Home Building Technology, Part XVII: The Reclamation of Southern Pine

Issue #18323 - June 2026 | Page #10

By Joe Kannapell

Technology, like we observed at last month’s Annual MSR Workshop, is the main reason Southern Pine has surpassed Douglas Fir as the predominant truss material. But, making this challenging transition has taken the work of lumber producers and their truss plant consumers. What’s more, the culmination of the lumber industry efforts was on display at the magnificent $210 Million Canfor sawmill that was the highlight of the MSR Workshop.

On the way to the Canfor mill, we drove through stands of Longleaf Southern Pine, the source of the best truss material in the world. We passed the site of the former Gulf Lumber sawmill, which had been tapping this abundant resource since 1887, but would underutilize it until the timber industry began its move toward the Southeast. Gulf’s product did not reach its full potential until Canfor purchased Gulf and invested in the latest technology. [For all images, See PDF or View in Full Issue.]

In 1955, just after the birth of the truss industry, Weyerhaeuser made its first bid to escape logging curtailments in the Northwest by buying 550,000 acres of timberland in the South. This began the increasing reliance of timber companies on Southern Pine lumber, but it did not change builder preferences for the straighter and more uniform western woods. However, Gulf Lumber was quickly recognized by truss manufacturers for their superior product, and many were willing to pay the extra freight to haul it from near the Gulf of Mexico to the Northeast, especially after 1979 when Gulf became one of the first southern mills to mechanically grade lumber with a machine stress-rated (MSR) lumber testing machine. With the availability of Gulf’s 2850f/2.3E MSR lumber, agricultural truss makers were able to span further with narrower-width material.

To address quality issues, a well-regarded Southern Pine producer, the Union Camp Company, focused on the kiln-drying process because Southern Pine is more porous than western woods and can have a moisture content exceeding 40% when cut. During the 1960s, Union Camp had devoted considerable capital toward regulating the moisture content of the wood going into their pulp and paper business, and in the early 1980s, they began directing resources toward that end in their lumber business. At their Franklin mill in rural Virginia, Larry Culpepper helped develop and later perfect the first computerized, multi-zoned dry kiln that dramatically improved the quality of the finished product. Union Camp added this technology to their mill in Meldrim, Georgia, so both mills then supplied the most sought-after product in the Southeast, and Larry Culpepper went on to consult with other mills to improve their drying processes.

In 1988, Weyerhaeuser began testing a new product which promised to take the best advantage of their lumber harvest in the South, called machine evaluated lumber (MEL). The first production of MEL came from a Plymouth, NC mill to the Virginia plant where I was GM. The product we tested was stamped M19 and had values comparable to the 2x4 #2 chord material that we had been using as chord material (M29 would have higher values today due to reduction in visually graded lumber values). We had no issues with the MEL product and soon learned that other Weyerhaeuser and Gilman (now West Fraser) mills were offering MEL.

This method of grading takes account of the wide variation, up to 31%, of the properties of the four species that comprise the Southern Pine grouping. For example, Longleaf Pine and Slash Pine generally have the same stiffness (MOE), while Slash Pine can carry more load before breaking (MOR) and can be assigned a higher allowable bending stress. But Longleaf Pine resists crushing better than Slash Pine. To account for this level of variability, the Southern Pine Inspection Bureau (SPIB) has prescribed 16 MSR and 21 MEL Pine grades that give mills the flexibility to select the best combination of properties based on their incoming timber. Assigning the optimal grades requires the technology that we had come to the Workshop to see.

On our mill tour, we ascended stairs and stepped onto a catwalk that ran parallel to the path of the thousand-pound logs beginning their rapid transit through the debarking process, attended by a single person, whose only job was to clear any congestion on the line. Not observable, but explained to us, was the end-to-end scanning of each log and computer-determined positioning of each log to optimize the yield of boards prior to cutting. Then came the remarkable grading process, where each finished board passes through more scanners that identify the knots, wane, and slope of grain that are the primary determinants of lumber grade. Last was the acoustic measurement of each board’s strength properties, finalizing its grade. (For more information on this grading technology, see the article by Linda Brown and Frank Woeste, Machine Graded Lumber: Technologies, Quality, and Benefits.)

Touring this Canfor facility and learning that $1 Billion of additional capital is pouring into southern mills indicates that the truss industry will continue to have a plentiful supply of structurally graded lumber. Regarding the quality of that supply, one of the attendees inquired, “Is the quality of Southern Pine lumber decreasing?” The somewhat unsatisfying answer was, “While the appearance of Canfor’s output may not be improving, its uniformity is assured.” In other words, with all of this investment and the improvements in drying technology, we can be assured of the structural integrity of Southern Pine, and the risk of shipping below-grade material is far lower than it has been with visually graded material. While we can be confident the product of these mills exceeds the strength of the Douglas Fir it is replacing, the need for culling will not be diminished. Even so, thanks to the increasing use of linear saws, culled chord members may be repurposed as web members, optimizing the yield of our lumber resource, just as we observed at the Canfor mill.