For thousands of years, humans have used wood as a primary building material for homes, businesses and public buildings of all types. Wooden churches in Norway built in the 12th and 13th centuries still stand today, and wooden homes from the 1600s can be found in the New England states.
Carpenters and skilled craftsmen have long valued wood for its many benefits. In 1848, William Brown wrote in The Carpenter’s Assistant, “The substance named wood is, for the most part, elastic, tenacious, durable, and easily fashioned – qualities which cause it to be in general request for articles of use and of luxury.” Today’s homebuilders rely on wood for the same reasons.
While wood has a long history of use in buildings, improvements in manufacturing and testing have resulted in a more consistent material and a greater understanding of how it performs in structures. The basic material remains the same, but technological advances in forestry, saw milling and processing have taken a trusted product and made it even better.
The hassle of culling through piles of lumber looking for straight boards, trimming or working around splits or wane (rounded, barked edges), and dealing with call-backs after installation may soon be a memory. Manufacturers are now beginning to offer lumber with enhanced performance characteristics. Such specially manufactured, sorted and packaged lumber in the future will be offered under brand names, rather than as a standard commodity, so builders know at a glance that it’s a superior product.
Whether used for stick-built construction, or in pre-built panelized framing components and systems, modern specialty lumber helps builders construct quality homes with greater ease.
To the Source: Advances in Forestry
When picking up a piece of solid lumber to saw, drill or nail, builders typically don’t think about the science and research that have gone into producing it. Centuries ago, builders felled their own timber, using whatever trees happened to be nearby. The condition and usability of the resulting boards varied significantly.Modern specialty lumber starts with laboratory research and careful selection of seeds and seedling trees, which are then grown in nurseries under carefully controlled conditions, then hand planted and monitored over time. In cultivated forests, trees that develop bends or twists are thinned and used for other products. When harvested, logs are evaluated and graded, with the most appropriate ones for lumber use sent to saw mills. In addition to managing forests for the quality of the trees and resulting lumber, modern forestry practices emphasize forest replanting and independent environmental certification of growing and logging operations.
Optimizing Quality at the Sawmill
Many people in the building industry have visited a sawmill at some point during their careers. But, those who have not been to a mill in recent years may be surprised at how dramatically lumber production has changed. Unlike the noisy mills of years past, coated in sawdust, a contemporary sawmill is a precision manufacturing plant where each step in the process is tightly managed.
In the most advanced mills, manufacturers employ 3-D scanning technology to evaluate each log. In a matter of seconds, computer-controlled equipment scans the log, checking the overall contour and presence of knots and surface irregularities or defects that could affect the quality of the finished lumber. Sophisticated computer programs then determine the optimum size and configuration of boards that can be obtained from the specific log. This process helps ensure that maximum yield of the available material is achieved and that the resulting products meet customer and quality control expectations.
After scanning, automated equipment orients the log and guides it through chipping and sawing machinery. Saws accurately rough cut the boards to pre-determined specifications, typically within ten-thousandths of an inch.
Optimizing Quality at the Planer
Rough-sawn lumber, either green or kiln dried, is processed through a planer to exact finished dimensions and is graded according to industry standards. Grading is done to match customers’ needs and the product application. Specifically, some applications, such as pre-built trusses and wood laminated beams, require tighter tolerances than others. Recent advances in the development and installation of computer-assisted grading has dramatically improved the consistency of visual quality characteristics in lumber packages. Likewise, technological advancements in grading individual boards for strength performance have resulted in more efficient use of the forest resource and enhanced reliability in highly demanding engineered applications. The result is a more precise understanding of the strength of each piece than is possible with visually graded lumber. To ensure all lumber is evaluated consistently between manufacturers, third-party agencies provide an independent check of all grading processes.
Drying Helps Ensure Lumber Consistency
Not every sawmill delivers the same quality. Careful attention to kiln drying the rough-sawn lumber before it is planed results in more stable lumber with a lower risk of warping and twisting after installation in the home. Because of large natural variations in the moisture content of lumber, and natural shrinkage characteristics as lumber dries, the challenge is to dry it in a manner that achieves a consistent end product. While industry standards require 19% or less moisture content, close monitoring of the process and drying details provides tighter moisture control and sets one sawmill apart from another.The Future of Lumber
Recent progress in lumber processing is helping builders enjoy the time-tested benefits of wood construction, while addressing some of the previous challenges and limitations. Looking ahead, lumber manufacturers are continuing to work with builders and dealers to better understand their needs and to develop further innovations in lumber products. What has historically been a commodity material with variable quality and characteristics is continually being refined through technology to meet the requirements of today’s homes.Looking further ahead, advances in lumber will likely include additional research on how solid-sawn lumber and engineered wood products can be designed to work even better together. As science helps increase our understanding of the performance characteristics of different materials, they can be further engineered and manufactured to optimum performance in the structural frame. Even today, builders can combine both types of lumber to create cost-effective, engineered solutions. Other promising developments include enhanced evaluation of the characteristics of each board to identify and eliminate those that do not meet the specifications of the builder.
Longer term, robust planning of lumber delivery, and more sophisticated delivery management, hold the promise to get lumber from the mill to the customer when required. On-time delivery helps lower the cost to the builder due to improved inventory management and decreased construction cycle times.
Given wood’s durability, ready availability and affordability, it’s no surprise that it has been one of the world’s most popular building materials throughout history. Research and technology are allowing humans to improve upon and make the most of Mother Nature, helping secure wood as a trusted building material of the future.
Rob Taylor is the vice president, Lumber Technologies, iLevel by Weyerhaeuser.
