April 14, 2004
ITDPT 303
McKeever (1997) characterized the history of engineered wood product started coming about in the early 1900's and softwood plywood was the first product . As of 1996, there were 32 mills in operation, down about 25% from 1965. Also since 1965 the annual capacity is down more than half because of the reduction of harvest on public land in 1980. Both mills on the coast and inland have seen a decline in the size of the logs. The inland mills average about 16 to 20 inches meanwhile the coastal mill are about 12 inches diameter.
"OSB is made from wood fibers that are arranged in a precisely controlled pattern, coated with resin, and compressed and cured under heat" (Jefferis and Smith 2002). McKeever (1997) states that Oriented Strand Board (OSB) comes in sheets that are 4' x 8' that are used in construction as sub-floors, sheathing on roofs, and on exterior walls for strength and to have something to attach the exterior finish such as siding. Canada was the first to produce OSB in 1964. Since then the productivity of OSB has been growing rapidly. In 1996 the rate had nearly doubled since 1990 also since then the number of mills went up by nearly 50%. The logs that are being harvested for the purpose of OSB in the western mills average about 10-12 inches in diameter, in the south about 8 inches in diameter, and in the north about 6-12 inches, all use some form of pine. According to Jefferis and Smith (2002) the pattern is laid at random but in a controlled manner were the grain is laid in the same direction. The glued used is phenol resorcinol formaldehyde.
Bailey
Skog
LVL stands for laminated veneer lumber. Some of the major uses for LVL are in headers, rafters, and wood I-joist (McKeever 5). Headers are horizontal members that supports the weight above a door, window, or any openings in a wall (Jefferis and Smith 2002). Rafters are inclined members that go on top of walls that support the weight of roof. Wood I-joist are used to support the weight of the floor or floors, any walls, and any dead or live weight. "LVL is made from ultrasonically graded Douglas fir veneers that are laminated with exterior grade adhesives under heat and pressure, with all grains parallel to each other" (Jefferis and Smith 2002). Jefferis and Smith (2002) states there is also some different forms of LVL some of them are PSL and OSL. PSL stands for parallel stand lumber and is made from laminated veneer strips. OSL stands for oriented strand lumber and is made with wood shavings. Both PSL and OSL are glued, compressed, and heated. The some of the reasons for the increasing use of laminated products is that they are stronger, come in a verity of sizes and shapes, they can be finished just like wood, and the lack of large trees. LVL, PSL, and OSL all use the same glue phenol formaldehyde. But PSL also adds a mixture of wax to restrict the moisture. According to the EML, the reason that we know that the wood is stronger is because of the different test that are done to the wood like bending , compression, and shear forces. The forces that are applied are by hydraulic and screw driven machines and the woods are tested until they collapse. A computer analysis provides manufacturing specifications for the structural integrity.
According to the State of California Air Resources Board, one big problem linked to engineered wood products in the past was because of the use of urea formaldehyde. Urea formaldehyde was considered to be a major source of indoor air pollution. Formaldehyde is an important chemical that was widely used by industry to manufacture building materials during 1970 until 1985. “These wood products are used extensively in the construction on conventional and mobile homes and are found in sub-floors, cabinets, shelves, hardwood wall paneling, laminated flooring, and doors.” Formaldehyde emissions are the highest when the products are new. Because homes today are constructed to be more energy efficient, they are more air-tight and do not allow much fresh air in or contaminated air out. If there any volatile organic compounds (VOC) in the air it maybe a problem.
McKeever said that the manufactures of the new technology of pre-engineered wood products hope that the can get their products into the construction of commercial building. With commercial building construction in 1995 was estimated about $299 billion that was 56% of all construction in the United States. With that kind of money out there know wander they want some of it. Even though the manufactures know that it will be hard to penetrate the ground levels because of the rotting of wood. Of all commercial construction only 1% used wood on the ground level. The place that manufactures want part of is anything above the ground level. With the use of wood the upper stories was 14%, exterior walls 10%, interior walls 13%, roofs 19%, and some exterior siding. One major reason that the roofs use more pre-engineered wood is that in some commercial building the owners want to have some form of shingles or something that is easier to attach to wood products.
McKeever
Sources:
USDA Forest Products Laboratory. Engineering Mechanics Laboratory Testing and Analysis (EML): (n.d.) Madison, WI. http://www.fpl.fs.fed.us/eml/tests.htm
USDA Forest Products Laboratory. Engineering Mechanics Laboratory Testing and Analysis (EML): (n.d.) Madison, WI. http://www.fpl.fs.fed.us/eml/machines.htm
Formaldehyde in The Home. Indoor Air Quality Guideline. Sept., 1991. April 14, 2004 http://www.arb.ca.gov/research/indoor/formald.htm.
Jefferis, Alan: Smith, Kenneth D. AIA. (2002). Commercial Drafting and Detailing. Delmar, A Division of Thomson Learning, Inc., 2nd Edition: Albany NY.
McKeever, D. B. (1997). Engineered wood products: A response to the changing resource. Pacific Rim Wood Market Report, No. 123, November: p. 5, 15. Gig Harbor, WA. April 14, 2004 http://www.fpl.fs.fed.us/documnts/pdf1997/mckee97b.pdf
McKeever, D. B. (1995). Wood products used in new nonresidential building construction. Prepared for the Wood Products Promotion Council; April 14, 2004 http://www.fpl.fs.fed.us/documnts/pdf1998/mckee98b.pdf
Skog, K. E. (1995). Wood products technology trends: changing the face of forestry. Journal of Forestry, Vol. 93 No. 12, December: p.30-33. April 14, 2004 http://www.fpl.fs.fed.us/documnts/pdf1995/skog95a.pdf
Bailey, Glenn (1996). OSB for the Forest Products unit. Department of Forestry, Australian National University: April 14, 2004 http://sres.anu.edu.au/associated/fpt/osb/2.html