Although 2 people could argue whether trees originated via evolution or design, they and everyone else must concur that trees exist … a lot of them … not only in numbers around the globe, but in various characteristics like species (over 23,000 worldwide), heights (sequoias over 375 feet tall), density, unit weight, age (bristlecone pines nearly 4,750 years old), grain, and color, as well as their ability to be worked and finished. By one estimate, 1/3 of the US is covered by forests having almost 247 billion trees over 1 inch in diameter. Wood is used extensively in construction from non-descript internal wall blocking to highly aesthetic wall paneling or door veneers. Several exotic species of domestic and international wood used for finished products were observed when the CSI Pittsburgh Chapter recently visited a local wood distributor who markets nationally.
This distributor stocks approximately 125 wood species, about 40% domestic and 60% imported. Although their most popular exotic wood is African walnut, they also had a number of African mahogany slabs that were 8/4 thick by 24 inches wide by 12 feet long at $9.00 per board foot to Pink Ivory, the most expensive, at $150.00 per board foot. Two definitions seem necessary with that last sentence: one is wood thickness, which is generally measured in quarters (x/4), where a piece of wood 4/4 is 1 inch thick and a 6/4 piece is 1-1/2 inch thick; and board foot, which is defined as a three-dimensional unit of measure where the volume is one square foot (one-foot length of a board by one foot wide) by one inch thick, which translates to 1 ft × 1 ft × 1 in = 12 in × 12 in × 1 in = 144 in³ or 1⁄12 ft³. Board Feet can be calculated as BF = W x T x L / 12, where BF = board feet, W = nominal lumber width (in), T = nominal lumber thickness (in), and L = nominal lumber length (ft). Most flooring, siding, and paneling are sold by the square foot, a two-dimensional unit of measure, which is the length x width, regardless of the thickness. A board foot will exactly match a square foot only when the thickness is 1 inch. On occasion, wood might also be sold by the linear foot, a one-dimensional unit of measure using length only. There are other rules based on whether: hardwoods or softwoods are being measured; wood lengths are shorter or longer than a whole number, i.e., 10’-0”; and lumber size is measured by nominal or actual dimensions.
When used for flooring, a stronger type wood that does not dent is better. One can relate hardness among woods via the Janka hardness test, which measures the resistance of a wood type to withstand denting and wear. It measures the pounds - force (lbf) required to embed an 11.28 mm (0.444 in) steel ball into wood to half the ball's diameter, obviously leaving an indentation in the wood. Out of 109 woods listed on one internet site where tests were performed according to ASTM D 1037 methods, the hardest is Australian Buloke, a species of ironwood, at 5060 lbf; ipe, a Brazilian type walnut used frequently for exterior decks, at 3684 lbf; stranded bamboo, technically a grass, at 3000 lbf; red oak at 1290 lbf; Douglas fir at 660 lbf; balsa at 100 lbf; and cuipo, the softest wood in the world, at 22 lbf.
Depending on its use and cost, exotic wood is used as an exposed veneer in a panel, such as on doors. The finest and rarest logs are sent to companies that produce veneer, which is accomplished either by ‘peeling’ the trunk of a tree or by slicing large rectangular blocks of wood known as flitches. The advantage to this practice is twofold: first, it provides the most financial gain to the log’s owner; and secondly, and of more importance to the woodworker, it greatly expands the amount of usable wood. While a log used for solid lumber is cut into thick pieces, usually no thinner than 1-1/8 inches (3 cm), veneers are sometimes cut as thin as 1/40 of an inch (0.6mm), the thickness used on flush wood doors.
The following are miscellaneous comments made by the distributor during our visit of their warehouse and woodworking shops: occasionally a project will require FSC rated wood to meet LEED requirements, but doing so will generally cost from 10% - 30% more due to higher amount of waste; soft wood has a higher amount of resin versus hard wood; ipe is very dense, will sink in water, and will not be bothered by insects; purpleheart is really purple in color, yellowheart is very yellow in color, and yellow sandher is actually orange in color. There were a number of elegant fine grained woods such as sapelle and white limba. Before the tour, I looked on the internet for different exotics and was struck by something called snakewood; it turns out the distributor had a half log of that species, but I did not notice that listing on the handout until after leaving the distributor’s facility.
Most wood species can be found on various internet websites. Following are a couple of exotic veneers to show ranges of various characteristics.
zebrawood (central America - Honduras, Nicaragua, & Brazil). Also known as Zebrano, which is imported from central Africa, (Gabon, Cameroon, and Congo). Pronounced dark stripes on straw colored background.
Miscellaneous Tree Facts: In one day, a large tree can lift up to 100 gallons of water out of the ground and discharge it into the air. One large tree can provide a day's supply of oxygen for up to four people. Most trees do not have a tap root or have roots that grow very deep but have roots that are in the top 12 inches of soil, sometimes extending two to three times the tree width. Trees receive an estimated 90% of their nutrition from the atmosphere and only 10% from the soil. No tree dies of old age, but is generally killed by insects, disease, or by people. One tree can absorb as much carbon in a year as a car produces while driving 10,000 miles. Burls are tree growths where the grain has grown in a deformed manner, commonly found in the form of a rounded outgrowth that is filled with small knots from dormant buds, and which can create an interesting aesthetic.
Odds and Ends: A local Pittsburgh building, The August Wilson Center for African American Culture, opened in the fall of 2009 and has first floor wood paneling and flush wood doors fabricated from zebrawood, a truly striking aesthetic. Lastly, I have a close friend who likes to smoke pipes with about 100 pipes in his collection. My favorite and the most exquisite is constructed from tiger maple, a wood species not previously known to me. My hope prior to retirement is having several projects where exotic woods species are selected and therefore need to be specified.
[PS. Upon completion and review of this blog entry for posting, I just read the article “The New Wood” on pages 18 - 27 in the December 2012 issue of The Construction Specifier, which has additional information on wood veneers, panel cores, and LEED related information. This issue should be downloadable from the CSI website.]