annual growth rate of anything, we automatically get its doubling time. The world population is currently growing at 1.48% annually, therefore its doubling time would be (70/1.48) 47.2 years if this rate held constant. World wood consumption is growing even faster than population.

Wood is a renewable resource, but we have to manage it sustainably. More wood, especially large, old, and high quality trees, are being put off-limits to harvesting. Yet wood is the most environmentally sound building material when compared to plastics, metals, and cements. This is where engineered wood products come in. We can employ technology to utilize traditionally less desirable species, smaller trees, and lower quality trees to engineer excellent wood products. This is the good news.

• Homeowners in high-risk coastal areas found that by using high-strength Engineered Wood framing materials, able to withstand higher wind speed, their insurance costs were lower.
• Analysis of earthquake damage in California and Japan revealed that panel sheathed wood frame structures fared better than did masonry and concrete building.
• When time constraints arose, the 1996 Olympics’ Centennial Olympic Park pavilion was built with engineered lumber.
• Pound for pound, wood is stronger than steel because it has a more favorable strength to weight ratio.
• A board foot, or 12 x 12 X 1, is the basic unit of measurement for lumber. Panels, on the other hand, are measured in more familiar square feet.
• The average size home these days is 2,085 square feet. A home that size uses about 13,125 board feet of lumber.
• Approximately one third of all new single family homes are manufactured homes.